Technical Reports

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  Illmer, Joachim ; Janke, Daniel ; Kayal, Hakan ; Knapp, Andreas ; van der Lucht, Joschka ; Lutz, Jonas ; Shamloonia, Mehrnaz ; Sommer, Kai ; et al.: Mars Base 2030 ( Nr. 500), 2017
  • [ BibTeX ]
  • [ URL ]
  @techreport{illmer2017, author = {Illmer, Joachim and Janke, Daniel and Kayal, Hakan and Knapp, Andreas and van der Lucht, Joschka and Lutz, Jonas and Shamloonia, Mehrnaz and Sommer, Kai and Sotnik, Dimitri}, keywords = {base}, month = {07}, number = 500, title = {Mars Base 2030}, year = 2017 }
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  Seipel, D. ; Hanus, M. ; Abreu, S. (eds.): Declare 2017 – Conference on Declarative Programming ( Nr. 499) : Institut für Informatik, 2017
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This technical report contains the papers presented at the Conference on Declarative Programming Declare 2017, in Würzburg, Germany, from September 19th to 22th, 2017. The joint conference consisted of the 21st International Conference on Applications of Declarative Programming and Knowledge Management INAP 2017, the 31st Workshop on Logic Programming WLP 2017, and the 25th Workshop on Functional and (Constraint) Logic Programming WFLP 2017. Declarative programming is an advanced paradigm for modeling and solving complex problems. This method has attracted increased attention over the last decades, e.g., in the domains of data and knowledge engineering, databases, artificial intelligence, natural language processing, modeling and processing combinatorial problems, and for establishing knowledge-based systems for the web. The conference Declare 2017 aims to promote the cross-fertilizing exchange of ideas and experiences among researches and students from the different communities interested in the foundations, applications, and combinations of high-level, declarative programming and related areas. It was be accompanied by a one-week summer school on Advanced Concepts for Databases and Logic Programming for students and PhD students.

  @techreport{seipel2017declare, abstract = {This technical report contains the papers presented at the Conference on Declarative Programming Declare 2017, in Würzburg, Germany, from September 19th to 22th, 2017. The joint conference consisted of the 21st International Conference on Applications of Declarative Programming and Knowledge Management INAP 2017, the 31st Workshop on Logic Programming WLP 2017, and the 25th Workshop on Functional and (Constraint) Logic Programming WFLP 2017. Declarative programming is an advanced paradigm for modeling and solving complex problems. This method has attracted increased attention over the last decades, e.g., in the domains of data and knowledge engineering, databases, artificial intelligence, natural language processing, modeling and processing combinatorial problems, and for establishing knowledge-based systems for the web. The conference Declare 2017 aims to promote the cross-fertilizing exchange of ideas and experiences among researches and students from the different communities interested in the foundations, applications, and combinations of high-level, declarative programming and related areas. It was be accompanied by a one-week summer school on Advanced Concepts for Databases and Logic Programming for students and PhD students.}, editor = {Seipel, Dietmar and Hanus, Michael and Abreu, Salvador}, institution = {Institut für Informatik}, keywords = {programming}, month = {09}, number = 499, title = {Declare 2017 – Conference on Declarative Programming}, year = 2017 }

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  Gebert, Steffen ; Zinner, Thomas ; Lange, Stanislav ; Schwartz, Christian ; Tran-Gia, Phuoc: Discrete-Time Analysis: Deriving the Distribution of the Number of Events in an Arbitrarily Distributed Interval ( Nr. 498), 2016
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  For the context of discrete-time analysis, this document describes how to derive the distribution of the number of events in an arbitrarily distributed interval.

  @techreport{gebert2016discretetime, abstract = {For the context of discrete-time analysis, this document describes how to derive the distribution of the number of events in an arbitrarily distributed interval.}, author = {Gebert, Steffen and Zinner, Thomas and Lange, Stanislav and Schwartz, Christian and Tran-Gia, Phuoc}, keywords = {Discrete-Time}, month = {06}, number = 498, title = {Discrete-Time Analysis: Deriving the Distribution of the Number of Events in an Arbitrarily Distributed Interval}, year = 2016 }

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  Hirth, Matthias ; Lehrieder, Frank ; Oberste-Vorth, Stephan ; Hoßfeld, Tobias ; Tran-Gia, Phuoc: Wikipedia and its Network of Human and Automated Authors from a Social Network Perspective ( Nr. 494), 2015
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Online social networks (OSNs) become more and more important in today’s social and business life. Therefore, considerable effort is put in research to gain a deeper knowledge of the development of these networks and their dynamics. However, most of the existing literature is based on very limited subsets of the network data, which is often filtered by the OSN operator providing the data or biased by the crawling mechanisms used to obtain the data. This makes it difficult to analyze the temporal evolution of OSNs based on complete data. For studying temporal evolution and time dynamics we investigate the dynamics of the publicly available collaboration network of the Wikipedia authors as an example for an OSN-like network. The authors are distinguished between human authors contributing to the articles and automated scripts, so called bots, which complete specialized tasks like spell-checking. In particular, we study the temporal evolution of this network since its beginning and demonstrate that it exhibits prominent similarities to well known social networks such as the small-world phenomenon. This indicates that the insights gained from the analysis of Wikipedia’s collaboration network might be transferable to social networks in general.

  @techreport{hirth2015wikipedia, abstract = {Online social networks (OSNs) become more and more important in today’s social and business life. Therefore, considerable effort is put in research to gain a deeper knowledge of the development of these networks and their dynamics. However, most of the existing literature is based on very limited subsets of the network data, which is often filtered by the OSN operator providing the data or biased by the crawling mechanisms used to obtain the data. This makes it difficult to analyze the temporal evolution of OSNs based on complete data. For studying temporal evolution and time dynamics we investigate the dynamics of the publicly available collaboration network of the Wikipedia authors as an example for an OSN-like network. The authors are distinguished between human authors contributing to the articles and automated scripts, so called bots, which complete specialized tasks like spell-checking. In particular, we study the temporal evolution of this network since its beginning and demonstrate that it exhibits prominent similarities to well known social networks such as the small-world phenomenon. This indicates that the insights gained from the analysis of Wikipedia’s collaboration network might be transferable to social networks in general.}, author = {Hirth, Matthias and Lehrieder, Frank and Oberste-Vorth, Stephan and Hoßfeld, Tobias and Tran-Gia, Phuoc}, keywords = {Structure}, month = {März}, number = 494, title = {Wikipedia and its Network of Human and Automated Authors from a Social Network Perspective}, year = 2015 }
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  Seufert, Michael ; Hoßfeld, Tobias ; Machado, Guilherme Sperb ; Bocek, Thomas ; Biancani, Matteo ; Cruschelli, Paolo ; Lapacz, Roman ; Darzanos, George ; et al.: A Survey of Cloud Services and Potential Applications of Social Awareness ( Nr. 496), 2015
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The variety of emerging cloud services and applications manifests in a multitude of network and hardware requirements, but also in different service and traffic characteristics. Due to the popularity of clouds, a set of issues emerges for the different stakeholders involved in providing and delivering cloud services to the end user. Not only pure network layer optimization, but especially the new field of socially-aware traffic management seems promising to overcome these issues. In this paper, the applicability of social awareness to different types of cloud services is discussed. For that purpose, cloud applications are classified according to relevant technical and non-technical characteristics. Based on this novel classification scheme, the benefits and challenges of social awareness are discussed and examples for the optimization of cloud services are given.

  @techreport{seufert2015survey, abstract = {The variety of emerging cloud services and applications manifests in a multitude of network and hardware requirements, but also in different service and traffic characteristics. Due to the popularity of clouds, a set of issues emerges for the different stakeholders involved in providing and delivering cloud services to the end user. Not only pure network layer optimization, but especially the new field of socially-aware traffic management seems promising to overcome these issues. In this paper, the applicability of social awareness to different types of cloud services is discussed. For that purpose, cloud applications are classified according to relevant technical and non-technical characteristics. Based on this novel classification scheme, the benefits and challenges of social awareness are discussed and examples for the optimization of cloud services are given.}, author = {Seufert, Michael and Hoßfeld, Tobias and Machado, Guilherme Sperb and Bocek, Thomas and Biancani, Matteo and Cruschelli, Paolo and Lapacz, Roman and Darzanos, George and Papafili, Ioanna and Wajda, Krzysztof}, keywords = {classification}, month = 11, number = 496, title = {A Survey of Cloud Services and Potential Applications of Social Awareness}, year = 2015 }
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  Kiesner, Maximilian ; Nehmeier, Marco ; Wolff von Gudenberg, Jürgen: ITF1788: An Interval Testframework for IEEE 1788 ( Nr. 495), 2015
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Libraries implementing the interval arithmetic standard IEEE 1788 have to be tested for errors. Although the standard is language agnostic, the different implementations are not. Therefore the same tests must be implemented in many different languages. Hence it is useful to only have to formulate the tests once – in a domain-specific language – and to subsequently generate the language-specific test code automatically. To save time and encourage test-driven development, we present a language for testing interval arithmetic libraries and a corresponding source code generator which produces language-specific unit tests.

  @techreport{kiesner2015itf1788, abstract = {Libraries implementing the interval arithmetic standard IEEE 1788 have to be tested for errors. Although the standard is language agnostic, the different implementations are not. Therefore the same tests must be implemented in many different languages. Hence it is useful to only have to formulate the tests once – in a domain-specific language – and to subsequently generate the language-specific test code automatically. To save time and encourage test-driven development, we present a language for testing interval arithmetic libraries and a corresponding source code generator which produces language-specific unit tests.}, author = {Kiesner, Maximilian and Nehmeier, Marco and Wolff von Gudenberg, Jürgen}, keywords = {interval}, month = {06}, number = 495, title = {ITF1788: An Interval Testframework for IEEE 1788}, year = 2015 }
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  Gebert, Steffen ; Schwartz, Christian ; Zinner, Thomas ; Tran-Gia, Phuoc: Agile Management of Software Based Networks ( Nr. 493), 2015
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The softwarization and cloudification of networks through mechanisms like Software Defined Networking and Network Functions Virtualisation promise a new degree of flexibility and agility. By moving logic from device firmware into application software and by applying mechanisms from software development, innovations can be introduced with lower effort. Concrete ways how to operate and orchestrate such systems, however, are not defined. The process of making changes to a controller software or a virtualized network function in a production network without the risk of network disruption is not covered by literature, yet. Complexity of systems bring the risk of unexpected side-effects and has so long been the show-stopper for administrators being relaxed while applying changes to networking devices. This paper suggests the adaption of the successful concept of continuous delivery into the software defined networking world. Mechanisms like Test-Driven Development and automatic acceptance tests demonstrate that the software engineering community already found ways to ensure that changes do not break a software's functionality. Applied to network engineering, the adaption of continuous delivery can be seen as an enabler for risk-free and frequent changes in production infrastructure through push button deployments.

  @techreport{gebert2015agile, abstract = {The softwarization and cloudification of networks through mechanisms like Software Defined Networking and Network Functions Virtualisation promise a new degree of flexibility and agility. By moving logic from device firmware into application software and by applying mechanisms from software development, innovations can be introduced with lower effort. Concrete ways how to operate and orchestrate such systems, however, are not defined. The process of making changes to a controller software or a virtualized network function in a production network without the risk of network disruption is not covered by literature, yet. Complexity of systems bring the risk of unexpected side-effects and has so long been the show-stopper for administrators being relaxed while applying changes to networking devices. This paper suggests the adaption of the successful concept of continuous delivery into the software defined networking world. Mechanisms like Test-Driven Development and automatic acceptance tests demonstrate that the software engineering community already found ways to ensure that changes do not break a software's functionality. Applied to network engineering, the adaption of continuous delivery can be seen as an enabler for risk-free and frequent changes in production infrastructure through push button deployments.}, author = {Gebert, Steffen and Schwartz, Christian and Zinner, Thomas and Tran-Gia, Phuoc}, keywords = {myown}, month = {01}, number = 493, title = {Agile Management of Software Based Networks}, year = 2015 }

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  Nalepa, Grzegorz J. ; Baumeister, Joachim: Proceedings of the 10th Workshop on Knowledge Engineering and Software Engineering (KESE) ( Nr. 492). Department of Computer Science, 2014
  • [ Abstract ]
  • [ BibTeX ]
  Knowledge Based Systems (KBS) have been successfully developed in various domains based on techniques and tools from Knowledge Engineering (KE). The classic KE approach to system modeling uses mostly symbolic logic-based symbolic knowledge representation methods, which are more specific from Artificial Intelligence (AI) in a broad sense, that has recently included computational intelligence techniques. Since most of the implementations of today KBS are software based, Software Engineering (SE) methods and tools play an important role in their development. Moreover, recent developments in SE emphasize the importance of the use of formalized symbolic representations in the software development process.

  @techreport{nalepa2014proceedings, abstract = {Knowledge Based Systems (KBS) have been successfully developed in various domains based on techniques and tools from Knowledge Engineering (KE). The classic KE approach to system modeling uses mostly symbolic logic-based symbolic knowledge representation methods, which are more specific from Artificial Intelligence (AI) in a broad sense, that has recently included computational intelligence techniques. Since most of the implementations of today KBS are software based, Software Engineering (SE) methods and tools play an important role in their development. Moreover, recent developments in SE emphasize the importance of the use of formalized symbolic representations in the software development process.}, address = {Department of Computer Science}, author = {Nalepa, Grzegorz J. and Baumeister, Joachim}, keywords = {myown}, month = {Oktober}, number = 492, title = {Proceedings of the 10th Workshop on Knowledge Engineering and Software Engineering (KESE)}, year = 2014 }
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  Wamser, Florian ; Klein, Dominik ; Tran-Gia, Phuoc: Second Interim Report for the DFG Project FunkOFDMA ( Nr. 489). Department of Computer Science, 2014
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  rthogonal Frequency Division Multiple Access (OFDMA) is the technology of choice for today's mobile communication networks. The WiMAX wireless broadband standard uses an OFDMA-based physical layer specified in the IEEE 802.16 standard. 3GPP Long Term Evolution (LTE) uses OFDMA on the downlink. The performance of these systems crucially depends on intelligent methods for managing radio resources. These should exploit the theoretical capacity as much as possible while also taking system and network architecture as well as user and application demands into account. The interim report provides an overview of the work of the third and fourth year of funding. Several studies on application-aware resource management in the air interface of an OFDMA network were conducted. First, a packet scheduling approach based on client feedback was proposed that takes into account the application state of YouTube. With this approach, it is possible to temporarily prefer YouTube over other applications to ensure a good quality for YouTube users. Second, it was shown that the adaptation capabilities of Skype can be exploited for the scheduling to some extent. The automatic adaptation of Skype allows to tolerate certain bandwidth limitations for Skype users without significant decrease in quality for the user. Third, a simulation study on an application-aware scheduling for file downloads was performed with the aim, not only to enhance the quality of the application, but also to save energy at the end-user device. For comparison of these application-specific approaches, a comprehensive statistical evaluation was finally conducted with different ideas of application-aware scheduling according to different metrics and information. The outcome is a quantification of the benefits and the impact on the applications of different application-aware mechanisms. The fundamental basis for the studies within this project phase, was an abstract modeling of YouTube, Skype, Dropbox, and web browsing. The models are required for the event-driven, time-variant simulation of the system consisting of users, applications, application behavior, TCP congestion control, and especially, packet scheduling and abstract data transmission at link-layer for LTE Release 8. The simulator was developed in cooperation with the Brno University of Technology, Czech Republic. Finally, a journal paper was published on general resource management approaches for YouTube in access networks which is based on several YouTube measurements for the modeling within a wireless access network. At present, it was not possible to measure and test these scheduling and resource management approaches in a commercial network, or to setup an own LTE communication network for tests due to the regulated radio licenses and the fact that many QoS functions are only described in specifications but not yet implemented by the vendors. For this reason, the measurements were performed in a wireless mesh access network.

  @techreport{florianwamserdominikklein2014second, abstract = {rthogonal Frequency Division Multiple Access (OFDMA) is the technology of choice for today's mobile communication networks. The WiMAX wireless broadband standard uses an OFDMA-based physical layer specified in the IEEE 802.16 standard. 3GPP Long Term Evolution (LTE) uses OFDMA on the downlink. The performance of these systems crucially depends on intelligent methods for managing radio resources. These should exploit the theoretical capacity as much as possible while also taking system and network architecture as well as user and application demands into account. The interim report provides an overview of the work of the third and fourth year of funding. Several studies on application-aware resource management in the air interface of an OFDMA network were conducted. First, a packet scheduling approach based on client feedback was proposed that takes into account the application state of YouTube. With this approach, it is possible to temporarily prefer YouTube over other applications to ensure a good quality for YouTube users. Second, it was shown that the adaptation capabilities of Skype can be exploited for the scheduling to some extent. The automatic adaptation of Skype allows to tolerate certain bandwidth limitations for Skype users without significant decrease in quality for the user. Third, a simulation study on an application-aware scheduling for file downloads was performed with the aim, not only to enhance the quality of the application, but also to save energy at the end-user device. For comparison of these application-specific approaches, a comprehensive statistical evaluation was finally conducted with different ideas of application-aware scheduling according to different metrics and information. The outcome is a quantification of the benefits and the impact on the applications of different application-aware mechanisms. The fundamental basis for the studies within this project phase, was an abstract modeling of YouTube, Skype, Dropbox, and web browsing. The models are required for the event-driven, time-variant simulation of the system consisting of users, applications, application behavior, TCP congestion control, and especially, packet scheduling and abstract data transmission at link-layer for LTE Release 8. The simulator was developed in cooperation with the Brno University of Technology, Czech Republic. Finally, a journal paper was published on general resource management approaches for YouTube in access networks which is based on several YouTube measurements for the modeling within a wireless access network. At present, it was not possible to measure and test these scheduling and resource management approaches in a commercial network, or to setup an own LTE communication network for tests due to the regulated radio licenses and the fact that many QoS functions are only described in specifications but not yet implemented by the vendors. For this reason, the measurements were performed in a wireless mesh access network.}, address = {Department of Computer Science}, author = {Wamser, Florian and Klein, Dominik and Tran-Gia, Phuoc}, keywords = {myown}, month = {März}, number = 489, title = {Second Interim Report for the DFG Project FunkOFDMA}, type = {Technical Report}, year = 2014 }
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  Hoßfeld, Tobias ; Seufert, Michael ; Sieber, Christian ; Zinner, Thomas: Crowdsourced subjective user study results on QoE influence factors of HTTP Adaptive Streaming ( Nr. 491), 2014
  • [ Abstract ]
  • [ BibTeX ]
  HTTP Adaptive Streaming (HAS) is employed by more and more video streaming services in the Internet. It allows to adapt the down- loaded video quality to the current network conditions, and thus, avoids stalling (i.e., playback interruptions) to the greatest possible extend. The adaptation of video streams is done by switching be- tween different quality representation levels, which influences the user perceived quality of the video stream. In this work, the in- fluence of several adaptation parameters, namely, switch amplitude (i.e., quality level difference), switching frequency, and recency ef- fects, on Quality of Experience (QoE) is investigated. Therefore, crowdsourcing experiments were conducted in order to collect sub- jective ratings for different adaptation-related test conditions. The results of these subjective studies indicate the influence of the adap- tation parameters, and based on these findings a simplified QoE model for HAS is presented, which only relies on the switch am- plitude and the playback time of each layer. he technical report includes detailed information on the subjective user studies of the authors' paper "Assessing effect sizes of influence factors towards a QoE model for HTTP adaptive streaming", International Workshop on Quality of Multimedia Experience (QoMEX) 2014.

  @techreport{hossfeld2014crowdsourced, abstract = {HTTP Adaptive Streaming (HAS) is employed by more and more video streaming services in the Internet. It allows to adapt the down- loaded video quality to the current network conditions, and thus, avoids stalling (i.e., playback interruptions) to the greatest possible extend. The adaptation of video streams is done by switching be- tween different quality representation levels, which influences the user perceived quality of the video stream. In this work, the in- fluence of several adaptation parameters, namely, switch amplitude (i.e., quality level difference), switching frequency, and recency ef- fects, on Quality of Experience (QoE) is investigated. Therefore, crowdsourcing experiments were conducted in order to collect sub- jective ratings for different adaptation-related test conditions. The results of these subjective studies indicate the influence of the adap- tation parameters, and based on these findings a simplified QoE model for HAS is presented, which only relies on the switch am- plitude and the playback time of each layer. he technical report includes detailed information on the subjective user studies of the authors' paper "Assessing effect sizes of influence factors towards a QoE model for HTTP adaptive streaming", International Workshop on Quality of Multimedia Experience (QoMEX) 2014.}, author = {Hoßfeld, Tobias and Seufert, Michael and Sieber, Christian and Zinner, Thomas}, keywords = {myown}, month = {07}, number = 491, title = {Crowdsourced subjective user study results on QoE influence factors of HTTP Adaptive Streaming}, year = 2014 }
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  Seufert, Michael ; Egger, Sebastian ; Slanina, Martin ; Zinner, Thomas ; Hoßfeld, Tobias ; Tran-Gia, Phuoc: A Survey on Quality of Experience of HTTP Adaptive Streaming ( Nr. 490), 2014
  • [ Abstract ]
  • [ BibTeX ]
  Changing network conditions pose severe problems to video streaming in the Internet. HTTP adaptive streaming (HAS) is a technology employed by numerous video services which relieves these issues by adapting the video to the current network conditions. It enables service providers to improve resource utilization and Quality of Experience (QoE) by incorporating information from different layers in order to deliver and adapt a video in its best possible quality. Thereby, it allows to take into account end user device capabilities, available video quality levels, current network conditions, and current server load. For end users, the major benefits of HAS compared to classical HTTP video streaming are reduced interruptions of the video playback and higher bandwidth utilization, which both generally result in a higher QoE. Adaptation is possible by changing the frame rate, resolution, or quantization of the video, which can be done with various adaptation strategies and related client- and server-side actions. The technical development of HAS, existing open standardized solutions, but also proprietary solutions are reviewed in this article as fundament to derive the QoE influence factors which emerge as a result of adaptation. The main contribution is a comprehensive survey of QoE related works from human computer interaction and networking domains which are structured according to the QoE impact of video adaptation. To be more precise, subjective studies which cover QoE aspects of adaptation dimensions and strategies are revisited. As a result, QoE influence factors of HAS and corresponding QoE models are identified, but also open issues and conflicting results are discussed. Furthermore, the interaction between HAS and other clients, which is often ignored in the context of HAS, affects QoE influence factors and is consequently analyzed. This survey gives the reader an overview of the current state of the art and recent developments. At the same time it targets networking researchers who develop new solutions for HTTP video streaming or assess video streaming from a user centric point of view. Therefore, the article is a major step towards truly improving HAS.

  @techreport{seufert2014survey, abstract = {Changing network conditions pose severe problems to video streaming in the Internet. HTTP adaptive streaming (HAS) is a technology employed by numerous video services which relieves these issues by adapting the video to the current network conditions. It enables service providers to improve resource utilization and Quality of Experience (QoE) by incorporating information from different layers in order to deliver and adapt a video in its best possible quality. Thereby, it allows to take into account end user device capabilities, available video quality levels, current network conditions, and current server load. For end users, the major benefits of HAS compared to classical HTTP video streaming are reduced interruptions of the video playback and higher bandwidth utilization, which both generally result in a higher QoE. Adaptation is possible by changing the frame rate, resolution, or quantization of the video, which can be done with various adaptation strategies and related client- and server-side actions. The technical development of HAS, existing open standardized solutions, but also proprietary solutions are reviewed in this article as fundament to derive the QoE influence factors which emerge as a result of adaptation. The main contribution is a comprehensive survey of QoE related works from human computer interaction and networking domains which are structured according to the QoE impact of video adaptation. To be more precise, subjective studies which cover QoE aspects of adaptation dimensions and strategies are revisited. As a result, QoE influence factors of HAS and corresponding QoE models are identified, but also open issues and conflicting results are discussed. Furthermore, the interaction between HAS and other clients, which is often ignored in the context of HAS, affects QoE influence factors and is consequently analyzed. This survey gives the reader an overview of the current state of the art and recent developments. At the same time it targets networking researchers who develop new solutions for HTTP video streaming or assess video streaming from a user centric point of view. Therefore, the article is a major step towards truly improving HAS.}, author = {Seufert, Michael and Egger, Sebastian and Slanina, Martin and Zinner, Thomas and Hoßfeld, Tobias and Tran-Gia, Phuoc}, keywords = {variable}, month = {04}, number = 490, title = {A Survey on Quality of Experience of HTTP Adaptive Streaming}, year = 2014 }
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  Cunis, Torbjørn ; Fischer, Wendelin ; Gillmann, Florian ; van gen Hassend, Max ; Hempfling, Christina ; Kayal, Hakan ; König, Frederik ; Lauterbach, Helge ; et al.: Moon Base 2030 ( Nr. 497), 2014
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this study, a potential manned lunar base, scheduled to the year 2030 of human return, has been studied by a group of twelve students within a course for the development of planetary bases. It contains analysis on objectives, requirements, simulations and the design of a future moon base including considerations on construction, life support, environmental conditions, power supply, communications, in situ resource utilization and surface transportation. The study

  @techreport{noauthororeditor2014, abstract = {In this study, a potential manned lunar base, scheduled to the year 2030 of human return, has been studied by a group of twelve students within a course for the development of planetary bases. It contains analysis on objectives, requirements, simulations and the design of a future moon base including considerations on construction, life support, environmental conditions, power supply, communications, in situ resource utilization and surface transportation. The study}, author = {Cunis, Torbjørn and Fischer, Wendelin and Gillmann, Florian and van gen Hassend, Max and Hempfling, Christina and Kayal, Hakan and König, Frederik and Lauterbach, Helge and Mohn, Helge and van der Wals, Dennis and Werner, Kai and Wenzel, Tobias and Wißmiller, Martin}, keywords = {lunar}, month = {02}, number = 497, title = {Moon Base 2030}, year = 2014 }

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  Schwartz, Christian ; Hossfeld, Tobias ; Lehrieder, Frank ; Tran-Gia, Phuoc: Performance Analysis of the Trade-off Between Signalling Load and Power Consumption for Popular Smartphone Apps in 3G Networks ( Nr. 485). Department of Computer Science, 2013
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The popularity of smartphones and mobile applications has experienced a considerable growth during recent years. As a consequence, efficient resource management mecha- nisms are required to cope with the increasing demands and user expectations. Since smartphones have only very limited energy resources, battery efficiency is one of the de- termining factors for a good user experience. Therefore, some smartphones tear down connections to the mobile network soon after a completed data transmission to reduce the power consumption of their transmission unit. However, frequent connection re- establishments caused by apps which send or receive small amounts of data often lead to a heavy signalling load within the mobile network. The investigation of this trade-off between energy consumption at the smartphone and the generated signalling traffic in the mobile network is one of the major contributions of this paper. We explain that this trade-off can be controlled by the connection release timeout and study the impact of this parameter for a number popular apps that cover a wide range of traffic characteristics in terms of bandwidth requirements and resulting signalling traffic. Finally, we study the impact of the timer settings on QoE for web traffic. This is an important aspect since connection establishments do not only lead to signalling traffic, but they also increase the load time of web pages.

  @techreport{TR485, abstract = {The popularity of smartphones and mobile applications has experienced a considerable growth during recent years. As a consequence, efficient resource management mecha- nisms are required to cope with the increasing demands and user expectations. Since smartphones have only very limited energy resources, battery efficiency is one of the de- termining factors for a good user experience. Therefore, some smartphones tear down connections to the mobile network soon after a completed data transmission to reduce the power consumption of their transmission unit. However, frequent connection re- establishments caused by apps which send or receive small amounts of data often lead to a heavy signalling load within the mobile network. The investigation of this trade-off between energy consumption at the smartphone and the generated signalling traffic in the mobile network is one of the major contributions of this paper. We explain that this trade-off can be controlled by the connection release timeout and study the impact of this parameter for a number popular apps that cover a wide range of traffic characteristics in terms of bandwidth requirements and resulting signalling traffic. Finally, we study the impact of the timer settings on QoE for web traffic. This is an important aspect since connection establishments do not only lead to signalling traffic, but they also increase the load time of web pages.}, address = {Department of Computer Science}, author = {Schwartz, Christian and Hossfeld, Tobias and Lehrieder, Frank and Tran-Gia, Phuoc}, keywords = {myown}, month = {01}, number = 485, title = {Performance Analysis of the Trade-off Between Signalling Load and Power Consumption for Popular Smartphone Apps in 3G Networks}, type = {Technical Report}, year = 2013 }
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  Hoßfeld, Tobias ; Keimel, Christian ; Hirth, Matthias ; Gardlo, Bruno ; Habigt, Julian ; Diepold, Klaus ; Tran-Gia, Phuoc: CrowdTesting: A Novel Methodology for Subjective User Studies and QoE Evaluation ( Nr. 486). Department of Computer Science, 2013
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The term "Crowdtesting" refers to subjective user studies which are conducted via crowdsourcing. The anonymous test subjects are remotly conducting the tests in their preferred environment. The advantages of crowdtesting are reduced time and costs for tests, large and diverse panel of international users, and realistic user settings. However, conceptual and technical challenges emerge due to the remote test settings. Key issues arising from crowdtesting include the reliability of user (ratings), incentives and payment schemes, and unknown context of user tests (e.g. environment, hardware, illumination, etc.). Countermeasures have to be developed, included in the test design, and implemented in the actual test campaign for which special attention is drawn to reliablity in this article. In particular, we focus on QoE assessment by means of crowdtesting. Furthermore, the test results have to be analyzed with respect to these features. Best practices collected from a large set of ownly conducted crowdtesting studies are presented in this paper in which we use the example of QoE testing for video streaming. The statistical analysis of experimental results guides how to analyze crowdtesting results and shows that the recommended two-stage crowdtesting design leads to reliable results.

  @techreport{TR486, abstract = {The term "Crowdtesting" refers to subjective user studies which are conducted via crowdsourcing. The anonymous test subjects are remotly conducting the tests in their preferred environment. The advantages of crowdtesting are reduced time and costs for tests, large and diverse panel of international users, and realistic user settings. However, conceptual and technical challenges emerge due to the remote test settings. Key issues arising from crowdtesting include the reliability of user (ratings), incentives and payment schemes, and unknown context of user tests (e.g. environment, hardware, illumination, etc.). Countermeasures have to be developed, included in the test design, and implemented in the actual test campaign for which special attention is drawn to reliablity in this article. In particular, we focus on QoE assessment by means of crowdtesting. Furthermore, the test results have to be analyzed with respect to these features. Best practices collected from a large set of ownly conducted crowdtesting studies are presented in this paper in which we use the example of QoE testing for video streaming. The statistical analysis of experimental results guides how to analyze crowdtesting results and shows that the recommended two-stage crowdtesting design leads to reliable results.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Keimel, Christian and Hirth, Matthias and Gardlo, Bruno and Habigt, Julian and Diepold, Klaus and Tran-Gia, Phuoc}, keywords = {myown}, month = {02}, number = 486, title = {CrowdTesting: A Novel Methodology for Subjective User Studies and QoE Evaluation}, type = {Technical Report}, year = 2013 }
• 
  Nalepa, Grzegorz J. ; Baumeister, Joachim: Proceedings of the 9th Workshop on Knowledge Engineering and Software Engineering (KESE) ( Nr. 487). Department of Computer Science, 2013
  • [ Abstract ]
  • [ BibTeX ]
  Research questions and practical exchange between Knowledge Engineering for intelligent systems and Software Engineering of advanced software programs have been fruitfully discussed over the last years. Many successful examples demonstrate the clear symbiosis between these two research areas. This proceedings contains the presented papers of the 9th Workshop on Knowledge Engineering and Software Engineering that was co-located with the 36th Annual Conference on Artificial Intelligence in Koblenz.

  @techreport{nalepa2013proceedings, abstract = {Research questions and practical exchange between Knowledge Engineering for intelligent systems and Software Engineering of advanced software programs have been fruitfully discussed over the last years. Many successful examples demonstrate the clear symbiosis between these two research areas. This proceedings contains the presented papers of the 9th Workshop on Knowledge Engineering and Software Engineering that was co-located with the 36th Annual Conference on Artificial Intelligence in Koblenz.}, address = {Department of Computer Science}, author = {Nalepa, Grzegorz J. and Baumeister, Joachim}, keywords = {myown}, month = {09}, number = 487, title = {Proceedings of the 9th Workshop on Knowledge Engineering and Software Engineering (KESE)}, type = {Technical Report}, year = 2013 }
• 
  Zinner, Thomas ; Hoßfeld, Tobias ; Tran-Gia, Phuoc ; Kellerer, Wolfgang: A Compass through SDN networks ( Nr. 488). Department of Computer Science, 2013
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  folgt

  @techreport{thomaszinner2013compass, abstract = {folgt}, address = {Department of Computer Science}, author = {Zinner, Thomas and Hoßfeld, Tobias and Tran-Gia, Phuoc and Kellerer, Wolfgang}, keywords = {myown}, month = {09}, number = 488, title = {A Compass through SDN networks}, type = {Technical Report}, year = 2013 }

• 
  Metzger, Florian ; Gebert, Steffen ; Salzlechner, Katharina ; Ratetseder, Albert ; Romirer, Peter ; Tutschku, Kurt: Research Report On Signaling Load and Tunnel Management in a 3G Core Network ( Nr. 484). Department of Computer Science, 2012
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This paper takes an initial look on the signaling behavior of mobile devices in mobile cellular core networks. In contrast to most contributions in this field, our focus does not lie on the wireless or user-oriented parts of the network, but on signaling in the core network. We evaluate GTP Tunnel Management signaling messages on the path between SGSN and GGSN, and the overhead imposed on user plane traffic. Furthermore, we attempt to correlate PDP Context durations to device specific parameters such as device class or operating system. From the context durations, we estimate the signaling overhead devices burden on the core network.

  @techreport{TR484, abstract = {This paper takes an initial look on the signaling behavior of mobile devices in mobile cellular core networks. In contrast to most contributions in this field, our focus does not lie on the wireless or user-oriented parts of the network, but on signaling in the core network. We evaluate GTP Tunnel Management signaling messages on the path between SGSN and GGSN, and the overhead imposed on user plane traffic. Furthermore, we attempt to correlate PDP Context durations to device specific parameters such as device class or operating system. From the context durations, we estimate the signaling overhead devices burden on the core network.}, address = {Department of Computer Science}, author = {Metzger, Florian and Gebert, Steffen and Salzlechner, Katharina and Ratetseder, Albert and Romirer, Peter and Tutschku, Kurt}, keywords = {myown}, month = {09}, number = 484, title = {Research Report On Signaling Load and Tunnel Management in a 3G Core Network}, type = {Technical Report}, year = 2012 }

• 
  Nehmeier, Marco: Generative Programming for Automatic Differentiation in C++0x ( Nr. 483). Department of Computer Science, 2011
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The computation of the first or higher derivatives of a function is a common problem in scientific computing. The most obvious approach to compute the derivative values is the symbolic differentiation which applies the well known rules of differentiation onto the expression to compute a formal expression of the derivative function. Another method called numerical differentiation is the approximation of the derivative with difference quotients. Superior to these approaches is the automatic differentiation which is a technique to compute a value of the expression and the derivative together by applying the well known rules of differentiation. The difference to symbolic differentiation is that it propagates numerical values instead of formal expressions. Commonly used implementations of automatic differentiation may be divided into two categories, the implementations using operator overloading to compute the values of the function and the derivative together in contrast to special tools applying the technique of source transformation to mix in the expressions to compute the derivatives. Both of these techniques are somehow inflexible in the manner that the operators are not overloaded for high order differentiation or additional tools are required for the source transformation. In this paper we use expression templates and template meta programming to mix in the code for the partial differentiation. The main concept is to apply the symbolic differentiation at compile time only onto the single operations of the expression tree to create the run time code for the automatic differentiation. This has two advantages, we can, in theory, compute derivatives of any order and secondly the differentiation of the operations is done with types. This means that the symbolic differentiation of an operation with a specified order is performed only once by the compiler. Our generic approach provides a domain specific language for partial automatic differentiation of an arbitrary order which is easily extendable by new types. Several C++ and especially C++0x template programming concepts and techniques like variadic templates, type lists or variadic tuples are used to realize the specification of the automatic differentiation at compile time. Common template meta programming techniques are refined. We tested the functionality, correctness and performance of our implementation in different case studies for floating point as well as interval data types and compared it against other implementations.

  @techreport{TR483, abstract = {The computation of the first or higher derivatives of a function is a common problem in scientific computing. The most obvious approach to compute the derivative values is the symbolic differentiation which applies the well known rules of differentiation onto the expression to compute a formal expression of the derivative function. Another method called numerical differentiation is the approximation of the derivative with difference quotients. Superior to these approaches is the automatic differentiation which is a technique to compute a value of the expression and the derivative together by applying the well known rules of differentiation. The difference to symbolic differentiation is that it propagates numerical values instead of formal expressions. Commonly used implementations of automatic differentiation may be divided into two categories, the implementations using operator overloading to compute the values of the function and the derivative together in contrast to special tools applying the technique of source transformation to mix in the expressions to compute the derivatives. Both of these techniques are somehow inflexible in the manner that the operators are not overloaded for high order differentiation or additional tools are required for the source transformation. In this paper we use expression templates and template meta programming to mix in the code for the partial differentiation. The main concept is to apply the symbolic differentiation at compile time only onto the single operations of the expression tree to create the run time code for the automatic differentiation. This has two advantages, we can, in theory, compute derivatives of any order and secondly the differentiation of the operations is done with types. This means that the symbolic differentiation of an operation with a specified order is performed only once by the compiler. Our generic approach provides a domain specific language for partial automatic differentiation of an arbitrary order which is easily extendable by new types. Several C++ and especially C++0x template programming concepts and techniques like variadic templates, type lists or variadic tuples are used to realize the specification of the automatic differentiation at compile time. Common template meta programming techniques are refined. We tested the functionality, correctness and performance of our implementation in different case studies for floating point as well as interval data types and compared it against other implementations.}, address = {Department of Computer Science}, author = {Nehmeier, Marco}, keywords = {myown}, month = 12, number = 483, title = {Generative Programming for Automatic Differentiation in C++0x}, type = {Technical Report}, year = 2011 }
• 
  Hoßfeld, Tobias ; Zinner, Thomas ; Schatz, Raimund ; Seufert, Michael ; Tran-Gia, Phuoc: Transport Protocol Influences on YouTube QoE ( Nr. 482). Department of Computer Science, 2011
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Video streaming currently dominates global Internet traffic and will be of even increasing importance in the future. In this paper we assess the impact of the underlying transport protocol on the user perceived quality for video streaming using YouTube as example. In particular, we investigate whether UDP or TCP fits better for Video-on-Demand delivery from the end user's perspective, when the video is transmitted over a bottleneck link. For UDP based streaming, the bottleneck link results in spatial and temporal video artifacts, decreasing the video quality. In contrast, in the case of TCP based streaming, the displayed content itself is not disturbed but playback suffers from stalling due to rebufferung. Due to the lack of existing Quality of Experience (QoE) models for online video services that are based on TCP-streaming, we propose a generic subjective QoE assessment methodology for multimedia applications (like online video) that is based on crowdsourcing - a highly cost-efficient, fast and flexible way of conducting user experiments. We demonstrate how our approach successfully leverages the inherent strengths of crowdsourcing while addressing critical aspects such as the reliability of the experimental data obtained. As a result, we present a dedicated QoE model for YouTube that takes into account the key influence factors (such as stalling events caused by network bottlenecks) that shape quality perception of this service. The results of subjective user studies for both scenarios (UDP based on related work, TCP based on own studies) are analyzed in order to assess the transport protocol influences on Quality of Experience of YouTube. To this end, application-level measurements are conducted for YouTube streaming over a network bottleneck in order to develop models for realistic stalling patterns. Furthermore, mapping functions are derived that accurately describe the relationship between network-level impairments and QoE for both protocols.

  @techreport{TR482, abstract = {Video streaming currently dominates global Internet traffic and will be of even increasing importance in the future. In this paper we assess the impact of the underlying transport protocol on the user perceived quality for video streaming using YouTube as example. In particular, we investigate whether UDP or TCP fits better for Video-on-Demand delivery from the end user's perspective, when the video is transmitted over a bottleneck link. For UDP based streaming, the bottleneck link results in spatial and temporal video artifacts, decreasing the video quality. In contrast, in the case of TCP based streaming, the displayed content itself is not disturbed but playback suffers from stalling due to rebufferung. Due to the lack of existing Quality of Experience (QoE) models for online video services that are based on TCP-streaming, we propose a generic subjective QoE assessment methodology for multimedia applications (like online video) that is based on crowdsourcing - a highly cost-efficient, fast and flexible way of conducting user experiments. We demonstrate how our approach successfully leverages the inherent strengths of crowdsourcing while addressing critical aspects such as the reliability of the experimental data obtained. As a result, we present a dedicated QoE model for YouTube that takes into account the key influence factors (such as stalling events caused by network bottlenecks) that shape quality perception of this service. The results of subjective user studies for both scenarios (UDP based on related work, TCP based on own studies) are analyzed in order to assess the transport protocol influences on Quality of Experience of YouTube. To this end, application-level measurements are conducted for YouTube streaming over a network bottleneck in order to develop models for realistic stalling patterns. Furthermore, mapping functions are derived that accurately describe the relationship between network-level impairments and QoE for both protocols.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Zinner, Thomas and Schatz, Raimund and Seufert, Michael and Tran-Gia, Phuoc}, keywords = {myown}, month = {07}, number = 482, title = {Transport Protocol Influences on YouTube QoE}, type = {Technical Report}, year = 2011 }
• 
  Tschorsch, F. ; Scheuermann, B.: Tor is Unfair - and What to Do About It ( Nr. 481). Department of Computer Science, 2011
  • [ BibTeX ]
  @techreport{TR481, address = {Department of Computer Science}, author = {Tschorsch, F. and Scheuermann, B.}, keywords = {myown}, month = {05}, number = 481, title = {Tor is Unfair - and What to Do About It}, type = {Technical Report}, year = 2011 }
• 
  Fleszar, K. ; Glaßer, Christian ; Lipp, F. ; Reitwießner, Christian ; Witek, Maximilian: The Complexity of Solving Multiobjective Optimization Problems and its Relation to Multivalued Functions ( Nr. 480). Department of Computer Science, 2011
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR480, address = {Department of Computer Science}, author = {Fleszar, K. and Glaßer, Christian and Lipp, F. and Reitwießner, Christian and Witek, Maximilian}, keywords = {myown}, month = {04}, number = 480, title = {The Complexity of Solving Multiobjective Optimization Problems and its Relation to Multivalued Functions}, type = {Technical Report}, year = 2011 }
• 
  Schlosser, Daniel ; Duelli, Michael ; Goll, Sebastian: Performance Comparison of Common Server Hardware Virtualization Solutions Regarding the Network Throughput of Virtualized Systems ( Nr. 479). Department of Computer Science, 2011
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Hosting virtual servers on a shared physical hardware by means of hardware virtualization is common use at data centers, web hosters, and research facilities. All virtualization platforms include isolation techniques that restrict resource consumption of the virtual guest systems. Therefore, they setup quotas for the virtual guest systems on the use of processors, memory, and hard disk of the host. However, these isolation techniques have an impact on the performance of the guest systems. In this technical report, we study how popular hardware virtualization approaches, namely OpenVZ, KVM, Xen v4, VirtualBox, and VMware ESXi, affect the network throughput of a virtualized system. We compare their performance impact in a dedicated and a shared host scenario as well as to the bare, i.e. not virtualized host system. Our results provide an overview on the performance of popular hardware virtualization platforms on commodity hardware in terms of network throughput and should be considered when performing scientific experiments in a virtualized environment or hosting virtual machines with service level agreements.

  @techreport{TR479, abstract = {Hosting virtual servers on a shared physical hardware by means of hardware virtualization is common use at data centers, web hosters, and research facilities. All virtualization platforms include isolation techniques that restrict resource consumption of the virtual guest systems. Therefore, they setup quotas for the virtual guest systems on the use of processors, memory, and hard disk of the host. However, these isolation techniques have an impact on the performance of the guest systems. In this technical report, we study how popular hardware virtualization approaches, namely OpenVZ, KVM, Xen v4, VirtualBox, and VMware ESXi, affect the network throughput of a virtualized system. We compare their performance impact in a dedicated and a shared host scenario as well as to the bare, i.e. not virtualized host system. Our results provide an overview on the performance of popular hardware virtualization platforms on commodity hardware in terms of network throughput and should be considered when performing scientific experiments in a virtualized environment or hosting virtual machines with service level agreements.}, address = {Department of Computer Science}, author = {Schlosser, Daniel and Duelli, Michael and Goll, Sebastian}, keywords = {myown}, month = {03}, number = 479, title = {Performance Comparison of Common Server Hardware Virtualization Solutions Regarding the Network Throughput of Virtualized Systems}, type = {Technical Report}, year = 2011 }
• 
  Hirth, Matthias ; Hoßfeld, Tobias ; Tran-Gia, Phuoc: Human Cloud as Emerging Internet Application - Anatomy of the Microworkers Crowdsourcing Platform ( Nr. 478). Department of Computer Science, 2011
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Since Jeff Howe introduced the term "crowdsourcing" in 2006 for the first time, crowdsourcing has be come a growing market in the current Internet. Thousands of workers categorize images, write articles or perform other small tasks on platforms like Amazon Mechanical Turk (MTurk), Microworkers or ShortTask. In this paper, we want to give an inside view of Microworkers and show that there are significant differences to the well studied MTurk. Further, we have a look at Microworkers from the perspective for a worker, an employer and the platform operator, in order to answer their most important questions: What jobs are most paid? How do I get my work done most quickly? When are the users of my platform active?

  @techreport{TR478, abstract = {Since Jeff Howe introduced the term "crowdsourcing" in 2006 for the first time, crowdsourcing has be come a growing market in the current Internet. Thousands of workers categorize images, write articles or perform other small tasks on platforms like Amazon Mechanical Turk (MTurk), Microworkers or ShortTask. In this paper, we want to give an inside view of Microworkers and show that there are significant differences to the well studied MTurk. Further, we have a look at Microworkers from the perspective for a worker, an employer and the platform operator, in order to answer their most important questions: What jobs are most paid? How do I get my work done most quickly? When are the users of my platform active?}, address = {Department of Computer Science}, author = {Hirth, Matthias and Hoßfeld, Tobias and Tran-Gia, Phuoc}, keywords = {myown}, month = {01}, number = 478, title = {Human Cloud as Emerging Internet Application - Anatomy of the Microworkers Crowdsourcing Platform}, type = {Technical Report}, year = 2011 }

• 
  Menth, Michael ; Hartmann, Matthias ; Klein, Dominik: Global Locator, Local Locator, and Identifier Split (GLI-Split) ( Nr. 470). Department of Computer Science, 2010
  • [ BibTeX ]
  @techreport{TR470, address = {Department of Computer Science}, author = {Menth, Michael and Hartmann, Matthias and Klein, Dominik}, keywords = {myown}, month = {04}, number = 470, title = {Global Locator, Local Locator, and Identifier Split (GLI-Split)}, type = {Technical Report}, year = 2010 }
• 
  Selivanov, Victor: Fine Hierarchies via Priestley Duality ( Nr. 466). Department of Computer Science, 2010
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR466, address = {Department of Computer Science}, author = {Selivanov, Victor}, keywords = {myown}, month = {02}, number = 466, title = {Fine Hierarchies via Priestley Duality}, type = {Technical Report}, year = 2010 }
• 
  Staehle, Barbara ; Hirth, Matthias ; Wamser, F. ; Pries, Rastin ; Staehle, Dirk: YoMo: A YouTube Application Comfort Monitoring Tool ( Nr. 467). Department of Computer Science, 2010
  • [ BibTeX ]
  @techreport{TR467, address = {Department of Computer Science}, author = {Staehle, Barbara and Hirth, Matthias and Wamser, F. and Pries, Rastin and Staehle, Dirk}, keywords = {myown}, month = {03}, number = 467, title = {YoMo: A YouTube Application Comfort Monitoring Tool}, type = {Technical Report}, year = 2010 }
• 
  Menth, Michael ; Lehrieder, Frank: PCN-Based Marked Flow Termination ( Nr. 469). Department of Computer Science, 2010
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Pre-congestion notification (PCN) uses packet metering and marking to notify network boundaries when the current traffic load on some links of a PCN domain exceeds their configured admissible or supportable rates. This feedback is used for PCN-based admission control and flow termination within single PCN domains (edge-to-edge PCN).While admission control is rather well understood, flow termination is a new flow control function and useful especially in case of failures or flash crowds. Originally, only measured rate termination was proposed. It operates on ingress-egress aggregates between ingress and egress nodes of a PCN domain, terminates overload traffic in one shot, and requires single-path routing. We present marked flow termination as a new paradigm. It works for both ingressegress aggregates and individual flows, terminates overload traffic gradually, and works well with multipath routing. The major contribution of this paper is the presentation of several marked flow termination methods, the study of their termination behavior, recommendations for their configuration, and the discussion of their benefits and shortcomings. A secondary contribution is the introduction of end-to-end PCN which moves the control from the boundaries of possibly several PCN domains to the end systems. Although end-to-end PCN has a trust problem in an Internet context, it might be useful for large corporate networks.

  @techreport{TR469, abstract = {Pre-congestion notification (PCN) uses packet metering and marking to notify network boundaries when the current traffic load on some links of a PCN domain exceeds their configured admissible or supportable rates. This feedback is used for PCN-based admission control and flow termination within single PCN domains (edge-to-edge PCN).While admission control is rather well understood, flow termination is a new flow control function and useful especially in case of failures or flash crowds. Originally, only measured rate termination was proposed. It operates on ingress-egress aggregates between ingress and egress nodes of a PCN domain, terminates overload traffic in one shot, and requires single-path routing. We present marked flow termination as a new paradigm. It works for both ingressegress aggregates and individual flows, terminates overload traffic gradually, and works well with multipath routing. The major contribution of this paper is the presentation of several marked flow termination methods, the study of their termination behavior, recommendations for their configuration, and the discussion of their benefits and shortcomings. A secondary contribution is the introduction of end-to-end PCN which moves the control from the boundaries of possibly several PCN domains to the end systems. Although end-to-end PCN has a trust problem in an Internet context, it might be useful for large corporate networks.}, address = {Department of Computer Science}, author = {Menth, Michael and Lehrieder, Frank}, keywords = {myown}, month = {03}, number = 469, title = {PCN-Based Marked Flow Termination}, type = {Technical Report}, year = 2010 }
• 
  Menth, Michael ; Lehrieder, Frank: Applicability of PCN-Based Admission Control ( Nr. 468). Department of Computer Science, 2010
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Pre-congestion notification (PCN) marks packets when the PCN traffic rate exceeds an admissible link rate and this marking information is used as feedback from the network to take admission decisions for new flows. This idea is currently under standardization in the IETF. Different marking algorithms are discussed and various admission control (AC) algorithms are proposed that decide based on the packet markings whether further flows should be accepted or blocked. In this paper, we investigate the applicability of PCN-based AC under challenging conditions and show the limitations of different marking and AC algorithms.

  @techreport{TR468, abstract = {Pre-congestion notification (PCN) marks packets when the PCN traffic rate exceeds an admissible link rate and this marking information is used as feedback from the network to take admission decisions for new flows. This idea is currently under standardization in the IETF. Different marking algorithms are discussed and various admission control (AC) algorithms are proposed that decide based on the packet markings whether further flows should be accepted or blocked. In this paper, we investigate the applicability of PCN-based AC under challenging conditions and show the limitations of different marking and AC algorithms.}, address = {Department of Computer Science}, author = {Menth, Michael and Lehrieder, Frank}, keywords = {myown}, month = {03}, number = 468, title = {Applicability of PCN-Based Admission Control}, type = {Technical Report}, year = 2010 }
• 
  Klein, Dominik ; Tutschku, Kurt ; Zinner, Thomas: Measurement-based Topology and Performance Investigations of D-A-CH Research Networks ( Nr. 473). Department of Computer Science, 2010
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The current Internet structure consists of several autonomous systems (ASs) which are usually administered by different authorities. ASs are connected at certain point of presences and all ASs together form the heterogeneous structure of the Internet. Due to this composition, only little knowledge is publicly available about the detailed structure within and between the ASs. The contribution of this technical report is to summarize current technologies for mapping Internet topologies as well as tools for measuring certain path metrics and to present an implementation of one approach to map the topology between about 30 universities in Germany, Austria and Switzerland.

  @techreport{TR473, abstract = {The current Internet structure consists of several autonomous systems (ASs) which are usually administered by different authorities. ASs are connected at certain point of presences and all ASs together form the heterogeneous structure of the Internet. Due to this composition, only little knowledge is publicly available about the detailed structure within and between the ASs. The contribution of this technical report is to summarize current technologies for mapping Internet topologies as well as tools for measuring certain path metrics and to present an implementation of one approach to map the topology between about 30 universities in Germany, Austria and Switzerland.}, address = {Department of Computer Science}, author = {Klein, Dominik and Tutschku, Kurt and Zinner, Thomas}, keywords = {myown}, month = {08}, number = 473, title = {Measurement-based Topology and Performance Investigations of D-A-CH Research Networks}, type = {Technical Report}, year = 2010 }
• 
  Pries, Rastin ; Staehle, Dirk ; Hock, David ; Hirth, Matthias: A Policy-Based Vertical Handover System ( Nr. 471). Department of Computer Science, 2010
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The integration of different wireless transmission technologies provides several opportunities to perform load control and to optimize the Quality of Experience (QoE) of the end user. However, several problems occur when integrating these technologies. Each technology has its strengths and weaknesses in certain areas and several different approaches have to be applied to measure the performance. The contribution of this work is a proposal of a combined WLAN-UMTS network. We introduce three different policies on which we base the vertical handover decision, the load in the cell, Quality of Service (QoS) constraints, and user mobility. Simulation results illustrate how the policies are applied.

  @techreport{TR471, abstract = {The integration of different wireless transmission technologies provides several opportunities to perform load control and to optimize the Quality of Experience (QoE) of the end user. However, several problems occur when integrating these technologies. Each technology has its strengths and weaknesses in certain areas and several different approaches have to be applied to measure the performance. The contribution of this work is a proposal of a combined WLAN-UMTS network. We introduce three different policies on which we base the vertical handover decision, the load in the cell, Quality of Service (QoS) constraints, and user mobility. Simulation results illustrate how the policies are applied.}, address = {Department of Computer Science}, author = {Pries, Rastin and Staehle, Dirk and Hock, David and Hirth, Matthias}, keywords = {myown}, month = {05}, number = 471, title = {A Policy-Based Vertical Handover System}, type = {Technical Report}, year = 2010 }
• 
  Menth, Michael ; Hartmann, Matthias ; Höfling, M.: Mapping Systems for Loc/ID Split Internet Routing ( Nr. 472). Department of Computer Science, 2010
  • [ BibTeX ]
  @techreport{TR472, address = {Department of Computer Science}, author = {Menth, Michael and Hartmann, Matthias and Höfling, M.}, keywords = {myown}, month = {05}, number = 472, title = {Mapping Systems for Loc/ID Split Internet Routing}, type = {Technical Report}, year = 2010 }
• 
  Mühlberger, Clemens: Integrating Time-Stamped Synchronization into a Periodical MAC Protocol - Problems and Experiences ( Nr. 477). Department of Computer Science, 2010
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  One main characteristic of a Wireless Sensor Network (WSN) is the wireless communication of the participating sensor nodes. Especially for complex and multi-hop topologies, a MAC protocol is essential to provide a (more or less) collision-free access to the shared communication medium. We prefer a periodical and self-organized MAC protocol because of its robustness, adaptivity and scalability. Another important service for various WSN applications is time synchronization. For this reason, several synchronization protocols and techniques have been investigated already. In this paper we present our real-world experiences when integrating a simple time-stamped synchronization protocol into a self-organized and periodical MAC protocol. This integrative approach requires just marginal additional data, but achieves quite accurate synchronization results. The problems and experiences during our real-world implementation are discussed in detail within this paper.

  @techreport{TR477, abstract = {One main characteristic of a Wireless Sensor Network (WSN) is the wireless communication of the participating sensor nodes. Especially for complex and multi-hop topologies, a MAC protocol is essential to provide a (more or less) collision-free access to the shared communication medium. We prefer a periodical and self-organized MAC protocol because of its robustness, adaptivity and scalability. Another important service for various WSN applications is time synchronization. For this reason, several synchronization protocols and techniques have been investigated already. In this paper we present our real-world experiences when integrating a simple time-stamped synchronization protocol into a self-organized and periodical MAC protocol. This integrative approach requires just marginal additional data, but achieves quite accurate synchronization results. The problems and experiences during our real-world implementation are discussed in detail within this paper.}, address = {Department of Computer Science}, author = {Mühlberger, Clemens}, keywords = {myown}, month = 12, number = 477, title = {Integrating Time-Stamped Synchronization into a Periodical MAC Protocol - Problems and Experiences}, type = {Technical Report}, year = 2010 }
• 
  Hirth, Matthias ; Hoßfeld, Tobias ; Tran-Gia, Phuoc: Cheat-Detection Mechanisms for Crowdsourcing ( Nr. 474). Department of Computer Science, 2010
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Crowdsourcing is becoming more and more important for commercial purposes. With the growth of crowdsourcing platforms like MTurk, Microworkers or Innocentive, a huge work force and a large knowledge base can be easily accessed and utilized. But due to the anonymity of the workers, they are encouraged to cheat the employers in order to maximize their income. Thus, this paper presents two crowd-based approaches to detect cheating workers. Both approaches are evaluated with regard to their detection quality, their costs and their applicability to different types of typical crowdsourcing tasks.

  @techreport{TR474, abstract = {Crowdsourcing is becoming more and more important for commercial purposes. With the growth of crowdsourcing platforms like MTurk, Microworkers or Innocentive, a huge work force and a large knowledge base can be easily accessed and utilized. But due to the anonymity of the workers, they are encouraged to cheat the employers in order to maximize their income. Thus, this paper presents two crowd-based approaches to detect cheating workers. Both approaches are evaluated with regard to their detection quality, their costs and their applicability to different types of typical crowdsourcing tasks.}, address = {Department of Computer Science}, author = {Hirth, Matthias and Hoßfeld, Tobias and Tran-Gia, Phuoc}, keywords = {myown}, month = {08}, number = 474, title = {Cheat-Detection Mechanisms for Crowdsourcing}, type = {Technical Report}, year = 2010 }
• 
  Nalepa, G. ; Baumeister, Joachim: KESE: tth Workshop on Knowledge Engineering and Software Engineering ( Nr. 475). Department of Computer Science, 2010
  • [ BibTeX ]
  @techreport{TR475, address = {Department of Computer Science}, author = {Nalepa, G. and Baumeister, Joachim}, keywords = {myown}, month = {09}, number = 475, title = {KESE: tth Workshop on Knowledge Engineering and Software Engineering}, type = {Technical Report}, year = 2010 }
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  Nehmeier, Marco ; von Gudenberg, Jürgen Wolff: Interval Comparisons and Lattice Operations based on the Interval Overlapping Relation ( Nr. 476). Department of Computer Science, 2010
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we start with the definition of the interval overlapping relation showing the 13 different cases that may occur when to compare two non-empty intervals. This paper serves 2 purposes: 1. to define a solid foundation for interval comparisons and lattice operations 2. to provide an advanced interface for language embedding and application programs.

  @techreport{TR476, abstract = {In this paper we start with the definition of the interval overlapping relation showing the 13 different cases that may occur when to compare two non-empty intervals. This paper serves 2 purposes: 1. to define a solid foundation for interval comparisons and lattice operations 2. to provide an advanced interface for language embedding and application programs.}, address = {Department of Computer Science}, author = {Nehmeier, Marco and von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = {09}, number = 476, title = {Interval Comparisons and Lattice Operations based on the Interval Overlapping Relation}, type = {Technical Report}, year = 2010 }

• 
  Klein, Alexander: Statistic-Based Routing (SBR) ( Nr. 453). Department of Computer Science, 2009
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The Statistic-Based Routing (SBR) protocol has been originally designed to meet the requirements of sensor networks. During the simulation and experimental phase it soon turned out that the protocol represents a good choice for mobile wireless mesh and ad hoc networks as well. The key characteristics of the protocol are high end-to-end reliability (in fix and mobile networks), load balancing capabilities, smooth continuous routing metrics, quick adaptation to changing network conditions, low processing and memory overhead, support of unidirectional links, and simplicity.

  @techreport{TR453, abstract = {The Statistic-Based Routing (SBR) protocol has been originally designed to meet the requirements of sensor networks. During the simulation and experimental phase it soon turned out that the protocol represents a good choice for mobile wireless mesh and ad hoc networks as well. The key characteristics of the protocol are high end-to-end reliability (in fix and mobile networks), load balancing capabilities, smooth continuous routing metrics, quick adaptation to changing network conditions, low processing and memory overhead, support of unidirectional links, and simplicity.}, address = {Department of Computer Science}, author = {Klein, Alexander}, keywords = {myown}, month = {01}, number = 453, title = {Statistic-Based Routing (SBR)}, type = {Technical Report}, year = 2009 }
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  Zinner, Thomas ; Tutschku, Kurt ; Nakao, Akihiro ; Tran-Gia, Phuoc: Influence of Packet Re-ordering on Concurrent Multipath Transmissions for Transport Virtualization ( Nr. 452). Department of Computer Science, 2009
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  From the viewpoint of communication networks Network Virtualization (NV) extends beyond pure operational issues and addresses many of the impasses of the current Internet. The idea of Transport Virtualization (TV) progresses the capabilities of NV and enables the independence from a specific network transport resource. The independence is achieved by pooling multiple transport resources and selecting the best resources for exclusive or concurrent use. However, the application and selection of concurrent paths is rather complex and introduces inevitable packet re-ordering due to different stochastic delay characteristics on the used paths. Packets arriving at the destination out-of-order have to be stored in a resequencing buffer before reassembled packets are forwarded to the application. Therefore we perform an analysis of the fundamental behaviors and factors for packet re-ordering in concurrent multipath transmissions. This analysis applies analytical and simulative techniques which are used to compute the buffer occupancy probability distribution.

  @techreport{TR452, abstract = {From the viewpoint of communication networks Network Virtualization (NV) extends beyond pure operational issues and addresses many of the impasses of the current Internet. The idea of Transport Virtualization (TV) progresses the capabilities of NV and enables the independence from a specific network transport resource. The independence is achieved by pooling multiple transport resources and selecting the best resources for exclusive or concurrent use. However, the application and selection of concurrent paths is rather complex and introduces inevitable packet re-ordering due to different stochastic delay characteristics on the used paths. Packets arriving at the destination out-of-order have to be stored in a resequencing buffer before reassembled packets are forwarded to the application. Therefore we perform an analysis of the fundamental behaviors and factors for packet re-ordering in concurrent multipath transmissions. This analysis applies analytical and simulative techniques which are used to compute the buffer occupancy probability distribution.}, address = {Department of Computer Science}, author = {Zinner, Thomas and Tutschku, Kurt and Nakao, Akihiro and Tran-Gia, Phuoc}, keywords = {myown}, month = {01}, number = 452, title = {Influence of Packet Re-ordering on Concurrent Multipath Transmissions for Transport Virtualization}, type = {Technical Report}, year = 2009 }
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  Staehle, Dirk ; Staehle, Barbara ; Pries, Rastin: Max-Min Fair Throughput in Multi-Gateway Multi-Rate Mesh Networks ( Nr. 454). Department of Computer Science, 2009
  • [ BibTeX ]
  @techreport{TR454, address = {Department of Computer Science}, author = {Staehle, Dirk and Staehle, Barbara and Pries, Rastin}, keywords = {myown}, month = {02}, number = 454, title = {Max-Min Fair Throughput in Multi-Gateway Multi-Rate Mesh Networks}, type = {Technical Report}, year = 2009 }
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  Baunach, Marcel ; Mühlberger, Clemens ; Appold, Christian ; Schröder, Martin ; Füller, Florian: Analysis of Radio Signal Parameters for Calibrating RSSI Localization Systems ( Nr. 455). Department of Computer Science, 2009
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  One important application field for wireless sensor networks (WSN) is object localization, thus various realizations yet exist. Here we are just interested in RSSI based localization systems. In particular, we focus on analyzing diverse system parameters, like radio base frequency, transmitting power, or modulation format, to improve the expressiveness of RSSI values. Hence, we built a real-world testbed based on sensor nodes equipped with CC1100 radio for investigating several radio configurations. Our results show that outdoor localization complies with wave propagation theory, but calibration of the radio hardware is mandatory. However, for indoor usage more knowledge about environmental effects has to be regarded to get more robust and persistent distance measurements the basis for localization. An outlook on our further research closes this paper.

  @techreport{TR455, abstract = {One important application field for wireless sensor networks (WSN) is object localization, thus various realizations yet exist. Here we are just interested in RSSI based localization systems. In particular, we focus on analyzing diverse system parameters, like radio base frequency, transmitting power, or modulation format, to improve the expressiveness of RSSI values. Hence, we built a real-world testbed based on sensor nodes equipped with CC1100 radio for investigating several radio configurations. Our results show that outdoor localization complies with wave propagation theory, but calibration of the radio hardware is mandatory. However, for indoor usage more knowledge about environmental effects has to be regarded to get more robust and persistent distance measurements the basis for localization. An outlook on our further research closes this paper.}, address = {Department of Computer Science}, author = {Baunach, Marcel and Mühlberger, Clemens and Appold, Christian and Schröder, Martin and Füller, Florian}, keywords = {myown}, month = {03}, number = 455, title = {Analysis of Radio Signal Parameters for Calibrating RSSI Localization Systems}, type = {Technical Report}, year = 2009 }
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  Zinner, Thomas ; Staehle, Dirk ; Oechsner, Simon ; Tran-Gia, Phuoc ; Tutschku, Kurt: An Analytical Model for the Evaluation of the Information Processing in Multi-Probe Networks ( Nr. 456). Department of Computer Science, 2009
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  For the Future Internet and the Internet of Things, access and transport networks with much higher capacity than today are expected. As a result the bottleneck in large scale multi-probe networks will move from the network to the processing units, denoted as information sinks. Our contribution is a generic analytical performance model which enables an analysis of the resource requirements and handling at these information sinks. We will consider the required amount of buffer space at the information sink for a certain target duration until all requests are processed within an interval. This duration is denoted as reaction time. The presented model and the performed investigations can support application designers to choose the right mechanisms required for their scenario.

  @techreport{TR456, abstract = {For the Future Internet and the Internet of Things, access and transport networks with much higher capacity than today are expected. As a result the bottleneck in large scale multi-probe networks will move from the network to the processing units, denoted as information sinks. Our contribution is a generic analytical performance model which enables an analysis of the resource requirements and handling at these information sinks. We will consider the required amount of buffer space at the information sink for a certain target duration until all requests are processed within an interval. This duration is denoted as reaction time. The presented model and the performed investigations can support application designers to choose the right mechanisms required for their scenario.}, address = {Department of Computer Science}, author = {Zinner, Thomas and Staehle, Dirk and Oechsner, Simon and Tran-Gia, Phuoc and Tutschku, Kurt}, keywords = {myown}, month = {03}, number = 456, title = {An Analytical Model for the Evaluation of the Information Processing in Multi-Probe Networks}, type = {Technical Report}, year = 2009 }
• 
  Freiberg, Martina: Usability Assessment of Knowledge-Based Consultation Systems ( Nr. 457). Department of Computer Science, 2009
  • [ BibTeX ]
  @techreport{TR457, address = {Department of Computer Science}, author = {Freiberg, Martina}, keywords = {myown}, month = {03}, number = 457, title = {Usability Assessment of Knowledge-Based Consultation Systems}, type = {Technical Report}, year = 2009 }
• 
  Mühlberger, Clemens ; Kolla, Reiner: Extended Desynchronization for Multi-Hop Topologies ( Nr. 460). Department of Computer Science, 2009
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Desynchronization is a biologically inspired primitive [8] for periodic but temporary exclusive access to a shared resource, like the transmission medium. In this paper, we recapitulate the single-hop desynchronization algorithm DESYNC [5, 2, 6] forWireless Sensor Networks (WSNs) and identify its lack of handling hidden nodes in multi-hop environments. We explain in detail our decentralized and selforganizing multi-hop extension EXTENDED-DESYNC, solving the hidden node problem although it uses just locally available information. We further inspect several scenarios and topologies to prove convergence of our algorithm and to demonstrate its robustness and flexibility against dynamic changes within multi-hop Wireless Sensor Networks, like adding or removing nodes. We thus show that EXTENDED-DESYNC desynchronizes well in spite of hidden nodes. We finally outline a few useful add-ons for our algorithm and its possible fields of application.

  @techreport{TR460, abstract = {Desynchronization is a biologically inspired primitive [8] for periodic but temporary exclusive access to a shared resource, like the transmission medium. In this paper, we recapitulate the single-hop desynchronization algorithm DESYNC [5, 2, 6] forWireless Sensor Networks (WSNs) and identify its lack of handling hidden nodes in multi-hop environments. We explain in detail our decentralized and selforganizing multi-hop extension EXTENDED-DESYNC, solving the hidden node problem although it uses just locally available information. We further inspect several scenarios and topologies to prove convergence of our algorithm and to demonstrate its robustness and flexibility against dynamic changes within multi-hop Wireless Sensor Networks, like adding or removing nodes. We thus show that EXTENDED-DESYNC desynchronizes well in spite of hidden nodes. We finally outline a few useful add-ons for our algorithm and its possible fields of application.}, address = {Department of Computer Science}, author = {Mühlberger, Clemens and Kolla, Reiner}, keywords = {myown}, month = {07}, number = 460, title = {Extended Desynchronization for Multi-Hop Topologies}, type = {Technical Report}, year = 2009 }
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  Atzmüller, Martin ; Nalepa, G.: Towards Rapid Knowledge Capture using Textual Subgroup Mining for Rule Prototyping ( Nr. 458). Department of Computer Science, 2009
  • [ BibTeX ]
  @techreport{TR458, address = {Department of Computer Science}, author = {Atzmüller, Martin and Nalepa, G.}, keywords = {myown}, month = {04}, number = 458, title = {Towards Rapid Knowledge Capture using Textual Subgroup Mining for Rule Prototyping}, type = {Technical Report}, year = 2009 }
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  Oechsner, Simon ; Lehrieder, Frank ; Hoßfeld, Tobias ; Metzger, Florian ; Pussep, K. ; Staehle, Dirk: Pushing the Performance of Biased Neighbor Selection through Biased Unchoking ( Nr. 459). Department of Computer Science, 2009
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Locality promotion in P2P content distribution networks is currently a major research topic. One of the goals of all discussed approaches is to reduce the interdomain traffic that causes high costs for ISPs. However, the focus of the work in this field is generally on the type of locality information that is provided to the overlay and on the entities that exchange this information. An aspect that is generally neglected or only shortly addressed is how this information is used by the peers. In this paper, we consider the predominant approach of Biased Neighbor Selection and compare it with Biased Unchoking, an alternative locality aware peer selection strategy we propose in this paper. We show that both mechanisms complement each other for the BitTorrent file sharing application and achieve the best performance when combined.

  @techreport{TR459, abstract = {Locality promotion in P2P content distribution networks is currently a major research topic. One of the goals of all discussed approaches is to reduce the interdomain traffic that causes high costs for ISPs. However, the focus of the work in this field is generally on the type of locality information that is provided to the overlay and on the entities that exchange this information. An aspect that is generally neglected or only shortly addressed is how this information is used by the peers. In this paper, we consider the predominant approach of Biased Neighbor Selection and compare it with Biased Unchoking, an alternative locality aware peer selection strategy we propose in this paper. We show that both mechanisms complement each other for the BitTorrent file sharing application and achieve the best performance when combined.}, address = {Department of Computer Science}, author = {Oechsner, Simon and Lehrieder, Frank and Hoßfeld, Tobias and Metzger, Florian and Pussep, K. and Staehle, Dirk}, keywords = {myown}, month = {07}, number = 459, title = {Pushing the Performance of Biased Neighbor Selection through Biased Unchoking}, type = {Technical Report}, year = 2009 }
• 
  Baumeister, Joachim ; Nalepa, G. J.: Proceedings of the 5th workshop on Knowledge Engineering and Software Engineering (KESE 2009) ( Nr. 461). Department of Computer Science, 2009
  • [ BibTeX ]
  @techreport{TR461, address = {Department of Computer Science}, author = {Baumeister, Joachim and Nalepa, G. J.}, keywords = {myown}, month = {07}, number = 461, title = {Proceedings of the 5th workshop on Knowledge Engineering and Software Engineering (KESE 2009)}, type = {Technical Report}, year = 2009 }
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  Glaßer, Christian ; Reitwießner, Christian ; Witek, Maximilian: Improved and Derandomized Approximations for Two-Criteria Metric Traveling Salesman ( Nr. 462). Department of Computer Science, 2009
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR462, address = {Department of Computer Science}, author = {Glaßer, Christian and Reitwießner, Christian and Witek, Maximilian}, keywords = {myown}, month = {08}, number = 462, title = {Improved and Derandomized Approximations for Two-Criteria Metric Traveling Salesman}, type = {Technical Report}, year = 2009 }
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  Atzmüller, Martin ; Lemmerich, F. ; Reutelshoefer, Jochen ; Puppe, Frank: An Extensible Architecture for Wiki-Enabled Semantic Data Mining ( Nr. 463). Department of Computer Science, 2009
  • [ BibTeX ]
  @techreport{TR463, address = {Department of Computer Science}, author = {Atzmüller, Martin and Lemmerich, F. and Reutelshoefer, Jochen and Puppe, Frank}, keywords = {myown}, month = 11, number = 463, title = {An Extensible Architecture for Wiki-Enabled Semantic Data Mining}, type = {Technical Report}, year = 2009 }
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  Hoßfeld, Tobias ; Hock, David ; Oechsner, Simon ; Lehrieder, Frank ; Despotovic, Z. ; Kellerer, W. ; Michel, M.: Measurement of BitTorrent Swarms and their AS Topologies ( Nr. 464). Department of Computer Science, 2009
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR464, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Hock, David and Oechsner, Simon and Lehrieder, Frank and Despotovic, Z. and Kellerer, W. and Michel, M.}, keywords = {myown}, month = 11, number = 464, title = {Measurement of BitTorrent Swarms and their AS Topologies}, type = {Technical Report}, year = 2009 }
• 
  Karl, Stefan: NP-Complete Ranges of Counting Functions of Nondeterministic Finite Automata ( Nr. 465). Department of Computer Science, 2009
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR465, address = {Department of Computer Science}, author = {Karl, Stefan}, keywords = {myown}, month = 12, number = 465, title = {NP-Complete Ranges of Counting Functions of Nondeterministic Finite Automata}, type = {Technical Report}, year = 2009 }

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  Fischer, Gregor ; Lusiardi, Joachim: JaML: XML Representation of Java source code ( Nr. 445). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this technical report, we define an XML representation of source code written in Java. Aside from giving a formal specification of the JaML format, we discuss design criteria, related work and give some insights in possible fields of application for JaML. As one import field of application JaML is used as foundation for Ehrengast, which is a frame work for handling language independent abstract syntax trees and high level language transformation.

  @techreport{TR445, abstract = {In this technical report, we define an XML representation of source code written in Java. Aside from giving a formal specification of the JaML format, we discuss design criteria, related work and give some insights in possible fields of application for JaML. As one import field of application JaML is used as foundation for Ehrengast, which is a frame work for handling language independent abstract syntax trees and high level language transformation.}, address = {Department of Computer Science}, author = {Fischer, Gregor and Lusiardi, Joachim}, keywords = {myown}, month = {05}, number = 445, title = {JaML: XML Representation of Java source code}, type = {Technical Report}, year = 2008 }
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  Spoerhase, Joachim ; Wirth, H.-C.: (r,p)-Centroid Problems on Paths and Trees. ( Nr. 441). Department of Computer Science, 2008
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR441, address = {Department of Computer Science}, author = {Spoerhase, Joachim and Wirth, H.-C.}, keywords = {myown}, month = {01}, number = 441, title = {(r,p)-Centroid Problems on Paths and Trees.}, type = {Technical Report}, year = 2008 }
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  Glaßer, Christian ; Reitwießner, Christian ; Selivanov, Victor: The Shrinking Property for NP and coNP. ( Nr. 440). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We study the shrinking and separation properties (two notions well-known in descriptive set theory) for NP and coNP and show that under reasonable complexity-theoretic assumptions, both properties do not hold for NP and the shrinking property does not hold for coNP. In particular we obtain the following results. 1. NP and coNP do not have the shrinking property, unless PH is finite. In general, Sigma_n and Pi_n do not have the shrinking property, unless PH is finite. This solves an open question from [Selivanov 94]. 2. The separation property does not hold for NP, unless UP subseteq coNP. 3. The shrinking property does not hold for NP, unless there exist NP-hard disjoint NP-pairs (existence of such pairs would contradict a conjecture by Even, Selman, and Yacobi). 4. The shrinking property does not hold for NP, unless there exist complete disjoint NP-pairs. Moreover, we prove that the assumption NP neq coNP is too weak to refute the shrinking property for NP in a relativizable way. For this we construct an oracle relative to which P = NP cap coNP, NP neq coNP, and NP has the shrinking property. This solves an open question by Blass and Gurevich who explicitly ask for such an oracle.

  @techreport{TR440, abstract = {We study the shrinking and separation properties (two notions well-known in descriptive set theory) for NP and coNP and show that under reasonable complexity-theoretic assumptions, both properties do not hold for NP and the shrinking property does not hold for coNP. In particular we obtain the following results. 1. NP and coNP do not have the shrinking property, unless PH is finite. In general, Sigma_n and Pi_n do not have the shrinking property, unless PH is finite. This solves an open question from [Selivanov 94]. 2. The separation property does not hold for NP, unless UP \subseteq coNP. 3. The shrinking property does not hold for NP, unless there exist NP-hard disjoint NP-pairs (existence of such pairs would contradict a conjecture by Even, Selman, and Yacobi). 4. The shrinking property does not hold for NP, unless there exist complete disjoint NP-pairs. Moreover, we prove that the assumption NP \neq coNP is too weak to refute the shrinking property for NP in a relativizable way. For this we construct an oracle relative to which P = NP \cap coNP, NP \neq coNP, and NP has the shrinking property. This solves an open question by Blass and Gurevich who explicitly ask for such an oracle.}, address = {Department of Computer Science}, author = {Glaßer, Christian and Reitwießner, Christian and Selivanov, Victor}, keywords = {myown}, month = {01}, number = 440, title = {The Shrinking Property for NP and coNP.}, type = {Technical Report}, year = 2008 }
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  Hoßfeld, Tobias ; Hock, David ; Tran-Gia, Phuoc ; Tutschku, Kurt ; Fiedler, Markus: Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711 ( Nr. 442). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Given the growing importance of quantitative relationships between user-perceived Quality of Experience (QoE) and network Quality of Service (QoS), this paper investigates the IQX hypothesis for two voice codecs, iLBC and G.711. This hypothesis expresses QoE as an exponential function of QoS degradation. The experiments are carried out in a controlled environment using the softphone SJPhone, the network emulator NIST Net, and a tool calculating the PESQ (Perceptual Evaluation of Speech Quality) from sent and received audio files. The IQX hypothesis is confirmed exactly for disturbances perceived on applications level, packet loss and packet reordering, which clearly correlate to the main sensitivities of the used softphone to packet-level disturbances such as loss, jitter and reordering. So, besides of providing a unified relationship between QoE and QoS, the IQX also proved to be capable of identifying the QoS parameters of relevance for QoE degradations. The study also points out interesting tracks for future work in terms of QoS degradations and related QoE evaluations.

  @techreport{TR442, abstract = {Given the growing importance of quantitative relationships between user-perceived Quality of Experience (QoE) and network Quality of Service (QoS), this paper investigates the IQX hypothesis for two voice codecs, iLBC and G.711. This hypothesis expresses QoE as an exponential function of QoS degradation. The experiments are carried out in a controlled environment using the softphone SJPhone, the network emulator NIST Net, and a tool calculating the PESQ (Perceptual Evaluation of Speech Quality) from sent and received audio files. The IQX hypothesis is confirmed exactly for disturbances perceived on applications level, packet loss and packet reordering, which clearly correlate to the main sensitivities of the used softphone to packet-level disturbances such as loss, jitter and reordering. So, besides of providing a unified relationship between QoE and QoS, the IQX also proved to be capable of identifying the QoS parameters of relevance for QoE degradations. The study also points out interesting tracks for future work in terms of QoS degradations and related QoE evaluations.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Hock, David and Tran-Gia, Phuoc and Tutschku, Kurt and Fiedler, Markus}, keywords = {myown}, month = {03}, number = 442, title = {Testing the IQX Hypothesis for Exponential Interdependency between QoS and QoE of Voice Codecs iLBC and G.711}, type = {Technical Report}, year = 2008 }
• 
  Fischer, Gregor ; Lusiardi, Joachim ; von Gudenberg, Jürgen Wolff: Source Code Model Hierarchies ( Nr. 444). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we consider various approaches to build up abstraction hierarchies for programming source code. We carefully distinguish between the concept (artifact) and its representation (notation). With the help of these models we can transform high-level languages to such an extent that analysis and model driven tools can be applied. The paper thus contributes to the Architecture Driven Modernization framework of the OMG.

  @techreport{TR444, abstract = {In this paper we consider various approaches to build up abstraction hierarchies for programming source code. We carefully distinguish between the concept (artifact) and its representation (notation). With the help of these models we can transform high-level languages to such an extent that analysis and model driven tools can be applied. The paper thus contributes to the Architecture Driven Modernization framework of the OMG.}, address = {Department of Computer Science}, author = {Fischer, Gregor and Lusiardi, Joachim and von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = {05}, number = 444, title = {Source Code Model Hierarchies}, type = {Technical Report}, year = 2008 }
• 
  Glaßer, Christian ; Reitwießner, Christian ; Schmitz, Heinz: Multiobjective Disk Cover Admits a PTAS ( Nr. 443). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We introduce multiobjective disk cover problems and study their approximability. We con- struct a polynomial-time approximation scheme (PTAS) for the multiobjective problem where k types of points (customers) in the plane have to be covered by disks (base stations) such that the number of disks is minimized and for each type of points, the number of covered points is maximized. Our approximation scheme can be extended so that it works with the following additional features: interferences, different services for different types of customers, different shapes of supply areas, weighted customers, individual costs for base stations, and payoff for the quality of the obtained service. In contrast to the good approximation properties of the multiobjective disk cover problems, we can show non-approximability results for several single-objective restrictions of these prob- lems. For example, if there are 2 types of customers, then maximizing the supplied customers of one type is not approximable within a constant factor, unless P = NP.

  @techreport{TR443, abstract = {We introduce multiobjective disk cover problems and study their approximability. We con- struct a polynomial-time approximation scheme (PTAS) for the multiobjective problem where k types of points (customers) in the plane have to be covered by disks (base stations) such that the number of disks is minimized and for each type of points, the number of covered points is maximized. Our approximation scheme can be extended so that it works with the following additional features: interferences, different services for different types of customers, different shapes of supply areas, weighted customers, individual costs for base stations, and payoff for the quality of the obtained service. In contrast to the good approximation properties of the multiobjective disk cover problems, we can show non-approximability results for several single-objective restrictions of these prob- lems. For example, if there are 2 types of customers, then maximizing the supplied customers of one type is not approximable within a constant factor, unless P = NP.}, address = {Department of Computer Science}, author = {Glaßer, Christian and Reitwießner, Christian and Schmitz, Heinz}, keywords = {myown}, month = {05}, number = 443, title = {Multiobjective Disk Cover Admits a PTAS}, type = {Technical Report}, year = 2008 }
• 
  Hoßfeld, Tobias ; Oechsner, Simon ; Lehrieder, Frank ; Bergner, Christian ; Tran-Gia, Phuoc: Investigation of chunk selection strategies in peer-assisted video-on-demand systems ( Nr. 446). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The applications for peer-to-peer (P2P) architectures recently have evolved from straightforward file download to more demanding services like Video-on-Demand (VoD). Here, not only the known advantages of P2P overlays are essential, but also a timely delivery of video frames for their play back. Since the video is watched during the download process, this poses a major challenge, which has to be mastered to guarantee a high service quality to the end user. One mechanism influencing the performance of a P2P content distribution network is the chunk selection strategy in systems using multi-source download. This paper aims at systematically investigating the impact of the chunk selection strategies on the system behavior and its self-organization capabilities, as well as the user perceived quality. In particular, we answer if just an adaptation of this strategy suffices to make such systems viable for VoD services.

  @techreport{TR446, abstract = {The applications for peer-to-peer (P2P) architectures recently have evolved from straightforward file download to more demanding services like Video-on-Demand (VoD). Here, not only the known advantages of P2P overlays are essential, but also a timely delivery of video frames for their play back. Since the video is watched during the download process, this poses a major challenge, which has to be mastered to guarantee a high service quality to the end user. One mechanism influencing the performance of a P2P content distribution network is the chunk selection strategy in systems using multi-source download. This paper aims at systematically investigating the impact of the chunk selection strategies on the system behavior and its self-organization capabilities, as well as the user perceived quality. In particular, we answer if just an adaptation of this strategy suffices to make such systems viable for VoD services.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Oechsner, Simon and Lehrieder, Frank and Bergner, Christian and Tran-Gia, Phuoc}, keywords = {myown}, month = {07}, number = 446, title = {Investigation of chunk selection strategies in peer-assisted video-on-demand systems}, type = {Technical Report}, year = 2008 }
• 
  Okhotin, Alexander ; Reitwießner, Christian: Conjunctive grammars with restricted disjuction ( Nr. 447). Department of Computer Science, 2008
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR447, address = {Department of Computer Science}, author = {Okhotin, Alexander and Reitwießner, Christian}, keywords = {myown}, month = {08}, number = 447, title = {Conjunctive grammars with restricted disjuction}, type = {Technical Report}, year = 2008 }
• 
  Baumeister, Joachim ; Atzmüller, Martin: Proceedings of LWA 2008 (Lernen, Wissen, Adaptivität) ( Nr. 448). Department of Computer Science, 2008
  • [ BibTeX ]
  @techreport{TR448, address = {Department of Computer Science}, author = {Baumeister, Joachim and Atzmüller, Martin}, keywords = {myown}, month = {09}, number = 448, title = {Proceedings of LWA 2008 (Lernen, Wissen, Adaptivität)}, type = {Technical Report}, year = 2008 }
• 
  Tutschku, Kurt ; Zinner, Thomas ; Nakao, Akihiro ; Tran-Gia, Phuoc: The Case of Network Virtualization: Concurrent Multipath Transmissions within Routing Overlays ( Nr. 449). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this report we will investigate the deficiencies and the achievements of today's Internet. We outline why and how Network Virtualization (NV) can overcome the shortfalls of the current system and how it paves the way for the future Internet. Furthermore, we investigate the performance of a concurrent multipath transmission mechanisms which is implemented using routing overlays and which is facilitated by Network Virtualization. The major building blocks of NV are the a) use of application-specific routing overlays, b) the safe consolidation of resources by OS virtualization on a generic infrastructure, and c) the exploitation of the network diversity for performance enhancements and for new business models, such as the provisioning of intermediates nodes or path oracles. The performance investigation the concurrent multipath transmission reveals that an appropriate engineering of the high capacity pipe is required. This means that the path selection and the dimensioning of its mechanisms has to be done carefully.

  @techreport{TR449, abstract = {In this report we will investigate the deficiencies and the achievements of today's Internet. We outline why and how Network Virtualization (NV) can overcome the shortfalls of the current system and how it paves the way for the future Internet. Furthermore, we investigate the performance of a concurrent multipath transmission mechanisms which is implemented using routing overlays and which is facilitated by Network Virtualization. The major building blocks of NV are the a) use of application-specific routing overlays, b) the safe consolidation of resources by OS virtualization on a generic infrastructure, and c) the exploitation of the network diversity for performance enhancements and for new business models, such as the provisioning of intermediates nodes or path oracles. The performance investigation the concurrent multipath transmission reveals that an appropriate engineering of the high capacity pipe is required. This means that the path selection and the dimensioning of its mechanisms has to be done carefully.}, address = {Department of Computer Science}, author = {Tutschku, Kurt and Zinner, Thomas and Nakao, Akihiro and Tran-Gia, Phuoc}, keywords = {myown}, month = 10, number = 449, title = {The Case of Network Virtualization: Concurrent Multipath Transmissions within Routing Overlays}, type = {Technical Report}, year = 2008 }
• 
  Freiberg, Martina ; Baumeister, Joachim: A Survey on Usability Evaluation Techniques and an Analysis of their actual Application ( Nr. 450). Department of Computer Science, 2008
  • [ BibTeX ]
  @techreport{TR450, address = {Department of Computer Science}, author = {Freiberg, Martina and Baumeister, Joachim}, keywords = {myown}, month = 10, number = 450, title = {A Survey on Usability Evaluation Techniques and an Analysis of their actual Application}, type = {Technical Report}, year = 2008 }
• 
  Pries, Rastin ; Staehle, Dirk ; Stoykova, Marieta: On the Usability of Genetic Algorithms for Wireless Mesh Network Planning and Optimization ( Nr. 451). Department of Computer Science, 2008
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Wireless Mesh Networks (WMNs) are a promising technology to provide broadband wireless connectivity for the end user. They offer more flexibility compared to traditional networks but on the expense of a complex structure. Thus, planning and optimization of WMNs is a challenge. In this paper we focus on routing and channel assignment in WMNs for throughput maximization using genetic algorithms. Genetic algorithms provide a good solution of large-scale WMNs in relatively small computation time. We propose different genetic operators which are adapted for the planning and optimization of WMNs. The results prove the effectiveness of the genetic operators and show the advantages of a genetic optimization.

  @techreport{TR451, abstract = {Wireless Mesh Networks (WMNs) are a promising technology to provide broadband wireless connectivity for the end user. They offer more flexibility compared to traditional networks but on the expense of a complex structure. Thus, planning and optimization of WMNs is a challenge. In this paper we focus on routing and channel assignment in WMNs for throughput maximization using genetic algorithms. Genetic algorithms provide a good solution of large-scale WMNs in relatively small computation time. We propose different genetic operators which are adapted for the planning and optimization of WMNs. The results prove the effectiveness of the genetic operators and show the advantages of a genetic optimization.}, address = {Department of Computer Science}, author = {Pries, Rastin and Staehle, Dirk and Stoykova, Marieta}, keywords = {myown}, month = 11, number = 451, title = {On the Usability of Genetic Algorithms for Wireless Mesh Network Planning and Optimization}, type = {Technical Report}, year = 2008 }

• 
  Mäder, Andreas ; Staehle, Dirk ; Spahn, Markus: Performance Comparison of HSDPA Transmit Power Allocation Schemes in UMTS Networks. ( Nr. 411). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In UMTS networks the transmit power for the HSDPA can be a large fraction of the total transmit power of a NodeB. We investigate the impact of three HSDPA transmit power allocation schemes on the performance of a UMTS system with dedicated channel users and HSDPA users. The continuous HSDPA power allocation scheme avoids large steps in power to prevent irregularities in the downlink power control of dedicated channels. In contrast, the traffic-aware scheme switches the HSDPA power on only if data has to be transmitted. The power-ramping scheme combines the continuous and the traffic-aware scheme. The simulation model considers the complete interference situation in the network and uses a novel model to calculate HSDPA bandwidths. The results suggest that the additional interference caused by the continuous scheme leads to performance losses, while the power-ramping scheme shows results close to the traffic-aware scheme.

  @techreport{TR411, abstract = {In UMTS networks the transmit power for the HSDPA can be a large fraction of the total transmit power of a NodeB. We investigate the impact of three HSDPA transmit power allocation schemes on the performance of a UMTS system with dedicated channel users and HSDPA users. The continuous HSDPA power allocation scheme avoids large steps in power to prevent irregularities in the downlink power control of dedicated channels. In contrast, the traffic-aware scheme switches the HSDPA power on only if data has to be transmitted. The power-ramping scheme combines the continuous and the traffic-aware scheme. The simulation model considers the complete interference situation in the network and uses a novel model to calculate HSDPA bandwidths. The results suggest that the additional interference caused by the continuous scheme leads to performance losses, while the power-ramping scheme shows results close to the traffic-aware scheme.}, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk and Spahn, Markus}, keywords = {myown}, month = {04}, number = 411, title = {Performance Comparison of HSDPA Transmit Power Allocation Schemes in UMTS Networks.}, type = {Technical Report}, year = 2007 }
• 
  Norros, Ilkka ; Pehkonen, Vesa ; Reittu, Hannu ; Binzenhöfer, Andreas ; Tutschku, Kurt: Relying on Randomness - PlanetLab Experiments with Distributed File-sharing Protocols. ( Nr. 407). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we present and evaluate a fully distributed file-sharing system architecture. Initially, a seeder node splits a large file into moderate-sized chunks and offers it for download. The seeder and all peers interested in downloading the file join a Chord-based overlay and contact each other randomly for chunk transfers. We report and discuss PlanetLab test on this system as well as on our modified Chord implementation which it is based on. We also describe algorithms for finding uniformly random peers in the overlay and for estimating the distribution of chunk copies and show that both have a significant effect on the performance.

  @techreport{TR407, abstract = {In this paper we present and evaluate a fully distributed file-sharing system architecture. Initially, a seeder node splits a large file into moderate-sized chunks and offers it for download. The seeder and all peers interested in downloading the file join a Chord-based overlay and contact each other randomly for chunk transfers. We report and discuss PlanetLab test on this system as well as on our modified Chord implementation which it is based on. We also describe algorithms for finding uniformly random peers in the overlay and for estimating the distribution of chunk copies and show that both have a significant effect on the performance.}, address = {Department of Computer Science}, author = {Norros, Ilkka and Pehkonen, Vesa and Reittu, Hannu and Binzenhöfer, Andreas and Tutschku, Kurt}, keywords = {myown}, month = {04}, number = 407, title = {Relying on Randomness - PlanetLab Experiments with Distributed File-sharing Protocols.}, type = {Technical Report}, year = 2007 }
• 
  Oechsner, Simon ; Tran-Gia, Phuoc: Performance Evaluation of a Reliable Content Mediation Platform in the Emerging Future Internet. ( Nr. 408). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In todays Internet, a trend towards distributed content delivery systems can be observed. These systems still have to offer the same functionality as centralized architectures, e.g. content localization. While several advantages like load distribution and cost reduction could be gained by using a decentralized distribution platform, they come with a tradeoff in resource consumption. In this paper, we analyze and evaluate a decentralized Content Distribution Application (CDA) with respect to the time needed to locate specific content. We introduce a node model based on queueing theory and provide methods to compute important characteristics like the mean search time. In this model, we do not only consider the external offered load, but also the internal traffic created as a consequence of decentralization.

  @techreport{TR408, abstract = {In todays Internet, a trend towards distributed content delivery systems can be observed. These systems still have to offer the same functionality as centralized architectures, e.g. content localization. While several advantages like load distribution and cost reduction could be gained by using a decentralized distribution platform, they come with a tradeoff in resource consumption. In this paper, we analyze and evaluate a decentralized Content Distribution Application (CDA) with respect to the time needed to locate specific content. We introduce a node model based on queueing theory and provide methods to compute important characteristics like the mean search time. In this model, we do not only consider the external offered load, but also the internal traffic created as a consequence of decentralization.}, address = {Department of Computer Science}, author = {Oechsner, Simon and Tran-Gia, Phuoc}, keywords = {myown}, month = {04}, number = 408, title = {Performance Evaluation of a Reliable Content Mediation Platform in the Emerging Future Internet.}, type = {Technical Report}, year = 2007 }
• 
  Emmert, Barbara ; Binzenhöfer, Andreas ; Schlosser, Daniel ; Weiss, Markus: Source Traffic Characterization for Thin Client Based Office Applications. ( Nr. 406). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  A thin client is a small network computer which is used as a remote screen visualizing the output of software applications running on a central server. To provide a seamless service to thin client users the network connection between the client and the server must be dimensioned properly. In this paper we therefore characterize the traffic generated by different types of thin client users when working with popular office applications like Microsoft Word, Excel, or PowerPoint. We analyze the traffic patterns measured in our testbed environment and thus provide a basis for subsequent research studies as well as for administrators to estimate the amount and the characteristics of user generated traffic.

  @techreport{TR406, abstract = {A thin client is a small network computer which is used as a remote screen visualizing the output of software applications running on a central server. To provide a seamless service to thin client users the network connection between the client and the server must be dimensioned properly. In this paper we therefore characterize the traffic generated by different types of thin client users when working with popular office applications like Microsoft Word, Excel, or PowerPoint. We analyze the traffic patterns measured in our testbed environment and thus provide a basis for subsequent research studies as well as for administrators to estimate the amount and the characteristics of user generated traffic.}, address = {Department of Computer Science}, author = {Emmert, Barbara and Binzenhöfer, Andreas and Schlosser, Daniel and Weiss, Markus}, keywords = {myown}, month = {04}, number = 406, title = {Source Traffic Characterization for Thin Client Based Office Applications.}, type = {Technical Report}, year = 2007 }
• 
  Menth, Michael ; Martin, Rüdiger ; Spörlein, Ulrich: Failure-Specific Self-Protecting Multipaths: Increased Capacity Savings or Overengineering?. ( Nr. 420). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The self-protection multipath (SPM) is a simple protection switching mechanism. It distributes the traffic over several disjoint paths from source to destination according to a traffic distribution function. When a path fails, the traffic is redistributed to the working paths according to another traffic distribution function, i.e., the traffic distribution function depends on the failed path. The contribution of this work is the introduction of a failure-specific traffic distribution function for the SPM that depends on the exact failure of the paths. We present a linear program for the global optimization of the traffic distribution function of all SPMs in all protected failure scenarios. Finally, we compare the amount of protected traffic that can be transported in the network for the conventional SPM and the new failure-specific SPM (FSPM).

  @techreport{TR420, abstract = {The self-protection multipath (SPM) is a simple protection switching mechanism. It distributes the traffic over several disjoint paths from source to destination according to a traffic distribution function. When a path fails, the traffic is redistributed to the working paths according to another traffic distribution function, i.e., the traffic distribution function depends on the failed path. The contribution of this work is the introduction of a failure-specific traffic distribution function for the SPM that depends on the exact failure of the paths. We present a linear program for the global optimization of the traffic distribution function of all SPMs in all protected failure scenarios. Finally, we compare the amount of protected traffic that can be transported in the network for the conventional SPM and the new failure-specific SPM (FSPM).}, address = {Department of Computer Science}, author = {Menth, Michael and Martin, Rüdiger and Spörlein, Ulrich}, keywords = {myown}, month = {04}, number = 420, title = {Failure-Specific Self-Protecting Multipaths: Increased Capacity Savings or Overengineering?.}, type = {Technical Report}, year = 2007 }
• 
  Menth, Michael ; Martin, Rüdiger ; Koster, Arie M.C.A. ; Orlowski, Sebastian: Overview of Resilience Mechanisms Based on Multipath Structures. ( Nr. 421). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Multipath structures are the base for many recently developed rerouting and protection switching mechanisms. All of these methods show a similar path layout, rely on traffic distribution, and promise resilience with only little backup capacity. Therefore, it is hard to recognize their commonalities and differences at first sight. This paper provides an overview of these related mechanisms and a comparative analysis regarding their applicability in optical and packet switched technologies, their path layout, their reaction time, their dynamic adaptability, and many other aspects.

  @techreport{TR421, abstract = {Multipath structures are the base for many recently developed rerouting and protection switching mechanisms. All of these methods show a similar path layout, rely on traffic distribution, and promise resilience with only little backup capacity. Therefore, it is hard to recognize their commonalities and differences at first sight. This paper provides an overview of these related mechanisms and a comparative analysis regarding their applicability in optical and packet switched technologies, their path layout, their reaction time, their dynamic adaptability, and many other aspects.}, address = {Department of Computer Science}, author = {Menth, Michael and Martin, Rüdiger and Koster, Arie M.C.A. and Orlowski, Sebastian}, keywords = {myown}, month = {04}, number = 421, title = {Overview of Resilience Mechanisms Based on Multipath Structures.}, type = {Technical Report}, year = 2007 }
• 
  Jansen, Lasse ; Gojmerac, Ivan ; Menth, Michael ; Reichl, Peter ; Tran-Gia, Phuoc: Discrete-Time Algorithms for Flow-Level Simulation of Data Networks. ( Nr. 416). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we present a comprehensive algorithmic framework for discrete-time flow-level simulation of data networks. We first provide a simple algorithm based upon iterative equations useful for the simulation of networks with static traffic demands, and we show how to determine packet loss and throughput rates using a simple example network. We then extend these basic equations to a simulation method capable of handling queue and link delays in dynamic traffic scenarios and compare results from flow-level simulation to those obtained by packet-level simulation. Finally, we illustrate the tradeoff between computational complexity and simulation accuracy which is controlled by the duration of a single iteration interval.

  @techreport{TR416, abstract = {In this paper, we present a comprehensive algorithmic framework for discrete-time flow-level simulation of data networks. We first provide a simple algorithm based upon iterative equations useful for the simulation of networks with static traffic demands, and we show how to determine packet loss and throughput rates using a simple example network. We then extend these basic equations to a simulation method capable of handling queue and link delays in dynamic traffic scenarios and compare results from flow-level simulation to those obtained by packet-level simulation. Finally, we illustrate the tradeoff between computational complexity and simulation accuracy which is controlled by the duration of a single iteration interval.}, address = {Department of Computer Science}, author = {Jansen, Lasse and Gojmerac, Ivan and Menth, Michael and Reichl, Peter and Tran-Gia, Phuoc}, keywords = {myown}, month = {04}, number = 416, title = {Discrete-Time Algorithms for Flow-Level Simulation of Data Networks.}, type = {Technical Report}, year = 2007 }
• 
  Binzenhöfer, Andreas ; Leibnitz, Kenji: Estimating Churn in Structured P2P Overlay Networks. ( Nr. 404). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Structured peer-to-peer (P2P) networks have become an important alternative to the classic client-server architecture. Participating peers can join and leave the system at arbitrary times, a process which is known as churn. Many recent studies revealed that churn is one of the main problems faced by any Distributed Hash Table (DHT). As a countermeasure most DHT protocols have to invest a significant amount of overhead to maintain both the structure of the overlay and the redundancy of the stored data. In order to automatically adapt this maintenance overhead and other parameters of the DHT to the changes in the overlay, an estimation of the current churn rate is required. In this paper we discuss different possibilities of how to estimate the current churn rate in the system. In particular, we show how to obtain a robust estimate which is independent of the implementation details of the DHT. We also investigate the trade-offs between accuracy, overhead, and responsiveness to changes.

  @techreport{TR404, abstract = {Structured peer-to-peer (P2P) networks have become an important alternative to the classic client-server architecture. Participating peers can join and leave the system at arbitrary times, a process which is known as churn. Many recent studies revealed that churn is one of the main problems faced by any Distributed Hash Table (DHT). As a countermeasure most DHT protocols have to invest a significant amount of overhead to maintain both the structure of the overlay and the redundancy of the stored data. In order to automatically adapt this maintenance overhead and other parameters of the DHT to the changes in the overlay, an estimation of the current churn rate is required. In this paper we discuss different possibilities of how to estimate the current churn rate in the system. In particular, we show how to obtain a robust estimate which is independent of the implementation details of the DHT. We also investigate the trade-offs between accuracy, overhead, and responsiveness to changes.}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Leibnitz, Kenji}, keywords = {myown}, month = {04}, number = 404, title = {Estimating Churn in Structured P2P Overlay Networks.}, type = {Technical Report}, year = 2007 }
• 
  Staehle, Dirk ; Mäder, Andreas: A Model for Time-Efficient HSDPA Simulations. ( Nr. 414). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  A Model for Time-Efficient HSDPA Simulations Models for the downlink capacity of WCDMA systems with dedicated channels as specified in the UMTS Release '99 rely on the orthogonality factor for approximating the intra-cell interference due to multi-path propagation. This model is no longer applicable for the HSDPA as the performance of fast scheduling and adaptive modulation and coding depends on the small-scale fading effects. This leads to the problem on how to produce reliable statistics for the long-term system-level behavior when small-scale fading effects are not negligible. In this paper we introduce a general framework on how to perform time-efficient simulations that capture the effects of small-scale fading.

  @techreport{TR414, abstract = {A Model for Time-Efficient HSDPA Simulations Models for the downlink capacity of WCDMA systems with dedicated channels as specified in the UMTS Release '99 rely on the orthogonality factor for approximating the intra-cell interference due to multi-path propagation. This model is no longer applicable for the HSDPA as the performance of fast scheduling and adaptive modulation and coding depends on the small-scale fading effects. This leads to the problem on how to produce reliable statistics for the long-term system-level behavior when small-scale fading effects are not negligible. In this paper we introduce a general framework on how to perform time-efficient simulations that capture the effects of small-scale fading.}, address = {Department of Computer Science}, author = {Staehle, Dirk and Mäder, Andreas}, keywords = {myown}, month = {04}, number = 414, title = {A Model for Time-Efficient HSDPA Simulations.}, type = {Technical Report}, year = 2007 }
• 
  Binzenhöfer, Andreas ; Schnabel, Holger: Improving the Performance and Robustness of Kademlia-based Overlay Networks. ( Nr. 405). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Structured peer-to-peer (p2p) networks are highly distributed systems with a potential to support business applications. There are numerous different suggestions on how to implement such systems. However, before legal p2p systems can become mainstream they need to offer improved efficiency, robustness, and stability. While Chord is the most researched and best understood mechanism, the Kademlia algorithm is widely-used in deployed applications. There are still many open questions concerning the performance of the latter. In this paper we identify the main problems of Kademlia by large scale simulations and present modifications which help to avoid those problems. This way, we are able to significantly improve the performance and robustness of Kademlia-based applications, especially in times of churn and in unstable states. In particular, we show how to increase the stability of the overlay, make searches more efficient, and adapt the maintenance traffic to the current churn rate in a self-organizing way.

  @techreport{TR405, abstract = {Structured peer-to-peer (p2p) networks are highly distributed systems with a potential to support business applications. There are numerous different suggestions on how to implement such systems. However, before legal p2p systems can become mainstream they need to offer improved efficiency, robustness, and stability. While Chord is the most researched and best understood mechanism, the Kademlia algorithm is widely-used in deployed applications. There are still many open questions concerning the performance of the latter. In this paper we identify the main problems of Kademlia by large scale simulations and present modifications which help to avoid those problems. This way, we are able to significantly improve the performance and robustness of Kademlia-based applications, especially in times of churn and in unstable states. In particular, we show how to increase the stability of the overlay, make searches more efficient, and adapt the maintenance traffic to the current churn rate in a self-organizing way.}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Schnabel, Holger}, keywords = {myown}, month = {04}, number = 405, title = {Improving the Performance and Robustness of Kademlia-based Overlay Networks.}, type = {Technical Report}, year = 2007 }
• 
  Mäder, Andreas ; Staehle, Dirk ; Barth, Hans: A Novel Performance Model for the HSDPA with Adaptive Resource Allocation. ( Nr. 409). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We propose a novel performance model for the HSDPA in presence of circuit-switched dedicated channels. The model consists of two parts: An HSDPA bandwidth model which considers the SIR distribution according to the multi-path model and the number of available channelization codes, and an analytical capacity model which integrates HSDPA and dedicated channels under assumption of adaptive resource allocation for the HSDPA. Additionally, the model considers the impact of location dependent bandwidths on the spatial user distribution. The accuracy of the model is demonstrated for an example scenario.

  @techreport{TR409, abstract = {We propose a novel performance model for the HSDPA in presence of circuit-switched dedicated channels. The model consists of two parts: An HSDPA bandwidth model which considers the SIR distribution according to the multi-path model and the number of available channelization codes, and an analytical capacity model which integrates HSDPA and dedicated channels under assumption of adaptive resource allocation for the HSDPA. Additionally, the model considers the impact of location dependent bandwidths on the spatial user distribution. The accuracy of the model is demonstrated for an example scenario.}, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk and Barth, Hans}, keywords = {myown}, month = {04}, number = 409, title = {A Novel Performance Model for the HSDPA with Adaptive Resource Allocation.}, type = {Technical Report}, year = 2007 }
• 
  Martin, Rüdiger ; Menth, Michael ; Hemmkeppler, Michael: Accuracy and Dynamics of Multi-Stage Load Balancing for Multipath Internet Routing. ( Nr. 419). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Flow-based load balancing algorithms for multipath Internet routing are often used for traffic engineering. However, the target load distribution and the load balanced result agree only on average, and there is a significant inaccuracy over time due to stochastic effects. Dynamic load balancing reduces this inaccuracy by relocating flows to other paths in regular time intervals. This causes packet reordering. Therefore, the flow reassignment rate should be kept low. In this paper we consider load balancing in networks. It differs from load balancing at a single node by the fact that several load balancing steps may be performed at consecutive nodes in series. This affects the flow reassignment rate and the load balancing accuracy due to interdependencies and polarization effects. We quantify the impact by simulation results, explain the observed phenomena, and give recommendations for load balancing in practice.

  @techreport{TR419, abstract = {Flow-based load balancing algorithms for multipath Internet routing are often used for traffic engineering. However, the target load distribution and the load balanced result agree only on average, and there is a significant inaccuracy over time due to stochastic effects. Dynamic load balancing reduces this inaccuracy by relocating flows to other paths in regular time intervals. This causes packet reordering. Therefore, the flow reassignment rate should be kept low. In this paper we consider load balancing in networks. It differs from load balancing at a single node by the fact that several load balancing steps may be performed at consecutive nodes in series. This affects the flow reassignment rate and the load balancing accuracy due to interdependencies and polarization effects. We quantify the impact by simulation results, explain the observed phenomena, and give recommendations for load balancing in practice.}, address = {Department of Computer Science}, author = {Martin, Rüdiger and Menth, Michael and Hemmkeppler, Michael}, keywords = {myown}, month = {04}, number = 419, title = {Accuracy and Dynamics of Multi-Stage Load Balancing for Multipath Internet Routing.}, type = {Technical Report}, year = 2007 }
• 
  Pries, Rastin ; Mäder, Andreas ; Staehle, Dirk: Performance of Header Compression for VoIP in Wireless LANs. ( Nr. 403). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The increasing number of Voice over IP (VoIP) phones in wired and wireless technologies leads us to the performance discussion of VoIP traffic in IEEE 802.11 WLAN environments. Originally designed to transport best effort data traffic, WLANs may experience some problems with delay-sensitive and low-rate voice traffic. This paper investigates the Voice over WLAN (VoWLAN) capacity for different WLAN standards. Our simulations show that the IEEE 802.11e Quality-of-Service (QoS) extension does not increase the system performance in terms of maximum number of supported VoWLAN users. Therefore, we try to improve the capacity by using a header compression mechanism which reduces the upper layer header to around 10 percent of its original size.

  @techreport{TR403, abstract = {The increasing number of Voice over IP (VoIP) phones in wired and wireless technologies leads us to the performance discussion of VoIP traffic in IEEE 802.11 WLAN environments. Originally designed to transport best effort data traffic, WLANs may experience some problems with delay-sensitive and low-rate voice traffic. This paper investigates the Voice over WLAN (VoWLAN) capacity for different WLAN standards. Our simulations show that the IEEE 802.11e Quality-of-Service (QoS) extension does not increase the system performance in terms of maximum number of supported VoWLAN users. Therefore, we try to improve the capacity by using a header compression mechanism which reduces the upper layer header to around 10 percent of its original size.}, address = {Department of Computer Science}, author = {Pries, Rastin and Mäder, Andreas and Staehle, Dirk}, keywords = {myown}, month = {04}, number = 403, title = {Performance of Header Compression for VoIP in Wireless LANs.}, type = {Technical Report}, year = 2007 }
• 
  Glaßer, Christian ; Reitwießner, Christian ; Travers, Stephen ; Waldherr, M.: Satisfiability of Algebraic Circuits over Sets of Natural Numbers. ( Nr. 402). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR402, address = {Department of Computer Science}, author = {Glaßer, Christian and Reitwießner, Christian and Travers, Stephen and Waldherr, M.}, keywords = {myown}, month = {03}, number = 402, title = {Satisfiability of Algebraic Circuits over Sets of Natural Numbers.}, type = {Technical Report}, year = 2007 }
• 
  Spoerhase, Joachim ; Wirth, H.-C.: Relaxed Voting and Competitive Location on Trees under Monotonuos Gain Functions. ( Nr. 401). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR401, address = {Department of Computer Science}, author = {Spoerhase, Joachim and Wirth, H.-C.}, keywords = {myown}, month = {03}, number = 401, title = {Relaxed Voting and Competitive Location on Trees under Monotonuos Gain Functions.}, type = {Technical Report}, year = 2007 }
• 
  Glaßer, Christian: Logspace Mitoticity. ( Nr. 400). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR400, address = {Department of Computer Science}, author = {Glaßer, Christian}, keywords = {myown}, month = {01}, number = 400, title = {Logspace Mitoticity.}, type = {Technical Report}, year = 2007 }
• 
  Tutschku, Kurt ; Hoßfeld, Tobias ; Berl, A. ; de Meer, Hermann ; Oberender, Jend: Mobile P2P Applications in Infrastructure-based Mobile Networks. ( Nr. 398). Department of Computer Science, 2007
  • [ BibTeX ]
  @techreport{TR398, address = {Department of Computer Science}, author = {Tutschku, Kurt and Hoßfeld, Tobias and Berl, A. and de Meer, Hermann and Oberender, Jend}, keywords = {myown}, month = {01}, number = 398, title = {Mobile P2P Applications in Infrastructure-based Mobile Networks.}, type = {Technical Report}, year = 2007 }
• 
  Tutschku, Kurt: P2P-based Network and Service Operation for the Emerging Future Internet. ( Nr. 397). Department of Computer Science, 2007
  • [ BibTeX ]
  @techreport{TR397, address = {Department of Computer Science}, author = {Tutschku, Kurt}, keywords = {myown}, month = {01}, number = 397, title = {P2P-based Network and Service Operation for the Emerging Future Internet.}, type = {Technical Report}, year = 2007 }
• 
  Baunach, Marcel ; Kolla, Reiner ; Mühlberger, Clemens: SNoW5:a modular platform for sophisticated real-time wireless sensor networking. ( Nr. 399). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This technical paper describes the architecture of SNoW^5, a low power sensor node for ad hoc wireless sensor networking (WSN). The nodes versatility turns it into an ideal tool for WSN research, educational and commercial applications. After explaining the basic concept, the hardware design will be shown in detail. An extensive comparison to existing nodes will be given regarding technical aspects like application specific customization, power consumption, wireless communication and operating system design. Outstanding features and internals of the newly developed real-time operating system SmartOS for sensor nodes will also be illustrated.

  @techreport{TR399, abstract = {This technical paper describes the architecture of SNoW^5, a low power sensor node for ad hoc wireless sensor networking (WSN). The nodes versatility turns it into an ideal tool for WSN research, educational and commercial applications. After explaining the basic concept, the hardware design will be shown in detail. An extensive comparison to existing nodes will be given regarding technical aspects like application specific customization, power consumption, wireless communication and operating system design. Outstanding features and internals of the newly developed real-time operating system SmartOS for sensor nodes will also be illustrated.}, address = {Department of Computer Science}, author = {Baunach, Marcel and Kolla, Reiner and Mühlberger, Clemens}, keywords = {myown}, month = {01}, number = 399, title = {SNoW5:a modular platform for sophisticated real-time wireless sensor networking.}, type = {Technical Report}, year = 2007 }
• 
  Mäder, Andreas ; Staehle, Dirk ; Spahn, Markus: Impact of HSDPA Radio Resource Allocation Schemes on the System Performance of UMTS Networks. ( Nr. 410). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In UMTS networks, HSDPA users share radio resources like transmit power and OSVF codes with QoS-users, which use dedicated channels as primary transport method. Several options for the resource allocation for HSDPA exist, which center around the question whether resources should be exclusively reserved for HSDPA, or whether the resources for the HSDPA should be adapted to the requirements of the QoS users. We investigate the impact of three radio resource allocation schemes on the HSDPA and on the dedicated channel performance by means of a time-dynamic simulation. The numerical results show the trade-offs between dedicated channel and HSDPA performance and the sensitivity of the system against power and code reservation parameters.

  @techreport{TR410, abstract = {In UMTS networks, HSDPA users share radio resources like transmit power and OSVF codes with QoS-users, which use dedicated channels as primary transport method. Several options for the resource allocation for HSDPA exist, which center around the question whether resources should be exclusively reserved for HSDPA, or whether the resources for the HSDPA should be adapted to the requirements of the QoS users. We investigate the impact of three radio resource allocation schemes on the HSDPA and on the dedicated channel performance by means of a time-dynamic simulation. The numerical results show the trade-offs between dedicated channel and HSDPA performance and the sensitivity of the system against power and code reservation parameters.}, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk and Spahn, Markus}, keywords = {myown}, month = {04}, number = 410, title = {Impact of HSDPA Radio Resource Allocation Schemes on the System Performance of UMTS Networks.}, type = {Technical Report}, year = 2007 }
• 
  Leibnitz, Kenji ; Hoßfeld, Tobias ; Wakamiya, Naoki ; Murata, Masayuki: Peer-to-Peer vs. Client/Server: Reliability and Efficiency of a Content Distribution Service. ( Nr. 422). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this work we evaluate the performance of a content distribution service with respect to reliability and efficiency. The considered technology for realizing such a service can either be a traditional client/server (CS) architecture or a peer-to-peer (P2P) network. In CS, the capacity of the server is the bottleneck and has to be dimensioned in such a way that all requests can be accommodated at any time, while a P2P system does not burden a single server since the content is distributed in the network among sharing peers. However, corrupted or fake files may diminish the reliability of the P2P service due to downloading of useless contents. We compare a CS system to P2P and evaluate the downloading time, success ratio, and fairness while considering flash crowd arrivals and corrupted contents. Furthermore, we take a look on the fairness of both systems and investigate methods for improving the reliability of content distribution.

  @techreport{TR422, abstract = {In this work we evaluate the performance of a content distribution service with respect to reliability and efficiency. The considered technology for realizing such a service can either be a traditional client/server (CS) architecture or a peer-to-peer (P2P) network. In CS, the capacity of the server is the bottleneck and has to be dimensioned in such a way that all requests can be accommodated at any time, while a P2P system does not burden a single server since the content is distributed in the network among sharing peers. However, corrupted or fake files may diminish the reliability of the P2P service due to downloading of useless contents. We compare a CS system to P2P and evaluate the downloading time, success ratio, and fairness while considering flash crowd arrivals and corrupted contents. Furthermore, we take a look on the fairness of both systems and investigate methods for improving the reliability of content distribution.}, address = {Department of Computer Science}, author = {Leibnitz, Kenji and Hoßfeld, Tobias and Wakamiya, Naoki and Murata, Masayuki}, keywords = {myown}, month = {04}, number = 422, title = {Peer-to-Peer vs. Client/Server: Reliability and Efficiency of a Content Distribution Service.}, type = {Technical Report}, year = 2007 }
• 
  Staehle, Dirk: On the Code and Soft Capacity of the UMTS FDD Downlink and the Capacity Increase by using a Secondary Scrambling Code. ( Nr. 413). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The downlink capacity of a UMTS FDD network is limited by the number of available channelization codes (code capacity) and by the available NodeB transmit power (soft capacity). The channelization codes of one sector are taken from an OVSF tree such that the number of codes per spreading factor is equal to the spreading factor itself. In the case that the codes of the OVSF tree are already exploited and the required transmit power is still clearly below its maximum, it is possible to establish another OVSF tree by using a secondary scrambling code. In this paper we develop a Monte Carlo simulation model for comparing the code capacity with the soft capacity of a UMTS network with sectorization, soft and softer handover. Several factors of influence like the orthogonality factor, the user activity, or the codes and power that are reserved for the HSDPA are investigated. Additionally, the capacity increase by using a second OVSF tree with the secondary scrambling code is studied.

  @techreport{TR413, abstract = {The downlink capacity of a UMTS FDD network is limited by the number of available channelization codes (code capacity) and by the available NodeB transmit power (soft capacity). The channelization codes of one sector are taken from an OVSF tree such that the number of codes per spreading factor is equal to the spreading factor itself. In the case that the codes of the OVSF tree are already exploited and the required transmit power is still clearly below its maximum, it is possible to establish another OVSF tree by using a secondary scrambling code. In this paper we develop a Monte Carlo simulation model for comparing the code capacity with the soft capacity of a UMTS network with sectorization, soft and softer handover. Several factors of influence like the orthogonality factor, the user activity, or the codes and power that are reserved for the HSDPA are investigated. Additionally, the capacity increase by using a second OVSF tree with the secondary scrambling code is studied.}, address = {Department of Computer Science}, author = {Staehle, Dirk}, keywords = {myown}, month = {04}, number = 413, title = {On the Code and Soft Capacity of the UMTS FDD Downlink and the Capacity Increase by using a Secondary Scrambling Code.}, type = {Technical Report}, year = 2007 }
• 
  Selivanov, Victor: Fine Hierarchies and m-Reducibilities in Theoretical Computer Science. ( Nr. 430). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR430, address = {Department of Computer Science}, author = {Selivanov, Victor}, keywords = {myown}, month = {08}, number = 430, title = {Fine Hierarchies and m-Reducibilities in Theoretical Computer Science.}, type = {Technical Report}, year = 2007 }
• 
  Pries, Rastin ; Staehle, Dirk ; Oechsner, Simon ; Menth, Michael ; Menth, Stefan: A New Perspective on the Unfair Channel Access Phenomenon in Wireless Local Area Networks. ( Nr. 439). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  A New Perspective on the Unfair Channel Access Phenomenon in Wireless Local Area NetworksWireless LAN, based on the IEEE 802.11 standards, has been extensively studied since its release. The topic of several of these research papers was the discrepancy of delays and buffer overflow probabilities that the Access Point on one hand and the stations on the other hand experience. This is widely referred to as the unfair channel access phenomenon. A related issue that has not yet been investigated is another kind of unfairness resulting from different collision probabilities. Interestingly, the latter unfairness favors the Access Point, contrary to the former. In this paper, we present an extensive simulation study of this problem and validate the results by means of analytical models. Here, mainly bi-directional voice traffic and TCP traffic flows are considered. The results reveal how pronounced these unfairness is and how the recent introduction of the Quality-of-Service extension exacerbates the unfair channel access phenomenon.

  @techreport{TR439, abstract = {A New Perspective on the Unfair Channel Access Phenomenon in Wireless Local Area NetworksWireless LAN, based on the IEEE 802.11 standards, has been extensively studied since its release. The topic of several of these research papers was the discrepancy of delays and buffer overflow probabilities that the Access Point on one hand and the stations on the other hand experience. This is widely referred to as the unfair channel access phenomenon. A related issue that has not yet been investigated is another kind of unfairness resulting from different collision probabilities. Interestingly, the latter unfairness favors the Access Point, contrary to the former. In this paper, we present an extensive simulation study of this problem and validate the results by means of analytical models. Here, mainly bi-directional voice traffic and TCP traffic flows are considered. The results reveal how pronounced these unfairness is and how the recent introduction of the Quality-of-Service extension exacerbates the unfair channel access phenomenon.}, address = {Department of Computer Science}, author = {Pries, Rastin and Staehle, Dirk and Oechsner, Simon and Menth, Michael and Menth, Stefan}, keywords = {myown}, month = 12, number = 439, title = {A New Perspective on the Unfair Channel Access Phenomenon in Wireless Local Area Networks.}, type = {Technical Report}, year = 2007 }
• 
  Wirth, H.-C.: On the Complexity of Budgeted Maximum Path Coverage on Trees. ( Nr. 438). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR438, address = {Department of Computer Science}, author = {Wirth, H.-C.}, keywords = {myown}, month = 12, number = 438, title = {On the Complexity of Budgeted Maximum Path Coverage on Trees.}, type = {Technical Report}, year = 2007 }
• 
  Glaßer, Christian ; Pavan, A. ; Travers, Stephen: False Positives and NP-Hard Sets. ( Nr. 435). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR435, address = {Department of Computer Science}, author = {Glaßer, Christian and Pavan, A. and Travers, Stephen}, keywords = {myown}, month = 10, number = 435, title = {False Positives and NP-Hard Sets.}, type = {Technical Report}, year = 2007 }
• 
  Spoerhase, Joachim ; Wirth, H.-C.: A Linear Time Algorithm for Absolute Optima under Monotonous Gain Functions on Trees. ( Nr. 433). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR433, address = {Department of Computer Science}, author = {Spoerhase, Joachim and Wirth, H.-C.}, keywords = {myown}, month = 10, number = 433, title = {A Linear Time Algorithm for Absolute Optima under Monotonous Gain Functions on Trees.}, type = {Technical Report}, year = 2007 }
• 
  Menth, Michael ; Lehrieder, Frank: Comparison of Marking Algorithms for PCN-Based Admission Control. ( Nr. 437). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The PCN working group of the IETF discusses the use of pre-congestion notification (PCN) to implement flow admission control. Packet meters and markers are used on all network links and packet markings are recorded as congestion level estimates (CLEs) the egress nodes. The working group currently discusses the pros and cons of possible marking algorithms that play a major role in this new architecture. This paper provides a detailed description of threshold and ramp marking based on a virtual queue formulation. We investigate the impact of the marking threshold and the virtual queue size on the marking behavior and develop different marking strategies. We test the robustness of the CLEs obtained for both marking schemes against different CLE parameters and traffic characteristics. Furthermore, we show that ramp marking can be well approximated by appropriately configured threshold marking.

  @techreport{TR437, abstract = {The PCN working group of the IETF discusses the use of pre-congestion notification (PCN) to implement flow admission control. Packet meters and markers are used on all network links and packet markings are recorded as congestion level estimates (CLEs) the egress nodes. The working group currently discusses the pros and cons of possible marking algorithms that play a major role in this new architecture. This paper provides a detailed description of threshold and ramp marking based on a virtual queue formulation. We investigate the impact of the marking threshold and the virtual queue size on the marking behavior and develop different marking strategies. We test the robustness of the CLEs obtained for both marking schemes against different CLE parameters and traffic characteristics. Furthermore, we show that ramp marking can be well approximated by appropriately configured threshold marking.}, address = {Department of Computer Science}, author = {Menth, Michael and Lehrieder, Frank}, keywords = {myown}, month = 10, number = 437, title = {Comparison of Marking Algorithms for PCN-Based Admission Control.}, type = {Technical Report}, year = 2007 }
• 
  Selivanov, Victor ; Wagner, Klaus: Complexity of Topological Properties of Regular omega-Languages. ( Nr. 436). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR436, address = {Department of Computer Science}, author = {Selivanov, Victor and Wagner, Klaus}, keywords = {myown}, month = 10, number = 436, title = {Complexity of Topological Properties of Regular omega-Languages.}, type = {Technical Report}, year = 2007 }
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  Seipel, Dietmar ; Hanus, M. ; Wolf, Armin ; Baumeister, Joachim: Proceedings INAP / WLP 2007. ( Nr. 434). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR434, address = {Department of Computer Science}, author = {Seipel, Dietmar and Hanus, M. and Wolf, Armin and Baumeister, Joachim}, keywords = {myown}, month = {09}, number = 434, title = {Proceedings INAP / WLP 2007.}, type = {Technical Report}, year = 2007 }
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  Glaßer, Christian ; Schmitz, Heinz ; Selivanov, Victor: Efficient Algorithms for Membership in Boolean Hierarchies of Regular Languages. ( Nr. 429). Department of Computer Science, 2007
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR429, address = {Department of Computer Science}, author = {Glaßer, Christian and Schmitz, Heinz and Selivanov, Victor}, keywords = {myown}, month = {08}, number = 429, title = {Efficient Algorithms for Membership in Boolean Hierarchies of Regular Languages.}, type = {Technical Report}, year = 2007 }
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  Tutschku, Kurt ; Tran-Gia, Phuoc ; Andersen, Frank-Uwe: Trends in Network and Service Operation for the Emerging Future Internet. ( Nr. 431). Department of Computer Science, 2007
  • [ BibTeX ]
  @techreport{TR431, address = {Department of Computer Science}, author = {Tutschku, Kurt and Tran-Gia, Phuoc and Andersen, Frank-Uwe}, keywords = {myown}, month = {08}, number = 431, title = {Trends in Network and Service Operation for the Emerging Future Internet.}, type = {Technical Report}, year = 2007 }
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  Martin, Rüdiger ; Menth, Michael ; Hartmann, Matthias: The Effect of Combining Loop-Free Alternates and Not-Via Addresses in IP Fast Reroute. ( Nr. 432). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The IETF currently discusses fast reroute mechanisms for IP networks (IP FRR) to accelerate the recovery in case of network element failures and to avoid microloops during network-wide routing re-convergence. Several mechanisms are proposed. Loop-free alternates (LFAs) are simple, but they cannot cover all single link and node failures. Not-via addresses are more complex and cover all single failures, but they potentially lead to longer backup paths and require tunnelling which may reduce the forwarding speed of the routers. In addition, they increase the size of the forwarding tables. This work studies the combination of those simple and complex mechanisms to achieve full single failure coverage with least overhead. First, we establish a taxonomy for LFAs according to their ability and propose combination options with not-vias for different resilience requirements. Then, we quantify the effect of combining both mechanisms regarding their applicability for the resilience requirements, routing table size, link utilization, backup path length, and amount of traffic requiring decapsulation per router. The results show that there are no strong advantages of the combined application of both mechanisms over not-via as the only IP FRR concept if 100% coverage for single link and node failures is required.

  @techreport{TR432, abstract = {The IETF currently discusses fast reroute mechanisms for IP networks (IP FRR) to accelerate the recovery in case of network element failures and to avoid microloops during network-wide routing re-convergence. Several mechanisms are proposed. Loop-free alternates (LFAs) are simple, but they cannot cover all single link and node failures. Not-via addresses are more complex and cover all single failures, but they potentially lead to longer backup paths and require tunnelling which may reduce the forwarding speed of the routers. In addition, they increase the size of the forwarding tables. This work studies the combination of those simple and complex mechanisms to achieve full single failure coverage with least overhead. First, we establish a taxonomy for LFAs according to their ability and propose combination options with not-vias for different resilience requirements. Then, we quantify the effect of combining both mechanisms regarding their applicability for the resilience requirements, routing table size, link utilization, backup path length, and amount of traffic requiring decapsulation per router. The results show that there are no strong advantages of the combined application of both mechanisms over not-via as the only IP FRR concept if 100% coverage for single link and node failures is required.}, address = {Department of Computer Science}, author = {Martin, Rüdiger and Menth, Michael and Hartmann, Matthias}, keywords = {myown}, month = {09}, number = 432, title = {The Effect of Combining Loop-Free Alternates and Not-Via Addresses in IP Fast Reroute.}, type = {Technical Report}, year = 2007 }
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  Duelli, Michael ; Hoßfeld, Tobias ; Staehle, Dirk: Impact of Vertical Handovers on Cooperative Content Distribution Systems. ( Nr. 428). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We evaluate the performance of a P2P-based content distribution system in heterogeneous, wireless networks. The mobile users coordinate each other with cooperation strategies enabled by the multi-source download mechanism, as in eDonkey or BitTorrent. Due to the mobility, vertical handovers between different wireless access technologies are required which may result in transmission delays and IP address changes of the switching peer. Hence, connections among users have to be reestablished and downloading users are requeued at a providing peer's waiting queue. In detail, we investigate the impact of requeueing with each VHO as well as the use of mechanisms that preserve the IP address and connections beyond VHOs, like MobileIP. Another important phenomenon occurring with VHOs is the abrupt change of the available bandwidth, e.g., from a fast WLAN connection to a rather slow UMTS connection. We evaluate the download times for files by means of simulation while considering different load scenarios in today's and future network layouts of the B3G network. As a result of the performance evaluation, we derive a new time-based cooperation strategy that counters the impact of mobility. Instead of downloading individual blocks of a file, a user gets a time slot at a providing peer. We show that this leads to a significant performance gain.

  @techreport{TR428, abstract = {We evaluate the performance of a P2P-based content distribution system in heterogeneous, wireless networks. The mobile users coordinate each other with cooperation strategies enabled by the multi-source download mechanism, as in eDonkey or BitTorrent. Due to the mobility, vertical handovers between different wireless access technologies are required which may result in transmission delays and IP address changes of the switching peer. Hence, connections among users have to be reestablished and downloading users are requeued at a providing peer's waiting queue. In detail, we investigate the impact of requeueing with each VHO as well as the use of mechanisms that preserve the IP address and connections beyond VHOs, like MobileIP. Another important phenomenon occurring with VHOs is the abrupt change of the available bandwidth, e.g., from a fast WLAN connection to a rather slow UMTS connection. We evaluate the download times for files by means of simulation while considering different load scenarios in today's and future network layouts of the B3G network. As a result of the performance evaluation, we derive a new time-based cooperation strategy that counters the impact of mobility. Instead of downloading individual blocks of a file, a user gets a time slot at a providing peer. We show that this leads to a significant performance gain.}, address = {Department of Computer Science}, author = {Duelli, Michael and Hoßfeld, Tobias and Staehle, Dirk}, keywords = {myown}, month = {06}, number = 428, title = {Impact of Vertical Handovers on Cooperative Content Distribution Systems.}, type = {Technical Report}, year = 2007 }
• 
  Martin, Rüdiger ; Menth, Michael ; Spörlein, Ulrich: Integer SPM: Intelligent Path Selection for Resilient Network. ( Nr. 417). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The self-protecting multipath (SPM) is a simple and efficient end-to-end protection switching mechanism. It distributes traffic according to a path failure specific load balancing function over several disjoint paths and redistributes it if one of these paths fails. SPMs with optimal load balancing functions (oSPMs) are unnecessarily complex because traffic aggregates potentially need to be split which is an obstacle for the deployment of SPMs in practice. The contribution of this paper is the proposal of an integer SPM (iSPM), i.e., the load balancing functions take only 0/1 values and effectively become path selection functions. In addition, we propose a greedy heuristic to optimize the 0/1 distributions. Finally, we show that the iSPM is only little less efficient than the oSPM and that the computation time of the heuristic for the iSPM is clearly faster than the linear program solver for the oSPM such that the iSPM can be deployed in significantly larger networks.

  @techreport{TR417, abstract = {The self-protecting multipath (SPM) is a simple and efficient end-to-end protection switching mechanism. It distributes traffic according to a path failure specific load balancing function over several disjoint paths and redistributes it if one of these paths fails. SPMs with optimal load balancing functions (oSPMs) are unnecessarily complex because traffic aggregates potentially need to be split which is an obstacle for the deployment of SPMs in practice. The contribution of this paper is the proposal of an integer SPM (iSPM), i.e., the load balancing functions take only 0/1 values and effectively become path selection functions. In addition, we propose a greedy heuristic to optimize the 0/1 distributions. Finally, we show that the iSPM is only little less efficient than the oSPM and that the computation time of the heuristic for the iSPM is clearly faster than the linear program solver for the oSPM such that the iSPM can be deployed in significantly larger networks.}, address = {Department of Computer Science}, author = {Martin, Rüdiger and Menth, Michael and Spörlein, Ulrich}, keywords = {myown}, month = {04}, number = 417, title = {Integer SPM: Intelligent Path Selection for Resilient Network.}, type = {Technical Report}, year = 2007 }
• 
  Menth, Michael ; Martin, Rüdiger ; Spörlein, Ulrich: Optimization of the Self-Protecting Multipath for Deployment in Legacy Networks. ( Nr. 418). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The self-protecting multipath (SPM) is a simple protection switching mechanism that can be implemented, e.g., by MPLS. We present a linear program for the optimization of the SPM load balancing parameters to maximize the amount of transportable traffic with resilience requirements. This is needed to configure the SPM for the deployment in legacy networks. Our study shows that the SPM is very efficient in the sense that it can carry 50% - 200% more protected traffic than IP rerouting in sufficiently meshed networks. The investigation of the computation time and the memory consumption recommends the COIN LP (CLP) as preferred LP solver. The computation time of the program depends mainly on the number of links in the network and networks with up to 240 links can be optimized within one hour on a standard PC.

  @techreport{TR418, abstract = {The self-protecting multipath (SPM) is a simple protection switching mechanism that can be implemented, e.g., by MPLS. We present a linear program for the optimization of the SPM load balancing parameters to maximize the amount of transportable traffic with resilience requirements. This is needed to configure the SPM for the deployment in legacy networks. Our study shows that the SPM is very efficient in the sense that it can carry 50% - 200% more protected traffic than IP rerouting in sufficiently meshed networks. The investigation of the computation time and the memory consumption recommends the COIN LP (CLP) as preferred LP solver. The computation time of the program depends mainly on the number of links in the network and networks with up to 240 links can be optimized within one hour on a standard PC.}, address = {Department of Computer Science}, author = {Menth, Michael and Martin, Rüdiger and Spörlein, Ulrich}, keywords = {myown}, month = {04}, number = 418, title = {Optimization of the Self-Protecting Multipath for Deployment in Legacy Networks.}, type = {Technical Report}, year = 2007 }
• 
  Menth, Michael ; Hartmann, Matthias ; Martin, Rüdiger: Robust IP Link Costs for Multilayer Resilience . ( Nr. 427). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this work we optimize administrative link costs of IP networks in such a way that the maximum utilization of all links is as low as possible for a set of considered failure scenarios (e.g., all single link failures). To that aim, we present the new "hill hopping" heuristic with three different variants and compare their computation times and the quality of their results. We adapt the objective function of the heuristic to make the link cost settings robust to single link failures, single node failures, and single link or node failures, and compare the results. In particular, we optimize the routing for multilayer networks where unused backup capacity of the link layer can be reused to redirect traffic on the network layer in case of an IP node failure.

  @techreport{TR427, abstract = {In this work we optimize administrative link costs of IP networks in such a way that the maximum utilization of all links is as low as possible for a set of considered failure scenarios (e.g., all single link failures). To that aim, we present the new "hill hopping" heuristic with three different variants and compare their computation times and the quality of their results. We adapt the objective function of the heuristic to make the link cost settings robust to single link failures, single node failures, and single link or node failures, and compare the results. In particular, we optimize the routing for multilayer networks where unused backup capacity of the link layer can be reused to redirect traffic on the network layer in case of an IP node failure.}, address = {Department of Computer Science}, author = {Menth, Michael and Hartmann, Matthias and Martin, Rüdiger}, keywords = {myown}, month = {05}, number = 427, title = {Robust IP Link Costs for Multilayer Resilience .}, type = {Technical Report}, year = 2007 }
• 
  Emmert, Barbara ; Staehle, Dirk: Impact of Energy Models on Energy Efficient Sensor Network Routing. ( Nr. 415). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Models and proposals to capture the energy consumption of sensor nodes are plentiful. Even if the majority of the various energy consumption models roughly agree about the energy consumed in the different states of the sensor node duty cycle, different approaches for abstracting the costs of radio operations exist. In our work, we investigate which factors are crucial for the modeling of transmission costs by establishing a general framework whose modular structure allows to compare existing abstractions. We analyze the impact of typical assumptions when they influence the creation of energy efficient routing topologies. We compare the resulting routing trees not only by topological characteristics, but also by estimating radio related energy consumptions, a metric which changes strongly with the MAC layer efficiency.

  @techreport{TR415, abstract = {Models and proposals to capture the energy consumption of sensor nodes are plentiful. Even if the majority of the various energy consumption models roughly agree about the energy consumed in the different states of the sensor node duty cycle, different approaches for abstracting the costs of radio operations exist. In our work, we investigate which factors are crucial for the modeling of transmission costs by establishing a general framework whose modular structure allows to compare existing abstractions. We analyze the impact of typical assumptions when they influence the creation of energy efficient routing topologies. We compare the resulting routing trees not only by topological characteristics, but also by estimating radio related energy consumptions, a metric which changes strongly with the MAC layer efficiency.}, address = {Department of Computer Science}, author = {Emmert, Barbara and Staehle, Dirk}, keywords = {myown}, month = {04}, number = 415, title = {Impact of Energy Models on Energy Efficient Sensor Network Routing.}, type = {Technical Report}, year = 2007 }
• 
  Klügl, Franziska: Towards a Formal Framework for Multi-Agent Simulation Models. ( Nr. 412). Department of Computer Science, 2007
  • [ BibTeX ]
  @techreport{TR412, address = {Department of Computer Science}, author = {Klügl, Franziska}, keywords = {myown}, month = {04}, number = 412, title = {Towards a Formal Framework for Multi-Agent Simulation Models.}, type = {Technical Report}, year = 2007 }
• 
  Hoßfeld, Tobias ; Tran-Gia, Phuoc ; Fiedler, Markus: Quantification of Quality of Experience for Edge-Based Applications. ( Nr. 423). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In future Internet, multi-network services correspond to a new paradigm that intelligence in network control is gradually moved to the edge of the network. As a consequence, the application itself can influence or determine the amount of consumed bandwidth. Thus the user behaviour may change dramatically. This impacts the Quality of Service (QoS) and the Quality of Experience (QoE), a subjective measure from the user perspective of the overall value of the provided service or application. A selfish user or application tries to maximize its own QoE rather than to optimize the network QoS, in contrast to a legacy altruistic user. In this paper we present the IQX hypothesis which assumes an exponential functional relationship between QoE and QoS. This contribution is a first step towards the quantification of the QoE for edge-based applications, where an example of VoIP is taken into account. Starting from a measurement of the Skype application, we show the basic properties of selfish and altruistic user behaviour in accordance to edge-based intelligence. The QoE is quantified in terms of MOS in dependence of the packet loss of the end-to-end connection, whereby Skype's iLBC voice codec is used exemplarily. It is shown that the IQX hypothesis is verified in this application scenario. Furthermore, selfish user behaviour with replicated sending of voice datagrams is investigated with respect to the obtained QoE of a single user. In addition, the impact of this user behaviour on congestion in the network is outlined by means of simulations.

  @techreport{TR423, abstract = {In future Internet, multi-network services correspond to a new paradigm that intelligence in network control is gradually moved to the edge of the network. As a consequence, the application itself can influence or determine the amount of consumed bandwidth. Thus the user behaviour may change dramatically. This impacts the Quality of Service (QoS) and the Quality of Experience (QoE), a subjective measure from the user perspective of the overall value of the provided service or application. A selfish user or application tries to maximize its own QoE rather than to optimize the network QoS, in contrast to a legacy altruistic user. In this paper we present the IQX hypothesis which assumes an exponential functional relationship between QoE and QoS. This contribution is a first step towards the quantification of the QoE for edge-based applications, where an example of VoIP is taken into account. Starting from a measurement of the Skype application, we show the basic properties of selfish and altruistic user behaviour in accordance to edge-based intelligence. The QoE is quantified in terms of MOS in dependence of the packet loss of the end-to-end connection, whereby Skype's iLBC voice codec is used exemplarily. It is shown that the IQX hypothesis is verified in this application scenario. Furthermore, selfish user behaviour with replicated sending of voice datagrams is investigated with respect to the obtained QoE of a single user. In addition, the impact of this user behaviour on congestion in the network is outlined by means of simulations.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Tran-Gia, Phuoc and Fiedler, Markus}, keywords = {myown}, month = {04}, number = 423, title = {Quantification of Quality of Experience for Edge-Based Applications.}, type = {Technical Report}, year = 2007 }
• 
  Menth, Michael ; Binzenhöfer, Andreas ; Mühleck, Stefan: Source Models for Speech Traffic Revisited. ( Nr. 426). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we analyze output traces of different voice codecs and present analytical models to describe them by stochastic processes. Both the G.711 and the G.729.1 codec yield constant bit rate traffic, the G.723.1 as well as the iLBC codec use silence detection leading to an on/off process, and the GSM AMR and the iSAC codec produce variable bit rate (VBR) traffic. We apply all codecs to a large set of typical speech samples and provide quantitative models that are based on standard and modified on/off processes as well as memory Markov chains. Our models are in good accordance with the original traces as they capture the complementary cumulative distribution function (CCDF) of the on/off phase durations and the packet sizes, the autocorrelation function (ACF) of consecutive packet sizes, and the queuing properties of the original traces. In addition, they are rather simple which makes them especially useful for application in analytical and simulative studies. The durations of the on/off phases in our model are an order of magnitude larger than those found by previous work and to the best of our knowledge this is the first paper presenting a model for VBR voice.

  @techreport{TR426, abstract = {In this paper, we analyze output traces of different voice codecs and present analytical models to describe them by stochastic processes. Both the G.711 and the G.729.1 codec yield constant bit rate traffic, the G.723.1 as well as the iLBC codec use silence detection leading to an on/off process, and the GSM AMR and the iSAC codec produce variable bit rate (VBR) traffic. We apply all codecs to a large set of typical speech samples and provide quantitative models that are based on standard and modified on/off processes as well as memory Markov chains. Our models are in good accordance with the original traces as they capture the complementary cumulative distribution function (CCDF) of the on/off phase durations and the packet sizes, the autocorrelation function (ACF) of consecutive packet sizes, and the queuing properties of the original traces. In addition, they are rather simple which makes them especially useful for application in analytical and simulative studies. The durations of the on/off phases in our model are an order of magnitude larger than those found by previous work and to the best of our knowledge this is the first paper presenting a model for VBR voice.}, address = {Department of Computer Science}, author = {Menth, Michael and Binzenhöfer, Andreas and Mühleck, Stefan}, keywords = {myown}, month = {05}, number = 426, title = {Source Models for Speech Traffic Revisited.}, type = {Technical Report}, year = 2007 }
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  Menth, Michael ; Martin, Rüdiger ; Hartmann, Matthias ; Spoerlein, Ulrich: Efficiency of Routing and Resilience Mechanisms in Packet-Switched Networks. ( Nr. 425). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This paper compares the efficiency of different routing and resilience mechanisms to avoid congestion in a network for a set of protected failures. A routing mechanism is more efficient than another one if it achieves a lower maximum link utilization in the same networking scenario. With resilience requirements, the maximum link utilization over the set of protected failure scenarios becomes the critical value. We consider standard and optimized configurations of single shortest path (SSP) and equal-cost multipath (ECMP) routing as well as several types of end-to-end (e2e) path protection and MPLS fast reroute (FRR). We investigate how well these resilience mechanisms can cope with different network structures and with different sets of protected failures. The results show that routing optimization reduces the maximum link utilization significantly both with and without protection of failures. The optimization potential for resilient routing is limited by the applied mechanism and heavily depends on the network structure and the set of protected failure scenarios.

  @techreport{TR425, abstract = {This paper compares the efficiency of different routing and resilience mechanisms to avoid congestion in a network for a set of protected failures. A routing mechanism is more efficient than another one if it achieves a lower maximum link utilization in the same networking scenario. With resilience requirements, the maximum link utilization over the set of protected failure scenarios becomes the critical value. We consider standard and optimized configurations of single shortest path (SSP) and equal-cost multipath (ECMP) routing as well as several types of end-to-end (e2e) path protection and MPLS fast reroute (FRR). We investigate how well these resilience mechanisms can cope with different network structures and with different sets of protected failures. The results show that routing optimization reduces the maximum link utilization significantly both with and without protection of failures. The optimization potential for resilient routing is limited by the applied mechanism and heavily depends on the network structure and the set of protected failure scenarios.}, address = {Department of Computer Science}, author = {Menth, Michael and Martin, Rüdiger and Hartmann, Matthias and Spoerlein, Ulrich}, keywords = {myown}, month = {05}, number = 425, title = {Efficiency of Routing and Resilience Mechanisms in Packet-Switched Networks.}, type = {Technical Report}, year = 2007 }
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  Baunach, Marcel ; Kolla, Reiner ; Mühlberger, Clemens: SNoW BAT: A high precise WSN based location system. ( Nr. 424). Department of Computer Science, 2007
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  As various applications require concrete knowledge about the position of objects, different methods for localization exist. Unfortunately, most off the shelf methods lack precision or are not applicable indoors. In this paper we present SNoW Bat, a full featured decentralized ultrasonic system for three dimensional localization and tracking of mobile objects. SNoW Bat is a sensor net solution supporting self-configuration for easy deployment, robustness for fault tolerance and simultaneous monitoring of several objects for increased scalability. Applied techniques and results will be discussed in detail allowing a brief comparison to similar systems available.

  @techreport{TR424, abstract = {As various applications require concrete knowledge about the position of objects, different methods for localization exist. Unfortunately, most off the shelf methods lack precision or are not applicable indoors. In this paper we present SNoW Bat, a full featured decentralized ultrasonic system for three dimensional localization and tracking of mobile objects. SNoW Bat is a sensor net solution supporting self-configuration for easy deployment, robustness for fault tolerance and simultaneous monitoring of several objects for increased scalability. Applied techniques and results will be discussed in detail allowing a brief comparison to similar systems available.}, address = {Department of Computer Science}, author = {Baunach, Marcel and Kolla, Reiner and Mühlberger, Clemens}, keywords = {myown}, month = {05}, number = 424, title = {SNoW BAT: A high precise WSN based location system.}, type = {Technical Report}, year = 2007 }

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  Reitwießner, Christian: Zusammenfalten des Postschen Verbandes mittels Operationen aus binären Booleschen Funktionen. ( Nr. 386). Department of Computer Science, 2006
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR386, address = {Department of Computer Science}, author = {Reitwießner, Christian}, keywords = {myown}, month = {06}, number = 386, title = {Zusammenfalten des Postschen Verbandes mittels Operationen aus binären Booleschen Funktionen.}, type = {Technical Report}, year = 2006 }
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  Chevul, Stefan ; Binzenhöfer, Andreas ; Schmid, Matthias ; Tutschku, Kurt ; Fiedler, Markus: A Self-Organizing Concept for Distributed End-to-End Quality Monitoring. ( Nr. 378). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The subjective service quality as perceived by the end-user is an aspect which is often neglected in classic network monitoring. Yet it is the end-user who decides whether he will continue to use the service or not. This is especially true for real time services like Voice over IP telephony (VoIP), whose experienced quality heavily depends on the current network situation. In this paper we present a self-organizing concept for distributed monitoring of the end-to-end quality, which will bridge the feedback gap between the user and the provider. It is based on a simple and robust measurement mechanism, which is running at the host of the end-user. As a proof-of-concept we implemented a prototype of our architecture and show the practicability of our concept using VoIP quality measurements.

  @techreport{TR378, abstract = {The subjective service quality as perceived by the end-user is an aspect which is often neglected in classic network monitoring. Yet it is the end-user who decides whether he will continue to use the service or not. This is especially true for real time services like Voice over IP telephony (VoIP), whose experienced quality heavily depends on the current network situation. In this paper we present a self-organizing concept for distributed monitoring of the end-to-end quality, which will bridge the feedback gap between the user and the provider. It is based on a simple and robust measurement mechanism, which is running at the host of the end-user. As a proof-of-concept we implemented a prototype of our architecture and show the practicability of our concept using VoIP quality measurements.}, address = {Department of Computer Science}, author = {Chevul, Stefan and Binzenhöfer, Andreas and Schmid, Matthias and Tutschku, Kurt and Fiedler, Markus}, keywords = {myown}, month = {01}, number = 378, title = {A Self-Organizing Concept for Distributed End-to-End Quality Monitoring.}, type = {Technical Report}, year = 2006 }
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  Milbrandt, Jens ; Menth, Michael ; Junker, Jan: Experience-Based Admission Control with Type-Specific Overbooking. ( Nr. 382). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Experience-based admission control (EBAC) is a hybrid approach combining the classical parameter-based and measurement-based admission control schemes. EBAC calculates an appropriate overbooking factor used to overbook link capacities with resource reservations in packet-based networks. This overbooking factor correlates with the average peak-to-mean rate ratio of all admitted traffic flows on the link. So far, a single overbooking factor is calculated for the entire traffic aggregate. In this paper, we propose type-specific EBAC which provides a compound overbooking factor considering different types of traffic that subsume flows with similar peak-to-mean rate ratios. The concept can be well implemented since it does not require type-specific traffic measurements. We give a proof of concept for this extension and compare it with the conventional EBAC approach. We show that EBAC with type-specific overbooking leads to better resource utilization under normal conditions and to faster response times for changing traffic mixes.

  @techreport{TR382, abstract = {Experience-based admission control (EBAC) is a hybrid approach combining the classical parameter-based and measurement-based admission control schemes. EBAC calculates an appropriate overbooking factor used to overbook link capacities with resource reservations in packet-based networks. This overbooking factor correlates with the average peak-to-mean rate ratio of all admitted traffic flows on the link. So far, a single overbooking factor is calculated for the entire traffic aggregate. In this paper, we propose type-specific EBAC which provides a compound overbooking factor considering different types of traffic that subsume flows with similar peak-to-mean rate ratios. The concept can be well implemented since it does not require type-specific traffic measurements. We give a proof of concept for this extension and compare it with the conventional EBAC approach. We show that EBAC with type-specific overbooking leads to better resource utilization under normal conditions and to faster response times for changing traffic mixes.}, address = {Department of Computer Science}, author = {Milbrandt, Jens and Menth, Michael and Junker, Jan}, keywords = {myown}, month = {03}, number = 382, title = {Experience-Based Admission Control with Type-Specific Overbooking.}, type = {Technical Report}, year = 2006 }
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  Menth, Michael ; Henjes, Robert ; Gehrsitz, Sebastian ; Zepfel, Christian: Throughput Comparison of Professional JMS Servers. ( Nr. 380). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The Java messaging service (JMS) facilitates communication among distributed software components according to the publish/subscribe principle. If the subscribers install filter rules on the JMS server, JMS can be used as a message routing platform, but it is not clear whether its message throughput is sufficiently high to support large-scale systems. In this paper, we investigate the capacity of three high performance JMS server implementations: FioranoMQ, SunMQ, and WebshereMQ. In contrast to other studies, we focus on the message throughput in the presence of filters and show that filtering reduces the performance significantly. We present models for the message processing time of each server and validate them by measurement. These models depend on the number of installed filters and the replication grade of the messages, and predict the overall message throughput for specific application scenarios. Finally, we illustrate the use of these models by comparing the message throughput of the three servers in four different application scenarios.

  @techreport{TR380, abstract = {The Java messaging service (JMS) facilitates communication among distributed software components according to the publish/subscribe principle. If the subscribers install filter rules on the JMS server, JMS can be used as a message routing platform, but it is not clear whether its message throughput is sufficiently high to support large-scale systems. In this paper, we investigate the capacity of three high performance JMS server implementations: FioranoMQ, SunMQ, and WebshereMQ. In contrast to other studies, we focus on the message throughput in the presence of filters and show that filtering reduces the performance significantly. We present models for the message processing time of each server and validate them by measurement. These models depend on the number of installed filters and the replication grade of the messages, and predict the overall message throughput for specific application scenarios. Finally, we illustrate the use of these models by comparing the message throughput of the three servers in four different application scenarios.}, address = {Department of Computer Science}, author = {Menth, Michael and Henjes, Robert and Gehrsitz, Sebastian and Zepfel, Christian}, keywords = {myown}, month = {03}, number = 380, title = {Throughput Comparison of Professional JMS Servers.}, type = {Technical Report}, year = 2006 }
• 
  Milbrandt, Jens ; Menth, Michael ; Junker, Jan: Performance of Experience-Based Admission Control in the Presence of Traffic Changes. ( Nr. 381). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This paper investigates the transient behavior of experience-based admission control (EBAC) in case of traffic changes. EBAC is a robust and resource-efficient admission control (AC) mechanism used for reservation overbooking of link capacities in packet-based networks. Recent analyses gave a proof of concept for EBAC and showed its efficiency and robustness through steady state simulation on a single link carrying traffic with constant properties. The contribution of this paper is an examination of the memory from which EBAC gains its experience and which strongly influences the behavior of EBAC in both, stationary and non-stationary state. For the latter, we investigate the transient behavior of the EBAC mechanism through simulation of strong traffic changes which are characterized by either a sudden decrease or increase of the traffic intensity. Our results show that the transient behavior of EBAC partly depends on its tunable memory and that it copes well with even strongly changing traffic characteristics.

  @techreport{TR381, abstract = {This paper investigates the transient behavior of experience-based admission control (EBAC) in case of traffic changes. EBAC is a robust and resource-efficient admission control (AC) mechanism used for reservation overbooking of link capacities in packet-based networks. Recent analyses gave a proof of concept for EBAC and showed its efficiency and robustness through steady state simulation on a single link carrying traffic with constant properties. The contribution of this paper is an examination of the memory from which EBAC gains its experience and which strongly influences the behavior of EBAC in both, stationary and non-stationary state. For the latter, we investigate the transient behavior of the EBAC mechanism through simulation of strong traffic changes which are characterized by either a sudden decrease or increase of the traffic intensity. Our results show that the transient behavior of EBAC partly depends on its tunable memory and that it copes well with even strongly changing traffic characteristics.}, address = {Department of Computer Science}, author = {Milbrandt, Jens and Menth, Michael and Junker, Jan}, keywords = {myown}, month = {03}, number = 381, title = {Performance of Experience-Based Admission Control in the Presence of Traffic Changes.}, type = {Technical Report}, year = 2006 }
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  Glaßer, Christian ; Selman, Alan L. ; Travers, Stephen ; Wagner, Klaus W.: The Complexity of Disjoint Unions. ( Nr. 384). Department of Computer Science, 2006
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR384, address = {Department of Computer Science}, author = {Glaßer, Christian and Selman, Alan L. and Travers, Stephen and Wagner, Klaus W.}, keywords = {myown}, month = {04}, number = 384, title = {The Complexity of Disjoint Unions.}, type = {Technical Report}, year = 2006 }
• 
  Binzenhöfer, Andreas ; Schlosser, Daniel ; auf dem Graben, Björn: A Novel Approach to Verify End-to-End Connectivity in an Autonomic Way. ( Nr. 383). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Computer networks are increasingly becoming more complex. As a consequence unacceptable user-perceived quality is often blamed on the network. However, it requires highly trained professionals to verify the connectivity between two communication partners. The concept of autonomic networks has been proposed in an effort to make such networks easier to manage. In this context, we present a plug-and-play mechanism to check the connectivity between two end points of the network. It will significantly decrease the amount of mundane work, which is usually involved in such a task. The main goal is to autonomically measure the current conditions between two communication partners and to visualize it in an easy to interpret way. The results can be used to indicate whether the current state of the network supports specific services like VoIP calls, videoconferencing, or file transfers.

  @techreport{TR383, abstract = {Computer networks are increasingly becoming more complex. As a consequence unacceptable user-perceived quality is often blamed on the network. However, it requires highly trained professionals to verify the connectivity between two communication partners. The concept of autonomic networks has been proposed in an effort to make such networks easier to manage. In this context, we present a plug-and-play mechanism to check the connectivity between two end points of the network. It will significantly decrease the amount of mundane work, which is usually involved in such a task. The main goal is to autonomically measure the current conditions between two communication partners and to visualize it in an easy to interpret way. The results can be used to indicate whether the current state of the network supports specific services like VoIP calls, videoconferencing, or file transfers.}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Schlosser, Daniel and auf dem Graben, Björn}, keywords = {myown}, month = {04}, number = 383, title = {A Novel Approach to Verify End-to-End Connectivity in an Autonomic Way.}, type = {Technical Report}, year = 2006 }
• 
  Schlosser, Daniel ; Hoßfeld, Tobias ; Tutschku, Kurt: Comparison of Robust Cooperation Strategies for P2P Content Distribution Networks with Multiple Source Download. ( Nr. 385). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The performance of Peer-to-Peer (P2P) content distribution networks depends highly on the coordination of the peers. Sophisticated cooperation strategies, such as the multiple source download, are the foundation for efficient file exchange. The detailed performance of the strategies are determined by the actual peer characteristics and the peer behavior, such as the number of parallel upload connections, the selfishness, or the altruistic re-distribution of data. The purpose of this work is to evaluate and investigate different cooperation strategies for multiple source download and select the best one for a scenario for even leeching peers, i.e. peers which depart as soon as they have finished their download. The question arises whether the cooperation strategy can smoothen the overall performance degradation caused by a selfish peer behavior. As performance indicator the evolution of the numbers of copies of a chunk and the experienced download times of files is applied. The considered scenarios comprise best-case (altruistic peers) and worst-case scenarios (selfish peers). We further propose a new cooperation strategy to improve the file transfer even when mainly selfish peers are present, the CygPriM (cyclic priority masking) strategy. The strategy allows an efficient P2P based content distribution using ordered chunk delivery with only local information available at a peer.

  @techreport{TR385, abstract = {The performance of Peer-to-Peer (P2P) content distribution networks depends highly on the coordination of the peers. Sophisticated cooperation strategies, such as the multiple source download, are the foundation for efficient file exchange. The detailed performance of the strategies are determined by the actual peer characteristics and the peer behavior, such as the number of parallel upload connections, the selfishness, or the altruistic re-distribution of data. The purpose of this work is to evaluate and investigate different cooperation strategies for multiple source download and select the best one for a scenario for even leeching peers, i.e. peers which depart as soon as they have finished their download. The question arises whether the cooperation strategy can smoothen the overall performance degradation caused by a selfish peer behavior. As performance indicator the evolution of the numbers of copies of a chunk and the experienced download times of files is applied. The considered scenarios comprise best-case (altruistic peers) and worst-case scenarios (selfish peers). We further propose a new cooperation strategy to improve the file transfer even when mainly selfish peers are present, the CygPriM (cyclic priority masking) strategy. The strategy allows an efficient P2P based content distribution using ordered chunk delivery with only local information available at a peer.}, address = {Department of Computer Science}, author = {Schlosser, Daniel and Hoßfeld, Tobias and Tutschku, Kurt}, keywords = {myown}, month = {05}, number = 385, title = {Comparison of Robust Cooperation Strategies for P2P Content Distribution Networks with Multiple Source Download.}, type = {Technical Report}, year = 2006 }
• 
  Milbrandt, Jens ; Humm, Korbinian ; Menth, Michael: Adaptive Bandwidth Allocation: Impact of Routing and Load Balancing on Tunnel Capacity Requirements. ( Nr. 379). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we consider adaptive bandwidth allocation (ABA) for capacity tunnels as an effective means for multi-hour network design. Traffic engineering (TE) tunnels established in a network from border-to-border (b2b) can be used not only for route pinning between ingress/egress node pairs but also for efficient implementation of resilient network admission control. If static bandwidth allocation (SBA) based on peak-rate traffic assumptions is used to dimension the b2b tunnels, fluctuations of the network traffic can lead to under- or overprovisioning of network capacity in the tunnels. If ABA is used instead, the tunnel sizes are dynamically adapted to current traffic conditions. The efficient use of network capacity assigned to TE tunnels strongly depends on the structure of these tunnels. The contribution of this paper is an assessment of the bandwidth savings that are achievable with ABA in comparison to SBA for various tunnel structures with different path layouts and load balancing strategies. Our results show that the capacity savings due to ABA depend on the routing and load balancing schemes provisioned in the network and that these savings may be increased by appropriately chosen tunnel implementations.

  @techreport{TR379, abstract = {In this paper, we consider adaptive bandwidth allocation (ABA) for capacity tunnels as an effective means for multi-hour network design. Traffic engineering (TE) tunnels established in a network from border-to-border (b2b) can be used not only for route pinning between ingress/egress node pairs but also for efficient implementation of resilient network admission control. If static bandwidth allocation (SBA) based on peak-rate traffic assumptions is used to dimension the b2b tunnels, fluctuations of the network traffic can lead to under- or overprovisioning of network capacity in the tunnels. If ABA is used instead, the tunnel sizes are dynamically adapted to current traffic conditions. The efficient use of network capacity assigned to TE tunnels strongly depends on the structure of these tunnels. The contribution of this paper is an assessment of the bandwidth savings that are achievable with ABA in comparison to SBA for various tunnel structures with different path layouts and load balancing strategies. Our results show that the capacity savings due to ABA depend on the routing and load balancing schemes provisioned in the network and that these savings may be increased by appropriately chosen tunnel implementations.}, address = {Department of Computer Science}, author = {Milbrandt, Jens and Humm, Korbinian and Menth, Michael}, keywords = {myown}, month = {02}, number = 379, title = {Adaptive Bandwidth Allocation: Impact of Routing and Load Balancing on Tunnel Capacity Requirements.}, type = {Technical Report}, year = 2006 }
• 
  Mäder, Andreas ; Staehle, Dirk: An Analytical Model for Best-Effort Traffic over the UMTS Enhanced Uplink. ( Nr. 388). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The next step in the evolution of UMTS is the Enhanced Uplink or high speed uplink packet access (HSUPA), which is designed for the efficient transport of packet switched data. One of the major novelties is the relocation of the scheduling control from the RNC to the NodeB which enables a faster reaction to cell load and radio condition variations. Our contribution is an analytic modelling approach for the performance evaluation of the UMTS uplink in a single cell with best-effort users over the enhanced uplink and QoS-users over dedicated channels. The model considers two different scheduling discplines for the enhanced uplink: Parallel scheduling and one-by-one scheduling. The model also considers the effect of power control errors and other-cell interference fluctuations as well as multiple dedicated channel service classes.

  @techreport{TR388, abstract = {The next step in the evolution of UMTS is the Enhanced Uplink or high speed uplink packet access (HSUPA), which is designed for the efficient transport of packet switched data. One of the major novelties is the relocation of the scheduling control from the RNC to the NodeB which enables a faster reaction to cell load and radio condition variations. Our contribution is an analytic modelling approach for the performance evaluation of the UMTS uplink in a single cell with best-effort users over the enhanced uplink and QoS-users over dedicated channels. The model considers two different scheduling discplines for the enhanced uplink: Parallel scheduling and one-by-one scheduling. The model also considers the effect of power control errors and other-cell interference fluctuations as well as multiple dedicated channel service classes.}, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk}, keywords = {myown}, month = {06}, number = 388, title = {An Analytical Model for Best-Effort Traffic over the UMTS Enhanced Uplink.}, type = {Technical Report}, year = 2006 }
• 
  von Gudenberg, Jürgen Wolff ; Niederle, A. ; Ebner, Marc ; Eichelberger, Holger: An Evolutionary Algorithm for the Layout of UML Class Diagrams. ( Nr. 391). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  An evolutionary algorithm that layouts UML class diagrams is developed and described. It evolves the layout by mutating the positions of class symbols, inheritance relations, and associations. The process is controled by a fitness function that is computed from several well-known and some new layout metrics.

  @techreport{TR391, abstract = {An evolutionary algorithm that layouts UML class diagrams is developed and described. It evolves the layout by mutating the positions of class symbols, inheritance relations, and associations. The process is controled by a fitness function that is computed from several well-known and some new layout metrics.}, address = {Department of Computer Science}, author = {von Gudenberg, Jürgen Wolff and Niederle, A. and Ebner, Marc and Eichelberger, Holger}, keywords = {myown}, month = {07}, number = 391, title = {An Evolutionary Algorithm for the Layout of UML Class Diagrams.}, type = {Technical Report}, year = 2006 }
• 
  Selivanov, Victor: Fine Hierarchy of Regular Aperiodic omega-Languages. ( Nr. 390). Department of Computer Science, 2006
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR390, address = {Department of Computer Science}, author = {Selivanov, Victor}, keywords = {myown}, month = {07}, number = 390, title = {Fine Hierarchy of Regular Aperiodic omega-Languages.}, type = {Technical Report}, year = 2006 }
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  Glaßer, Christian ; Selman, Alan L. ; Travers, Stephen ; Zhang, Liyu: Non-Mitotic Sets. ( Nr. 389). Department of Computer Science, 2006
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR389, address = {Department of Computer Science}, author = {Glaßer, Christian and Selman, Alan L. and Travers, Stephen and Zhang, Liyu}, keywords = {myown}, month = {07}, number = 389, title = {Non-Mitotic Sets.}, type = {Technical Report}, year = 2006 }
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  Meister, D.: Generating maximal spanning forests for some geometric graph classes. ( Nr. 393). Department of Computer Science, 2006
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR393, address = {Department of Computer Science}, author = {Meister, D.}, keywords = {myown}, month = {09}, number = 393, title = {Generating maximal spanning forests for some geometric graph classes.}, type = {Technical Report}, year = 2006 }
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  Glaßer, Christian ; Herr, K. ; Reitwießner, Christian ; Travers, Stephen ; Waldherr, M.: Equivalence Problems for Circuits over Sets of Natural Numbers. ( Nr. 392). Department of Computer Science, 2006
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR392, address = {Department of Computer Science}, author = {Glaßer, Christian and Herr, K. and Reitwießner, Christian and Travers, Stephen and Waldherr, M.}, keywords = {myown}, month = {09}, number = 392, title = {Equivalence Problems for Circuits over Sets of Natural Numbers.}, type = {Technical Report}, year = 2006 }
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  Brümmer, N. ; Baumeister, Joachim ; Puppe, Frank: Relations between Visual and Textual Representations of Temporal Patterns for Medical Data Abstraction. ( Nr. 394). Department of Computer Science, 2006
  • [ BibTeX ]
  @techreport{TR394, address = {Department of Computer Science}, author = {Brümmer, N. and Baumeister, Joachim and Puppe, Frank}, keywords = {myown}, month = 10, number = 394, title = {Relations between Visual and Textual Representations of Temporal Patterns for Medical Data Abstraction.}, type = {Technical Report}, year = 2006 }
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  Selivanov, Victor: Classifying omega-Regular Partitions. ( Nr. 396). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We try to develop a theory of \($\omega$\)-regular partitions in parallel with the theory around the Wagner hierarchy of regular \($\omega$\)-languages. In particular, we generalize a theorem of L. Staiger and K. Wagner to the case of partitions, prove decidability of all levels of the Boolean hierarchy of regular partitions over open sets, establish coincidence of reducibilities by continuous functions and by functions computed by finite automata on the class of regular \(${\bf\Delta}^0_2$\)-partitions, and show undecidability of the first-order theory of the structure of Wadge degrees of regular \($k$\)-partitions for all \($k>2$\).

  @techreport{TR396, abstract = {We try to develop a theory of $\omega$-regular partitions in parallel with the theory around the Wagner hierarchy of regular $\omega$-languages. In particular, we generalize a theorem of L. Staiger and K. Wagner to the case of partitions, prove decidability of all levels of the Boolean hierarchy of regular partitions over open sets, establish coincidence of reducibilities by continuous functions and by functions computed by finite automata on the class of regular ${\bf\Delta}^0_2$-partitions, and show undecidability of the first-order theory of the structure of Wadge degrees of regular $k$-partitions for all $k>2$.}, address = {Department of Computer Science}, author = {Selivanov, Victor}, keywords = {myown}, month = 12, number = 396, title = {Classifying omega-Regular Partitions.}, type = {Technical Report}, year = 2006 }
• 
  Pries, Rastin ; Mäder, Andreas ; Staehle, Dirk: UMTS Load Metrics for a Policy-Based Vertical Handover Framework. ( Nr. 395). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In most European countries, UMTS networks have been set up and completely cover urban areas. At the beginning of UMTS, there were only a few users but with a special pricing policy, the number of users is increasing drastically. A few providers already offer flat rates for UMTS and their networks get more and more crowded. Therefore, an efficient radio resource management (RRM) is one of the key aspects. In UMTS, the capacity is limited by the allowed NodeB transmit power on the downlink, the interference on the uplink, and the number of used channelization codes. In this paper, we will show how to examine both loads and furthermore, compute the code utilization.

  @techreport{TR395, abstract = {In most European countries, UMTS networks have been set up and completely cover urban areas. At the beginning of UMTS, there were only a few users but with a special pricing policy, the number of users is increasing drastically. A few providers already offer flat rates for UMTS and their networks get more and more crowded. Therefore, an efficient radio resource management (RRM) is one of the key aspects. In UMTS, the capacity is limited by the allowed NodeB transmit power on the downlink, the interference on the uplink, and the number of used channelization codes. In this paper, we will show how to examine both loads and furthermore, compute the code utilization.}, address = {Department of Computer Science}, author = {Pries, Rastin and Mäder, Andreas and Staehle, Dirk}, keywords = {myown}, month = 11, number = 395, title = {UMTS Load Metrics for a Policy-Based Vertical Handover Framework.}, type = {Technical Report}, year = 2006 }
• 
  Mäder, Andreas ; Staehle, Dirk ; Liu, Tony ; Barth, Hans: Feasible Load Regions for different RRM Strategies for the Enhanced Uplink in UMTS Networks. ( Nr. 387). Department of Computer Science, 2006
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The UMTS enhanced uplink or high speed uplink packet access (HSUPA) provides efficient mechanisms for the radio resource management of radio bearers for best effort traffic. The resources available for the enhanced uplink users depend on several factors like the spatial configuration of the mobiles in the cells, the number of QoS users and the implemented RRM strategy. In this work, we provide a framework for the calculation of the resources assigned to the enhanced uplink users. It considers the maximum transmit power and down-grants for the reduction of the other-cell interference. We further show the impact of centralized and de-centralized radio resource management strategies on the feasible load region.

  @techreport{TR387, abstract = {The UMTS enhanced uplink or high speed uplink packet access (HSUPA) provides efficient mechanisms for the radio resource management of radio bearers for best effort traffic. The resources available for the enhanced uplink users depend on several factors like the spatial configuration of the mobiles in the cells, the number of QoS users and the implemented RRM strategy. In this work, we provide a framework for the calculation of the resources assigned to the enhanced uplink users. It considers the maximum transmit power and down-grants for the reduction of the other-cell interference. We further show the impact of centralized and de-centralized radio resource management strategies on the feasible load region.}, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk and Liu, Tony and Barth, Hans}, keywords = {myown}, month = {06}, number = 387, title = {Feasible Load Regions for different RRM Strategies for the Enhanced Uplink in UMTS Networks.}, type = {Technical Report}, year = 2006 }

• 
  Fiedler, M. ; Chevul, S. ; Radtke, O. ; Tutschku, Kurt ; Binzenhöfer, Andreas: The Network Utility Function: A Practicable Concept for Assessing Network Impact on Distributed Services. ( Nr. 355). Department of Computer Science, 2005
  • [ BibTeX ]
  @techreport{TR355, address = {Department of Computer Science}, author = {Fiedler, M. and Chevul, S. and Radtke, O. and Tutschku, Kurt and Binzenhöfer, Andreas}, keywords = {myown}, month = {03}, number = 355, title = {The Network Utility Function: A Practicable Concept for Assessing Network Impact on Distributed Services.}, type = {Technical Report}, year = 2005 }
• 
  Meister, D.: The structure of separator graphs and efficient algorithms for minimal triangulations problems of permutation graphs. ( Nr. 361). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR361, address = {Department of Computer Science}, author = {Meister, D.}, keywords = {myown}, month = {05}, number = 361, title = {The structure of separator graphs and efficient algorithms for minimal triangulations problems of permutation graphs.}, type = {Technical Report}, year = 2005 }
• 
  Martin, Rüdiger ; Menth, Michael ; Charzinski, Joachim: Comparison of Link-by-Link Admission Control and Capacity Overprovisioning. ( Nr. 360). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Today's Internet offers (almost) global reachability at low cost. On the one hand, the "Best-Effort" delivery of packets does not guarantee any Quality of Service (QoS) level, but it is often sufficient even for high bit rate transfers. On the other hand, there is an ever increasing tendency to move value added services like telephony or video conferencing onto the Internet, which require bounded packet delay and predictable throughput. High precision applications like tele-surgery, tele-robotics or tele-music additionally require extremely low packet loss rates. Therefore, QoS in terms of short packet delay and low packet loss will be required in future versions of the Internet, so called ``next generation networks'' (NGNs), to support these services. QoS can be achieved by introducing an admission control (AC) infrastructure into the network. Demanding applications reserve network resources before transmitting traffic over the network, at least in high-QoS classes. AC blocks out reservations when the capacity does not suffice to guarantee the required QoS level both for the new reservation and for the already established reservations. Of course, the blocking probability has to be small in order not to annoy customers such that AC admits all reservations most of the time. This fact is exploited by the capacity overprovisioning (CO) approach that simply trades in complexity cost for bandwidth cost. Instead of blocking flows in overload situations, the CO approach tries to provide enough bandwidth so that the resulting QoS violations are low enough to be tolerated by the relevant applications. Many investigations compare blocking probabilities and required capacity for different AC schemes, for which several signalling protocols exist but none has been introduced on a large scale on the Internet. Introducing an AC architecture for the Internet would require significant investment into control plane elements and operation. Thus, currently all high-quality providers apply CO, leading to a low utilization of core networks \cite{Odly03. In this paper, we quantify the capacity requirements for networks relying on AC or CO for QoS provisioning to economically assess both approaches. We assume the traditional AC approach of deciding link by link if a reservation can be admitted. We concentrate on the high priority traffic with given bandwidth requirements per flow and compute the network capacity required for it. To explain the fundamental relations between flow bandwidth and link capacity requirements, we evaluate first the single link scenario. Then, we extend the study to an entire network domain to reflect realistic scenarios.

  @techreport{TR360, abstract = {Today's Internet offers (almost) global reachability at low cost. On the one hand, the "Best-Effort" delivery of packets does not guarantee any Quality of Service (QoS) level, but it is often sufficient even for high bit rate transfers. On the other hand, there is an ever increasing tendency to move value added services like telephony or video conferencing onto the Internet, which require bounded packet delay and predictable throughput. High precision applications like tele-surgery, tele-robotics or tele-music additionally require extremely low packet loss rates. Therefore, QoS in terms of short packet delay and low packet loss will be required in future versions of the Internet, so called ``next generation networks'' (NGNs), to support these services. QoS can be achieved by introducing an admission control (AC) infrastructure into the network. Demanding applications reserve network resources before transmitting traffic over the network, at least in high-QoS classes. AC blocks out reservations when the capacity does not suffice to guarantee the required QoS level both for the new reservation and for the already established reservations. Of course, the blocking probability has to be small in order not to annoy customers such that AC admits all reservations most of the time. This fact is exploited by the capacity overprovisioning (CO) approach that simply trades in complexity cost for bandwidth cost. Instead of blocking flows in overload situations, the CO approach tries to provide enough bandwidth so that the resulting QoS violations are low enough to be tolerated by the relevant applications. Many investigations compare blocking probabilities and required capacity for different AC schemes, for which several signalling protocols exist but none has been introduced on a large scale on the Internet. Introducing an AC architecture for the Internet would require significant investment into control plane elements and operation. Thus, currently all high-quality providers apply CO, leading to a low utilization of core networks \cite{Odly03}. In this paper, we quantify the capacity requirements for networks relying on AC or CO for QoS provisioning to economically assess both approaches. We assume the traditional AC approach of deciding link by link if a reservation can be admitted. We concentrate on the high priority traffic with given bandwidth requirements per flow and compute the network capacity required for it. To explain the fundamental relations between flow bandwidth and link capacity requirements, we evaluate first the single link scenario. Then, we extend the study to an entire network domain to reflect realistic scenarios.}, address = {Department of Computer Science}, author = {Martin, Rüdiger and Menth, Michael and Charzinski, Joachim}, keywords = {myown}, month = {05}, number = 360, title = {Comparison of Link-by-Link Admission Control and Capacity Overprovisioning.}, type = {Technical Report}, year = 2005 }
• 
  Böhler, Elmar ; Schnoor, H.: The Complexity of the Descriptiveness of Boolean Circuits Over Different Sets of Gates. ( Nr. 357). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR357, address = {Department of Computer Science}, author = {Böhler, Elmar and Schnoor, H.}, keywords = {myown}, month = {04}, number = 357, title = {The Complexity of the Descriptiveness of Boolean Circuits Over Different Sets of Gates.}, type = {Technical Report}, year = 2005 }
• 
  Yanenko, E. ; Schuhmacher, E. ; Spörlein, U. ; Tutschku, Kurt: An O(n log n) Heuristic for the Euclidean Traveling Salesman Problem. ( Nr. 358). Department of Computer Science, 2005
  • [ BibTeX ]
  @techreport{TR358, address = {Department of Computer Science}, author = {Yanenko, E. and Schuhmacher, E. and Spörlein, U. and Tutschku, Kurt}, keywords = {myown}, month = {04}, number = 358, title = {An O(n log n) Heuristic for the Euclidean Traveling Salesman Problem.}, type = {Technical Report}, year = 2005 }
• 
  Böhler, Elmar ; Reith, Steffen ; Schnoor, H. ; Vollmer, Heribert: Simple Bases for Boolean Co-Clones. ( Nr. 350). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR350, address = {Department of Computer Science}, author = {Böhler, Elmar and Reith, Steffen and Schnoor, H. and Vollmer, Heribert}, keywords = {myown}, month = {01}, number = 350, title = {Simple Bases for Boolean Co-Clones.}, type = {Technical Report}, year = 2005 }
• 
  Hoßfeld, Tobias ; Mäder, Andreas ; Tutschku, Kurt ; Tran-Gia, Phuoc ; Andersen, Frank-Uwe ; de Meer, Hermann ; Dedinski, I.: Comparison of Crawling Strategies for an Optimized Mobile P2P Architecture. ( Nr. 356). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Mobile networks differ from their wireline counterparts mainly by the high costs for air transmissions and by the mobility of the users. A new entity, denoted as the crawling peer, is suggested in order to optimize the resource mediation mechanism for a mobile P2P file sharing application. The crawling peer locates content on behalf of mobile peers. It is placed in the wireline part of the mobile network and thus, does not suffer from the above mentioned restrictions. The crawling peer is part of a comprehensive mobile P2P file sharing architecture which is based on the popular eDonkey file sharing application. The performance of three querying strategies of the crawling peer is investigated with respect to banning at the index servers and the response time of requests, i.e. the time to find a file. The results show that the selection of an appropriate request strategy for the crawling peer maximizes the probability of locating a file while the probability to be banned by an eDonkey index server is minimized.

  @techreport{TR356, abstract = {Mobile networks differ from their wireline counterparts mainly by the high costs for air transmissions and by the mobility of the users. A new entity, denoted as the crawling peer, is suggested in order to optimize the resource mediation mechanism for a mobile P2P file sharing application. The crawling peer locates content on behalf of mobile peers. It is placed in the wireline part of the mobile network and thus, does not suffer from the above mentioned restrictions. The crawling peer is part of a comprehensive mobile P2P file sharing architecture which is based on the popular eDonkey file sharing application. The performance of three querying strategies of the crawling peer is investigated with respect to banning at the index servers and the response time of requests, i.e. the time to find a file. The results show that the selection of an appropriate request strategy for the crawling peer maximizes the probability of locating a file while the probability to be banned by an eDonkey index server is minimized.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Mäder, Andreas and Tutschku, Kurt and Tran-Gia, Phuoc and Andersen, Frank-Uwe and de Meer, Hermann and Dedinski, I.}, keywords = {myown}, month = {03}, number = 356, title = {Comparison of Crawling Strategies for an Optimized Mobile P2P Architecture.}, type = {Technical Report}, year = 2005 }
• 
  Böhler, Elmar: On the Lattice of Clones Below the Polynomial Time Functions. ( Nr. 352). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR352, address = {Department of Computer Science}, author = {Böhler, Elmar}, keywords = {myown}, month = {02}, number = 352, title = {On the Lattice of Clones Below the Polynomial Time Functions.}, type = {Technical Report}, year = 2005 }
• 
  Glaßer, Christian ; Travers, Stephen ; Wagner, Klaus W.: A Reducibility that Corresponds to Unbalanced Leaf-Language Classes. ( Nr. 354). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR354, address = {Department of Computer Science}, author = {Glaßer, Christian and Travers, Stephen and Wagner, Klaus W.}, keywords = {myown}, month = {02}, number = 354, title = {A Reducibility that Corresponds to Unbalanced Leaf-Language Classes.}, type = {Technical Report}, year = 2005 }
• 
  Bauland, M. ; Böhler, Elmar ; Creignou, N. ; Reith, Steffen ; Schnoor, H. ; Vollmer, Heribert: Quantified Constraints: The Complexity of Decision and Counting for Bounded Alternation. ( Nr. 353). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR353, address = {Department of Computer Science}, author = {Bauland, M. and Böhler, Elmar and Creignou, N. and Reith, Steffen and Schnoor, H. and Vollmer, Heribert}, keywords = {myown}, month = {02}, number = 353, title = {Quantified Constraints: The Complexity of Decision and Counting for Bounded Alternation.}, type = {Technical Report}, year = 2005 }
• 
  Binzenhöfer, Andreas ; Tutschku, Kurt ; auf dem Graben, Björn ; Fiedler, Markus ; Carlsson, Patrik: A P2P-based Framework for Distributed Network Management. ( Nr. 351). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we present a novel framework supporting distributed network management using a self-organizing peer-to-peer overlay network. The overlay consists of several Distributed Network Agentswhich can perform distributed tests and distributed monitoring for fault and performance management. In that way, the concept is able to overcome disadvantages that come along with a central management unit like scalability and reliability. The self-organization of the overlay is achieved by the application of a Distributed Hash Table (DHT) based on the Kademlia algorithm. The DHT mechanism implements a distributed index for the rapid localization of other agents or resources. The framework provides a reliable and scalable basis for distributed tests, like e.g. the identification of performance degradation in IP networks using throughput statistics. The framework is not intended to replace the central network manager, but rather to support it in testing and surveying the status of the corresponding network.

  @techreport{TR351, abstract = {In this paper we present a novel framework supporting distributed network management using a self-organizing peer-to-peer overlay network. The overlay consists of several Distributed Network Agentswhich can perform distributed tests and distributed monitoring for fault and performance management. In that way, the concept is able to overcome disadvantages that come along with a central management unit like scalability and reliability. The self-organization of the overlay is achieved by the application of a Distributed Hash Table (DHT) based on the Kademlia algorithm. The DHT mechanism implements a distributed index for the rapid localization of other agents or resources. The framework provides a reliable and scalable basis for distributed tests, like e.g. the identification of performance degradation in IP networks using throughput statistics. The framework is not intended to replace the central network manager, but rather to support it in testing and surveying the status of the corresponding network.}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Tutschku, Kurt and auf dem Graben, Björn and Fiedler, Markus and Carlsson, Patrik}, keywords = {myown}, month = {01}, number = 351, title = {A P2P-based Framework for Distributed Network Management.}, type = {Technical Report}, year = 2005 }
• 
  Tran-Gia, Phuoc ; Binzenhöfer, Andreas: On the Stochastic Scalability of Information Sharing Platforms. ( Nr. 364). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Recently, centrally controlled information distribution systems are rapidly emerging to decentralized structures. This tendency can be observed in software distribution applications using BitTorrent or information sharing platforms based on distributed hash table structures like Chord or Kademlia. To ensure that the emerging platforms will function properly with a growing number of users and services the issue of scalability turned into one of the hottest research topics. Traditionally, the term scalability often restricts to the functional scalability, which describes the scalability in terms of the system size. In this regard the basic structure is stationary, i.e. it does not fluctuate frequently. However, when the stochastic behavior of system components, the network structure, and user applications has to be taken into account, the stochastic scalability has to be investigated in the context of performance evaluation. In this paper we discuss the stochastic scalability of information sharing platforms. We give a classification of current information sharing platforms and define the terms functional and stochastic scalability in detail. A distributed phone book based on a Chord ring will be discussed as an example to motivate other areas of application and to show the potential of the evaluation of stochastic scalability.

  @techreport{TR364, abstract = {Recently, centrally controlled information distribution systems are rapidly emerging to decentralized structures. This tendency can be observed in software distribution applications using BitTorrent or information sharing platforms based on distributed hash table structures like Chord or Kademlia. To ensure that the emerging platforms will function properly with a growing number of users and services the issue of scalability turned into one of the hottest research topics. Traditionally, the term scalability often restricts to the functional scalability, which describes the scalability in terms of the system size. In this regard the basic structure is stationary, i.e. it does not fluctuate frequently. However, when the stochastic behavior of system components, the network structure, and user applications has to be taken into account, the stochastic scalability has to be investigated in the context of performance evaluation. In this paper we discuss the stochastic scalability of information sharing platforms. We give a classification of current information sharing platforms and define the terms functional and stochastic scalability in detail. A distributed phone book based on a Chord ring will be discussed as an example to motivate other areas of application and to show the potential of the evaluation of stochastic scalability.}, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc and Binzenhöfer, Andreas}, keywords = {myown}, month = {06}, number = 364, title = {On the Stochastic Scalability of Information Sharing Platforms.}, type = {Technical Report}, year = 2005 }
• 
  Milbrandt, Jens ; Menth, Michael ; Kopf, Stefan: Adaptive Bandwidth Allocation: Concepts and Efficiency for Admission-Controlled Capacity Tunnels. ( Nr. 362). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we propose mechanisms for an adaptive bandwidth allocation (ABA) based on border-to-border (b2b) bandwidth budgets. These budgets can be considered as virtual capacity tunnels binding a fraction of the network capacity and connecting different network border routers. Unlike MPLS label switched paths or ATM virtual path connections associated with a certain bandwidth, these tunnels support multi-path routing. Moreover, they can be used to implement resilient b2b budget-based network admission control. If static bandwidth allocation (SBA) based on peak-rate traffic assumptions is used to dimension the b2b budgets, fluctuations of the network traffic can lead to under- or overprovisioning of network capacity within these budgets. The contribution of this paper is twofold. Firstly, we address this problem by two new ABA mechanisms - complete capacity reassignment (CCR) and selective capacity reassignment (SCR) - which adapt the sizes of the b2b budgets with regard to their current bandwidth requirements. Secondly, we investigate the bandwidth savings potential of these meachanisms by the construction of synthetically shifted but constantly loaded traffic matrices. Though focused on the above two aspects, the study of ABA based on b2b budgets is not finished and further investigations are currently in progress.

  @techreport{TR362, abstract = {In this paper, we propose mechanisms for an adaptive bandwidth allocation (ABA) based on border-to-border (b2b) bandwidth budgets. These budgets can be considered as virtual capacity tunnels binding a fraction of the network capacity and connecting different network border routers. Unlike MPLS label switched paths or ATM virtual path connections associated with a certain bandwidth, these tunnels support multi-path routing. Moreover, they can be used to implement resilient b2b budget-based network admission control. If static bandwidth allocation (SBA) based on peak-rate traffic assumptions is used to dimension the b2b budgets, fluctuations of the network traffic can lead to under- or overprovisioning of network capacity within these budgets. The contribution of this paper is twofold. Firstly, we address this problem by two new ABA mechanisms - complete capacity reassignment (CCR) and selective capacity reassignment (SCR) - which adapt the sizes of the b2b budgets with regard to their current bandwidth requirements. Secondly, we investigate the bandwidth savings potential of these meachanisms by the construction of synthetically shifted but constantly loaded traffic matrices. Though focused on the above two aspects, the study of ABA based on b2b budgets is not finished and further investigations are currently in progress.}, address = {Department of Computer Science}, author = {Milbrandt, Jens and Menth, Michael and Kopf, Stefan}, keywords = {myown}, month = {06}, number = 362, title = {Adaptive Bandwidth Allocation: Concepts and Efficiency for Admission-Controlled Capacity Tunnels.}, type = {Technical Report}, year = 2005 }
• 
  Martin, Rüdiger ; Menth, Michael ; Charzinski, Joachim: Comparison of Border-to-Border Budget Based Network Admission Control and Capacity Overprovisioning. ( Nr. 359). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The traditional Internet offers a best effort service and almost global reachability at low cost. Bulk transfers require high throughput, value added services like telephony or video conference depend on short packet delays and predictable throughput, and precision applications like tele-medicine or tele-robotics cannot even afford packet loss. Therefore, Quality of Service (QoS) in terms of short packet delay and low packet loss is required for next generation networks (NGNs) to support these services. QoS can be achieved by limiting the traffic volume in the network by admission control (AC) and thereby preventing overload situations. As an alternative, sufficient capacity can be provisioned such that no congestion occurs. This is called capacity overprovisioning (CO). On the one side, many investigations compare blocking probabilities of different AC schemes for which several signalling protocols exist. On the other side, practical experience shows that CO is already applied since the utilization of core networks today is very low. In this paper we quantify the capacity requirements for networks that rely on AC and CO for QoS provisioning, which is crucial for an economic assessment of both approaches. We focus on the simplest method for network AC (NAC), namely on border-to-border (b2b) budget (BBB) based NAC. We consider networks with only high priority real-time traffic which is not elastic and which has a connection structure. This is a typical scenario in, e.g., core networks for cellular systems. We consider first an unrealistically simple static traffic model on a single link. We add overload situations and extend the study to entire networks such that our final results reflect realistic scenarios.

  @techreport{TR359, abstract = {The traditional Internet offers a best effort service and almost global reachability at low cost. Bulk transfers require high throughput, value added services like telephony or video conference depend on short packet delays and predictable throughput, and precision applications like tele-medicine or tele-robotics cannot even afford packet loss. Therefore, Quality of Service (QoS) in terms of short packet delay and low packet loss is required for next generation networks (NGNs) to support these services. QoS can be achieved by limiting the traffic volume in the network by admission control (AC) and thereby preventing overload situations. As an alternative, sufficient capacity can be provisioned such that no congestion occurs. This is called capacity overprovisioning (CO). On the one side, many investigations compare blocking probabilities of different AC schemes for which several signalling protocols exist. On the other side, practical experience shows that CO is already applied since the utilization of core networks today is very low. In this paper we quantify the capacity requirements for networks that rely on AC and CO for QoS provisioning, which is crucial for an economic assessment of both approaches. We focus on the simplest method for network AC (NAC), namely on border-to-border (b2b) budget (BBB) based NAC. We consider networks with only high priority real-time traffic which is not elastic and which has a connection structure. This is a typical scenario in, e.g., core networks for cellular systems. We consider first an unrealistically simple static traffic model on a single link. We add overload situations and extend the study to entire networks such that our final results reflect realistic scenarios.}, address = {Department of Computer Science}, author = {Martin, Rüdiger and Menth, Michael and Charzinski, Joachim}, keywords = {myown}, month = {05}, number = 359, title = {Comparison of Border-to-Border Budget Based Network Admission Control and Capacity Overprovisioning.}, type = {Technical Report}, year = 2005 }
• 
  Milbrandt, Jens ; Menth, Michael ; Kopf, Stefan: Adaptive Bandwidth Allocation: Impact of Traffic Demand Models for Wide Area Networks. ( Nr. 363). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we consider configurable capacity tunnels. Static bandwidth allocation (SBA) assigns the network capacity to the tunnels according to the busy hours of their traffic aggregates. At secondary times, their capacity is underutilized and can not be used to accommodate excess traffic of other tunnels. The contribution of this paper is twofold. Firstly, we propose two mechanisms for adaptive bandwidth allocation (ABA) for the tunnels: complete capacity reassignment (CCR) and selective capacity reassignment (SCR). They both adapt the tunnel capacities to the current traffic demands but differ in their implementation, signaling, and configuration complexity. Secondly, we asses the bandwidth savings of ABA vs. SBA in wide area networks where the transfer rates of traffic aggregates fluctuate over time according to busy hours. Our results show that the capacity savings strongly depend on the traffic model and that they may be increased by time-aware routing.

  @techreport{TR363, abstract = {In this paper, we consider configurable capacity tunnels. Static bandwidth allocation (SBA) assigns the network capacity to the tunnels according to the busy hours of their traffic aggregates. At secondary times, their capacity is underutilized and can not be used to accommodate excess traffic of other tunnels. The contribution of this paper is twofold. Firstly, we propose two mechanisms for adaptive bandwidth allocation (ABA) for the tunnels: complete capacity reassignment (CCR) and selective capacity reassignment (SCR). They both adapt the tunnel capacities to the current traffic demands but differ in their implementation, signaling, and configuration complexity. Secondly, we asses the bandwidth savings of ABA vs. SBA in wide area networks where the transfer rates of traffic aggregates fluctuate over time according to busy hours. Our results show that the capacity savings strongly depend on the traffic model and that they may be increased by time-aware routing.}, address = {Department of Computer Science}, author = {Milbrandt, Jens and Menth, Michael and Kopf, Stefan}, keywords = {myown}, month = {06}, number = 363, title = {Adaptive Bandwidth Allocation: Impact of Traffic Demand Models for Wide Area Networks.}, type = {Technical Report}, year = 2005 }
• 
  Wagner, Klaus W.: Leaf Language Classes. ( Nr. 372). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  http://www1.pub.informatik.uni-wuerzburg.de/pub/TRs/Abstracts/tr372.html

  @techreport{TR372, abstract = {http://www1.pub.informatik.uni-wuerzburg.de/pub/TRs/Abstracts/tr372.html}, address = {Department of Computer Science}, author = {Wagner, Klaus W.}, keywords = {myown}, month = 11, number = 372, title = {Leaf Language Classes.}, type = {Technical Report}, year = 2005 }
• 
  Mäder, Andreas ; Staehle, Dirk ; Schröder, Bernd: Dimensioning of Hardware Components in UMTS Networks with Sectorized NodeBs. ( Nr. 365). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The dimensioning of hardware components takes place at the end of the UMTS radio network planning process when a suitable NodeB site configuration has been found. Each connection to a NodeB requires a service specific number of hardware components and an incoming connection is blocked if not enough components are available. The aim of hardware dimensioning is to find the cost-optimal hardware configuration for given service-specific target blocking probabilities. The challenge for the dimensioning process is that additionally to the hard blocking also system-inherent soft blocking occurs. We propose an algorithm for the cost-optimal dimensioning of the shared hardware components in the NodeB according to the service specific blocking targets. The algorithm considers the sector-individual soft capacities and the requirements on the shared hardware pool at the NodeB. We show that ignoring the system-inherent soft blocking of the UMTS radio interface leads to considerable over- or under-dimensioning and therefore has to be included in a proper dimensioning algorithm.

  @techreport{TR365, abstract = {The dimensioning of hardware components takes place at the end of the UMTS radio network planning process when a suitable NodeB site configuration has been found. Each connection to a NodeB requires a service specific number of hardware components and an incoming connection is blocked if not enough components are available. The aim of hardware dimensioning is to find the cost-optimal hardware configuration for given service-specific target blocking probabilities. The challenge for the dimensioning process is that additionally to the hard blocking also system-inherent soft blocking occurs. We propose an algorithm for the cost-optimal dimensioning of the shared hardware components in the NodeB according to the service specific blocking targets. The algorithm considers the sector-individual soft capacities and the requirements on the shared hardware pool at the NodeB. We show that ignoring the system-inherent soft blocking of the UMTS radio interface leads to considerable over- or under-dimensioning and therefore has to be included in a proper dimensioning algorithm.}, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk and Schröder, Bernd}, keywords = {myown}, month = {06}, number = 365, title = {Dimensioning of Hardware Components in UMTS Networks with Sectorized NodeBs.}, type = {Technical Report}, year = 2005 }
• 
  Hoßfeld, Tobias ; Binzenhöfer, Andreas ; Fiedler, M. ; Tutschku, Kurt: Measurement and Analysis of Skype VoIP Traffic in 3G UMTS Systems. ( Nr. 377). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Voice-over-IP (VoIP) telephony becomes more and more popular in the wired Internet because of easy-to-use applications with high sound quality like Skype. UMTS operators promise to offer large data rates which should also make VoIP possible in a mobile environment. However, the success of those application strongly depends on the user perceived voice quality. In this paper, we therefore analyze the achievable and the actual quality of IP-based telephony calls using Skype. This is done performing measurements in both a real UMTS network and a test environment. The latter is used to emulate rate control mechanisms and changing system conditions of UMTS networks. The results show whether Skype over UMTS is able to keep pace with existing mobile telephony systems and how it reacts to different network characteristics. The investigated performance measures comprise the Perceptual Evaluation of Speech Quality (PESQ) to evaluate the voice quality, the packet loss, the inter-packet delay, and the throughput to capture network-based factors. In this context, the concept of the Network Utility Function (NUF) is applied to describe the impact of the network on the voice quality as perceived by the end-user.

  @techreport{TR377, abstract = {Voice-over-IP (VoIP) telephony becomes more and more popular in the wired Internet because of easy-to-use applications with high sound quality like Skype. UMTS operators promise to offer large data rates which should also make VoIP possible in a mobile environment. However, the success of those application strongly depends on the user perceived voice quality. In this paper, we therefore analyze the achievable and the actual quality of IP-based telephony calls using Skype. This is done performing measurements in both a real UMTS network and a test environment. The latter is used to emulate rate control mechanisms and changing system conditions of UMTS networks. The results show whether Skype over UMTS is able to keep pace with existing mobile telephony systems and how it reacts to different network characteristics. The investigated performance measures comprise the Perceptual Evaluation of Speech Quality (PESQ) to evaluate the voice quality, the packet loss, the inter-packet delay, and the throughput to capture network-based factors. In this context, the concept of the Network Utility Function (NUF) is applied to describe the impact of the network on the voice quality as perceived by the end-user.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Binzenhöfer, Andreas and Fiedler, M. and Tutschku, Kurt}, keywords = {myown}, month = 12, number = 377, title = {Measurement and Analysis of Skype VoIP Traffic in 3G UMTS Systems.}, type = {Technical Report}, year = 2005 }
• 
  Hoßfeld, Tobias ; Mäder, Andreas ; Tutschku, Kurt ; Andersen, Frank-Uwe: Time-Discrete Analysis of the Crawling Strategy in an Optimized Mobile P2P Architecture. ( Nr. 374). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Mobile networks differ from their wireline counterparts mainly by the high costs for air transmissions and by the mobility of the users. A new entity, denoted as the crawling peer, is suggested in order to optimize the resource mediation mechanism for a mobile P2P file sharing application. In a former work, we have investigated the performance of a crawling peer by means of simulations. Now, we show a time-discrete analysis of the crawling peer's performance in order to investigate different scenarios and to enable parameter-sensitivity studies for further improvements of the crawling peer's strategy.

  @techreport{TR374, abstract = {Mobile networks differ from their wireline counterparts mainly by the high costs for air transmissions and by the mobility of the users. A new entity, denoted as the crawling peer, is suggested in order to optimize the resource mediation mechanism for a mobile P2P file sharing application. In a former work, we have investigated the performance of a crawling peer by means of simulations. Now, we show a time-discrete analysis of the crawling peer's performance in order to investigate different scenarios and to enable parameter-sensitivity studies for further improvements of the crawling peer's strategy.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Mäder, Andreas and Tutschku, Kurt and Andersen, Frank-Uwe}, keywords = {myown}, month = 11, number = 374, title = {Time-Discrete Analysis of the Crawling Strategy in an Optimized Mobile P2P Architecture.}, type = {Technical Report}, year = 2005 }
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  Binzenhöfer, Andreas ; Kunzmann, Gerald ; Henjes, Robert: A Scalable Algorithm to Monitor Chord-based P2P Systems at Runtime. ( Nr. 373). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Peer-to-peer (p2p) systems are a highly decentralized, fault tolerant, and cost effective alternative to the classical client-server architecture. Yet companies hesitate to use p2p algorithms to build new applications. Due to the decentralized nature of such a p2p system the carrier does not know anything about the current size, performance and stability of its application. In this paper we present an entirely distributed and scalable algorithm to monitor a running p2p network. The snapshot of the system enables a telecommunication carrier to gather information about the current performance parameters of the running system as well as to react to discovered errors.

  @techreport{TR373, abstract = {Peer-to-peer (p2p) systems are a highly decentralized, fault tolerant, and cost effective alternative to the classical client-server architecture. Yet companies hesitate to use p2p algorithms to build new applications. Due to the decentralized nature of such a p2p system the carrier does not know anything about the current size, performance and stability of its application. In this paper we present an entirely distributed and scalable algorithm to monitor a running p2p network. The snapshot of the system enables a telecommunication carrier to gather information about the current performance parameters of the running system as well as to react to discovered errors.}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Kunzmann, Gerald and Henjes, Robert}, keywords = {myown}, month = 11, number = 373, title = {A Scalable Algorithm to Monitor Chord-based P2P Systems at Runtime.}, type = {Technical Report}, year = 2005 }
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  Glaßer, Christian ; Travers, Stephen: Machines that can Output Empty Words. ( Nr. 376). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR376, address = {Department of Computer Science}, author = {Glaßer, Christian and Travers, Stephen}, keywords = {myown}, month = 12, number = 376, title = {Machines that can Output Empty Words.}, type = {Technical Report}, year = 2005 }
• 
  Fiedler, Markus ; Tutschku, Kurt ; Chevul, Stefan ; Isaksson, Lennart ; Binzenhöfer, Andreas: The Throughput Utility Function: Assessing Network Impact on Mobile Services. ( Nr. 375). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Based on the need for distributed end-to-end quality management for next-generation mobile Internet services, this paper presents a ready-to-deploy quality assessment concept for the impact of the network on the performance of mobile services. We consider the Throughput Utility Function (TUF) as a special case of the Network Utility Function (NUF). These functions combine the observed network utility at the inlet and the outlet of a mobile network. NUF and TUF capture the damping effect of the network onto user-perceived quality from an end-to-end perspective. As opposed to incomprehensible QoS parameters such as delay and loss, the NUF is highly intuitive due to its mapping to a simple value between 0 and 100 %. We demonstrate the capabilities of the proposed TUF by measurements of applicationperceived throughput conducted in mobile networks.

  @techreport{TR375, abstract = {Based on the need for distributed end-to-end quality management for next-generation mobile Internet services, this paper presents a ready-to-deploy quality assessment concept for the impact of the network on the performance of mobile services. We consider the Throughput Utility Function (TUF) as a special case of the Network Utility Function (NUF). These functions combine the observed network utility at the inlet and the outlet of a mobile network. NUF and TUF capture the damping effect of the network onto user-perceived quality from an end-to-end perspective. As opposed to incomprehensible QoS parameters such as delay and loss, the NUF is highly intuitive due to its mapping to a simple value between 0 and 100 %. We demonstrate the capabilities of the proposed TUF by measurements of applicationperceived throughput conducted in mobile networks.}, address = {Department of Computer Science}, author = {Fiedler, Markus and Tutschku, Kurt and Chevul, Stefan and Isaksson, Lennart and Binzenhöfer, Andreas}, keywords = {myown}, month = 11, number = 375, title = {The Throughput Utility Function: Assessing Network Impact on Mobile Services.}, type = {Technical Report}, year = 2005 }
• 
  Hoßfeld, Tobias ; Binzenhöfer, Andreas ; Schlosser, Daniel ; Eger, Kolja ; Oberender, Jend ; Dedinski, Ivan ; Kunzmann, Gerald: Towards Efficient Simulation of Large Scale P2P Networks. ( Nr. 371). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The algorithms and methods of the Peer-to-Peer (P2P) technology are often applied to networks and services with a demand for scalability. In contrast to traditional client/server architectures, an arbitrary large number of users, called peers, may participate in the network and use the service without losing any performance. In order to evaluate quantitatively and qualitatively such P2P services and their corresponding networks, different possibilities like analytical apporaches or simulative techniques can be used to improve the implementation of a simulation in general. This task is even more important for large scale P2P networks due to the number of peers, the state space of the P2P network, and the interactions and relationships between peers and states. The goal of this work is to show how large scale P2P networks can be efficiently evaluated. Methods are demonstrated how to avoid problems occuring in simulations of P2P services. Efficient data structures are required to deal with a large number of events, e.g. the application of a calendar queue for the simulation of a Kademlia-based P2P network, or the priority queue management to simulate eDonkey networks. In order to speed up computational time the simulation has to be implemented in an efficient way, asking for sophisticated programming. This can be achieved for example by using parallel simulation techniques which utilize the distribution and autonomy of the peers in the network. Appropriate levels of abstraction and models for different application scenarios also improve the computational time for simulations of large scale P2P networks. An example is the simulation of throughput and round trip times in networks. We investigate a BitTorrent network on packet level, thereby, all details on the different layers are taken into account enabling us to study cross-layer interactions. Next, we take a look on P2P network for signalling in voice/video over IP systems. In this context, the round trip time is crucial for the performance of the system. The packet layer and its most important characteristics are modeled in order to decrease memory consumption and computational power. Finally, an eDonkey network in a mobile telecommunication system is investigated. In that case we can neglect simulating packets and instead use a stream oriented approach for modeling the transmission of data.

  @techreport{TR371, abstract = {The algorithms and methods of the Peer-to-Peer (P2P) technology are often applied to networks and services with a demand for scalability. In contrast to traditional client/server architectures, an arbitrary large number of users, called peers, may participate in the network and use the service without losing any performance. In order to evaluate quantitatively and qualitatively such P2P services and their corresponding networks, different possibilities like analytical apporaches or simulative techniques can be used to improve the implementation of a simulation in general. This task is even more important for large scale P2P networks due to the number of peers, the state space of the P2P network, and the interactions and relationships between peers and states. The goal of this work is to show how large scale P2P networks can be efficiently evaluated. Methods are demonstrated how to avoid problems occuring in simulations of P2P services. Efficient data structures are required to deal with a large number of events, e.g. the application of a calendar queue for the simulation of a Kademlia-based P2P network, or the priority queue management to simulate eDonkey networks. In order to speed up computational time the simulation has to be implemented in an efficient way, asking for sophisticated programming. This can be achieved for example by using parallel simulation techniques which utilize the distribution and autonomy of the peers in the network. Appropriate levels of abstraction and models for different application scenarios also improve the computational time for simulations of large scale P2P networks. An example is the simulation of throughput and round trip times in networks. We investigate a BitTorrent network on packet level, thereby, all details on the different layers are taken into account enabling us to study cross-layer interactions. Next, we take a look on P2P network for signalling in voice/video over IP systems. In this context, the round trip time is crucial for the performance of the system. The packet layer and its most important characteristics are modeled in order to decrease memory consumption and computational power. Finally, an eDonkey network in a mobile telecommunication system is investigated. In that case we can neglect simulating packets and instead use a stream oriented approach for modeling the transmission of data.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Binzenhöfer, Andreas and Schlosser, Daniel and Eger, Kolja and Oberender, Jend and Dedinski, Ivan and Kunzmann, Gerald}, keywords = {myown}, month = 10, number = 371, title = {Towards Efficient Simulation of Large Scale P2P Networks.}, type = {Technical Report}, year = 2005 }
• 
  Hoßfeld, Tobias ; Oechsner, Simon ; Tutschku, Kurt ; Andersen, Frank-Uwe: Evaluation of a Pastry-based P2P Overlay for Supporting Vertical Handover. ( Nr. 368). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Vertical handovers (VHO) are expected to be a key feature in Beyond 3G (B3G) networks. This paper presents and evaluates a Pastry-based P2P overlay network for supporting vertical handover in B3G networks. The P2P overlay is used to quickly locate attachment points (APs) for mobile entities and to retrieve rapidly the configuration and coverage information of these APs. The advantage of the P2P-based solution is its distributed nature, its scalability, and its self-organizing capability. The performance of the P2P-based VHO support architecture is evaluated in terms of the search time for APs, the scalability of the algorithm, and for homogenous and heterogeneous network layouts. In addition, the solution is compared with the conventional client-server approach.

  @techreport{TR368, abstract = {Vertical handovers (VHO) are expected to be a key feature in Beyond 3G (B3G) networks. This paper presents and evaluates a Pastry-based P2P overlay network for supporting vertical handover in B3G networks. The P2P overlay is used to quickly locate attachment points (APs) for mobile entities and to retrieve rapidly the configuration and coverage information of these APs. The advantage of the P2P-based solution is its distributed nature, its scalability, and its self-organizing capability. The performance of the P2P-based VHO support architecture is evaluated in terms of the search time for APs, the scalability of the algorithm, and for homogenous and heterogeneous network layouts. In addition, the solution is compared with the conventional client-server approach.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Oechsner, Simon and Tutschku, Kurt and Andersen, Frank-Uwe}, keywords = {myown}, month = 10, number = 368, title = {Evaluation of a Pastry-based P2P Overlay for Supporting Vertical Handover.}, type = {Technical Report}, year = 2005 }
• 
  Meister, D.: The complexity of problems concerning matrix powers and the numbers of paths in a graph. ( Nr. 369). Department of Computer Science, 2005
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR369, address = {Department of Computer Science}, author = {Meister, D.}, keywords = {myown}, month = 10, number = 369, title = {The complexity of problems concerning matrix powers and the numbers of paths in a graph.}, type = {Technical Report}, year = 2005 }
• 
  Oechsner, Simon ; Hoßfeld, Tobias ; Tutschku, Kurt ; Andersen, Frank-Uwe ; Caviglione, L.: Using Kademlia for the Configuration of B3G Radio Access Nodes. ( Nr. 370). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Configuration and management of radio access nodes in Beyond 3G (B3G) networks such as NodeBs, Wireless LAN or WIMAX access points is a complex task that consumes a high amount of resources. Most configuration changes have to be done by an operator, especially when it comes to the adaption of a node to its environment, i.e., the cells surrounding its own. This is an expensive and inflexible method. Moreover, the required manual interference hampers the adaptivity of B3G networks towards topology changes. In this work, we present an architecture that allows for the detection of neighboring cells, thereby enabling an easy or even autonomic configuration of the access nodes. In addition to this, the presented Kademlia-based overlay network enables the storage of information needed for network management, such as configuration data or performance measures.

  @techreport{TR370, abstract = {Configuration and management of radio access nodes in Beyond 3G (B3G) networks such as NodeBs, Wireless LAN or WIMAX access points is a complex task that consumes a high amount of resources. Most configuration changes have to be done by an operator, especially when it comes to the adaption of a node to its environment, i.e., the cells surrounding its own. This is an expensive and inflexible method. Moreover, the required manual interference hampers the adaptivity of B3G networks towards topology changes. In this work, we present an architecture that allows for the detection of neighboring cells, thereby enabling an easy or even autonomic configuration of the access nodes. In addition to this, the presented Kademlia-based overlay network enables the storage of information needed for network management, such as configuration data or performance measures.}, address = {Department of Computer Science}, author = {Oechsner, Simon and Hoßfeld, Tobias and Tutschku, Kurt and Andersen, Frank-Uwe and Caviglione, L.}, keywords = {myown}, month = 10, number = 370, title = {Using Kademlia for the Configuration of B3G Radio Access Nodes.}, type = {Technical Report}, year = 2005 }
• 
  Hoßfeld, Tobias ; Oechsner, Simon ; Tutschku, Kurt ; Andersen, Frank-Uwe ; Caviglione, L.: Supporting Vertical Handover by Using a Pastry Peer-to-Peer Overlay Network. ( Nr. 367). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Vertical handovers (VHO) are expected to be a key feature in Beyond 3G (B3G) networks. This paper presents a Pastry-based P2P overlay network for supporting vertical handover in B3G networks. The P2P overlay is used to quickly locate attachment points (APs) for mobile entities and to rapidly retrieve the configuration and coverage information of these APs. The advantage of the P2P-based solution is its distributed nature, its scalability, and its self-organizing capability.

  @techreport{TR367, abstract = {Vertical handovers (VHO) are expected to be a key feature in Beyond 3G (B3G) networks. This paper presents a Pastry-based P2P overlay network for supporting vertical handover in B3G networks. The P2P overlay is used to quickly locate attachment points (APs) for mobile entities and to rapidly retrieve the configuration and coverage information of these APs. The advantage of the P2P-based solution is its distributed nature, its scalability, and its self-organizing capability.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Oechsner, Simon and Tutschku, Kurt and Andersen, Frank-Uwe and Caviglione, L.}, keywords = {myown}, month = {09}, number = 367, title = {Supporting Vertical Handover by Using a Pastry Peer-to-Peer Overlay Network.}, type = {Technical Report}, year = 2005 }
• 
  Hoßfeld, Tobias ; Leibnitz, Kenji ; Wakamiya, Naoki ; Murata, Masayuki: Impact of Interferers on the Epidemic Diffusion in Peer-to-Peer File-Sharing Networks. ( Nr. 366). Department of Computer Science, 2005
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we propose an analytical model for file diffusion in a peer-to-peer (P2P) file-sharing network based on biological epidemics. During the downloading process, the peer shares the downloaded parts of the file and, thus, contributes to distributing it in the network. This behavior is similar to the spreading of epidemic diseases which is a well researched subject in mathematical biology. With our model we investigate the dynamics of file diffusion focusing on the effects of inhibiting influences, e.g. fake or corrupted files.

  @techreport{TR366, abstract = {In this paper we propose an analytical model for file diffusion in a peer-to-peer (P2P) file-sharing network based on biological epidemics. During the downloading process, the peer shares the downloaded parts of the file and, thus, contributes to distributing it in the network. This behavior is similar to the spreading of epidemic diseases which is a well researched subject in mathematical biology. With our model we investigate the dynamics of file diffusion focusing on the effects of inhibiting influences, e.g. fake or corrupted files.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Leibnitz, Kenji and Wakamiya, Naoki and Murata, Masayuki}, keywords = {myown}, month = {08}, number = 366, title = {Impact of Interferers on the Epidemic Diffusion in Peer-to-Peer File-Sharing Networks.}, type = {Technical Report}, year = 2005 }

• 
  Böhler, Elmar ; Glaßer, Christian ; Schwarz, Bernhard ; Wagner, Klaus W.: Generation Problems. ( Nr. 329). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR329, address = {Department of Computer Science}, author = {Böhler, Elmar and Glaßer, Christian and Schwarz, Bernhard and Wagner, Klaus W.}, keywords = {myown}, month = {04}, number = 329, title = {Generation Problems.}, type = {Technical Report}, year = 2004 }
• 
  Meister, D.: A complete characterisation of minimal triangulations of co-square-free graphs. ( Nr. 328). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR328, address = {Department of Computer Science}, author = {Meister, D.}, keywords = {myown}, month = {03}, number = 328, title = {A complete characterisation of minimal triangulations of co-square-free graphs.}, type = {Technical Report}, year = 2004 }
• 
  Böhler, Elmar ; Creignou, N. ; Reith, Steffen ; Vollmer, Heribert: Playing with Boolean Blocks: Post’s Lattice with Applications to Complexity Theory. ( Nr. 317). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR317, address = {Department of Computer Science}, author = {Böhler, Elmar and Creignou, N. and Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {02}, number = 317, title = {Playing with Boolean Blocks: Post's Lattice with Applications to Complexity Theory.}, type = {Technical Report}, year = 2004 }
• 
  Menth, Michael ; Milbrandt, Jens ; Oechsner, Simon: Experience Based Admission Control (EBAC). ( Nr. 325). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Classical admission control approaches take either descriptor or measurement based information about the traffic into account without relating them to each other. We propose a experience-based AC (EBAC) which uses an empirical percentile of the effective reservation utilization to determine a suitable overbooking factor. In this paper, we show the impact of different measurement time scale resolutions and different quantiles on the performance of the system. We propose aging mechanisms for statistic collection to make the system adaptive to traffic mixes that change over time. We illustrate their effectiveness by simulation results.

  @techreport{TR325, abstract = {Classical admission control approaches take either descriptor or measurement based information about the traffic into account without relating them to each other. We propose a experience-based AC (EBAC) which uses an empirical percentile of the effective reservation utilization to determine a suitable overbooking factor. In this paper, we show the impact of different measurement time scale resolutions and different quantiles on the performance of the system. We propose aging mechanisms for statistic collection to make the system adaptive to traffic mixes that change over time. We illustrate their effectiveness by simulation results.}, address = {Department of Computer Science}, author = {Menth, Michael and Milbrandt, Jens and Oechsner, Simon}, keywords = {myown}, month = {02}, number = 325, title = {Experience Based Admission Control (EBAC).}, type = {Technical Report}, year = 2004 }
• 
  Menth, Michael: A Framework for Modelling and Solving Discrete Finite Markov Chains. ( Nr. 326). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Discrete time Markov chains (DTMCs) are commonly described by a state transition matrix that contains sufficient information to figure out the stationary state distribution of the Markov model. In this work, we propose recursive stochastic equations as an alternative description that clearly separates the functional behavior of the model from its random influences that determine the state transition matrix. For the computation of the stationary state distribution, several optimization methods are proposed that take partly advantage of the new specification scheme and that can be applied both to aperiodic and periodic Markov chains. We have written a compiler that converts the recursive equations with all optimization steps in a numerical program to evaluate even large and multi-dimensional Markov models in a short time.

  @techreport{TR326, abstract = {Discrete time Markov chains (DTMCs) are commonly described by a state transition matrix that contains sufficient information to figure out the stationary state distribution of the Markov model. In this work, we propose recursive stochastic equations as an alternative description that clearly separates the functional behavior of the model from its random influences that determine the state transition matrix. For the computation of the stationary state distribution, several optimization methods are proposed that take partly advantage of the new specification scheme and that can be applied both to aperiodic and periodic Markov chains. We have written a compiler that converts the recursive equations with all optimization steps in a numerical program to evaluate even large and multi-dimensional Markov models in a short time.}, address = {Department of Computer Science}, author = {Menth, Michael}, keywords = {myown}, month = {02}, number = 326, title = {A Framework for Modelling and Solving Discrete Finite Markov Chains.}, type = {Technical Report}, year = 2004 }
• 
  Menth, Michael ; Milbrandt, Jens ; Zeiger, Florian: Elastic Token Bucket - A Traffic Characterization for Time-Limited Bursty Traffic. ( Nr. 324). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we present the Elastic Token Bucket (ETB) as a dynamic traffic characterization for traffic shaping purposes, i.e. for traffic policing and spacing. We describe the ETB and study the impact of its parameters on the resulting packet delay and maximum throughput. In contrast to simple Constant Bit Rate (CBR) or Token Bucket (TB) based solutions, economy of scale can be achieved regarding queuing time and required buffer space when many ETB-regulated traffic sources are multiplexed.

  @techreport{TR324, abstract = {In this paper, we present the Elastic Token Bucket (ETB) as a dynamic traffic characterization for traffic shaping purposes, i.e. for traffic policing and spacing. We describe the ETB and study the impact of its parameters on the resulting packet delay and maximum throughput. In contrast to simple Constant Bit Rate (CBR) or Token Bucket (TB) based solutions, economy of scale can be achieved regarding queuing time and required buffer space when many ETB-regulated traffic sources are multiplexed.}, address = {Department of Computer Science}, author = {Menth, Michael and Milbrandt, Jens and Zeiger, Florian}, keywords = {myown}, month = {02}, number = 324, title = {Elastic Token Bucket - A Traffic Characterization for Time-Limited Bursty Traffic.}, type = {Technical Report}, year = 2004 }
• 
  Martin, Ruediger ; Menth, Michael ; Phan-Gia, V.: Performance of TCP/IP with MEDF Scheduling. ( Nr. 323). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  To achieve Quality of Service in next generation networks, DiffServ implements appropriate Per Hop Behavior (PHB) for service differentiation. Different flow classes compete for buffer space and forwarding speed in the routers. This is influenced by buffer management and packet scheduling. We examine space priority mechanisms for buffer management like Full Buffer Sharing (FBS), Buffer Sharing with Space Priority (BSSP), and Random Early Detection (RED) gateways and time priority mechanisms for packet scheduling like First In First Out (FIFO), Static Priority (SP) and Modified Earliest Deadline First (MEDF). In particular, we focus on the characteristics of MEDF in TCP/IP networks. Our performance study reveals that MEDF is an attractive mechanism to achieve service differentiation for TCP flows already in presence of low and medium overload. Other mechanisms appear less adequate. RED, for instance, is only effective in extremely high overload situations.

  @techreport{TR323, abstract = {To achieve Quality of Service in next generation networks, DiffServ implements appropriate Per Hop Behavior (PHB) for service differentiation. Different flow classes compete for buffer space and forwarding speed in the routers. This is influenced by buffer management and packet scheduling. We examine space priority mechanisms for buffer management like Full Buffer Sharing (FBS), Buffer Sharing with Space Priority (BSSP), and Random Early Detection (RED) gateways and time priority mechanisms for packet scheduling like First In First Out (FIFO), Static Priority (SP) and Modified Earliest Deadline First (MEDF). In particular, we focus on the characteristics of MEDF in TCP/IP networks. Our performance study reveals that MEDF is an attractive mechanism to achieve service differentiation for TCP flows already in presence of low and medium overload. Other mechanisms appear less adequate. RED, for instance, is only effective in extremely high overload situations.}, address = {Department of Computer Science}, author = {Martin, Ruediger and Menth, Michael and Phan-Gia, V.}, keywords = {myown}, month = {02}, number = 323, title = {Performance of TCP/IP with MEDF Scheduling.}, type = {Technical Report}, year = 2004 }
• 
  Schwarz, Bernhard: The Complexity of Satisfiability Problems over Finite Lattices. ( Nr. 314). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We study the computational complexity of problems defined by formulas over fixed finite lattices. We consider evaluation, satisfiability, tautology, counting, and quantified formulas. It turns out that evaluation and tautology always can be decided in alternating logarithmic time. For satisfiability we obtain the following dichotomy result: If the lattice is distributive, satisfiability is in alternating logarithmic time. Otherwise, it is NP-complete. Counting is #P-complete for every lattice with at least two elements. For quantified formulas over non-distributive lattices we obtain PSPACE-completeness, while the problem is in alternating logarithmic time, if the lattice is distributive.

  @techreport{TR314, abstract = {We study the computational complexity of problems defined by formulas over fixed finite lattices. We consider evaluation, satisfiability, tautology, counting, and quantified formulas. It turns out that evaluation and tautology always can be decided in alternating logarithmic time. For satisfiability we obtain the following dichotomy result: If the lattice is distributive, satisfiability is in alternating logarithmic time. Otherwise, it is NP-complete. Counting is #P-complete for every lattice with at least two elements. For quantified formulas over non-distributive lattices we obtain PSPACE-completeness, while the problem is in alternating logarithmic time, if the lattice is distributive.}, address = {Department of Computer Science}, author = {Schwarz, Bernhard}, keywords = {myown}, month = {01}, number = 314, title = {The Complexity of Satisfiability Problems over Finite Lattices.}, type = {Technical Report}, year = 2004 }
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  Böhler, Elmar ; Creignou, N. ; Reith, Steffen ; Vollmer, Heribert: Playing with Boolean Blocks: Constraint Satisfaction Problems. ( Nr. 318). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR318, address = {Department of Computer Science}, author = {Böhler, Elmar and Creignou, N. and Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {02}, number = 318, title = {Playing with Boolean Blocks: Constraint Satisfaction Problems.}, type = {Technical Report}, year = 2004 }
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  Menth, Michael ; Milbrandt, Jens ; Kopf, St.: Capacity Assignment for NAC Budgets in Resilient Networks. ( Nr. 319). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
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  This paper addresses Quality of Service (QoS) in the presence of network failures. QoS is ensured by Network Admission Control (NAC) mechanisms along virtual tunnels through the network. Their capacity budgets must be set such that the expected traffic can be transported and that unintended overbooking of the physical network capacity is avoided. This paper presents an adaptation for resilient networks, i.e., traffic rerouting is respected in case of local network outages.

  @techreport{TR319, abstract = {This paper addresses Quality of Service (QoS) in the presence of network failures. QoS is ensured by Network Admission Control (NAC) mechanisms along virtual tunnels through the network. Their capacity budgets must be set such that the expected traffic can be transported and that unintended overbooking of the physical network capacity is avoided. This paper presents an adaptation for resilient networks, i.e., traffic rerouting is respected in case of local network outages.}, address = {Department of Computer Science}, author = {Menth, Michael and Milbrandt, Jens and Kopf, St.}, keywords = {myown}, month = {02}, number = 319, title = {Capacity Assignment for NAC Budgets in Resilient Networks.}, type = {Technical Report}, year = 2004 }
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  Menth, Michael ; Reifert, Andreas ; Milbrandt, Jens: Optimization of End-to-End Protection Switching Mechanisms for MPLS Networks. ( Nr. 320). Department of Computer Science, 2004
  • [ Abstract ]
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  • [ URL ]
  In this paper we propose and investigate several end-to-end (e2e) protection switching mechanisms with application in Multiprotocol Label Switching (MPLS) networks. In case of local outages, the traffic of affected paths is switched to other e2e paths. In this case, Quality of Service can only be provided if sufficient extra capacity is available on the backup paths. If backup capacity can be shared among different backup paths, multi-path routing allows for considerable savings regarding this extra capacity. We propose simple e2e backup mechanisms based on multi-path routing and optimize the load balancing by polynomial-time algorithms to minimize the extra capacity. The mechanisms are simple because the multi-paths consist of disjoint paths that are easy to configure and only traffic of failed paths is switched onto backup paths. Our results illustrate that the savings potential depends on the network topology and that 20% additional resources are sufficient for full resilience against all single router and link failures in well designed networks.

  @techreport{TR320, abstract = {In this paper we propose and investigate several end-to-end (e2e) protection switching mechanisms with application in Multiprotocol Label Switching (MPLS) networks. In case of local outages, the traffic of affected paths is switched to other e2e paths. In this case, Quality of Service can only be provided if sufficient extra capacity is available on the backup paths. If backup capacity can be shared among different backup paths, multi-path routing allows for considerable savings regarding this extra capacity. We propose simple e2e backup mechanisms based on multi-path routing and optimize the load balancing by polynomial-time algorithms to minimize the extra capacity. The mechanisms are simple because the multi-paths consist of disjoint paths that are easy to configure and only traffic of failed paths is switched onto backup paths. Our results illustrate that the savings potential depends on the network topology and that 20% additional resources are sufficient for full resilience against all single router and link failures in well designed networks.}, address = {Department of Computer Science}, author = {Menth, Michael and Reifert, Andreas and Milbrandt, Jens}, keywords = {myown}, month = {02}, number = 320, title = {Optimization of End-to-End Protection Switching Mechanisms for MPLS Networks.}, type = {Technical Report}, year = 2004 }
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  Staehle, Dirk ; Mäder, Andreas: An Analytic Model for Deriving the Node-B Transmit Power in Heterogeneous UMTS Networks. ( Nr. 316). Department of Computer Science, 2004
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  @techreport{TR316, address = {Department of Computer Science}, author = {Staehle, Dirk and Mäder, Andreas}, keywords = {myown}, month = {02}, number = 316, title = {An Analytic Model for Deriving the Node-B Transmit Power in Heterogeneous UMTS Networks.}, type = {Technical Report}, year = 2004 }
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  Seipel, Dietmar ; Hanus, M. ; Geske, U. ; Bartenstein, O.: Proceedings of INAP / WLP 2004. ( Nr. 327). Department of Computer Science, 2004
  • [ BibTeX ]
  @techreport{TR327, address = {Department of Computer Science}, author = {Seipel, Dietmar and Hanus, M. and Geske, U. and Bartenstein, O.}, keywords = {myown}, month = {02}, number = 327, title = {Proceedings of INAP / WLP 2004.}, type = {Technical Report}, year = 2004 }
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  Menth, Michael ; Milbrandt, Jens ; Reifert, Andreas: Sensitivity of Backup Capacity Requirements to Traffic Distribution and Resilience Constraints. ( Nr. 322). Department of Computer Science, 2004
  • [ Abstract ]
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  In this work, we present several end-to-end protection switching mechanisms for application in Multiprotocol Label Switching (MPLS). In case of local outages in the network, they deviate the traffic around the failed element over backup paths. They are easy to implement and reduce the additional capacity to maintain the Quality of Service (QoS) on the backup paths. We study the capacity savings of the presented methods for various protection schemes with different traffic matrices. We further test the influence of different resilience constraints such as the set of protected failure scenarios, bandwidth reuse restrictions due to optical communication, and traffic reduction due to failed border routers.

  @techreport{TR322, abstract = {In this work, we present several end-to-end protection switching mechanisms for application in Multiprotocol Label Switching (MPLS). In case of local outages in the network, they deviate the traffic around the failed element over backup paths. They are easy to implement and reduce the additional capacity to maintain the Quality of Service (QoS) on the backup paths. We study the capacity savings of the presented methods for various protection schemes with different traffic matrices. We further test the influence of different resilience constraints such as the set of protected failure scenarios, bandwidth reuse restrictions due to optical communication, and traffic reduction due to failed border routers.}, address = {Department of Computer Science}, author = {Menth, Michael and Milbrandt, Jens and Reifert, Andreas}, keywords = {myown}, month = {02}, number = 322, title = {Sensitivity of Backup Capacity Requirements to Traffic Distribution and Resilience Constraints.}, type = {Technical Report}, year = 2004 }
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  Glaßer, Christian: Counting with Counterfree Automata. ( Nr. 315). Department of Computer Science, 2004
  • [ Abstract ]
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  We study the power of balanced and unbalanced regular leaf-languages. First, we investigate (i) regular languages that are polylog-time reducible to languages in dot-depth 1/2 and (ii) regular languages that are polylog-time decidable. For both classes we provide - forbidden-pattern characterizations, and - characterizations in terms of regular expressions. Both classes are decidable. The intersection of class (i) with its complement is exactly class (ii). We apply our observations and obtain three consequences. 1. Gap theorems for balanced regular-leaf-language definable classes C and D: - Either C is contained in NP, or C contains coUP. - Either D is contained in P, or D contains UP or coUP. Also we extend both theorems such that no promise classes are involved. Formerly, such gap theorems were known only for the unbalanced approach. 2. Polylog-time reductions can tremendously decrease dot-depth complexity (despite that they cannot count). We exploit a weak type of counting which can be done by counterfree automata, and construct languages of arbitrary dot-depth that are reducible to languages in dot-depth 1/2. 3. Unbalanced starfree leaf-languages can be much stronger than balanced ones. We construct starfree regular languages L(n) such that the balanced leaf-language class of L(n) is contained in NP, but the unbalanced leaf-language class of L(n) contains level n of the unambiguous alternation hierarchy. This demonstrates the power of unbalanced computations.

  @techreport{TR315, abstract = {We study the power of balanced and unbalanced regular leaf-languages. First, we investigate (i) regular languages that are polylog-time reducible to languages in dot-depth 1/2 and (ii) regular languages that are polylog-time decidable. For both classes we provide - forbidden-pattern characterizations, and - characterizations in terms of regular expressions. Both classes are decidable. The intersection of class (i) with its complement is exactly class (ii). We apply our observations and obtain three consequences. 1. Gap theorems for balanced regular-leaf-language definable classes C and D: - Either C is contained in NP, or C contains coUP. - Either D is contained in P, or D contains UP or coUP. Also we extend both theorems such that no promise classes are involved. Formerly, such gap theorems were known only for the unbalanced approach. 2. Polylog-time reductions can tremendously decrease dot-depth complexity (despite that they cannot count). We exploit a weak type of counting which can be done by counterfree automata, and construct languages of arbitrary dot-depth that are reducible to languages in dot-depth 1/2. 3. Unbalanced starfree leaf-languages can be much stronger than balanced ones. We construct starfree regular languages L(n) such that the balanced leaf-language class of L(n) is contained in NP, but the unbalanced leaf-language class of L(n) contains level n of the unambiguous alternation hierarchy. This demonstrates the power of unbalanced computations.}, address = {Department of Computer Science}, author = {Glaßer, Christian}, keywords = {myown}, month = {01}, number = 315, title = {Counting with Counterfree Automata.}, type = {Technical Report}, year = 2004 }
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  Binzenhöfer, Andreas ; Tran-Gia, Phuoc: Delay Analysis of a Chord-based Peer-to-Peer File-Sharing System. ( Nr. 332). Department of Computer Science, 2004
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  In recent years emerging file sharing systems like Gnutella, eDonkey, Overnet, and Kazaa strongly influenced the behaviour of Internet traffic. These platforms employ different peer-to-peer mechanisms, where the application areas are just beginning to shift from undemanding content sharing towards new business case services. Those new requirements brought out new Peer-to-Peer overlay architectures like Chord and Kademlia based on Distributed Hash Tables. The new algorithms satisfy the needs of distributed applications like, e.g. telephone directories supporting ``anywhere'' VoIP. In this paper we investigate the delay of the search process in such a peer-to-peer directory service, where the Chord algorithm is used and the peers are connected through the internet with varying end-to-end transport delay. To guaranty real-time services, quantiles of the search delay are analytically computed. The study also contains the analysis of the scalability of the system, where the impact of the peer population on the search delay characteristic is investigated.

  @techreport{TR332, abstract = {In recent years emerging file sharing systems like Gnutella, eDonkey, Overnet, and Kazaa strongly influenced the behaviour of Internet traffic. These platforms employ different peer-to-peer mechanisms, where the application areas are just beginning to shift from undemanding content sharing towards new business case services. Those new requirements brought out new Peer-to-Peer overlay architectures like Chord and Kademlia based on Distributed Hash Tables. The new algorithms satisfy the needs of distributed applications like, e.g. telephone directories supporting ``anywhere'' VoIP. In this paper we investigate the delay of the search process in such a peer-to-peer directory service, where the Chord algorithm is used and the peers are connected through the internet with varying end-to-end transport delay. To guaranty real-time services, quantiles of the search delay are analytically computed. The study also contains the analysis of the scalability of the system, where the impact of the peer population on the search delay characteristic is investigated.}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Tran-Gia, Phuoc}, keywords = {myown}, month = {04}, number = 332, title = {Delay Analysis of a Chord-based Peer-to-Peer File-Sharing System.}, type = {Technical Report}, year = 2004 }
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  Mäder, Andreas ; Staehle, Dirk: Analytic Modelling of the WCDMA Downlink Capacity in Multi-Service Environments. ( Nr. 330). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR330, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk}, keywords = {myown}, month = {04}, number = 330, title = {Analytic Modelling of the WCDMA Downlink Capacity in Multi-Service Environments.}, type = {Technical Report}, year = 2004 }
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  Menth, Michael ; Reifert, Andreas ; Milbrandt, Jens: Self-Protecting Multipaths - A Simple and Resource-Efficient Protection Switching Mechanism for MPLS Networks. ( Nr. 321). Department of Computer Science, 2004
  • [ Abstract ]
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  In this paper we propose the concept of an end-to-end (e2e) Self-Protecting Multi-Path (SPM) as a protection switching mechanism that may be implemented, e.g., in Multiprotocol Label Switching (MPLS) networks. In case of local outages, resilient networks redirect the traffic from a failed link over an e2e backup path to its destination. In this case, Quality of Service (QoS) can only be provided if sufficient extra capacity is available. If backup capacity can be shared among different backup paths, multi-path routing allows for considerable savings regarding this extra capacity. The SPM consists of disjoint paths that carry the traffic both in normal operation mode and during local outages. If a partial path is affected by a network failure, the traffic is just distributed to the remaining working paths. This structure is easy to configure and the switching to failure mode operation is simple since no signalling is required. Based on analytical results, we show that load balancing of the traffic across the disjoint paths can reduce the required backup capacity significantly. The backup performance depends strongly on the network topology, and the SPM outperforms simple Open Shortest Path First (OSPF) rerouting by far.

  @techreport{TR321, abstract = {In this paper we propose the concept of an end-to-end (e2e) Self-Protecting Multi-Path (SPM) as a protection switching mechanism that may be implemented, e.g., in Multiprotocol Label Switching (MPLS) networks. In case of local outages, resilient networks redirect the traffic from a failed link over an e2e backup path to its destination. In this case, Quality of Service (QoS) can only be provided if sufficient extra capacity is available. If backup capacity can be shared among different backup paths, multi-path routing allows for considerable savings regarding this extra capacity. The SPM consists of disjoint paths that carry the traffic both in normal operation mode and during local outages. If a partial path is affected by a network failure, the traffic is just distributed to the remaining working paths. This structure is easy to configure and the switching to failure mode operation is simple since no signalling is required. Based on analytical results, we show that load balancing of the traffic across the disjoint paths can reduce the required backup capacity significantly. The backup performance depends strongly on the network topology, and the SPM outperforms simple Open Shortest Path First (OSPF) rerouting by far.}, address = {Department of Computer Science}, author = {Menth, Michael and Reifert, Andreas and Milbrandt, Jens}, keywords = {myown}, month = {02}, number = 321, title = {Self-Protecting Multipaths - A Simple and Resource-Efficient Protection Switching Mechanism for MPLS Networks.}, type = {Technical Report}, year = 2004 }
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  Martin, R. ; Menth, Michael: Improving the Timeliness of Rate Measurements. ( Nr. 331). Department of Computer Science, 2004
  • [ Abstract ]
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  Rate measurements are required for many purposes, e.g. for system analysis and modelling or for live systems that react to measurements. For off-line measurement all data is available in advance. Here, time delay between data collection and data analysis is not an issue. On-line measurement, however, measures rates on the fly. Thus, measurement algorithms that provide their output as timely as possible are required. We present three well known algorithms for rate measurement: The Disjoint Intervals method, the Moving Average, and the Exponentially Weighted Moving Average over Disjoint Intervals. We analyze and compare their properties and find problems like heavy time delay or overreaction to random fluctuations. To address these problems, we derive a new algorithm called Time Exponentially Weighted Moving Average as a continuous version of the Exponentially Weighted Moving Average. Finally, we compare this algorithm to the other methods and show that it solves these problems.

  @techreport{TR331, abstract = {Rate measurements are required for many purposes, e.g. for system analysis and modelling or for live systems that react to measurements. For off-line measurement all data is available in advance. Here, time delay between data collection and data analysis is not an issue. On-line measurement, however, measures rates on the fly. Thus, measurement algorithms that provide their output as timely as possible are required. We present three well known algorithms for rate measurement: The Disjoint Intervals method, the Moving Average, and the Exponentially Weighted Moving Average over Disjoint Intervals. We analyze and compare their properties and find problems like heavy time delay or overreaction to random fluctuations. To address these problems, we derive a new algorithm called Time Exponentially Weighted Moving Average as a continuous version of the Exponentially Weighted Moving Average. Finally, we compare this algorithm to the other methods and show that it solves these problems.}, address = {Department of Computer Science}, author = {Martin, R. and Menth, Michael}, keywords = {myown}, month = {04}, number = 331, title = {Improving the Timeliness of Rate Measurements.}, type = {Technical Report}, year = 2004 }
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  Staehle, Dirk: An Analytic Method for Coverage Prediction in the UMTS Radio Network Planning Process. ( Nr. 342). Department of Computer Science, 2004
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  @techreport{TR342, address = {Department of Computer Science}, author = {Staehle, Dirk}, keywords = {myown}, month = 10, number = 342, title = {An Analytic Method for Coverage Prediction in the UMTS Radio Network Planning Process.}, type = {Technical Report}, year = 2004 }
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  Mäder, Andreas ; Staehle, Dirk: Uplink Blocking Probabilities in Heterogenous WCDMA Networks considering Other-Cell Interference. ( Nr. 333). Department of Computer Science, 2004
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  The Univeral Mobile Communication System (UMTS) operates with Wideband Code Division Multiple Access (WCDMA) over the air interface. The uplink capacity in WCDMA strongly depends on the interference situation in the network. The fraction of interference received at a NodeB originating from mobile stations (MS) in foreign cells is called other-cell interference. In the literature, this interference is often approximated by a constant factor or an independent random variable. In this paper, we propose an analytic algorithm to calculate the uplink blocking probabilities in a WCDMA network in order to answer the question how much traffic the network can carry. The algorithm considers the other-cell interference by calculating the mutual generated load between all cells in the network. Furthermore, the system model considers multiple service classes and the effects of imperfect power control.

  @techreport{TR333, abstract = {The Univeral Mobile Communication System (UMTS) operates with Wideband Code Division Multiple Access (WCDMA) over the air interface. The uplink capacity in WCDMA strongly depends on the interference situation in the network. The fraction of interference received at a NodeB originating from mobile stations (MS) in foreign cells is called other-cell interference. In the literature, this interference is often approximated by a constant factor or an independent random variable. In this paper, we propose an analytic algorithm to calculate the uplink blocking probabilities in a WCDMA network in order to answer the question how much traffic the network can carry. The algorithm considers the other-cell interference by calculating the mutual generated load between all cells in the network. Furthermore, the system model considers multiple service classes and the effects of imperfect power control.}, address = {Department of Computer Science}, author = {Mäder, Andreas and Staehle, Dirk}, keywords = {myown}, month = {05}, number = 333, title = {Uplink Blocking Probabilities in Heterogenous WCDMA Networks considering Other-Cell Interference.}, type = {Technical Report}, year = 2004 }
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  Binzenhöfer, Andreas ; Staehle, Dirk ; Henjes, Robert: Estimating the Size of a Chord Ring. ( Nr. 348). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The Chord system is a decentralized peer-to-peer mechanism designed to store and search key/value pairs. The peers in a Chord overlay network are represented on a circle, whereas each peer has to maintain log2(n) neighbors to guarantee a stable overlay structure in the presence of high churn rates. A single peer, however, does not know the current size n of the Chord ring. Choosing a constant value for the number of neighbors does not scale to large networks and involves unnecessary overhead in small networks. In this paper we therefore introduce an estimator for the current size of the Chord ring based on a peer's neighbor- and fingerlists. To be able to rate the goodness of the estimator we show how to calculate the corresponding confidence intervals. Estimating the Size of a Chord Ring

  @techreport{TR348, abstract = {The Chord system is a decentralized peer-to-peer mechanism designed to store and search key/value pairs. The peers in a Chord overlay network are represented on a circle, whereas each peer has to maintain log2(n) neighbors to guarantee a stable overlay structure in the presence of high churn rates. A single peer, however, does not know the current size n of the Chord ring. Choosing a constant value for the number of neighbors does not scale to large networks and involves unnecessary overhead in small networks. In this paper we therefore introduce an estimator for the current size of the Chord ring based on a peer's neighbor- and fingerlists. To be able to rate the goodness of the estimator we show how to calculate the corresponding confidence intervals. Estimating the Size of a Chord Ring}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Staehle, Dirk and Henjes, Robert}, keywords = {myown}, month = 11, number = 348, title = {Estimating the Size of a Chord Ring.}, type = {Technical Report}, year = 2004 }
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  Hoßfeld, Tobias ; Tutschku, Kurt ; Andersen, Frank-Uwe ; de Meer, Hermann ; Oberender, Jend: Simulative Performance Evaluation of a Mobile Peer-to-Peer File-Sharing System. ( Nr. 345). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Peer-to-Peer (P2P) file-sharing has become the killer application in the wired Internet and might also be highly attractive for mobile networks. In particular since UMTS operators are searching for new applications which do both: a) exploit the potential of the UMTS technology and b) motivate the user to adopt the new technology. In this work we are investigating the performance of an eDonkey-based mobile P2P file-sharing system by means of time-dynamic simulation. Mobile networks differ from wireline networks by the limited capacity of the radio link and the mobility of the users. P2P networks, in contrast, are overlays which consider the transport network in an abstract way. In a mobile environment, the question arises, whether the abstraction can be maintained and what will be the performance impact if there is any. We will show in detail how the mobile access technology (GPRS or UMTS), the churn behavior of mobile users, the file size of mobile specific content, and special infrastructure entities, such as a cache peer, influences the performance of the suggested mobile P2P file-sharing service.

  @techreport{TR345, abstract = {Peer-to-Peer (P2P) file-sharing has become the killer application in the wired Internet and might also be highly attractive for mobile networks. In particular since UMTS operators are searching for new applications which do both: a) exploit the potential of the UMTS technology and b) motivate the user to adopt the new technology. In this work we are investigating the performance of an eDonkey-based mobile P2P file-sharing system by means of time-dynamic simulation. Mobile networks differ from wireline networks by the limited capacity of the radio link and the mobility of the users. P2P networks, in contrast, are overlays which consider the transport network in an abstract way. In a mobile environment, the question arises, whether the abstraction can be maintained and what will be the performance impact if there is any. We will show in detail how the mobile access technology (GPRS or UMTS), the churn behavior of mobile users, the file size of mobile specific content, and special infrastructure entities, such as a cache peer, influences the performance of the suggested mobile P2P file-sharing service.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Tutschku, Kurt and Andersen, Frank-Uwe and de Meer, Hermann and Oberender, Jend}, keywords = {myown}, month = 11, number = 345, title = {Simulative Performance Evaluation of a Mobile Peer-to-Peer File-Sharing System.}, type = {Technical Report}, year = 2004 }
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  Hoßfeld, Tobias ; Tutschku, Kurt ; Andersen, Frank-Uwe: Mapping of File-Sharing onto Mobile Environments: Enhancement by UMTS. ( Nr. 343). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Peer-to-Peer (P2P) file-sharing has become the killer application in the Internet with respect to traffic volume which is even surpassing web usage. This characteristic makes P2P commercially attractive to network operators interested in increased traffic. In parallel, the demand for wireless services has caused wireless networks to grow enormously. We assume that P2P file-sharing will be mapped onto mobile environments by its users. This results in a mobile P2P file-sharing service. In this paper, we examine the feasibility of the eDonkey file-sharing service in GPRS and UMTS mobile networks, detect problems of the interaction between P2P and the mobile network, and outline first solutions to overcome them. The goal is the analysis of feasibility for an Internet-based file-sharing application in mobile networks and to provide real-world measurements. The measurements haven been carried out for two German GPRS network providers and, for the first time, for a UMTS network.

  @techreport{TR343, abstract = {Peer-to-Peer (P2P) file-sharing has become the killer application in the Internet with respect to traffic volume which is even surpassing web usage. This characteristic makes P2P commercially attractive to network operators interested in increased traffic. In parallel, the demand for wireless services has caused wireless networks to grow enormously. We assume that P2P file-sharing will be mapped onto mobile environments by its users. This results in a mobile P2P file-sharing service. In this paper, we examine the feasibility of the eDonkey file-sharing service in GPRS and UMTS mobile networks, detect problems of the interaction between P2P and the mobile network, and outline first solutions to overcome them. The goal is the analysis of feasibility for an Internet-based file-sharing application in mobile networks and to provide real-world measurements. The measurements haven been carried out for two German GPRS network providers and, for the first time, for a UMTS network.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Tutschku, Kurt and Andersen, Frank-Uwe}, keywords = {myown}, month = 11, number = 343, title = {Mapping of File-Sharing onto Mobile Environments: Enhancement by UMTS.}, type = {Technical Report}, year = 2004 }
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  Hoßfeld, Tobias ; Mäder, Andreas ; Tutschku, Kurt ; Andersen, Frank-Uwe ; Kappler, Cornelia ; de Meer, Hermann ; Dedinski, I. ; Oberender, Jend: An Architecture Concept for Mobile P2P File Sharing Services. ( Nr. 344). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  P2P file sharing systems account for a high percentage of the traffic volume in the fixed Internet, having exceeded web or email traffic. The increasing availability of mobile data networks such as GPRS and UMTS in conjunction with attractive pricing schemes makes P2P file sharing an interesting application in the mobile context. But the operation of P2P systems in mobile environments encounters several problems, such as a relatively narrow and expensive air interface, highly varying online-states (presence) of the subscribers, a hierarchical network structure, and limited device capabilities. In this paper we present a P2P file-sharing architecture optimized for mobile networks. We discuss the applicability of current P2P resource access and mediation techniques in the context of 2.5G/3G mobile networks. We investigate a mobile P2P architecture that is able to reconcile the decentralized operation of P2P file sharing with the interests of network operators, e.g. traffic control. The architecture is based on the popular eDonkey protcol and is enhanced by additional caching entities, crawlers and proxies. We identify caching parameters and introduce caching strategies for mobile networks. In order to evaluate the system performance, we define a simulation model and present numerical results on the performance of the different strategies.

  @techreport{TR344, abstract = {P2P file sharing systems account for a high percentage of the traffic volume in the fixed Internet, having exceeded web or email traffic. The increasing availability of mobile data networks such as GPRS and UMTS in conjunction with attractive pricing schemes makes P2P file sharing an interesting application in the mobile context. But the operation of P2P systems in mobile environments encounters several problems, such as a relatively narrow and expensive air interface, highly varying online-states (presence) of the subscribers, a hierarchical network structure, and limited device capabilities. In this paper we present a P2P file-sharing architecture optimized for mobile networks. We discuss the applicability of current P2P resource access and mediation techniques in the context of 2.5G/3G mobile networks. We investigate a mobile P2P architecture that is able to reconcile the decentralized operation of P2P file sharing with the interests of network operators, e.g. traffic control. The architecture is based on the popular eDonkey protcol and is enhanced by additional caching entities, crawlers and proxies. We identify caching parameters and introduce caching strategies for mobile networks. In order to evaluate the system performance, we define a simulation model and present numerical results on the performance of the different strategies.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Mäder, Andreas and Tutschku, Kurt and Andersen, Frank-Uwe and Kappler, Cornelia and de Meer, Hermann and Dedinski, I. and Oberender, Jend}, keywords = {myown}, month = 11, number = 344, title = {An Architecture Concept for Mobile P2P File Sharing Services.}, type = {Technical Report}, year = 2004 }
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  Binzenhöfer, Andreas ; Staehle, Dirk ; Henjes, Robert: On the Stability of Chord-based P2P Systems. ( Nr. 347). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The current generation of P2P networks is intended to provide cost-effective alternatives to the traditional client-server architecture. The main goal is to be able to store and retrieve data in a decentralized manner. The challenge in doing so consists in creating a stable overlay network that allows for fast and efficient searches. In this paper we consider the Chord P2P algorithm in this context and analyze its stability and efficiency with stochastic methods. We present realistic probabilities for the problem of a disconnection and confirm the scalability of key lookups.

  @techreport{TR347, abstract = {The current generation of P2P networks is intended to provide cost-effective alternatives to the traditional client-server architecture. The main goal is to be able to store and retrieve data in a decentralized manner. The challenge in doing so consists in creating a stable overlay network that allows for fast and efficient searches. In this paper we consider the Chord P2P algorithm in this context and analyze its stability and efficiency with stochastic methods. We present realistic probabilities for the problem of a disconnection and confirm the scalability of key lookups.}, address = {Department of Computer Science}, author = {Binzenhöfer, Andreas and Staehle, Dirk and Henjes, Robert}, keywords = {myown}, month = 11, number = 347, title = {On the Stability of Chord-based P2P Systems.}, type = {Technical Report}, year = 2004 }
• 
  Pries, Rastin ; Heck, Klaus ; Wirth, Thomas ; Tran-Gia, Phuoc: Robustness Analysis of the Wireless LAN MAC Protocols with QoS Support. ( Nr. 346). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In the past months the deployment of Wireless Local Area Network (WLAN) hot spots has vastly increased in many places world-wide and the IEEE 802.11 standard is playing a more and more important role in future mobile radio networks of the 4th Generation (4G). In order to fulfill the requirements of such 4G networks the WLAN technology has to provide mechanisms for the transport of Quality-of-Service (QoS) traffic. Therefore, service differentiation between the different types of multimedia traffic and best-effort traffic is inevitable. In this paper, we study the robustness of current and future QoS Medium Access Control (MAC) protocols in three different scenarios with overlapping cells.

  @techreport{TR346, abstract = {In the past months the deployment of Wireless Local Area Network (WLAN) hot spots has vastly increased in many places world-wide and the IEEE 802.11 standard is playing a more and more important role in future mobile radio networks of the 4th Generation (4G). In order to fulfill the requirements of such 4G networks the WLAN technology has to provide mechanisms for the transport of Quality-of-Service (QoS) traffic. Therefore, service differentiation between the different types of multimedia traffic and best-effort traffic is inevitable. In this paper, we study the robustness of current and future QoS Medium Access Control (MAC) protocols in three different scenarios with overlapping cells.}, address = {Department of Computer Science}, author = {Pries, Rastin and Heck, Klaus and Wirth, Thomas and Tran-Gia, Phuoc}, keywords = {myown}, month = 11, number = 346, title = {Robustness Analysis of the Wireless LAN MAC Protocols with QoS Support.}, type = {Technical Report}, year = 2004 }
• 
  Selivanov, Victor L.: Some Hierarchies and Reducibilities on Regular Languages. ( Nr. 349). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We discuss some known and introduce some new hierarchies and reducibilities on regular sets. We establish some facts on the corresponding degree structures and relate some reducibilities to the hierarchies of regular sets. As an application, we characterize regular languages whose leaf-language classes (in the balanced model) are contained in the polynomial hierarchy. For any reducibility we try to give some motivation and interesting open questions, in a hope to convince the reader that study of these reducibilities is important for automata theory and computational complexity.

  @techreport{TR349, abstract = {We discuss some known and introduce some new hierarchies and reducibilities on regular sets. We establish some facts on the corresponding degree structures and relate some reducibilities to the hierarchies of regular sets. As an application, we characterize regular languages whose leaf-language classes (in the balanced model) are contained in the polynomial hierarchy. For any reducibility we try to give some motivation and interesting open questions, in a hope to convince the reader that study of these reducibilities is important for automata theory and computational complexity.}, address = {Department of Computer Science}, author = {Selivanov, Victor L.}, keywords = {myown}, month = 12, number = 349, title = {Some Hierarchies and Reducibilities on Regular Languages.}, type = {Technical Report}, year = 2004 }
• 
  Hoßfeld, Tobias ; Staehle, Dirk: A Semi-Analytic Model of the UMTS Downlink Capacity with WWW Traffic on Dedicated Channels. ( Nr. 340). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  One of the main advances of 3G networks like UMTS is the ability to support a large variety of different services. These services are subdivided in two domains, circuit-switched services and packet-switched services. The main application expected for packet-switched services is the browsing of the World Wide Web (WWW). The web traffic is usually described by quite sophisticated source traffic models and the packet arrivals on IP layer are determined by TCP. On the other hand, the planning process for UMTS networks relies on analytic methods or Monte Carlo simulations that assume the number of users to be Poisson distributed. The intention of this work is to examine if it is possible to apply the existing planning methods to web traffic. We are able to show that the Poisson assumption holds for the number of web users that simultaneously transmit over the air interface and that the resulting NodeB transmit power distribution is valid. We use the Monte Carlo simulation technique to evaluate the web capacity of an example UMTS network.

  @techreport{TR340, abstract = {One of the main advances of 3G networks like UMTS is the ability to support a large variety of different services. These services are subdivided in two domains, circuit-switched services and packet-switched services. The main application expected for packet-switched services is the browsing of the World Wide Web (WWW). The web traffic is usually described by quite sophisticated source traffic models and the packet arrivals on IP layer are determined by TCP. On the other hand, the planning process for UMTS networks relies on analytic methods or Monte Carlo simulations that assume the number of users to be Poisson distributed. The intention of this work is to examine if it is possible to apply the existing planning methods to web traffic. We are able to show that the Poisson assumption holds for the number of web users that simultaneously transmit over the air interface and that the resulting NodeB transmit power distribution is valid. We use the Monte Carlo simulation technique to evaluate the web capacity of an example UMTS network.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Staehle, Dirk}, keywords = {myown}, month = {09}, number = 340, title = {A Semi-Analytic Model of the UMTS Downlink Capacity with WWW Traffic on Dedicated Channels.}, type = {Technical Report}, year = 2004 }
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  Hoßfeld, Tobias ; Leibnitz, Kenji ; Pries, Rastin ; Tutschku, Kurt ; Tran-Gia, Phuoc ; Pawlikowski, Krysztof: Information Diffusion in eDonkey Filesharing Networks. ( Nr. 341). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Peer-to-Peer (P2P) applications have become highly popular in today's Internet due to the spread of file sharing platforms such as KaZaa, eDonkey, and BitTorrent. P2P technologies have emerged from disruptive, grey-scale applications to developments of business-cases. In this paper we investigate the diffusion behavior in an eDonkey-like system. We use non-stationary simulation techniques to investigate how a file is spread out in such a P2P environment. The influence of parameters like sharing probability, request arrival rate, or file size on the diffusion process is also investigated.

  @techreport{TR341, abstract = {Peer-to-Peer (P2P) applications have become highly popular in today's Internet due to the spread of file sharing platforms such as KaZaa, eDonkey, and BitTorrent. P2P technologies have emerged from disruptive, grey-scale applications to developments of business-cases. In this paper we investigate the diffusion behavior in an eDonkey-like system. We use non-stationary simulation techniques to investigate how a file is spread out in such a P2P environment. The influence of parameters like sharing probability, request arrival rate, or file size on the diffusion process is also investigated.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Leibnitz, Kenji and Pries, Rastin and Tutschku, Kurt and Tran-Gia, Phuoc and Pawlikowski, Krysztof}, keywords = {myown}, month = {09}, number = 341, title = {Information Diffusion in eDonkey Filesharing Networks.}, type = {Technical Report}, year = 2004 }
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  Pries, Rastin ; Heck, Klaus: Performance Comparison of Handover Mechanisms in Wireless LAN Networks. ( Nr. 339). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The upcoming discussion about integrating theWireless LAN standard into future mobile networks of the 4th Generation (4G) does not only strengthen the importance of the IEEE 802.11 standard family, but neccessitates the support of Qality-of-Service (QoS) even when the user moves between different Access Points. In this paper, we study different Wireless LAN handover mechanisms and their ability to support QoS traffic. Therefore, we implemented the handover mechanisms and additional proposals in a simulation environment and analyzed their ability to support a specific QoS level.

  @techreport{TR339, abstract = {The upcoming discussion about integrating theWireless LAN standard into future mobile networks of the 4th Generation (4G) does not only strengthen the importance of the IEEE 802.11 standard family, but neccessitates the support of Qality-of-Service (QoS) even when the user moves between different Access Points. In this paper, we study different Wireless LAN handover mechanisms and their ability to support QoS traffic. Therefore, we implemented the handover mechanisms and additional proposals in a simulation environment and analyzed their ability to support a specific QoS level.}, address = {Department of Computer Science}, author = {Pries, Rastin and Heck, Klaus}, keywords = {myown}, month = {09}, number = 339, title = {Performance Comparison of Handover Mechanisms in Wireless LAN Networks.}, type = {Technical Report}, year = 2004 }
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  Hoßfeld, Tobias ; Tutschku, Kurt ; Andersen, Frank-Uwe: Mapping of File-Sharing onto Mobile Environments: Feasibility and Performance of eDonkey with GPRS. ( Nr. 338). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Peer-to-Peer (P2P) file-sharing has become a major application in the Internet with respect to traffic volume which is even surpassing web usage. This characteristic makes P2P commercially attractive to network operators interested in increased traffic. In parallel, the demand for wireless services has caused wireless networks to grow enormously. We assume that P2P file-sharing will be mapped onto mobile environments by its users. This results in a mobile P2P file-sharing service, which we denote as mobile P2P. In this paper, we examine the feasibility of the eDonkey file-sharing service in GPRS networks, detect problems of the interaction between P2P and the mobile network, and find solutions to overcome them. Furthermore, this paper measures and analyzes the characteristics of mobile P2P and gives first empirical performance values. Summarizing, the goal is the analysis of feasibility for an Internet-based file-sharing application in a mobile network and to provide first measurements from two real-world networks.

  @techreport{TR338, abstract = {Peer-to-Peer (P2P) file-sharing has become a major application in the Internet with respect to traffic volume which is even surpassing web usage. This characteristic makes P2P commercially attractive to network operators interested in increased traffic. In parallel, the demand for wireless services has caused wireless networks to grow enormously. We assume that P2P file-sharing will be mapped onto mobile environments by its users. This results in a mobile P2P file-sharing service, which we denote as mobile P2P. In this paper, we examine the feasibility of the {eDonkey} file-sharing service in GPRS networks, detect problems of the interaction between P2P and the mobile network, and find solutions to overcome them. Furthermore, this paper measures and analyzes the characteristics of mobile P2P and gives first empirical performance values. Summarizing, the goal is the analysis of feasibility for an Internet-based file-sharing application in a mobile network and to provide first measurements from two real-world networks.}, address = {Department of Computer Science}, author = {Hoßfeld, Tobias and Tutschku, Kurt and Andersen, Frank-Uwe}, keywords = {myown}, month = {08}, number = 338, title = {Mapping of File-Sharing onto Mobile Environments: Feasibility and Performance of eDonkey with GPRS.}, type = {Technical Report}, year = 2004 }
• 
  Wagner, Klaus W.: New BCSV Theorem. ( Nr. 337). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR337, address = {Department of Computer Science}, author = {Wagner, Klaus W.}, keywords = {myown}, month = {08}, number = 337, title = {New BCSV Theorem.}, type = {Technical Report}, year = 2004 }
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  Meister, D.: Membership problems for recurrent systems over the power set of the natural numbers. ( Nr. 336). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR336, address = {Department of Computer Science}, author = {Meister, D.}, keywords = {myown}, month = {06}, number = 336, title = {Membership problems for recurrent systems over the power set of the natural numbers.}, type = {Technical Report}, year = 2004 }
• 
  Travers, Stephen: The Complexity of Membership Problems for Circuits over Sets of Integers. ( Nr. 334). Department of Computer Science, 2004
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR334, address = {Department of Computer Science}, author = {Travers, Stephen}, keywords = {myown}, month = {05}, number = 334, title = {The Complexity of Membership Problems for Circuits over Sets of Integers.}, type = {Technical Report}, year = 2004 }
• 
  Menth, Michael ; Martin, Ruediger: Network Resilience through Multi-Topology Routing. ( Nr. 335). Department of Computer Science, 2004
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we propose the use of multi-topology (MT) routing to achieve fault tolerance against failures of network elements which is also called network resilience. The shortest path routing trees seen from any node is calculated based on the link costs. To provide different routing topologies, an n-dimensional vector of different costs is provided for each link in the network and allows for the calculation of n different routing topologies. We suggest to set these vectors in such a way that any node has a valid path to any other destination in case of a link or router failure. If a router recognizes the outage of an interface, it can switch the traffic from a broken routing topology to a valid routing topology which leads to a very fast reaction time to failures. The failover time can be compared with MPLS solutions that are based on explicit routing. However, we change the implementation of MT routing also in such a way that the new concept is still based on the shortest path convergence mechanism. This offers the potential to maintain the robustness of the Internet routing in case of multiple failures.

  @techreport{TR335, abstract = {In this paper we propose the use of multi-topology (MT) routing to achieve fault tolerance against failures of network elements which is also called network resilience. The shortest path routing trees seen from any node is calculated based on the link costs. To provide different routing topologies, an n-dimensional vector of different costs is provided for each link in the network and allows for the calculation of n different routing topologies. We suggest to set these vectors in such a way that any node has a valid path to any other destination in case of a link or router failure. If a router recognizes the outage of an interface, it can switch the traffic from a broken routing topology to a valid routing topology which leads to a very fast reaction time to failures. The failover time can be compared with MPLS solutions that are based on explicit routing. However, we change the implementation of MT routing also in such a way that the new concept is still based on the shortest path convergence mechanism. This offers the potential to maintain the robustness of the Internet routing in case of multiple failures.}, address = {Department of Computer Science}, author = {Menth, Michael and Martin, Ruediger}, keywords = {myown}, month = {05}, number = 335, title = {Network Resilience through Multi-Topology Routing.}, type = {Technical Report}, year = 2004 }

• 
  Menth, Michael ; Kopf, Stefan ; Charzinski, Joachim: Impact of Network Topology on the Performance of Network Admission Control Methods. ( Nr. 308). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Budget based network admission control (NAC) mechanisms can be categorized into four basically distinct approaches such that most resource management schemes can be classified by them. Since they have different complexity and efficiency, we compare their resource utilization in different networking scenarios. Our results show that the network size, the connectivity, and the internal structure of the network have a significant impact on the resource efficiency. Some NAC approaches can achieve a very high utilization if the offered load is large enough while the performance of others is limited by the network topology. This study does not focus on a specific protocol and it is the first comparative study bringing all NAC approaches together. It is intended to ease the choice of the NAC design in future QoS networks.

  @techreport{TR308, abstract = {Budget based network admission control (NAC) mechanisms can be categorized into four basically distinct approaches such that most resource management schemes can be classified by them. Since they have different complexity and efficiency, we compare their resource utilization in different networking scenarios. Our results show that the network size, the connectivity, and the internal structure of the network have a significant impact on the resource efficiency. Some NAC approaches can achieve a very high utilization if the offered load is large enough while the performance of others is limited by the network topology. This study does not focus on a specific protocol and it is the first comparative study bringing all NAC approaches together. It is intended to ease the choice of the NAC design in future QoS networks.}, address = {Department of Computer Science}, author = {Menth, Michael and Kopf, Stefan and Charzinski, Joachim}, keywords = {myown}, month = {02}, number = 308, title = {Impact of Network Topology on the Performance of Network Admission Control Methods.}, type = {Technical Report}, year = 2003 }
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  Menth, Michael ; Kopf, Stefan ; Charzinski, Joachim: Impact of Resilience Requirements on the Performance of Network Admission Control Methods. ( Nr. 309). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we review four fundamental approaches for different network admission control (NAC). We explain how budgets and links may be dimensioned to keep the blocking probability low. In order to provide resilience against link outages, fast rerouting may be done without involving any further real-time admission control decisions. However, quality of service (QoS) can only be maintained if the network has sufficient backup capacity. We explain appropriate resource dimensioning to satisfy resilience requirements for the different NAC categories. Finally, we show the resource utilization under different NAC mechanisms in networking scenarios with and without resilience requirements and for single- and multi-path routing.

  @techreport{TR309, abstract = {In this paper, we review four fundamental approaches for different network admission control (NAC). We explain how budgets and links may be dimensioned to keep the blocking probability low. In order to provide resilience against link outages, fast rerouting may be done without involving any further real-time admission control decisions. However, quality of service (QoS) can only be maintained if the network has sufficient backup capacity. We explain appropriate resource dimensioning to satisfy resilience requirements for the different NAC categories. Finally, we show the resource utilization under different NAC mechanisms in networking scenarios with and without resilience requirements and for single- and multi-path routing.}, address = {Department of Computer Science}, author = {Menth, Michael and Kopf, Stefan and Charzinski, Joachim}, keywords = {myown}, month = {02}, number = 309, title = {Impact of Resilience Requirements on the Performance of Network Admission Control Methods.}, type = {Technical Report}, year = 2003 }
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  Köhler, Stefan ; Binzenhöfer, Andreas: MPLS Traffic Engineering in OSPF Networks - A combined Approach. ( Nr. 304). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this research report we investigated possibility of combining common network technologies like IGP and MPLS to a Traffic Engineering system. We introduced a fast linear optimization approach for MPLS networks, with a remarkable objective function for TE and compared default, optimized OSPF routing and MPLS TE and to reveal the advantages of MPLS TE. The proposed overlay model consisting of a mix of the OSPF and the MPLS routing scheme reduces the state space and offers simplified configuration for network operators. In general, our routing optimization works well for a given traffic distribution. However, the real internet traffic is not static but varies over time. The quality of our result, applied to varying traffic demands, still has to be investigated. This leads to the question of how to compare two different routing schemes in general and also of how to evaluate the quality of a routing decision. In our work the results were compared mainly by the average and maximum link utilizations of sample networks. To deploy a more general approach to evaluate routing strategies independent from the network would be a fascinating but difficult task. And last but not least, the influence of different traffic classes and QoS would be an interesting point to investigate in detail, as well.

  @techreport{TR304, abstract = {In this research report we investigated possibility of combining common network technologies like IGP and MPLS to a Traffic Engineering system. We introduced a fast linear optimization approach for MPLS networks, with a remarkable objective function for TE and compared default, optimized OSPF routing and MPLS TE and to reveal the advantages of MPLS TE. The proposed overlay model consisting of a mix of the OSPF and the MPLS routing scheme reduces the state space and offers simplified configuration for network operators. In general, our routing optimization works well for a given traffic distribution. However, the real internet traffic is not static but varies over time. The quality of our result, applied to varying traffic demands, still has to be investigated. This leads to the question of how to compare two different routing schemes in general and also of how to evaluate the quality of a routing decision. In our work the results were compared mainly by the average and maximum link utilizations of sample networks. To deploy a more general approach to evaluate routing strategies independent from the network would be a fascinating but difficult task. And last but not least, the influence of different traffic classes and QoS would be an interesting point to investigate in detail, as well.}, address = {Department of Computer Science}, author = {Köhler, Stefan and Binzenhöfer, Andreas}, keywords = {myown}, month = {02}, number = 304, title = {MPLS Traffic Engineering in OSPF Networks - A combined Approach.}, type = {Technical Report}, year = 2003 }
• 
  Menth, Michael ; Kopf, Stefan ; Milbrandt, Jens: Impact of Traffic Matrix and Routing on the Performance of Network Admission Control Methods. ( Nr. 307). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we consider the performance of different network admission control (NAC) methods. In contrast to link admission control (LAC), they limit the traffic within a network by distributed protocols. We introduce four basic budget based NAC approaches such that most resource management schemes can be classified by them from a performance point of view. Since they have different complexity and efficiency, we compare their resource utilization in different networking scenarios. Our results show that the performance is rather independent of the traffic matrix for realistic scenarios while the routing protocol -- single- or multi-path routing -- has a significant impact on the resource efficiency of the IB/EB NAC, ILB NAC, and ILB/ELB NAC. Thus, our investigation helps to understand the performance implications of different resource allocation protocols and eases the design of efficient next generation QoS networks.

  @techreport{TR307, abstract = {In this paper we consider the performance of different network admission control (NAC) methods. In contrast to link admission control (LAC), they limit the traffic within a network by distributed protocols. We introduce four basic budget based NAC approaches such that most resource management schemes can be classified by them from a performance point of view. Since they have different complexity and efficiency, we compare their resource utilization in different networking scenarios. Our results show that the performance is rather independent of the traffic matrix for realistic scenarios while the routing protocol – single- or multi-path routing – has a significant impact on the resource efficiency of the IB/EB NAC, ILB NAC, and ILB/ELB NAC. Thus, our investigation helps to understand the performance implications of different resource allocation protocols and eases the design of efficient next generation QoS networks.}, address = {Department of Computer Science}, author = {Menth, Michael and Kopf, Stefan and Milbrandt, Jens}, keywords = {myown}, month = {02}, number = 307, title = {Impact of Traffic Matrix and Routing on the Performance of Network Admission Control Methods.}, type = {Technical Report}, year = 2003 }
• 
  Menth, Michael ; Gehrsitz, S. ; Milbrandt, Jens: Fair Assignment of Efficient Network Admission Control Budgets. ( Nr. 306). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we review several network admission control (NAC) methods. We explain how the NAC budgets and the required link capacities can be dimensioned based on a traffic matrix, a desired blocking probability, and the routing. The content of this work is the inversion of that process. Based on a traffic matrix, the routing, and given link capacities, the budgets are to be assigned such that their blocking probabilities are as low as possible. We present an algorithm for fair resource sharing and illustrate its effect on a single link. We extend this mechanism to entire networks, such that it is adaptable to all budget-based NAC approaches. The evaluation of our concept shows that it is most effective in real networking scenarios where heterogeneous traffic patterns occur.

  @techreport{TR306, abstract = {In this paper, we review several network admission control (NAC) methods. We explain how the NAC budgets and the required link capacities can be dimensioned based on a traffic matrix, a desired blocking probability, and the routing. The content of this work is the inversion of that process. Based on a traffic matrix, the routing, and given link capacities, the budgets are to be assigned such that their blocking probabilities are as low as possible. We present an algorithm for fair resource sharing and illustrate its effect on a single link. We extend this mechanism to entire networks, such that it is adaptable to all budget-based NAC approaches. The evaluation of our concept shows that it is most effective in real networking scenarios where heterogeneous traffic patterns occur.}, address = {Department of Computer Science}, author = {Menth, Michael and Gehrsitz, S. and Milbrandt, Jens}, keywords = {myown}, month = {02}, number = 306, title = {Fair Assignment of Efficient Network Admission Control Budgets.}, type = {Technical Report}, year = 2003 }
• 
  Menth, Michael ; Kopf, St. ; Milbrandt, J.: A Performance Evaluation Framework for Network Admission Control Methods. ( Nr. 305). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we explain the difference between link and network admission control (LAC, NAC). We introduce three fundamentally different budget based NAC methods that categorize most of today's implemented NAC approaches and establish a performance evaluation framework for their comparison. We propose a capacity dimensioning method for multi-rate traffic and illustrate its sensitivity on a singe link to various traffic characteristics, leading to a suitable definition of blocking probability. An extension of that method to distributed NAC budgets in the network needs the setting of adapted budget blocking probabilities and yields the required link capacities. Finally, we compare the different NAC methods under varying load conditions, using their obtainable resource utilization as performance measure.

  @techreport{TR305, abstract = {In this paper we explain the difference between link and network admission control (LAC, NAC). We introduce three fundamentally different budget based NAC methods that categorize most of today's implemented NAC approaches and establish a performance evaluation framework for their comparison. We propose a capacity dimensioning method for multi-rate traffic and illustrate its sensitivity on a singe link to various traffic characteristics, leading to a suitable definition of blocking probability. An extension of that method to distributed NAC budgets in the network needs the setting of adapted budget blocking probabilities and yields the required link capacities. Finally, we compare the different NAC methods under varying load conditions, using their obtainable resource utilization as performance measure.}, address = {Department of Computer Science}, author = {Menth, Michael and Kopf, St. and Milbrandt, J.}, keywords = {myown}, month = {02}, number = 305, title = {A Performance Evaluation Framework for Network Admission Control Methods.}, type = {Technical Report}, year = 2003 }
• 
  Staehle, Dirk ; Mäder, Andreas: An Analytic Approximation of the Uplink Capacity in a UMTS Network with Heterogeneous Traffic. ( Nr. 310). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The fast computation of blocking probabilities and the resulting capacity is one of the crucial tasks in the planning process of UMTS networks. The admission control in WCDMA networks bases on the momentary interference which includes both own-cell and other-cell interference. Since both interference terms are stochastic values we speak of soft blocking. The number of users in the system is not sufficient for deciding whether to accept a new call or not. Instead, it is blocked with a certain probability depending on the number of users in the system, the activity of the users, and the other cell interference. In this paper we present a time efficient algorithm to compute blocking probabilities in a WCDMA network operating with several services. Assuming Bernoulli activity and modelling the other cell interference as a lognormal random variable the blocking probabilities are computed using an approximation based on the Kaufman-Roberts recursion.

  @techreport{TR310, abstract = {The fast computation of blocking probabilities and the resulting capacity is one of the crucial tasks in the planning process of UMTS networks. The admission control in WCDMA networks bases on the momentary interference which includes both own-cell and other-cell interference. Since both interference terms are stochastic values we speak of soft blocking. The number of users in the system is not sufficient for deciding whether to accept a new call or not. Instead, it is blocked with a certain probability depending on the number of users in the system, the activity of the users, and the other cell interference. In this paper we present a time efficient algorithm to compute blocking probabilities in a WCDMA network operating with several services. Assuming Bernoulli activity and modelling the other cell interference as a lognormal random variable the blocking probabilities are computed using an approximation based on the Kaufman-Roberts recursion.}, address = {Department of Computer Science}, author = {Staehle, Dirk and Mäder, Andreas}, keywords = {myown}, month = {03}, number = 310, title = {An Analytic Approximation of the Uplink Capacity in a UMTS Network with Heterogeneous Traffic.}, type = {Technical Report}, year = 2003 }
• 
  Böhler, Elmar ; Wagner, Klaus W.: Polynomial Time Generation Problems. ( Nr. 312). Department of Computer Science, 2003
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR312, address = {Department of Computer Science}, author = {Böhler, Elmar and Wagner, Klaus W.}, keywords = {myown}, month = {07}, number = 312, title = {Polynomial Time Generation Problems.}, type = {Technical Report}, year = 2003 }
• 
  Böhler, Elmar ; Glaßer, Christian ; Meister, D.: Small Bounded-Error Computations and Completeness. ( Nr. 311). Department of Computer Science, 2003
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR311, address = {Department of Computer Science}, author = {Böhler, Elmar and Glaßer, Christian and Meister, D.}, keywords = {myown}, month = {07}, number = 311, title = {Small Bounded-Error Computations and Completeness.}, type = {Technical Report}, year = 2003 }
• 
  Selivanov, Victor L. ; Wagner, Klaus W.: A Reducibility for the Dot-Depth Hierarchy. ( Nr. 313). Department of Computer Science, 2003
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Hierarchies considered in computability theory and in complexity theory are related to some reducibilities in the sense that levels of the hierarchies are downward closed and have complete sets. In this paper we propose a reducibility having similar relationship to the Brzozowski's dot-depth hierarchy and some its refinements. We prove some basic facts on the corresponding degree structure and discuss relationships of the reducibility to complexity theory (via the leaf-language approach).

  @techreport{TR313, abstract = {Hierarchies considered in computability theory and in complexity theory are related to some reducibilities in the sense that levels of the hierarchies are downward closed and have complete sets. In this paper we propose a reducibility having similar relationship to the Brzozowski's dot-depth hierarchy and some its refinements. We prove some basic facts on the corresponding degree structure and discuss relationships of the reducibility to complexity theory (via the leaf-language approach).}, address = {Department of Computer Science}, author = {Selivanov, Victor L. and Wagner, Klaus W.}, keywords = {myown}, month = 12, number = 313, title = {A Reducibility for the Dot-Depth Hierarchy.}, type = {Technical Report}, year = 2003 }

• 
  Staehle, Dirk ; Leibnitz, Kenji ; Heck, Klaus ; Schröder, Bernd ; Weller, Albert ; Tran-Gia, Phuoc: An Approximation of Othercell Interference Distributions for UMTS Systems using Fixed-Point Equations. ( Nr. 292). Department of Computer Science, 2002
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we present an analytical model for computing the othercell interference distribution in a third generation UMTS network. Our proposed model is based on an iterative calculation of a fixed point equation which describes the interdependency of the interference levels at neighboring base stations. Furthermore, we developed an efficient algorithm based on Lognormal approximations to compute the mean and standard deviation of the othercell interference. We will show that our model is accurate and fast enough to be used in UMTS network planning tools, e.g. T-Mobiles Pegasos.

  @techreport{TR292, abstract = {In this paper we present an analytical model for computing the othercell interference distribution in a third generation UMTS network. Our proposed model is based on an iterative calculation of a fixed point equation which describes the interdependency of the interference levels at neighboring base stations. Furthermore, we developed an efficient algorithm based on Lognormal approximations to compute the mean and standard deviation of the othercell interference. We will show that our model is accurate and fast enough to be used in UMTS network planning tools, e.g. T-Mobiles Pegasos.}, address = {Department of Computer Science}, author = {Staehle, Dirk and Leibnitz, Kenji and Heck, Klaus and Schröder, Bernd and Weller, Albert and Tran-Gia, Phuoc}, keywords = {myown}, month = {01}, number = 292, title = {An Approximation of Othercell Interference Distributions for UMTS Systems using Fixed-Point Equations.}, type = {Technical Report}, year = 2002 }
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  Menth, Michael ; Rose, Oliver: Performance Tradeoffs for Header Compression in MPLS Networks. ( Nr. 291). Department of Computer Science, 2002
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we propose the use of compression techniques for RTP/UDP/IP/MPLS headers in MPLS networks to enable header compression over several IP hops. We consider the transmission of low-bitrate real-time traffic and analytical results illustrate performance tradeoffs regarding network utilization by user data. Header compression reduces the gross rate of low-bitrate streams and increases the transmission capacity of the network for voice traffic by 150%. For circuit switched data services it is important to choose a suited packet size to maximize the performance. This explains why the reduced burstiness by header compression leads also to a more than intuitively expected performance gain on low-bandwidth access links.

  @techreport{TR291, abstract = {In this paper, we propose the use of compression techniques for RTP/UDP/IP/MPLS headers in MPLS networks to enable header compression over several IP hops. We consider the transmission of low-bitrate real-time traffic and analytical results illustrate performance tradeoffs regarding network utilization by user data. Header compression reduces the gross rate of low-bitrate streams and increases the transmission capacity of the network for voice traffic by 150\%. For circuit switched data services it is important to choose a suited packet size to maximize the performance. This explains why the reduced burstiness by header compression leads also to a more than intuitively expected performance gain on low-bandwidth access links.}, address = {Department of Computer Science}, author = {Menth, Michael and Rose, Oliver}, keywords = {myown}, month = {01}, number = 291, title = {Performance Tradeoffs for Header Compression in MPLS Networks.}, type = {Technical Report}, year = 2002 }
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  Böhler, Elmar ; Vollmer, Heribert: Boolean Functions and Post’s Lattice with Applications to Complexity Theory. ( Nr. 290). Department of Computer Science, 2002
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR290, address = {Department of Computer Science}, author = {Böhler, Elmar and Vollmer, Heribert}, keywords = {myown}, month = {01}, number = 290, title = {Boolean Functions and Post's Lattice with Applications to Complexity Theory.}, type = {Technical Report}, year = 2002 }
• 
  Milbrandt, Jens ; Köhler, Stefan ; Staehle, Dirk ; Berry, L.: Decomposition of Large IP Networks for Routing Optimization. ( Nr. 293). Department of Computer Science, 2002
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Optimizing the routing is one of the key issues to enable Quality of Service in todays IP networks. Therefore, the topic of routing optimization has been recently addressed in a number of scientific papers [1, 3, 4, 5]. But until now, all presented proposals have one major drawback in common, namely, the mechanisms are not scaling well with increasing network size. In order to overcome this fundamental problem we propose to use a Divide & Conquer approach as a heuristic to cope with networks that are too large to be handled with conventional optimization methods. In the following a general framework to decompose arbitrary networks is presented, where the network is partitioned in a first step, followed by the conventional optimization of the individual subnetworks and the merging of the partial optimization results to an overall solution.

  @techreport{TR293, abstract = {Optimizing the routing is one of the key issues to enable Quality of Service in todays IP networks. Therefore, the topic of routing optimization has been recently addressed in a number of scientific papers [1, 3, 4, 5]. But until now, all presented proposals have one major drawback in common, namely, the mechanisms are not scaling well with increasing network size. In order to overcome this fundamental problem we propose to use a Divide & Conquer approach as a heuristic to cope with networks that are too large to be handled with conventional optimization methods. In the following a general framework to decompose arbitrary networks is presented, where the network is partitioned in a first step, followed by the conventional optimization of the individual subnetworks and the merging of the partial optimization results to an overall solution.}, address = {Department of Computer Science}, author = {Milbrandt, Jens and Köhler, Stefan and Staehle, Dirk and Berry, L.}, keywords = {myown}, month = {02}, number = 293, title = {Decomposition of Large IP Networks for Routing Optimization.}, type = {Technical Report}, year = 2002 }
• 
  Heck, Klaus ; Staehle, Dirk ; Leibnitz, Kenji: Diversity Effects on the Soft Handover Gain in UMTS networks. ( Nr. 295). Department of Computer Science, 2002
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In cellular Wideband Code Division Multiple Access (WCDMA) networks, interference on the uplink is the limiting factor for the number of users that can be served in a single cell. Thus, interference reduction mechanisms are of significant importance. Soft handover, which is primarily a mechanism for seamless handovers (make before break), also reduces the interference within the cells by exploiting multiple simultaneous connections to lower the transmit power of the mobile stations. In this article we present an analytical model for soft handover where multiple connections between a mobile station and the base stations within reach are taken into account. An approximation of the frame error rate based on the received signal strength in the uplink is provided for 12.2 kbps service. In addition the approach taken to calculate the soft handover gain is described and results are presented.

  @techreport{TR295, abstract = {In cellular Wideband Code Division Multiple Access (WCDMA) networks, interference on the uplink is the limiting factor for the number of users that can be served in a single cell. Thus, interference reduction mechanisms are of significant importance. Soft handover, which is primarily a mechanism for seamless handovers (make before break), also reduces the interference within the cells by exploiting multiple simultaneous connections to lower the transmit power of the mobile stations. In this article we present an analytical model for soft handover where multiple connections between a mobile station and the base stations within reach are taken into account. An approximation of the frame error rate based on the received signal strength in the uplink is provided for 12.2 kbps service. In addition the approach taken to calculate the soft handover gain is described and results are presented.}, address = {Department of Computer Science}, author = {Heck, Klaus and Staehle, Dirk and Leibnitz, Kenji}, keywords = {myown}, month = {04}, number = 295, title = {Diversity Effects on the Soft Handover Gain in UMTS networks.}, type = {Technical Report}, year = 2002 }
• 
  Ebner, Marc: A Parallel Algorithm for Color Constancy. ( Nr. 296). Department of Computer Science, 2002
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR296, address = {Department of Computer Science}, author = {Ebner, Marc}, keywords = {myown}, month = {04}, number = 296, title = {A Parallel Algorithm for Color Constancy.}, type = {Technical Report}, year = 2002 }
• 
  Menth, Michael ; Schmid, Matthias ; Heiß, Herbert ; Reim, Thomas: MEDF - A Simple Scheduling Algorithm for Two Real-Time Transport Service Classes with Application in the UTRAN. ( Nr. 294). Department of Computer Science, 2002
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we consider speech traffic, circuit-switched data (CSD) and packet-switched data (PSD) in the UMTS Terrestrial Radio Access Network (UTRAN). The focus is on the single low-bandwidth link that interconnects the Radio Network Controller (RNC) and the base station (Node B). We show that all traffic on this link has real-time characteristics. But we take advantage of the upper layer protocols and formulate suitable quality of service (QoS) criteria that lead to two different transport service classes (TSC): A stringent TSC for speech traffic and CSD, and a tolerant TSC for PSD. The RNC transmits packets from both TSCs via a single low-bandwidth link to the Node B. Since transmission capacity on this interface is a serious cost factor in the UTRAN, the link utilization should be optimized while respecting the QoS requirements of both TSCs. We propose a modified version (MEDF) of the Earliest Deadline First (EDF) algorithm for that task. It is easy to implement and does not require the knowledge of the traffic mix to set its parameters. The simulation results show its superiority over FIFO, Static Priority (SP), and Weighted Round Robin (WRR) scheduling. The analysis of the waiting time distribution explains why MEDF is better than the other scheduling strategies.

  @techreport{TR294, abstract = {In this paper, we consider speech traffic, circuit-switched data (CSD) and packet-switched data (PSD) in the UMTS Terrestrial Radio Access Network (UTRAN). The focus is on the single low-bandwidth link that interconnects the Radio Network Controller (RNC) and the base station (Node B). We show that all traffic on this link has real-time characteristics. But we take advantage of the upper layer protocols and formulate suitable quality of service (QoS) criteria that lead to two different transport service classes (TSC): A stringent TSC for speech traffic and CSD, and a tolerant TSC for PSD. The RNC transmits packets from both TSCs via a single low-bandwidth link to the Node B. Since transmission capacity on this interface is a serious cost factor in the UTRAN, the link utilization should be optimized while respecting the QoS requirements of both TSCs. We propose a modified version (MEDF) of the Earliest Deadline First (EDF) algorithm for that task. It is easy to implement and does not require the knowledge of the traffic mix to set its parameters. The simulation results show its superiority over FIFO, Static Priority (SP), and Weighted Round Robin (WRR) scheduling. The analysis of the waiting time distribution explains why MEDF is better than the other scheduling strategies.}, address = {Department of Computer Science}, author = {Menth, Michael and Schmid, Matthias and Heiß, Herbert and Reim, Thomas}, keywords = {myown}, month = {02}, number = 294, title = {MEDF - A Simple Scheduling Algorithm for Two Real-Time Transport Service Classes with Application in the UTRAN.}, type = {Technical Report}, year = 2002 }
• 
  Menth, Michael ; Reifert, Andreas: CSPF Routed and Traffic-Driven Construction of LSP Hierarchies. ( Nr. 297). Department of Computer Science, 2002
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The objective of that work is the description and analysis of a network protocol architecture for scalable quality of service (QoS) support. Packets are forwarded like in Differentiated Services (DiffServ) with only little scheduling overhead but admission control is done on a per flow basis at the access and resource allocation is based on reservations. The reservations of individual flows are aggregated recursively to achieve scalability in the core. Multiprotocol Label Switching (MPLS) is applied to reflect these aggregates in label switched path (LSPs) for scalable packet classification. The construction of the LSP hierarchy is traffic-driven and based on explicit routes that are determined by constraint shortest path first (CSPF) routing. We describe the architecture of that system and suggest several mechanisms to operate it also in networking scenarios with heavy signaling load.

  @techreport{TR297, abstract = {The objective of that work is the description and analysis of a network protocol architecture for scalable quality of service (QoS) support. Packets are forwarded like in Differentiated Services (DiffServ) with only little scheduling overhead but admission control is done on a per flow basis at the access and resource allocation is based on reservations. The reservations of individual flows are aggregated recursively to achieve scalability in the core. Multiprotocol Label Switching (MPLS) is applied to reflect these aggregates in label switched path (LSPs) for scalable packet classification. The construction of the LSP hierarchy is traffic-driven and based on explicit routes that are determined by constraint shortest path first (CSPF) routing. We describe the architecture of that system and suggest several mechanisms to operate it also in networking scenarios with heavy signaling load.}, address = {Department of Computer Science}, author = {Menth, Michael and Reifert, Andreas}, keywords = {myown}, month = {06}, number = 297, title = {CSPF Routed and Traffic-Driven Construction of LSP Hierarchies.}, type = {Technical Report}, year = 2002 }
• 
  Eichelberger, Holger: JTransform - A Java Source Code Transformation Framework. ( Nr. 303). Department of Computer Science, 2002
  • [ Abstract ]
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  In this report we describe the architecture and the applications of JTransform, a general Java source code transformation framework, which consists out of a Java parser generating a parse tree and various visitors (transformers, tree evaluators) which produce different kind of outputs. After a brief introduction, an overview of the current and planned applications is given. Then the architecture and implementation of JTransform is described. The fourth chapter gives advise how to use JTransform and how to construct new applications. In the last chapter we outline some details of the existing applications.

  @techreport{TR303, abstract = {In this report we describe the architecture and the applications of JTransform, a general Java source code transformation framework, which consists out of a Java parser generating a parse tree and various visitors (transformers, tree evaluators) which produce different kind of outputs. After a brief introduction, an overview of the current and planned applications is given. Then the architecture and implementation of JTransform is described. The fourth chapter gives advise how to use JTransform and how to construct new applications. In the last chapter we outline some details of the existing applications.}, address = {Department of Computer Science}, author = {Eichelberger, Holger}, keywords = {myown}, month = 12, number = 303, title = {JTransform - A Java Source Code Transformation Framework.}, type = {Technical Report}, year = 2002 }
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  Meister, D.: Recognizing and computing minimal triangulations efficiently. ( Nr. 302). Department of Computer Science, 2002
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR302, address = {Department of Computer Science}, author = {Meister, D.}, keywords = {myown}, month = 12, number = 302, title = {Recognizing and computing minimal triangulations efficiently.}, type = {Technical Report}, year = 2002 }
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  Eichelberger, Holger: Evaluation-Report on the Layout Facilities of UML Tools. ( Nr. 298). Department of Computer Science, 2002
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR298, address = {Department of Computer Science}, author = {Eichelberger, Holger}, keywords = {myown}, month = {07}, number = 298, title = {Evaluation-Report on the Layout Facilities of UML Tools.}, type = {Technical Report}, year = 2002 }
• 
  Obeth, Thomas ; Wolz, Frank ; Kolla, Reiner: Ein multiprozessorfähiger Prozessorcore auf FPGA-Basis. ( Nr. 301). Department of Computer Science, 2002
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Vorgestellt wird ein Ansatz zur Realisierung eines Mikroprozessorcores in Field-Programmable Gate Arrays (FPGAs). Der Prozessorcore wurde für den Einsatz in Single-Chip-Multiprozessorsystemen hinsichtlich Kommunikationsstrukturen für gemeinsamen Speicher und Peripherie, Prozeßverwaltung und -synchronisation, aber auch hinsichtlich Platzverbrauch optimiert.

  @techreport{TR301, abstract = {Vorgestellt wird ein Ansatz zur Realisierung eines Mikroprozessorcores in Field-Programmable Gate Arrays (FPGAs). Der Prozessorcore wurde für den Einsatz in Single-Chip-Multiprozessorsystemen hinsichtlich Kommunikationsstrukturen für gemeinsamen Speicher und Peripherie, Prozeßverwaltung und -synchronisation, aber auch hinsichtlich Platzverbrauch optimiert.}, address = {Department of Computer Science}, author = {Obeth, Thomas and Wolz, Frank and Kolla, Reiner}, keywords = {myown}, month = 12, number = 301, title = {Ein multiprozessorfähiger Prozessorcore auf FPGA-Basis.}, type = {Technical Report}, year = 2002 }
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  Becker, M. ; Heine, Chr. ; Herrler, R. ; Krempels, K.-H.: OntHoS - an Ontology for Hospital Scenarios. ( Nr. 300). Department of Computer Science, 2002
  • [ BibTeX ]
  @techreport{TR300, address = {Department of Computer Science}, author = {Becker, M. and Heine, Chr. and Herrler, R. and Krempels, K.-H.}, keywords = {myown}, month = {09}, number = 300, title = {OntHoS - an Ontology for Hospital Scenarios.}, type = {Technical Report}, year = 2002 }
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  Böhler, Elmar ; Glaßer, Christian ; Meister, D.: Error-bounded probabilistic computations between MA and AM. ( Nr. 299). Department of Computer Science, 2002
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR299, address = {Department of Computer Science}, author = {Böhler, Elmar and Glaßer, Christian and Meister, D.}, keywords = {myown}, month = {08}, number = 299, title = {Error-bounded probabilistic computations between MA and AM.}, type = {Technical Report}, year = 2002 }

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  Leibnitz, Kenji ; Krauss, Armin: Performance Evaluation of Interference and Cell Loading in UMTS Networks. ( Nr. 268). Department of Computer Science, 2001
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Third generation (3G) wireless systems will be operating with Wideband Code Division Multiple Access (WCDMA) over the air interface. This access technology requires a tight power control by the base station on the uplink in order to reduce the interference in the cell and thus increase the capacity. Furthermore, with the introduction of 3G systems, data services will be offered that permit data rates of up to 2 Mbps and varying quality of service requirements in terms of received bit-energy-to-noise ratio. In this paper we will present a performance evaluation of a WCDMA system that is based on a simulation of the power control loops on the uplink in order to investigate the influence of the traffic given by the user distribution and traffic mix on the interference in a cell. Furthermore, we will show that it is possible to use approximations of the power control loops in order to evaluate more complex scenarios.

  @techreport{TR268, abstract = {Third generation (3G) wireless systems will be operating with Wideband Code Division Multiple Access (WCDMA) over the air interface. This access technology requires a tight power control by the base station on the uplink in order to reduce the interference in the cell and thus increase the capacity. Furthermore, with the introduction of 3G systems, data services will be offered that permit data rates of up to 2 Mbps and varying quality of service requirements in terms of received bit-energy-to-noise ratio. In this paper we will present a performance evaluation of a WCDMA system that is based on a simulation of the power control loops on the uplink in order to investigate the influence of the traffic given by the user distribution and traffic mix on the interference in a cell. Furthermore, we will show that it is possible to use approximations of the power control loops in order to evaluate more complex scenarios.}, address = {Department of Computer Science}, author = {Leibnitz, Kenji and Krauss, Armin}, keywords = {myown}, month = {02}, number = 268, title = {Performance Evaluation of Interference and Cell Loading in UMTS Networks.}, type = {Technical Report}, year = 2001 }
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  Menth, Michael: A Scalable Protocol Architecture for End-to-End Signaling and Resource Reservation in IP Networks. ( Nr. 278). Department of Computer Science, 2001
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This paper presents a concept of a scalable networking architecture with end-to-end QoS signaling and resource reservation support. It is a synthesis of both the Differentiated Services and the Integrated Services approach. The approach relies on end-to-end resource reservation and takes advantage of traffic aggregation to reduce the number of reservation states in the router MIBs. Signaling costs are further decreased by making overreservation, i.e. bandwidth efficiency is traded for signaling reduction. We give recommendations to dimension the degree of overreservation and compute the resulting tradeoff analytically. The numerical results show that networks running the proposed architecture can be operated efficiently in spite of overreservation.

  @techreport{TR278, abstract = {This paper presents a concept of a scalable networking architecture with end-to-end QoS signaling and resource reservation support. It is a synthesis of both the Differentiated Services and the Integrated Services approach. The approach relies on end-to-end resource reservation and takes advantage of traffic aggregation to reduce the number of reservation states in the router MIBs. Signaling costs are further decreased by making overreservation, i.e. bandwidth efficiency is traded for signaling reduction. We give recommendations to dimension the degree of overreservation and compute the resulting tradeoff analytically. The numerical results show that networks running the proposed architecture can be operated efficiently in spite of overreservation.}, address = {Department of Computer Science}, author = {Menth, Michael}, keywords = {myown}, month = {07}, number = 278, title = {A Scalable Protocol Architecture for End-to-End Signaling and Resource Reservation in IP Networks.}, type = {Technical Report}, year = 2001 }
• 
  Galota, M. ; Vollmer, Heribert: A Generalization of the Büchi-Elgot-Trakhtenbrot Theorem. ( Nr. 271). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR271, address = {Department of Computer Science}, author = {Galota, M. and Vollmer, Heribert}, keywords = {myown}, month = {02}, number = 271, title = {A Generalization of the Büchi-Elgot-Trakhtenbrot Theorem.}, type = {Technical Report}, year = 2001 }
• 
  Reith, Steffen ; Vollmer, Heribert: Ist P=NP? Einführung in die Theorie der NP-Vollständigkeit. ( Nr. 269). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR269, address = {Department of Computer Science}, author = {Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {02}, number = 269, title = {Ist P=NP? Einführung in die Theorie der NP-Vollständigkeit.}, type = {Technical Report}, year = 2001 }
• 
  Lautemann, C. ; McKenzie, P. ; Schwentick, T. ; Vollmer, Heribert: The Descriptive Complexity Approach to LOGCFL. ( Nr. 273). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR273, address = {Department of Computer Science}, author = {Lautemann, C. and McKenzie, P. and Schwentick, T. and Vollmer, Heribert}, keywords = {myown}, month = {02}, number = 273, title = {The Descriptive Complexity Approach to LOGCFL.}, type = {Technical Report}, year = 2001 }
• 
  Eichelberger, Holger ; von Gudenberg, Jürgen Wolff: UMLscript Sprachspezifikation. ( Nr. 272). Department of Computer Science, 2001
  • [ BibTeX ]
  @techreport{TR272, address = {Department of Computer Science}, author = {Eichelberger, Holger and von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = {02}, number = 272, title = {UMLscript Sprachspezifikation.}, type = {Technical Report}, year = 2001 }
• 
  Selivanov, Victor L.: Relating Automata-theoretic Hierarchies to Complexity-theoretic Hierarchies. ( Nr. 275). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR275, address = {Department of Computer Science}, author = {Selivanov, Victor L.}, keywords = {myown}, month = {03}, number = 275, title = {Relating Automata-theoretic Hierarchies to Complexity-theoretic Hierarchies.}, type = {Technical Report}, year = 2001 }
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  Selivanov, Victor L.: Boolean Hierarchy of Partitions over Reducible Bases. ( Nr. 276). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR276, address = {Department of Computer Science}, author = {Selivanov, Victor L.}, keywords = {myown}, month = {03}, number = 276, title = {Boolean Hierarchy of Partitions over Reducible Bases.}, type = {Technical Report}, year = 2001 }
• 
  Schwentick, T. ; Therien, D. ; Vollmer, Heribert: Partially-ordered Two-way Automata: A New Characterization of DA. ( Nr. 274). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR274, address = {Department of Computer Science}, author = {Schwentick, T. and Therien, D. and Vollmer, Heribert}, keywords = {myown}, month = {03}, number = 274, title = {Partially-ordered Two-way Automata: A New Characterization of DA.}, type = {Technical Report}, year = 2001 }
• 
  Eichelberger, Holger ; Tischler, German ; von Gudenberg, Jürgen Wolff: Comprehensive Graphical Description of the STL. ( Nr. 270). Department of Computer Science, 2001
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this report we show how the specification of the Standard Template Library STL and its implementation can be described by UML diagrams. We define appropriate stereotypes to describe STL concepts like containers, iterators, function objects and global algorithms. For the graphical description of the implementation of the STL we extend the UML metamodel. A full set of diagrams comprehending the functional specification of the STL and its implementation is given.

  @techreport{TR270, abstract = {In this report we show how the specification of the Standard Template Library STL and its implementation can be described by UML diagrams. We define appropriate stereotypes to describe STL concepts like containers, iterators, function objects and global algorithms. For the graphical description of the implementation of the STL we extend the UML metamodel. A full set of diagrams comprehending the functional specification of the STL and its implementation is given.}, address = {Department of Computer Science}, author = {Eichelberger, Holger and Tischler, German and von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = {02}, number = 270, title = {Comprehensive Graphical Description of the STL.}, type = {Technical Report}, year = 2001 }
• 
  Kosub, Sven ; Vollmer, Heribert: 44. Workshop über Komplexitätstheorie, Datenstrukturen und Effiziente Algorithmen. ( Nr. 277). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR277, address = {Department of Computer Science}, author = {Kosub, Sven and Vollmer, Heribert}, keywords = {myown}, month = {07}, number = 277, title = {44. Workshop über Komplexitätstheorie, Datenstrukturen und Effiziente Algorithmen.}, type = {Technical Report}, year = 2001 }
• 
  Grigore, Adrian ; Heffner, Alexander ; Ebner, Marc ; Albert, Jürgen: Evolution virtueller Pflanzen. ( Nr. 280). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR280, address = {Department of Computer Science}, author = {Grigore, Adrian and Heffner, Alexander and Ebner, Marc and Albert, Jürgen}, keywords = {myown}, month = {08}, number = 280, title = {Evolution virtueller Pflanzen.}, type = {Technical Report}, year = 2001 }
• 
  Menth, Michael ; Martin, Rüdiger: Performance Evaluation of the Extensions for Control Message Retransmissions in RSVP. ( Nr. 288). Department of Computer Science, 2001
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Quality of Service for real-time transmission can be achieved by resource reservation in the routers on the data path. In the recent years several protocols and extensions to them have been designed for signaling resource reservation in different ways. This work reviews various protocols that exhibit different signaling concepts. Then we study control message retransmissions for RSVP-like protocols. Numerical results illustrate their behavior in different networking scenarios and quantify the performance gain.

  @techreport{TR288, abstract = {Quality of Service for real-time transmission can be achieved by resource reservation in the routers on the data path. In the recent years several protocols and extensions to them have been designed for signaling resource reservation in different ways. This work reviews various protocols that exhibit different signaling concepts. Then we study control message retransmissions for RSVP-like protocols. Numerical results illustrate their behavior in different networking scenarios and quantify the performance gain.}, address = {Department of Computer Science}, author = {Menth, Michael and Martin, Rüdiger}, keywords = {myown}, month = 11, number = 288, title = {Performance Evaluation of the Extensions for Control Message Retransmissions in RSVP.}, type = {Technical Report}, year = 2001 }
• 
  Lerch, Michael ; Tischler, German ; von Gudenberg, Jürgen Wolff: filib++ -Interval Library and Reference Manual. ( Nr. 279). Department of Computer Science, 2001
  • [ BibTeX ]
  @techreport{TR279, address = {Department of Computer Science}, author = {Lerch, Michael and Tischler, German and von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = {08}, number = 279, title = {filib++ -Interval Library and Reference Manual.}, type = {Technical Report}, year = 2001 }
• 
  Böhler, Elmar: On the Relative Complexity of Post’s Classes. ( Nr. 286). Department of Computer Science, 2001
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR286, address = {Department of Computer Science}, author = {Böhler, Elmar}, keywords = {myown}, month = 11, number = 286, title = {On the Relative Complexity of Post's Classes.}, type = {Technical Report}, year = 2001 }
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  Menth, Michael ; Hauck, N.: A Graph Theoretical Concept for LSP Hierarchies. ( Nr. 287). Department of Computer Science, 2001
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we propose the use of Multiprotocol Label Switching (MPLS) to achieve scalability of resource management that is needed to provide quality of service guarantees in IP networks. We suggest a hierarchical structure of Label Switched Paths (LSPs) to reduce the stored reservation information to a minimum. We lay a graph theoretic foundation for LSP hierarchies and define cost functions that help to find a least cost overlay network in terms of state maintenance. The simulation results demonstrate the efficiency of the concept. The overlay network can be used for configuration of MPLS networks.

  @techreport{TR287, abstract = {In this paper we propose the use of Multiprotocol Label Switching (MPLS) to achieve scalability of resource management that is needed to provide quality of service guarantees in IP networks. We suggest a hierarchical structure of Label Switched Paths (LSPs) to reduce the stored reservation information to a minimum. We lay a graph theoretic foundation for LSP hierarchies and define cost functions that help to find a least cost overlay network in terms of state maintenance. The simulation results demonstrate the efficiency of the concept. The overlay network can be used for configuration of MPLS networks.}, address = {Department of Computer Science}, author = {Menth, Michael and Hauck, N.}, keywords = {myown}, month = 11, number = 287, title = {A Graph Theoretical Concept for LSP Hierarchies.}, type = {Technical Report}, year = 2001 }
• 
  Wolz, Frank ; Kolla, Reiner: Zu Routingflexibilität und Optimierung konfigurierbarer Multiplexer-Netzwerke. ( Nr. 289). Department of Computer Science, 2001
  • [ Abstract ]
  • [ BibTeX ]
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  Diese Arbeit betrachtet die Verdrahtungsflexibilität und die Optimierung konfigurierbarer Multiplexer-Netzwerke (KMN). Nach einer formalen Modellierung der Netzwerke und der Verdrahtungsaufgaben (R-Tasks), werden Eigenschaften hinsichtlich der Flexibilität einer gleichzeitigen Realisierung mehrerer Tasks gezeigt. Schließlich wird die Möglichkeit der Minimierung von KMN nach den Kostenkriterien Platzverbrauch und Signalverzögerung - unter Erhaltung der Verträglichkeit von Taskmengen - untersucht.

  @techreport{TR289, abstract = {Diese Arbeit betrachtet die Verdrahtungsflexibilität und die Optimierung konfigurierbarer Multiplexer-Netzwerke (KMN). Nach einer formalen Modellierung der Netzwerke und der Verdrahtungsaufgaben (R-Tasks), werden Eigenschaften hinsichtlich der Flexibilität einer gleichzeitigen Realisierung mehrerer Tasks gezeigt. Schließlich wird die Möglichkeit der Minimierung von KMN nach den Kostenkriterien Platzverbrauch und Signalverzögerung - unter Erhaltung der Verträglichkeit von Taskmengen - untersucht.}, address = {Department of Computer Science}, author = {Wolz, Frank and Kolla, Reiner}, keywords = {myown}, month = 12, number = 289, title = {Zu Routingflexibilität und Optimierung konfigurierbarer Multiplexer-Netzwerke.}, type = {Technical Report}, year = 2001 }
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  Hieß, S. ; Schäfer, D.: Taskbasierte Positionsverfolgung und Zielsuche autonomer mobiler Roboter. ( Nr. 285). Department of Computer Science, 2001
  • [ BibTeX ]
  @techreport{TR285, address = {Department of Computer Science}, author = {Hieß, S. and Schäfer, D.}, keywords = {myown}, month = 10, number = 285, title = {Taskbasierte Positionsverfolgung und Zielsuche autonomer mobiler Roboter.}, type = {Technical Report}, year = 2001 }
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  Staehle, Dirk ; Leibnitz, Kenji ; Tsipotis, K.: QoS of Internet Access with GPRS. ( Nr. 283). Department of Computer Science, 2001
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper we examine the effects of Internet traffic on the quality of service (QoS) in GPRS wireless networks. With a stochastic source traffic model describing the user behavior, we will derive subjective and objective quality of service measures in terms of WWW downloading time and the transmission bandwidths on TCP and TBF level. Comparing the obtained values with wireline network modems and ISDN yields a slowdown factor which indicates the subjective degradation that the wireless user experiences.

  @techreport{TR283, abstract = {In this paper we examine the effects of Internet traffic on the quality of service (QoS) in GPRS wireless networks. With a stochastic source traffic model describing the user behavior, we will derive subjective and objective quality of service measures in terms of WWW downloading time and the transmission bandwidths on TCP and TBF level. Comparing the obtained values with wireline network modems and ISDN yields a slowdown factor which indicates the subjective degradation that the wireless user experiences.}, address = {Department of Computer Science}, author = {Staehle, Dirk and Leibnitz, Kenji and Tsipotis, K.}, keywords = {myown}, month = 10, number = 283, title = {QoS of Internet Access with GPRS.}, type = {Technical Report}, year = 2001 }
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  Staehle, Dirk ; Leibnitz, Kenji ; Heck, Klaus ; Schröder, Bernd ; Weller, Albert ; Tran-Gia, Phuoc: Analytical Characterization of the Soft Handover Gain in UMTS. ( Nr. 284). Department of Computer Science, 2001
  • [ Abstract ]
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  In this paper we present an analytical model for computing the interference distribution in a third generation UMTS network. Our main focus lies on quantifying the interference reduction due to the combination of the power control signals from multiple base stations when the mobile stations are in soft handover. Our model also includes upper bounds of the mobiles transmission power, i.e. outage is considered. These effects influence the coverage areas and, therefore, play an important role in the planning of UMTS networks.

  @techreport{TR284, abstract = {In this paper we present an analytical model for computing the interference distribution in a third generation UMTS network. Our main focus lies on quantifying the interference reduction due to the combination of the power control signals from multiple base stations when the mobile stations are in soft handover. Our model also includes upper bounds of the mobiles transmission power, i.e. outage is considered. These effects influence the coverage areas and, therefore, play an important role in the planning of UMTS networks.}, address = {Department of Computer Science}, author = {Staehle, Dirk and Leibnitz, Kenji and Heck, Klaus and Schröder, Bernd and Weller, Albert and Tran-Gia, Phuoc}, keywords = {myown}, month = 10, number = 284, title = {Analytical Characterization of the Soft Handover Gain in UMTS.}, type = {Technical Report}, year = 2001 }
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  Böhler, Elmar ; Hemaspaandra, E. ; Reith, Steffen ; Vollmer, Heribert: Equivalence Problems for Boolean Constraint Satisfaction. ( Nr. 282). Department of Computer Science, 2001
  • [ BibTeX ]
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  @techreport{TR282, address = {Department of Computer Science}, author = {Böhler, Elmar and Hemaspaandra, E. and Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {09}, number = 282, title = {Equivalence Problems for Boolean Constraint Satisfaction.}, type = {Technical Report}, year = 2001 }
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  Galota, M. ; Kosub, Sven ; Vollmer, Heribert: Generic Separations and Leaf Languages. ( Nr. 281). Department of Computer Science, 2001
  • [ BibTeX ]
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  @techreport{TR281, address = {Department of Computer Science}, author = {Galota, M. and Kosub, Sven and Vollmer, Heribert}, keywords = {myown}, month = {09}, number = 281, title = {Generic Separations and Leaf Languages.}, type = {Technical Report}, year = 2001 }

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  Glaßer, Christian: Consequences of the Existence of Sparse Sets Hard for NP under a Subclass of Truth-Table Reductions. ( Nr. 245). Department of Computer Science, 2000
  • [ BibTeX ]
  @techreport{TR245, address = {Department of Computer Science}, author = {Glaßer, Christian}, keywords = {myown}, month = {01}, number = 245, title = {Consequences of the Existence of Sparse Sets Hard for NP under a Subclass of Truth-Table Reductions.}, type = {Technical Report}, year = 2000 }
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  Menth, Michael: Carrying Wireless Traffic over IP Using RTP Multiplexing. ( Nr. 247). Department of Computer Science, 2000
  • [ Abstract ]
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  The RTP/UDP/IP protocol suite is in the process of being standardized for multiplexing realtime flows. It aims at reducing header overhead, therefore, it is apt for transporting compressed voice in access links or in the core of mobile communication networks. To provide realtime quality of service, networks require traffic parameters which can be met using a spacer. In this paper, an exact analysis for the RTP/UDP/IP multiplexing scheme including spacing is derived. Influences on the performance of the system are investigated and an optimum value for the multiplexing timer is found. A numerical comparison to the data tunneling method is also presented. Additionally, a leaky bucket description of the multiplexed IP packet output stream is given as an alternative to spacing. The affinity to AAL-2 multiplexing in ATM is pointed out and the fundamental differences with respect to performance are explained.

  @techreport{TR247, abstract = {The RTP/UDP/IP protocol suite is in the process of being standardized for multiplexing realtime flows. It aims at reducing header overhead, therefore, it is apt for transporting compressed voice in access links or in the core of mobile communication networks. To provide realtime quality of service, networks require traffic parameters which can be met using a spacer. In this paper, an exact analysis for the RTP/UDP/IP multiplexing scheme including spacing is derived. Influences on the performance of the system are investigated and an optimum value for the multiplexing timer is found. A numerical comparison to the data tunneling method is also presented. Additionally, a leaky bucket description of the multiplexed IP packet output stream is given as an alternative to spacing. The affinity to AAL-2 multiplexing in ATM is pointed out and the fundamental differences with respect to performance are explained.}, address = {Department of Computer Science}, author = {Menth, Michael}, keywords = {myown}, month = {01}, number = 247, title = {Carrying Wireless Traffic over IP Using RTP Multiplexing.}, type = {Technical Report}, year = 2000 }
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  Vicari, Norbert ; Köhler, Stefan ; Charzinski, J.: The Dependence of Internet User Characteristics on Access Speed. ( Nr. 246). Department of Computer Science, 2000
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  @techreport{TR246, address = {Department of Computer Science}, author = {Vicari, Norbert and Köhler, Stefan and Charzinski, J.}, keywords = {myown}, month = {01}, number = 246, title = {The Dependence of Internet User Characteristics on Access Speed.}, type = {Technical Report}, year = 2000 }
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  McKenzie, P. ; Schwentick, T. ; Therien, D. ; Vollmer, Heribert: The Many Faces of a Translation. ( Nr. 248). Department of Computer Science, 2000
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  @techreport{TR248, address = {Department of Computer Science}, author = {McKenzie, P. and Schwentick, T. and Therien, D. and Vollmer, Heribert}, keywords = {myown}, month = {02}, number = 248, title = {The Many Faces of a Translation.}, type = {Technical Report}, year = 2000 }
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  Wolz, Frank ; Kolla, Reiner: Discrete Floorplanning by Multidimensional Pattern Matching. ( Nr. 249). Department of Computer Science, 2000
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  In this paper, we show a new approach for solving discrete floorplanning problems. Modules to be placed and the target architecture are modelled by periodic graphs. The objective is, to find a valid assignment of module nodes to slot nodes of the target architecture, such that a cost function on the placement will be minimized. We use an algorithm which is abstracted and derived from a traditional pattern matching technique. Our method has time complexity O(m d n^d a), where m is the number of modules to place, d is the dimension of the periodic graph, n is the maximum node count in the target architecture along a dimension and a is the complexity to decide the validity of an assignment.

  @techreport{TR249, abstract = {In this paper, we show a new approach for solving discrete floorplanning problems. Modules to be placed and the target architecture are modelled by periodic graphs. The objective is, to find a valid assignment of module nodes to slot nodes of the target architecture, such that a cost function on the placement will be minimized. We use an algorithm which is abstracted and derived from a traditional pattern matching technique. Our method has time complexity O(m d n^d a), where m is the number of modules to place, d is the dimension of the periodic graph, n is the maximum node count in the target architecture along a dimension and a is the complexity to decide the validity of an assignment.}, address = {Department of Computer Science}, author = {Wolz, Frank and Kolla, Reiner}, keywords = {myown}, month = {02}, number = 249, title = {Discrete Floorplanning by Multidimensional Pattern Matching.}, type = {Technical Report}, year = 2000 }
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  Glaßer, Christian ; Schmitz, Heinz: Concatenation Hierarchies and Forbidden Patterns. ( Nr. 256). Department of Computer Science, 2000
  • [ BibTeX ]
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  @techreport{TR256, address = {Department of Computer Science}, author = {Glaßer, Christian and Schmitz, Heinz}, keywords = {myown}, month = {03}, number = 256, title = {Concatenation Hierarchies and Forbidden Patterns.}, type = {Technical Report}, year = 2000 }
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  Reith, Steffen ; Wagner, Klaus W.: The Complexity of Problems Defined by Boolean Circuits. ( Nr. 255). Department of Computer Science, 2000
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  @techreport{TR255, address = {Department of Computer Science}, author = {Reith, Steffen and Wagner, Klaus W.}, keywords = {myown}, month = {03}, number = 255, title = {The Complexity of Problems Defined by Boolean Circuits.}, type = {Technical Report}, year = 2000 }
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  Glaßer, Christian ; Reith, Steffen ; Vollmer, Heribert: The Complexity of Base Station Positioning in Cellular Networks. ( Nr. 252). Department of Computer Science, 2000
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  @techreport{TR252, address = {Department of Computer Science}, author = {Glaßer, Christian and Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {03}, number = 252, title = {The Complexity of Base Station Positioning in Cellular Networks.}, type = {Technical Report}, year = 2000 }
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  Dümmler, Mathias ; Rose, Oliver: Analysis of the Short Term Impact of Changes in Product Mix. ( Nr. 254). Department of Computer Science, 2000
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  In this paper we use a simulation model of an existing semiconductor fab to study the effects of changes in product mix on fab performance. We observe how short-term increases in wafer starts of a product influence the cycle time and WIP of this product and of the other products. It is examined how the fab recovers from production surges under different dispatch rules and how fab performance is affected if the product mix is changed on a weekly basis. The methodology used to study the transient behavior of a wafer fab using simulation is discussed.

  @techreport{TR254, abstract = {In this paper we use a simulation model of an existing semiconductor fab to study the effects of changes in product mix on fab performance. We observe how short-term increases in wafer starts of a product influence the cycle time and WIP of this product and of the other products. It is examined how the fab recovers from production surges under different dispatch rules and how fab performance is affected if the product mix is changed on a weekly basis. The methodology used to study the transient behavior of a wafer fab using simulation is discussed.}, address = {Department of Computer Science}, author = {Dümmler, Mathias and Rose, Oliver}, keywords = {myown}, month = {03}, number = 254, title = {Analysis of the Short Term Impact of Changes in Product Mix.}, type = {Technical Report}, year = 2000 }
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  Klügl, Franziska ; Puppe, Frank ; und H. Szczerbicka, P. Schwarz: Multiagentsystems and Individual-Based Simulation. ( Nr. 253). Department of Computer Science, 2000
  • [ BibTeX ]
  @techreport{TR253, address = {Department of Computer Science}, author = {Klügl, Franziska and Puppe, Frank and und H. Szczerbicka, P. Schwarz}, keywords = {myown}, month = {03}, number = 253, title = {Multiagentsystems and Individual-Based Simulation.}, type = {Technical Report}, year = 2000 }
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  Rose, Oliver ; Dümmler, Mathias ; Schömig, Alexander: On the Validity of Approximation Formulae for Machine Downtimes. ( Nr. 250). Department of Computer Science, 2000
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  In this paper we investigate how simplifying assumptions in the stochastic modeling of machine downtimes affect the output performance measures. Typically, literature in this area either addresses the estimation of statistical input modeling as such or investigates how sensitive output performance measures of queueing or simulation models are to the choice of stochastic properties of the input distributions. Practitioners, however, often prefer to use simplified formulae for a rough-cut analysis. The results presented clearly show, that unjustified simplification might lead to erroneous results. The immediate conclusion out of the results is that sampling shop-floor data should not only include first order statistics, but also measures that allow to monitor and model the variability of the machinery.

  @techreport{TR250, abstract = {In this paper we investigate how simplifying assumptions in the stochastic modeling of machine downtimes affect the output performance measures. Typically, literature in this area either addresses the estimation of statistical input modeling as such or investigates how sensitive output performance measures of queueing or simulation models are to the choice of stochastic properties of the input distributions. Practitioners, however, often prefer to use simplified formulae for a rough-cut analysis. The results presented clearly show, that unjustified simplification might lead to erroneous results. The immediate conclusion out of the results is that sampling shop-floor data should not only include first order statistics, but also measures that allow to monitor and model the variability of the machinery.}, address = {Department of Computer Science}, author = {Rose, Oliver and Dümmler, Mathias and Schömig, Alexander}, keywords = {myown}, month = {02}, number = 250, title = {On the Validity of Approximation Formulae for Machine Downtimes.}, type = {Technical Report}, year = 2000 }
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  Reith, Steffen ; Vollmer, Heribert: Optimal Satisfiability for Propositional Calculi and Constraint Satisfaction Problems. ( Nr. 251). Department of Computer Science, 2000
  • [ BibTeX ]
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  @techreport{TR251, address = {Department of Computer Science}, author = {Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {03}, number = 251, title = {Optimal Satisfiability for Propositional Calculi and Constraint Satisfaction Problems.}, type = {Technical Report}, year = 2000 }
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  Menth, Michael: The Performance of Multiplexing Voice and Circuit Switched Data in UMTS over IP-Networks. ( Nr. 263). Department of Computer Science, 2000
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  For the transmission of voice traffic in IP-networks the commonly used protocol suite for realtime data transfer in IP-networks leads to a very large protocol overhead for voice data and a poor utilization of the bandwidth for user data. Multiplexing several flows on a route into one IP packet overcomes this problem. In the future UMTS, realtime traffic like voice and circuit switched data are transported over the same network in the wireline part of the UMTS terrestrial access network. The following investigation shows the performance tradeoffs of multiplexing in two different types of quality of service enhanced IP-networks. The analytical results take into account both voice and circuit switched data. Various multiplexing and tunneling schemes are compared.

  @techreport{TR263, abstract = {For the transmission of voice traffic in IP-networks the commonly used protocol suite for realtime data transfer in IP-networks leads to a very large protocol overhead for voice data and a poor utilization of the bandwidth for user data. Multiplexing several flows on a route into one IP packet overcomes this problem. In the future UMTS, realtime traffic like voice and circuit switched data are transported over the same network in the wireline part of the UMTS terrestrial access network. The following investigation shows the performance tradeoffs of multiplexing in two different types of quality of service enhanced IP-networks. The analytical results take into account both voice and circuit switched data. Various multiplexing and tunneling schemes are compared.}, address = {Department of Computer Science}, author = {Menth, Michael}, keywords = {myown}, month = {07}, number = 263, title = {The Performance of Multiplexing Voice and Circuit Switched Data in UMTS over IP-Networks.}, type = {Technical Report}, year = 2000 }
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  Kosub, Sven: Types of Separability. ( Nr. 267). Department of Computer Science, 2000
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR267, address = {Department of Computer Science}, author = {Kosub, Sven}, keywords = {myown}, month = 11, number = 267, title = {Types of Separability.}, type = {Technical Report}, year = 2000 }
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  Kosub, Sven: Boolean Partitions and Projective Closure. ( Nr. 266). Department of Computer Science, 2000
  • [ BibTeX ]
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  @techreport{TR266, address = {Department of Computer Science}, author = {Kosub, Sven}, keywords = {myown}, month = 11, number = 266, title = {Boolean Partitions and Projective Closure.}, type = {Technical Report}, year = 2000 }
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  von Gudenberg, Jürgen Wolff: Multimedia Architectures and Interval Arithmetic. ( Nr. 265). Department of Computer Science, 2000
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  In this paper, we show how to implement interval arithmetic on multimedia architecture extensions. Due to the difficulties that current architectures have with the directed rounding modes the speed-up is rather modest. The study, nevertheless, may be helpful in future design of hardware extensions for interval arithmetic.

  @techreport{TR265, abstract = {In this paper, we show how to implement interval arithmetic on multimedia architecture extensions. Due to the difficulties that current architectures have with the directed rounding modes the speed-up is rather modest. The study, nevertheless, may be helpful in future design of hardware extensions for interval arithmetic.}, address = {Department of Computer Science}, author = {von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = 10, number = 265, title = {Multimedia Architectures and Interval Arithmetic.}, type = {Technical Report}, year = 2000 }
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  Galota, M. ; Glaßer, Christian ; Reith, Steffen ; Vollmer, Heribert: A Polynomial-Time Approximation Scheme for Base Station Positioning in UMTS Networks. ( Nr. 264). Department of Computer Science, 2000
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR264, address = {Department of Computer Science}, author = {Galota, M. and Glaßer, Christian and Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {08}, number = 264, title = {A Polynomial-Time Approximation Scheme for Base Station Positioning in UMTS Networks.}, type = {Technical Report}, year = 2000 }
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  Kosub, Sven: On NP-Partitions over Posets with an Application to Reducing the Set of Solutions of NP Problems. ( Nr. 257). Department of Computer Science, 2000
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR257, address = {Department of Computer Science}, author = {Kosub, Sven}, keywords = {myown}, month = {04}, number = 257, title = {On NP-Partitions over Posets with an Application to Reducing the Set of Solutions of NP Problems.}, type = {Technical Report}, year = 2000 }
• 
  Berry, L. ; Köhler, Stefan ; Staehle, Dirk ; Tran-Gia, Phuoc: Fast heuristics for optimal routing in large IP networks. ( Nr. 262). Department of Computer Science, 2000
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We consider the problem of computing optimal sets of paths between source-destination pairs in large IP networks. Given the traffic demands between the pair of nodes, link capacities and the topological structure of the network we wish to allocate the traffic streams to routes such that either the maximum link utilisation minimized, or the average link utilisation of the network is minimized. An interesting feature of the optimisation is that the set of paths selected, for all pairs, must be constrained to satisfy shortest path principles. Two approaches are developed. The first, based on use of k'th shortest paths, iteratively modifies link costs to achieve the selected objective. The second method seeks to apply network decomposition effectively such that the LP technique of Staehle, Köhler and Kohlhaas [11] may be implemented on each subgraph in an iterative algorithm.

  @techreport{TR262, abstract = {We consider the problem of computing optimal sets of paths between source-destination pairs in large IP networks. Given the traffic demands between the pair of nodes, link capacities and the topological structure of the network we wish to allocate the traffic streams to routes such that either the maximum link utilisation minimized, or the average link utilisation of the network is minimized. An interesting feature of the optimisation is that the set of paths selected, for all pairs, must be constrained to satisfy shortest path principles. Two approaches are developed. The first, based on use of k'th shortest paths, iteratively modifies link costs to achieve the selected objective. The second method seeks to apply network decomposition effectively such that the LP technique of Staehle, Köhler and Kohlhaas [11] may be implemented on each subgraph in an iterative algorithm.}, address = {Department of Computer Science}, author = {Berry, L. and Köhler, Stefan and Staehle, Dirk and Tran-Gia, Phuoc}, keywords = {myown}, month = {07}, number = 262, title = {Fast heuristics for optimal routing in large IP networks.}, type = {Technical Report}, year = 2000 }
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  Köhler, Stefan ; Menth, Michael ; Vicari, Norbert: Analytic Performance Evaluation of the RED Algorithm for QoS in TCP/IP Networks. ( Nr. 259). Department of Computer Science, 2000
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The Random Early Detection algorithm is considered as a promising algorithm for Differentiated Services to cope with feedback oriented traffic like TCP. In this paper, we model the salient features of TCP and RED and evaluate the model using a discrete-time analysis. The novelty of our investigation is the analytic approach to the composed model, i.e., TCP feedback traffic over a RED queue. Deriving not only mean values but also distributions for the performance measures, we obtain insights of the behaviour of TCP under RED.

  @techreport{TR259, abstract = {The Random Early Detection algorithm is considered as a promising algorithm for Differentiated Services to cope with feedback oriented traffic like TCP. In this paper, we model the salient features of TCP and RED and evaluate the model using a discrete-time analysis. The novelty of our investigation is the analytic approach to the composed model, i.e., TCP feedback traffic over a RED queue. Deriving not only mean values but also distributions for the performance measures, we obtain insights of the behaviour of TCP under RED.}, address = {Department of Computer Science}, author = {Köhler, Stefan and Menth, Michael and Vicari, Norbert}, keywords = {myown}, month = {05}, number = 259, title = {Analytic Performance Evaluation of the RED Algorithm for QoS in TCP/IP Networks.}, type = {Technical Report}, year = 2000 }
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  Staehle, Dirk ; Köhler, Stefan ; Kohlhaas, U.: Towards an optimization of the routing parameters for IP networks. ( Nr. 258). Department of Computer Science, 2000
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Routing is one of the key issues in IP networks. However, few methods exist to optimize the routing for a particular network. Most effort is invested to improve the routing protocols itself. In this work a possibility to specify appropriate values for the link costs of a given network with linear programs is presented. The obtained link costs can be directly translated into values suitable for the metrics of the two currently most important routing protocols EIGRP and OSPF in today's Internet. With this method a homogeneous distribution of tra c in IP-based networks can be achieved.

  @techreport{TR258, abstract = {Routing is one of the key issues in IP networks. However, few methods exist to optimize the routing for a particular network. Most effort is invested to improve the routing protocols itself. In this work a possibility to specify appropriate values for the link costs of a given network with linear programs is presented. The obtained link costs can be directly translated into values suitable for the metrics of the two currently most important routing protocols EIGRP and OSPF in today's Internet. With this method a homogeneous distribution of tra c in IP-based networks can be achieved.}, address = {Department of Computer Science}, author = {Staehle, Dirk and Köhler, Stefan and Kohlhaas, U.}, keywords = {myown}, month = {05}, number = 258, title = {Towards an optimization of the routing parameters for IP networks.}, type = {Technical Report}, year = 2000 }
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  Klügl, Franziska: Visuelles Programmieren als Basis einer Modellierumgebung: Eigenschaften, Konzepte, Anforderungen. ( Nr. 260). Department of Computer Science, 2000
  • [ BibTeX ]
  @techreport{TR260, address = {Department of Computer Science}, author = {Klügl, Franziska}, keywords = {myown}, month = {05}, number = 260, title = {Visuelles Programmieren als Basis einer Modellierumgebung: Eigenschaften, Konzepte, Anforderungen.}, type = {Technical Report}, year = 2000 }
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  Staehle, Dirk ; Leibnitz, Kenji ; Tran-Gia, Phuoc: Source Traffic Modeling of Wireless Applications. ( Nr. 261). Department of Computer Science, 2000
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Data applications are expected to play an increasingly important role in the next generation mobile communication services. To plan these networks detailed models of data users with diverse applications are required. The purpose of this study is to provide practically usable traffic models for data users in GPRS networks. We start with a discussion of well-known models in the literature, where the focus is on their applicability in mobile networks. A practical model of mobile HTTP users, based on an extrapolation of WWW users in current wire-line networks, is presented; this model is expected to be accurate enough to be used in simulation studies for network planning purposes. Finally, models for other emerging data applications are also taken into account.

  @techreport{TR261, abstract = {Data applications are expected to play an increasingly important role in the next generation mobile communication services. To plan these networks detailed models of data users with diverse applications are required. The purpose of this study is to provide practically usable traffic models for data users in GPRS networks. We start with a discussion of well-known models in the literature, where the focus is on their applicability in mobile networks. A practical model of mobile HTTP users, based on an extrapolation of WWW users in current wire-line networks, is presented; this model is expected to be accurate enough to be used in simulation studies for network planning purposes. Finally, models for other emerging data applications are also taken into account.}, address = {Department of Computer Science}, author = {Staehle, Dirk and Leibnitz, Kenji and Tran-Gia, Phuoc}, keywords = {myown}, month = {06}, number = 261, title = {Source Traffic Modeling of Wireless Applications.}, type = {Technical Report}, year = 2000 }

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  Peichl, T. ; Vollmer, Heribert: Finite Automata with Generalized Acceptance Criteria. ( Nr. 221). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR221, address = {Department of Computer Science}, author = {Peichl, T. and Vollmer, Heribert}, keywords = {myown}, month = {01}, number = 221, title = {Finite Automata with Generalized Acceptance Criteria.}, type = {Technical Report}, year = 1999 }
• 
  Dümmler, Mathias: Using Simulation and Genetic Algorithms to Improve Cluster Tool Performance. ( Nr. 227). Department of Computer Science, 1999
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we present an approach to generate optimal processing sequences of lots at cluster tools. We consider the problem of sequencing n lots, where each lot can be processed by any of m available cluster tools. The proposed method combines simulation and a genetic algorithm to generate lot sequences. We show that our approach leads to a significant reduction of cycle times at cluster tools.

  @techreport{TR227, abstract = {In this paper, we present an approach to generate optimal processing sequences of lots at cluster tools. We consider the problem of sequencing n lots, where each lot can be processed by any of m available cluster tools. The proposed method combines simulation and a genetic algorithm to generate lot sequences. We show that our approach leads to a significant reduction of cycle times at cluster tools.}, address = {Department of Computer Science}, author = {Dümmler, Mathias}, keywords = {myown}, month = {05}, number = 227, title = {Using Simulation and Genetic Algorithms to Improve Cluster Tool Performance.}, type = {Technical Report}, year = 1999 }
• 
  Schmitz, Heinz: Generalized Deterministic Languages and their Automata: A Characterization of Restricted Temporal Logic. ( Nr. 226). Department of Computer Science, 1999
  • [ BibTeX ]
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  @techreport{TR226, address = {Department of Computer Science}, author = {Schmitz, Heinz}, keywords = {myown}, month = {04}, number = 226, title = {Generalized Deterministic Languages and their Automata: A Characterization of Restricted Temporal Logic.}, type = {Technical Report}, year = 1999 }
• 
  Ehrenberger, U. ; Leibnitz, Kenji: Impact of Clustered Traffic Distributions in CDMA Radio Network Planning. ( Nr. 223). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR223, address = {Department of Computer Science}, author = {Ehrenberger, U. and Leibnitz, Kenji}, keywords = {myown}, month = {03}, number = 223, title = {Impact of Clustered Traffic Distributions in CDMA Radio Network Planning.}, type = {Technical Report}, year = 1999 }
• 
  Vollmer, Heribert: Was leistet die Komplexitätstheorie für die Praxis? ( Nr. 224). Department of Computer Science, 1999
  • [ BibTeX ]
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  @techreport{TR224, address = {Department of Computer Science}, author = {Vollmer, Heribert}, keywords = {myown}, month = {03}, number = 224, title = {Was leistet die Komplexitätstheorie für die Praxis?}, type = {Technical Report}, year = 1999 }
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  Schmitz, Heinz: Some Forbidden Patterns in Automata for Dot-Depth One Languages. ( Nr. 220). Department of Computer Science, 1999
  • [ BibTeX ]
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  @techreport{TR220, address = {Department of Computer Science}, author = {Schmitz, Heinz}, keywords = {myown}, month = {01}, number = 220, title = {Some Forbidden Patterns in Automata for Dot-Depth One Languages.}, type = {Technical Report}, year = 1999 }
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  Reith, Steffen ; Wagner, Klaus W.: The Complexity of Problems Defined by Subclasses of Boolean Functions. ( Nr. 218). Department of Computer Science, 1999
  • [ BibTeX ]
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  @techreport{TR218, address = {Department of Computer Science}, author = {Reith, Steffen and Wagner, Klaus W.}, keywords = {myown}, month = {01}, number = 218, title = {The Complexity of Problems Defined by Subclasses of Boolean Functions.}, type = {Technical Report}, year = 1999 }
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  Vollmer, Heribert: Uniform Characterizations of Complexity Classes. ( Nr. 222). Department of Computer Science, 1999
  • [ BibTeX ]
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  @techreport{TR222, address = {Department of Computer Science}, author = {Vollmer, Heribert}, keywords = {myown}, month = {01}, number = 222, title = {Uniform Characterizations of Complexity Classes.}, type = {Technical Report}, year = 1999 }
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  Glaßer, Christian ; Wechsung, G.: Relativizing Function Classes. ( Nr. 219). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR219, address = {Department of Computer Science}, author = {Glaßer, Christian and Wechsung, G.}, keywords = {myown}, month = {01}, number = 219, title = {Relativizing Function Classes.}, type = {Technical Report}, year = 1999 }
• 
  Kolla, Reiner ; Vodopivec, A. ; von Gudenberg, Jürgen Wolff: The IAX Architecture: Interval Arithmetic Extension. ( Nr. 225). Department of Computer Science, 1999
  • [ Abstract ]
  • [ BibTeX ]
  In this paper we discuss a processor architecture for interval arithmetic. Firstly it is shown that double precision FPUs can cheaply be split to support single precision interval addition/subtraction or multiplication, secondly we propose hardware support for double precision interval arithmetic and compare the effort and performance with software implementations on current architectures.

  @techreport{TR225, abstract = {In this paper we discuss a processor architecture for interval arithmetic. Firstly it is shown that double precision FPUs can cheaply be split to support single precision interval addition/subtraction or multiplication, secondly we propose hardware support for double precision interval arithmetic and compare the effort and performance with software implementations on current architectures.}, address = {Department of Computer Science}, author = {Kolla, Reiner and Vodopivec, A. and von Gudenberg, Jürgen Wolff}, keywords = {myown}, number = 225, title = {The IAX Architecture: Interval Arithmetic Extension.}, type = {Technical Report}, year = 1999 }
• 
  Harris, Richard ; Köhler, Stefan: Possibilities for QoS in Existing Internet Routing Protocols. ( Nr. 228). Department of Computer Science, 1999
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In classical circuit switching networks Quality of Service is an essential aspect which influence the entire network design process, including routing consideration. Due to the efforts to introduce Quality of Service (QoS) into IP-based networks, design routing to support QoS becomes increasingly important, e.g. in such concepts like integrated service and differentiated service IP networks. In this we give an overview of the possibility to introduce QoS in existing routing schemes and give an outlook to new QoS routing protocols currently discussed in the internet community such as the IETF. First of all we give asurvey of different routing algorithms used in unicast Interior Gateway Protocols and Exterior Gateway Protocols. We describe in detail (E)IGRP a proprietary CISCO routing protocol, followed by a short overview of the different aspects for QoS routing protocols in the Internet.

  @techreport{TR228, abstract = {In classical circuit switching networks Quality of Service is an essential aspect which influence the entire network design process, including routing consideration. Due to the efforts to introduce Quality of Service (QoS) into IP-based networks, design routing to support QoS becomes increasingly important, e.g. in such concepts like integrated service and differentiated service IP networks. In this we give an overview of the possibility to introduce QoS in existing routing schemes and give an outlook to new QoS routing protocols currently discussed in the internet community such as the IETF. First of all we give asurvey of different routing algorithms used in unicast Interior Gateway Protocols and Exterior Gateway Protocols. We describe in detail (E)IGRP a proprietary CISCO routing protocol, followed by a short overview of the different aspects for QoS routing protocols in the Internet.}, address = {Department of Computer Science}, author = {Harris, Richard and Köhler, Stefan}, keywords = {myown}, month = {05}, number = 228, title = {Possibilities for QoS in Existing Internet Routing Protocols.}, type = {Technical Report}, year = 1999 }
• 
  Heister, Frank ; Müller, Rainer: An approach for the identification of nonlinear, dynamic processes with Kalman Filter-trained recurrent neural structures. ( Nr. 229). Department of Computer Science, 1999
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this article we demonstrate the identification of a nonlinear, dynamic process with recurrent neural structures. The employed network-structure is a Recurrent Multilayer Perceptron (RMLP), which combines feedforward-- and recurrent architectures. We will show that RMLPs are capable of learning the temporal behavior and characteristic of an arbitrary, nonlinear, dynamic process. Apart from conventional gradient-based algorithms, a sophisticated statistical method has been considered for this challenging task - Global Extended Kalman Filtering (GEKF). This powerful algorithm yields neural structures with a significantly better performance, compared to conventional gradient-based approaches. The new element in this work is the application of the GEKF-Algorithm for recurrent neural structures, which are employed in the identification of nonlinear, dynamic processes. In order to supervise the quality of network-training, appropriate performance-indexes for neural identification are introduced. The distribution of the Moving Average Squared Error (MASE) is employed as an objective optimality-criterion, in order to survey the actual performance of recurrent neural structures during training.

  @techreport{TR229, abstract = {In this article we demonstrate the identification of a nonlinear, dynamic process with recurrent neural structures. The employed network-structure is a Recurrent Multilayer Perceptron (RMLP), which combines feedforward– and recurrent architectures. We will show that RMLPs are capable of learning the temporal behavior and characteristic of an arbitrary, nonlinear, dynamic process. Apart from conventional gradient-based algorithms, a sophisticated statistical method has been considered for this challenging task - Global Extended Kalman Filtering (GEKF). This powerful algorithm yields neural structures with a significantly better performance, compared to conventional gradient-based approaches. The new element in this work is the application of the GEKF-Algorithm for recurrent neural structures, which are employed in the identification of nonlinear, dynamic processes. In order to supervise the quality of network-training, appropriate performance-indexes for neural identification are introduced. The distribution of the Moving Average Squared Error (MASE) is employed as an objective optimality-criterion, in order to survey the actual performance of recurrent neural structures during training.}, address = {Department of Computer Science}, author = {Heister, Frank and Müller, Rainer}, keywords = {myown}, month = {05}, number = 229, title = {An approach for the identification of nonlinear, dynamic processes with Kalman Filter-trained recurrent neural structures.}, type = {Technical Report}, year = 1999 }
• 
  Glaßer, Christian: The Boolean Hierarchy over Dot-Depth 1/2. ( Nr. 230). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR230, address = {Department of Computer Science}, author = {Glaßer, Christian}, keywords = {myown}, month = {06}, number = 230, title = {The Boolean Hierarchy over Dot-Depth 1/2.}, type = {Technical Report}, year = 1999 }
• 
  Dümmler, Mathias ; Vicari, Norbert: A Numerical Analysis of the M/D^b/N Queueing System. ( Nr. 235). Department of Computer Science, 1999
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In this paper, we provide a numerical analysis of the M/D^b/N queueing system. This system consists of an infinite buffer and N identical batch servers with batch capacity b. It serves as a model for various types of workstations in the manufacturing context. Using an approach presented by Crommelin, we derive the distribution of the number of lots waiting in queue at arbitrary time instants and the distribution of the waiting time of lots. The results are of an exact nature and the computation is of low complexity concerning run time and memory usage.

  @techreport{TR235, abstract = {In this paper, we provide a numerical analysis of the M/D^b/N queueing system. This system consists of an infinite buffer and N identical batch servers with batch capacity b. It serves as a model for various types of workstations in the manufacturing context. Using an approach presented by Crommelin, we derive the distribution of the number of lots waiting in queue at arbitrary time instants and the distribution of the waiting time of lots. The results are of an exact nature and the computation is of low complexity concerning run time and memory usage.}, address = {Department of Computer Science}, author = {Dümmler, Mathias and Vicari, Norbert}, keywords = {myown}, month = {07}, number = 235, title = {A Numerical Analysis of the M/D^b/N Queueing System.}, type = {Technical Report}, year = 1999 }
• 
  Ebert, T. ; Vollmer, Heribert: On the Autoreducibility of Random Sequences. ( Nr. 239). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR239, address = {Department of Computer Science}, author = {Ebert, T. and Vollmer, Heribert}, keywords = {myown}, month = 10, number = 239, title = {On the Autoreducibility of Random Sequences.}, type = {Technical Report}, year = 1999 }
• 
  Kluge, B. ; Schäfer, D.: Featurebasierte Lokalisation eines autonomen mobilen Roboters - Experimentelle Fallstudie. ( Nr. 244). Department of Computer Science, 1999
  • [ BibTeX ]
  @techreport{TR244, address = {Department of Computer Science}, author = {Kluge, B. and Schäfer, D.}, keywords = {myown}, month = 12, number = 244, title = {Featurebasierte Lokalisation eines autonomen mobilen Roboters - Experimentelle Fallstudie.}, type = {Technical Report}, year = 1999 }
• 
  Glaßer, Christian ; Schmitz, Heinz: Languages of Dot-Depth 3/2. ( Nr. 243). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR243, address = {Department of Computer Science}, author = {Glaßer, Christian and Schmitz, Heinz}, keywords = {myown}, month = 11, number = 243, title = {Languages of Dot-Depth 3/2.}, type = {Technical Report}, year = 1999 }
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  Hertrampf, Ulrich ; Reith, Steffen ; Vollmer, Heribert: A note on closure properties of logspace MOD classes. ( Nr. 241). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR241, address = {Department of Computer Science}, author = {Hertrampf, Ulrich and Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = 10, number = 241, title = {A note on closure properties of logspace MOD classes.}, type = {Technical Report}, year = 1999 }
• 
  Schmitz, Heinz: Boolean Hierarchies inside Dot-Depth One. ( Nr. 240). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR240, address = {Department of Computer Science}, author = {Schmitz, Heinz}, keywords = {myown}, month = 10, number = 240, title = {Boolean Hierarchies inside Dot-Depth One.}, type = {Technical Report}, year = 1999 }
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  Vicari, Norbert ; Köhler, Stefan: Measuring Internet User Traffic Behavior Dependent on Access Speed. ( Nr. 238). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR238, address = {Department of Computer Science}, author = {Vicari, Norbert and Köhler, Stefan}, keywords = {myown}, month = 10, number = 238, title = {Measuring Internet User Traffic Behavior Dependent on Access Speed.}, type = {Technical Report}, year = 1999 }
• 
  McKenzie, P. ; Vollmer, Heribert ; Wagner, Klaus W.: Arithmetic Circuits and Polynomial Replacement Systems. ( Nr. 242). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR242, address = {Department of Computer Science}, author = {McKenzie, P. and Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = 11, number = 242, title = {Arithmetic Circuits and Polynomial Replacement Systems.}, type = {Technical Report}, year = 1999 }
• 
  Köhler, Stefan ; Schäfer, Uwe: Performance Comparison of different Class-and-Drop treatment of Data and Acknowledgements in DiffServ IP Networks. ( Nr. 237). Department of Computer Science, 1999
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In differentiated services IP networks the sender of a TCP connection determines the class of data packets he emits. The receiver chooses the class of the acknowledgements sent back, independently of the received class. In this work, we examine the impact of different drop precedence in a class and the assignment of different classes for data and acknowledgements. The results show that the throughput of a TCP connection depends not only on the data class, but also on the right choice for the acknowledgements. Some combinations of classes for data and ACKs could even lead to an ``unfair'' use of bandwidth. On the other hand, for a high throughput the selection of the drop precedence is in most cases only important for data packets.

  @techreport{TR237, abstract = {In differentiated services IP networks the sender of a TCP connection determines the class of data packets he emits. The receiver chooses the class of the acknowledgements sent back, independently of the received class. In this work, we examine the impact of different drop precedence in a class and the assignment of different classes for data and acknowledgements. The results show that the throughput of a TCP connection depends not only on the data class, but also on the right choice for the acknowledgements. Some combinations of classes for data and ACKs could even lead to an ``unfair'' use of bandwidth. On the other hand, for a high throughput the selection of the drop precedence is in most cases only important for data packets.}, address = {Department of Computer Science}, author = {Köhler, Stefan and Schäfer, Uwe}, keywords = {myown}, month = {08}, number = 237, title = {Performance Comparison of different Class-and-Drop treatment of Data and Acknowledgements in DiffServ IP Networks.}, type = {Technical Report}, year = 1999 }
• 
  Dümmler, Mathias: Simulation und Leistungsbewertung von Cluster Tools in der Halbleiterfertigung. ( Nr. 231). Department of Computer Science, 1999
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Cluster Tools kommen in den letzten Jahren verstärkt bei der Fertigung von Halbleiterchips zum Einsatz. In diesem Beitrag wird auf die wesentlichen Eigenschaften von Cluster Tools und auf die Probleme bei deren Einsatz eingegangen. Ein Programm zur Modellierung und Simulation von Cluster Tools wird vorgestellt. Anhand einer Studie wird die Verwendung des Simulators in Kombination mit Genetischen Algorithmen zur Verbesserung der Durchlaufzeiten in Cluster Tools demonstriert.

  @techreport{TR231, abstract = {Cluster Tools kommen in den letzten Jahren verstärkt bei der Fertigung von Halbleiterchips zum Einsatz. In diesem Beitrag wird auf die wesentlichen Eigenschaften von Cluster Tools und auf die Probleme bei deren Einsatz eingegangen. Ein Programm zur Modellierung und Simulation von Cluster Tools wird vorgestellt. Anhand einer Studie wird die Verwendung des Simulators in Kombination mit Genetischen Algorithmen zur Verbesserung der Durchlaufzeiten in Cluster Tools demonstriert.}, address = {Department of Computer Science}, author = {Dümmler, Mathias}, keywords = {myown}, month = {07}, number = 231, title = {Simulation und Leistungsbewertung von Cluster Tools in der Halbleiterfertigung.}, type = {Technical Report}, year = 1999 }
• 
  Kluge, B. ; Schäfer, D.: Featurebasierte Lokalisation eines autonomen mobilen Roboters. ( Nr. 234). Department of Computer Science, 1999
  • [ BibTeX ]
  @techreport{TR234, address = {Department of Computer Science}, author = {Kluge, B. and Schäfer, D.}, keywords = {myown}, month = {07}, number = 234, title = {Featurebasierte Lokalisation eines autonomen mobilen Roboters.}, type = {Technical Report}, year = 1999 }
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  Kosub, Sven ; Wagner, Klaus W.: The Boolean Hierarchy of Partitions. ( Nr. 233). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR233, address = {Department of Computer Science}, author = {Kosub, Sven and Wagner, Klaus W.}, keywords = {myown}, month = {07}, number = 233, title = {The Boolean Hierarchy of Partitions.}, type = {Technical Report}, year = 1999 }
• 
  Glaßer, Christian ; Reith, Steffen ; Vollmer, Heribert: Approximation Algorithms for Cellular Network Optimization. ( Nr. 232). Department of Computer Science, 1999
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR232, address = {Department of Computer Science}, author = {Glaßer, Christian and Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {07}, number = 232, title = {Approximation Algorithms for Cellular Network Optimization.}, type = {Technical Report}, year = 1999 }
• 
  Buck, M. ; Noltemeier, Hartmut ; Schäfer, D.: Practical Strategies for Hypotheses Elimination on the Self-Localization Problem. ( Nr. 236). Department of Computer Science, 1999
  • [ BibTeX ]
  @techreport{TR236, address = {Department of Computer Science}, author = {Buck, M. and Noltemeier, Hartmut and Schäfer, D.}, keywords = {myown}, month = {08}, number = 236, title = {Practical Strategies for Hypotheses Elimination on the Self-Localization Problem.}, type = {Technical Report}, year = 1999 }

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  Glaßer, Christian: Klassifizierung der Nicht-Approximierbarkeit eines Basisstationsproblems mit Interferenzen. ( Nr. 197). Department of Computer Science, 1998
  • [ BibTeX ]
  @techreport{TR197, address = {Department of Computer Science}, author = {Glaßer, Christian}, keywords = {myown}, month = {03}, number = 197, title = {Klassifizierung der Nicht-Approximierbarkeit eines Basisstationsproblems mit Interferenzen.}, type = {Technical Report}, year = 1998 }
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  Schmitz, Heinz ; Wagner, Klaus W.: The Boolean Hierarchy over Level 1/2 of the Straubing-Therien Hierarchy. ( Nr. 201). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR201, address = {Department of Computer Science}, author = {Schmitz, Heinz and Wagner, Klaus W.}, keywords = {myown}, month = {04}, number = 201, title = {The Boolean Hierarchy over Level 1/2 of the Straubing-Therien Hierarchy.}, type = {Technical Report}, year = 1998 }
• 
  Gerlich, Notker ; Menth, Michael: The Performance of AAL-2 Carrying CDMA Voice Traffic. ( Nr. 199). Department of Computer Science, 1998
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Due to cost e ciency, future personal communication networks likely will utilize the Asynchronous Transfer Mode (ATM) technology to connect components of the land network infrastructure. In order to cope with bandwidth limitation on the radio access, voice is transmitted as compressed low bit-rate information. The ATM Adaptation Layer 2 (AAL-2) is designed to handle this type of low bit-rate traffic. This paper discusses the capability of using AAL-2 connections to carry compressed voice between components of a CDMA network. To this end we analyze a discrete-time queuing model of the the AAL-2 mechanism combined with tra c shaping.

  @techreport{TR199, abstract = {Due to cost e ciency, future personal communication networks likely will utilize the Asynchronous Transfer Mode (ATM) technology to connect components of the land network infrastructure. In order to cope with bandwidth limitation on the radio access, voice is transmitted as compressed low bit-rate information. The ATM Adaptation Layer 2 (AAL-2) is designed to handle this type of low bit-rate traffic. This paper discusses the capability of using AAL-2 connections to carry compressed voice between components of a CDMA network. To this end we analyze a discrete-time queuing model of the the AAL-2 mechanism combined with tra c shaping.}, address = {Department of Computer Science}, author = {Gerlich, Notker and Menth, Michael}, keywords = {myown}, month = {04}, number = 199, title = {The Performance of AAL-2 Carrying CDMA Voice Traffic.}, type = {Technical Report}, year = 1998 }
• 
  Vicari, Norbert: Models of WWW-Traffic: a Comparison of Pareto and Logarithmic Histogram Models. ( Nr. 198). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR198, address = {Department of Computer Science}, author = {Vicari, Norbert}, keywords = {myown}, month = {03}, number = 198, title = {Models of WWW-Traffic: a Comparison of Pareto and Logarithmic Histogram Models.}, type = {Technical Report}, year = 1998 }
• 
  Reith, Steffen ; Vollmer, Heribert: The Complexity of Computing Optimal Assignments of Generalized Propositional Formulae. ( Nr. 196). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR196, address = {Department of Computer Science}, author = {Reith, Steffen and Vollmer, Heribert}, keywords = {myown}, month = {03}, number = 196, title = {The Complexity of Computing Optimal Assignments of Generalized Propositional Formulae.}, type = {Technical Report}, year = 1998 }
• 
  Bamberger, S.K. ; Schwingeler, S. ; Ziegler, S.: KBA-D3: Ein wissensbasiertes Diagnose- und Informationssystem für Druckmaschinen. ( Nr. 194). Department of Computer Science, 1998
  • [ BibTeX ]
  @techreport{TR194, address = {Department of Computer Science}, author = {Bamberger, S.K. and Schwingeler, S. and Ziegler, S.}, keywords = {myown}, month = {02}, number = 194, title = {KBA-D3: Ein wissensbasiertes Diagnose- und Informationssystem für Druckmaschinen.}, type = {Technical Report}, year = 1998 }
• 
  Reith, Steffen ; Wagner, Klaus W.: On Boolean Lowness and Boolean Highness. ( Nr. 195). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR195, address = {Department of Computer Science}, author = {Reith, Steffen and Wagner, Klaus W.}, keywords = {myown}, month = {03}, number = 195, title = {On Boolean Lowness and Boolean Highness.}, type = {Technical Report}, year = 1998 }
• 
  Tran-Gia, Phuoc ; Jain, N. ; Leibnitz, Kenji: Code Division Multiple Access wireless network planning considering clustered spatial customer traffic. ( Nr. 192). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR192, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc and Jain, N. and Leibnitz, Kenji}, keywords = {myown}, month = {02}, number = 192, title = {Code Division Multiple Access wireless network planning considering clustered spatial customer traffic.}, type = {Technical Report}, year = 1998 }
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  Leibnitz, Kenji ; Tran-Gia, Phuoc ; Miller, J.E.: Analysis of the Dynamics of CDMA Reverse Link Power Control. ( Nr. 193). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR193, address = {Department of Computer Science}, author = {Leibnitz, Kenji and Tran-Gia, Phuoc and Miller, J.E.}, keywords = {myown}, month = {02}, number = 193, title = {Analysis of the Dynamics of CDMA Reverse Link Power Control.}, type = {Technical Report}, year = 1998 }
• 
  Reith, Steffen ; Wagner, Klaus W.: On High and Low Sets for the Boolean Hierarchy. ( Nr. 191). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR191, address = {Department of Computer Science}, author = {Reith, Steffen and Wagner, Klaus W.}, keywords = {myown}, month = {01}, number = 191, title = {On High and Low Sets for the Boolean Hierarchy.}, type = {Technical Report}, year = 1998 }
• 
  Ritter, Michael: Discrete-Time Modeling of the Frame-Based Generic Cell Rate Algorithm. ( Nr. 190). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR190, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = {01}, number = 190, title = {Discrete-Time Modeling of the Frame-Based Generic Cell Rate Algorithm.}, type = {Technical Report}, year = 1998 }
• 
  Nöth, Winfried ; Kolla, Reiner: Spanning Tree Based State Encoding for Low Power Dissipation. ( Nr. 200). Department of Computer Science, 1998
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We address the problem of state encoding for synchronous finite state machines. The primary goal is the reduction of switching activity in the state register. At the beginning the state transition graph is transformed into an undirected graph where the edges are labeled with the state transition probabilities. Next a maximum spanning tree of the undirected graph is constructed, and we formulate the state encoding problem as an embedding of the spanning tree into a Boolean hypercube of unknown dimension. At this point a modification of Prim's maximum spanning tree algorithm is presented to limit the dimension of the hypercube for area constraints. Then we propose a polynomial time embedding heuristic, which removes the restriction of previous works, where the number of state bits used for encoding of a k-state FSM was generally limited to log2(k). Next a more sophisticated embedding algorithm is presented, which takes into account the state transition probabilities not covered by the spanning tree. The resulting encodings of both algorithms in many cases exhibit a considerable lower switching activity in comparison with a known heuristic for low power state encoding. Despite a usually larger state register this also leads to significant reduced power dissipation for many MCNC FSM examples, as synthesized and evaluated by SIS.

  @techreport{TR200, abstract = {We address the problem of state encoding for synchronous finite state machines. The primary goal is the reduction of switching activity in the state register. At the beginning the state transition graph is transformed into an undirected graph where the edges are labeled with the state transition probabilities. Next a maximum spanning tree of the undirected graph is constructed, and we formulate the state encoding problem as an embedding of the spanning tree into a Boolean hypercube of unknown dimension. At this point a modification of Prim's maximum spanning tree algorithm is presented to limit the dimension of the hypercube for area constraints. Then we propose a polynomial time embedding heuristic, which removes the restriction of previous works, where the number of state bits used for encoding of a k-state FSM was generally limited to log2(k). Next a more sophisticated embedding algorithm is presented, which takes into account the state transition probabilities not covered by the spanning tree. The resulting encodings of both algorithms in many cases exhibit a considerable lower switching activity in comparison with a known heuristic for low power state encoding. Despite a usually larger state register this also leads to significant reduced power dissipation for many MCNC FSM examples, as synthesized and evaluated by SIS.}, address = {Department of Computer Science}, author = {Nöth, Winfried and Kolla, Reiner}, keywords = {myown}, month = {04}, number = 200, title = {Spanning Tree Based State Encoding for Low Power Dissipation.}, type = {Technical Report}, year = 1998 }
• 
  Rose, Oliver: WIP Evolution of a Semiconductor Factory After a Bottleneck Workcenter Breakdown. ( Nr. 203). Department of Computer Science, 1998
  • [ BibTeX ]
  @techreport{TR203, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {04}, number = 203, title = {WIP Evolution of a Semiconductor Factory After a Bottleneck Workcenter Breakdown.}, type = {Technical Report}, year = 1998 }
• 
  Kosub, Sven: Persistent Computations. ( Nr. 217). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR217, address = {Department of Computer Science}, author = {Kosub, Sven}, keywords = {myown}, month = 12, number = 217, title = {Persistent Computations.}, type = {Technical Report}, year = 1998 }
• 
  Steffan, J. ; Wirth, H.-C.: ANDI - Approximation Algorithms for Network Design and Network Improvement. ( Nr. 202). Department of Computer Science, 1998
  • [ BibTeX ]
  @techreport{TR202, address = {Department of Computer Science}, author = {Steffan, J. and Wirth, H.-C.}, keywords = {myown}, month = {04}, number = 202, title = {ANDI - Approximation Algorithms for Network Design and Network Improvement.}, type = {Technical Report}, year = 1998 }
• 
  Remiche, M.-A. ; Leibnitz, Kenji: Adaptive Soft-Handoff Thresholds for CDMA Systems with Spatial Traffic. ( Nr. 212). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR212, address = {Department of Computer Science}, author = {Remiche, M.-A. and Leibnitz, Kenji}, keywords = {myown}, month = 10, number = 212, title = {Adaptive Soft-Handoff Thresholds for CDMA Systems with Spatial Traffic.}, type = {Technical Report}, year = 1998 }
• 
  Rose, Oliver: Interdeparture Time Correlations of the Discrete-time GI/GI/1 Queue. ( Nr. 204). Department of Computer Science, 1998
  • [ BibTeX ]
  @techreport{TR204, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {04}, number = 204, title = {Interdeparture Time Correlations of the Discrete-time GI/GI/1 Queue.}, type = {Technical Report}, year = 1998 }
• 
  Dümmler, Mathias ; Schömig, Alexander: Using Discrete-time Analysis in the Performance Evaluation of Manufacturing. ( Nr. 215). Department of Computer Science, 1998
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Discrete-time analysis (DTA) is a modelling technique that is mainly applied to the analysis of communication systems. In this paper, we show how DTA can be adopted to the numerical analysis of manufacturing systems. The modelling concepts of DTA are introduced and the advantages of DTA over other methods like discrete-event simulation are indicated. We apply DTA to two sample applications, namely the analysis of a simple batch server and a batch server with bounded idle time.

  @techreport{TR215, abstract = {Discrete-time analysis (DTA) is a modelling technique that is mainly applied to the analysis of communication systems. In this paper, we show how DTA can be adopted to the numerical analysis of manufacturing systems. The modelling concepts of DTA are introduced and the advantages of DTA over other methods like discrete-event simulation are indicated. We apply DTA to two sample applications, namely the analysis of a simple batch server and a batch server with bounded idle time.}, address = {Department of Computer Science}, author = {Dümmler, Mathias and Schömig, Alexander}, keywords = {myown}, month = 11, number = 215, title = {Using Discrete-time Analysis in the Performance Evaluation of Manufacturing.}, type = {Technical Report}, year = 1998 }
• 
  Gerlich, Notker ; Menth, Michael: A Numerical Framework for Solving Discrete Markov Models Applied to the AAL-2 Protocol. ( Nr. 211). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR211, address = {Department of Computer Science}, author = {Gerlich, Notker and Menth, Michael}, keywords = {myown}, month = 10, number = 211, title = {A Numerical Framework for Solving Discrete Markov Models Applied to the AAL-2 Protocol.}, type = {Technical Report}, year = 1998 }
• 
  Duckstein, Franz ; Kolla, Reiner: Ray Tracing Of Parametric Surfaces Based On Adaptive Simplicial Complexes. ( Nr. 213). Department of Computer Science, 1998
  • [ BibTeX ]
  @techreport{TR213, address = {Department of Computer Science}, author = {Duckstein, Franz and Kolla, Reiner}, keywords = {myown}, month = 10, number = 213, title = {Ray Tracing Of Parametric Surfaces Based On Adaptive Simplicial Complexes.}, type = {Technical Report}, year = 1998 }
• 
  Vicari, Norbert: Effects of Variations in the Available Bandwidth on the Performance of the GFR Service. ( Nr. 214). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR214, address = {Department of Computer Science}, author = {Vicari, Norbert}, keywords = {myown}, month = 10, number = 214, title = {Effects of Variations in the Available Bandwidth on the Performance of the GFR Service.}, type = {Technical Report}, year = 1998 }
• 
  Glaßer, Christian: A Normalform for Classes of Concatenation Hierarchies. ( Nr. 216). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR216, address = {Department of Computer Science}, author = {Glaßer, Christian}, keywords = {myown}, month = 12, number = 216, title = {A Normalform for Classes of Concatenation Hierarchies.}, type = {Technical Report}, year = 1998 }
• 
  Dümmler, Mathias: Analysis of the departure process of a batch server queueing system. ( Nr. 210). Department of Computer Science, 1998
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  We investigate a queueing system with batch service or bulk service. Batch servers are common in many areas of manufacturing, for example in the manufacturing of semiconductors. In particular, we study a batch server operated under the minimum batch size rule. Under this rule, a service will be initiated as soon as the number of lots waiting for service reaches a certain threshold. This threshold can be arbitrarily chosen. Using discrete-time analysis, we derive the interdeparture time distribution for batches and for single lots. It is shown that the interdeparture time distribution of a batch service system has characteristic properties that can not be approximated with sufficient accuracy by other commonly used distributions. We further study the distribution of the number of lots in the departing batches and the correlation between interdeparture times and batch sizes.

  @techreport{TR210, abstract = {We investigate a queueing system with batch service or bulk service. Batch servers are common in many areas of manufacturing, for example in the manufacturing of semiconductors. In particular, we study a batch server operated under the minimum batch size rule. Under this rule, a service will be initiated as soon as the number of lots waiting for service reaches a certain threshold. This threshold can be arbitrarily chosen. Using discrete-time analysis, we derive the interdeparture time distribution for batches and for single lots. It is shown that the interdeparture time distribution of a batch service system has characteristic properties that can not be approximated with sufficient accuracy by other commonly used distributions. We further study the distribution of the number of lots in the departing batches and the correlation between interdeparture times and batch sizes.}, address = {Department of Computer Science}, author = {Dümmler, Mathias}, keywords = {myown}, month = {09}, number = 210, title = {Analysis of the departure process of a batch server queueing system.}, type = {Technical Report}, year = 1998 }
• 
  Glaßer, Christian: On the approximability of problems for cellular networks. ( Nr. 208). Department of Computer Science, 1998
  • [ BibTeX ]
  @techreport{TR208, address = {Department of Computer Science}, author = {Glaßer, Christian}, keywords = {myown}, month = {09}, number = 208, title = {On the approximability of problems for cellular networks.}, type = {Technical Report}, year = 1998 }
• 
  Vicari, Norbert ; Schedel, R.: Performance of the GFR-Service with Constant Available Bandwidth. ( Nr. 207). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR207, address = {Department of Computer Science}, author = {Vicari, Norbert and Schedel, R.}, keywords = {myown}, month = {07}, number = 207, title = {Performance of the GFR-Service with Constant Available Bandwidth.}, type = {Technical Report}, year = 1998 }
• 
  Jodl, W. ; Heuler, M. ; Rothaug, U. ; Leibnitz, Kenji: Einsatz von topologieerhaltenden neuronalen Netzen zur Interpretation von Leiterplattendaten. ( Nr. 206). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR206, address = {Department of Computer Science}, author = {Jodl, W. and Heuler, M. and Rothaug, U. and Leibnitz, Kenji}, keywords = {myown}, month = {07}, number = 206, title = {Einsatz von topologieerhaltenden neuronalen Netzen zur Interpretation von Leiterplattendaten.}, type = {Technical Report}, year = 1998 }
• 
  Galota, M.: Blattsprachen und endliche Automaten. ( Nr. 205). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR205, address = {Department of Computer Science}, author = {Galota, M.}, keywords = {myown}, month = {05}, number = 205, title = {Blattsprachen und endliche Automaten.}, type = {Technical Report}, year = 1998 }
• 
  Vollmer, Heribert: A Generalized Quantifier Concept in Computational Complexity Theory. ( Nr. 209). Department of Computer Science, 1998
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR209, address = {Department of Computer Science}, author = {Vollmer, Heribert}, keywords = {myown}, month = {09}, number = 209, title = {A Generalized Quantifier Concept in Computational Complexity Theory.}, type = {Technical Report}, year = 1998 }

• 
  Nöth, Winfried ; Kolla, Reiner: Node Normalization and Decomposition in Low Power Technology Mapping. ( Nr. 166). Department of Computer Science, 1997
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  In static CMOS technology the decomposition of the nodes of a circuit netlist can significantly reduce the overall power dissipation of the circuit. We present a normalization algorithm which extracts the largest recognizable nodes of the given structure. Then we examine a known decomposition algorithm for the normalized nodes and propose a new one which is provable optimal and tractable for moderate node size. Resulting reduction of the overall switching activity on standard benchmark circuits is shown for ROBDD computed as well as uncorrelated signal probabilities.

  @techreport{TR166, abstract = {In static CMOS technology the decomposition of the nodes of a circuit netlist can significantly reduce the overall power dissipation of the circuit. We present a normalization algorithm which extracts the largest recognizable nodes of the given structure. Then we examine a known decomposition algorithm for the normalized nodes and propose a new one which is provable optimal and tractable for moderate node size. Resulting reduction of the overall switching activity on standard benchmark circuits is shown for ROBDD computed as well as uncorrelated signal probabilities.}, address = {Department of Computer Science}, author = {Nöth, Winfried and Kolla, Reiner}, keywords = {myown}, month = {02}, number = 166, title = {Node Normalization and Decomposition in Low Power Technology Mapping.}, type = {Technical Report}, year = 1997 }
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  Ritter, Michael: A Decomposition Approach for User-Network Interface Modeling in ATM Networks. ( Nr. 169). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR169, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = {04}, number = 169, title = {A Decomposition Approach for User-Network Interface Modeling in ATM Networks.}, type = {Technical Report}, year = 1997 }
• 
  Vicari, Norbert: Resource-Based Charging of ATM Connections. ( Nr. 170). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR170, address = {Department of Computer Science}, author = {Vicari, Norbert}, keywords = {myown}, month = {04}, number = 170, title = {Resource-Based Charging of ATM Connections.}, type = {Technical Report}, year = 1997 }
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  Tutschku, Kurt ; Leskien, T. ; Tran-Gia, Phuoc: Traffic estimation and characterization for the design of mobile communication networks. ( Nr. 171). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR171, address = {Department of Computer Science}, author = {Tutschku, Kurt and Leskien, T. and Tran-Gia, Phuoc}, keywords = {myown}, month = {04}, number = 171, title = {Traffic estimation and characterization for the design of mobile communication networks.}, type = {Technical Report}, year = 1997 }
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  Wastl, R.: Tableau Methods for Computing Stable Models and Query Answering in Disjunctive Deductive Databases. ( Nr. 167). Department of Computer Science, 1997
  • [ BibTeX ]
  @techreport{TR167, address = {Department of Computer Science}, author = {Wastl, R.}, keywords = {myown}, month = {03}, number = 167, title = {Tableau Methods for Computing Stable Models and Query Answering in Disjunctive Deductive Databases.}, type = {Technical Report}, year = 1997 }
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  Bartelsen, S. ; Mittler, Manfred: A Bernoulli Feedback Queue with Batch Service. ( Nr. 168). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR168, address = {Department of Computer Science}, author = {Bartelsen, S. and Mittler, Manfred}, keywords = {myown}, month = {03}, number = 168, title = {A Bernoulli Feedback Queue with Batch Service.}, type = {Technical Report}, year = 1997 }
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  Dümmler, Mathias ; Schömig, Alexander: Discrete-time Analysis of Batch Servers with Bounded Idle Time and Two Job Classes. ( Nr. 162). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR162, address = {Department of Computer Science}, author = {Dümmler, Mathias and Schömig, Alexander}, keywords = {myown}, month = {01}, number = 162, title = {Discrete-time Analysis of Batch Servers with Bounded Idle Time and Two Job Classes.}, type = {Technical Report}, year = 1997 }
• 
  Hinsberger, Uwe ; Kolla, Reiner ; Wild, Markus: A parallel hybrid approach to hard optimization problems. ( Nr. 163). Department of Computer Science, 1997
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This paper presents a software platform for the distributed solution of complex optimization problems. For such problems there are often no outstanding approaches which always perform well. That is why we propose to use different solution methods simultaneously. They can communicate and thus profitate from each other. Some general paradigms are applicable to a wide class of problems. Our platform contains reusable implementations of such paradigms. A first application to set covering problems is presented. Experimental results for this application demonstrate the quality of such an approach.

  @techreport{TR163, abstract = {This paper presents a software platform for the distributed solution of complex optimization problems. For such problems there are often no outstanding approaches which always perform well. That is why we propose to use different solution methods simultaneously. They can communicate and thus profitate from each other. Some general paradigms are applicable to a wide class of problems. Our platform contains reusable implementations of such paradigms. A first application to set covering problems is presented. Experimental results for this application demonstrate the quality of such an approach.}, address = {Department of Computer Science}, author = {Hinsberger, Uwe and Kolla, Reiner and Wild, Markus}, keywords = {myown}, month = {01}, number = 163, title = {A parallel hybrid approach to hard optimization problems.}, type = {Technical Report}, year = 1997 }
• 
  Gerlich, Notker: On the Spatial Multiplexing Gain of SDMA for Wireless Local Loop Access. ( Nr. 161). Department of Computer Science, 1997
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The high teletraffic demand of local loop customers as compared to cellular mobile customers requires a cellular system to have a higher capacity if used for wireless local loop access. To cope with this fact Space Division Multiple Access is proposed to be implemented on top of a cellular F/TDMA system. SDMA allows the spatial user distribution to be exploited for multiple access. Thus, the properties of the user distribution are crucial for the resulting multiplexing gain. In this paper we model the user distribution in a cell by a planar point process and derive measures of the spatial multiplexing gain.

  @techreport{TR161, abstract = {The high teletraffic demand of local loop customers as compared to cellular mobile customers requires a cellular system to have a higher capacity if used for wireless local loop access. To cope with this fact Space Division Multiple Access is proposed to be implemented on top of a cellular F/TDMA system. SDMA allows the spatial user distribution to be exploited for multiple access. Thus, the properties of the user distribution are crucial for the resulting multiplexing gain. In this paper we model the user distribution in a cell by a planar point process and derive measures of the spatial multiplexing gain.}, address = {Department of Computer Science}, author = {Gerlich, Notker}, keywords = {myown}, month = {01}, number = 161, title = {On the Spatial Multiplexing Gain of SDMA for Wireless Local Loop Access.}, type = {Technical Report}, year = 1997 }
• 
  Wastl, R.: Unfolding in Disjunctive Deductive Databases with respect to 3-Valued Stable Models. ( Nr. 165). Department of Computer Science, 1997
  • [ BibTeX ]
  @techreport{TR165, address = {Department of Computer Science}, author = {Wastl, R.}, keywords = {myown}, month = {01}, number = 165, title = {Unfolding in Disjunctive Deductive Databases with respect to 3-Valued Stable Models.}, type = {Technical Report}, year = 1997 }
• 
  Hafner, U. ; Frank, S.W.M. ; Unger, M. ; Albert, Jürgen: Hybrid Weighted Finite Automata for image and video compression. ( Nr. 160). Department of Computer Science, 1997
  • [ BibTeX ]
  @techreport{TR160, address = {Department of Computer Science}, author = {Hafner, U. and Frank, S.W.M. and Unger, M. and Albert, Jürgen}, keywords = {myown}, month = {01}, number = 160, title = {Hybrid Weighted Finite Automata for image and video compression.}, type = {Technical Report}, year = 1997 }
• 
  Ritter, Michael: Analysis of a Queueing Model with Delayed Feedback and its Application to the ABR Flow Control. ( Nr. 164). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR164, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = {01}, number = 164, title = {Analysis of a Queueing Model with Delayed Feedback and its Application to the ABR Flow Control.}, type = {Technical Report}, year = 1997 }
• 
  Bartelsen, S. ; Mittler, Manfred ; Rose, Oliver: Approximate Flow Time Distribution of a Queue with Batch Service. ( Nr. 174). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR174, address = {Department of Computer Science}, author = {Bartelsen, S. and Mittler, Manfred and Rose, Oliver}, keywords = {myown}, month = {06}, number = 174, title = {Approximate Flow Time Distribution of a Queue with Batch Service.}, type = {Technical Report}, year = 1997 }
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  Kosub, Sven: On Cluster Machines and Function Classes. ( Nr. 172). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR172, address = {Department of Computer Science}, author = {Kosub, Sven}, keywords = {myown}, month = {05}, number = 172, title = {On Cluster Machines and Function Classes.}, type = {Technical Report}, year = 1997 }
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  Hinsberger, Uwe ; Kolla, Reiner: TEMPLATE: a generic TEchnology Mapping PLATform. ( Nr. 186). Department of Computer Science, 1997
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Technology mapping problems arize in logic synthesis systems, when the gap between a synthesized boolean network and the implementation of that network within a given target technology has to be bridged. This paper presents a modular, versatile technology mapping system that supports many different target technologies. Guided by a complexity analysis of the problem, we develop a variety of efficient, exact or heuristic methods for technology driven network clustering. Depending on the target technology and optimization methods and goals, different subnetworks must be provided as candidates for clustering. Methods to achieve this are also included. We conclude with experimental results we obtained with several configurations of the system for different target technologies.

  @techreport{TR186, abstract = {Technology mapping problems arize in logic synthesis systems, when the gap between a synthesized boolean network and the implementation of that network within a given target technology has to be bridged. This paper presents a modular, versatile technology mapping system that supports many different target technologies. Guided by a complexity analysis of the problem, we develop a variety of efficient, exact or heuristic methods for technology driven network clustering. Depending on the target technology and optimization methods and goals, different subnetworks must be provided as candidates for clustering. Methods to achieve this are also included. We conclude with experimental results we obtained with several configurations of the system for different target technologies.}, address = {Department of Computer Science}, author = {Hinsberger, Uwe and Kolla, Reiner}, keywords = {myown}, month = 11, number = 186, title = {TEMPLATE: a generic TEchnology Mapping PLATform.}, type = {Technical Report}, year = 1997 }
• 
  Wagner, Klaus W.: A Note on Parallel Queries and the Difference Hierarchy. ( Nr. 173). Department of Computer Science, 1997
  • [ BibTeX ]
  @techreport{TR173, address = {Department of Computer Science}, author = {Wagner, Klaus W.}, keywords = {myown}, month = {06}, number = 173, title = {A Note on Parallel Queries and the Difference Hierarchy.}, type = {Technical Report}, year = 1997 }
• 
  Kunjan, T. ; Hinsberger, Uwe ; Kolla, Reiner: Approximative Representation of boolean Functions by size controllable ROBDD’s. ( Nr. 182). Department of Computer Science, 1997
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  ROBDDs are a very popular datastructure for the representation and manipulation of boolean functions. They have tractable sizes for many boolean functions and come up with efficient algorithms for boolean operations. In the worst case however, size and time complexity grows exponentially when performing a polynomial number of operations. However, there are applications where an approximate knowledge about a boolean function like a lower or upper bound may be sufficient. In this paper we present a datastructure based on ROBDDs, that allows to trade space and time efficiency for precision. The basic extension is provided by the computation of least upper resp. greatest lower bounds of a boolean function under a size constraint for its ROBDD. As a first practical application we conclude some experimental results for the computation of local don't cares in combinational circuits.

  @techreport{TR182, abstract = {ROBDDs are a very popular datastructure for the representation and manipulation of boolean functions. They have tractable sizes for many boolean functions and come up with efficient algorithms for boolean operations. In the worst case however, size and time complexity grows exponentially when performing a polynomial number of operations. However, there are applications where an approximate knowledge about a boolean function like a lower or upper bound may be sufficient. In this paper we present a datastructure based on ROBDDs, that allows to trade space and time efficiency for precision. The basic extension is provided by the computation of least upper resp. greatest lower bounds of a boolean function under a size constraint for its ROBDD. As a first practical application we conclude some experimental results for the computation of local don't cares in combinational circuits.}, address = {Department of Computer Science}, author = {Kunjan, T. and Hinsberger, Uwe and Kolla, Reiner}, keywords = {myown}, month = {09}, number = 182, title = {Approximative Representation of boolean Functions by size controllable ROBDD's.}, type = {Technical Report}, year = 1997 }
• 
  Gerlich, Notker ; Ritter, Michael: Carrying CDMA Traffic over ATM Using AAL-2: A Performance Study. ( Nr. 188). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR188, address = {Department of Computer Science}, author = {Gerlich, Notker and Ritter, Michael}, keywords = {myown}, month = 11, number = 188, title = {Carrying CDMA Traffic over ATM Using AAL-2: A Performance Study.}, type = {Technical Report}, year = 1997 }
• 
  Duckstein, Franz ; Kolla, Reiner: Gültigkeitsmetriken für animierte gerenderte Szenen in der Echtzeitcomputergraphik. ( Nr. 175). Department of Computer Science, 1997
  • [ BibTeX ]
  @techreport{TR175, address = {Department of Computer Science}, author = {Duckstein, Franz and Kolla, Reiner}, keywords = {myown}, month = {06}, number = 175, title = {Gültigkeitsmetriken für animierte gerenderte Szenen in der Echtzeitcomputergraphik.}, type = {Technical Report}, year = 1997 }
• 
  Gerlich, Notker: The Performance of Base Station Interconnection Alternatives in CDMA Networks. ( Nr. 189). Department of Computer Science, 1997
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Code Division Multiple Access (CDMA) technology emerges as one of the key technologies for third generation personal communication systems. Although the air link capacity is the scarce resource in a wireless system, it is nevertheless important to design the land interconnecting network efficiently. In this paper we discuss the capacities of architecture alternatives for the interconnection of Base Transceiver Systems (BTS) and their Base Station Controller (BSC) in CDMA mobile communication networks. To this end, queuing models of architecture alternatives are derived. We analyze the models using discrete-time analysis techniques and verify the results by simulation. Numerical results are provided for the maximum number of CDMA voice sources that can be supported by a given capacity of the interconnecting links. This enables us to compare the architecture alternatives in terms of teletraffic capacity.

  @techreport{TR189, abstract = {Code Division Multiple Access (CDMA) technology emerges as one of the key technologies for third generation personal communication systems. Although the air link capacity is the scarce resource in a wireless system, it is nevertheless important to design the land interconnecting network efficiently. In this paper we discuss the capacities of architecture alternatives for the interconnection of Base Transceiver Systems (BTS) and their Base Station Controller (BSC) in CDMA mobile communication networks. To this end, queuing models of architecture alternatives are derived. We analyze the models using discrete-time analysis techniques and verify the results by simulation. Numerical results are provided for the maximum number of CDMA voice sources that can be supported by a given capacity of the interconnecting links. This enables us to compare the architecture alternatives in terms of teletraffic capacity.}, address = {Department of Computer Science}, author = {Gerlich, Notker}, keywords = {myown}, month = 12, number = 189, title = {The Performance of Base Station Interconnection Alternatives in CDMA Networks.}, type = {Technical Report}, year = 1997 }
• 
  Seemann, Jochen ; von Gudenberg, Jürgen Wolff: OMT-Script - eine Programmiersprache für objektorientierten Entwurf. ( Nr. 187). Department of Computer Science, 1997
  • [ BibTeX ]
  @techreport{TR187, address = {Department of Computer Science}, author = {Seemann, Jochen and von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = 11, number = 187, title = {OMT-Script - eine Programmiersprache für objektorientierten Entwurf.}, type = {Technical Report}, year = 1997 }
• 
  Vicari, Norbert: Measurement and Modeling of WWW-Sessions. ( Nr. 184). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR184, address = {Department of Computer Science}, author = {Vicari, Norbert}, keywords = {myown}, month = {09}, number = 184, title = {Measurement and Modeling of WWW-Sessions.}, type = {Technical Report}, year = 1997 }
• 
  Hinsberger, Uwe ; Kolla, Reiner: Matching a Boolean Function against a Set of Functions. ( Nr. 185). Department of Computer Science, 1997
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  Boolean matching tackles the problem whether a subcircuit of a boolean network can be substituted by a cell from a cell library. In previous approaches each pair of a subcircuit and a cell is tested for NPN-equivalence. This becomes very expensive if the cell library is large. In our approach the time complexity for matching a subcircuit against a library L is almost independent of the size of L. The CPU time also remains the same for matching a subcircuit against the huge set of functions obtained by bridging and fixing cell inputs; but the use of these functions in technology mapping is very profitable. Our method is based on a canonical representative for each NPN-equivalence class. We show how this representative can be computed efficiently and how it can be used for matching a boolean function against a set of library functions.

  @techreport{TR185, abstract = {Boolean matching tackles the problem whether a subcircuit of a boolean network can be substituted by a cell from a cell library. In previous approaches each pair of a subcircuit and a cell is tested for NPN-equivalence. This becomes very expensive if the cell library is large. In our approach the time complexity for matching a subcircuit against a library L is almost independent of the size of L. The CPU time also remains the same for matching a subcircuit against the huge set of functions obtained by bridging and fixing cell inputs; but the use of these functions in technology mapping is very profitable. Our method is based on a canonical representative for each NPN-equivalence class. We show how this representative can be computed efficiently and how it can be used for matching a boolean function against a set of library functions.}, address = {Department of Computer Science}, author = {Hinsberger, Uwe and Kolla, Reiner}, keywords = {myown}, month = 11, number = 185, title = {Matching a Boolean Function against a Set of Functions.}, type = {Technical Report}, year = 1997 }
• 
  von Gudenberg, Jürgen Wolff: Objektorientierte Programmierung im wissenschaftlichen Rechnen. ( Nr. 181). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR181, address = {Department of Computer Science}, author = {von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = {09}, number = 181, title = {Objektorientierte Programmierung im wissenschaftlichen Rechnen.}, type = {Technical Report}, year = 1997 }
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  Wahler, S. ; Schoemig, Alexander ; Rose, Oliver: Implementierung und Test neuartiger Zufallszahlengeneratoren. ( Nr. 180). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR180, address = {Department of Computer Science}, author = {Wahler, S. and Schoemig, Alexander and Rose, Oliver}, keywords = {myown}, month = {08}, number = 180, title = {Implementierung und Test neuartiger Zufallszahlengeneratoren.}, type = {Technical Report}, year = 1997 }
• 
  Baier, Herbert ; Wagner, Klaus W.: Bounding Queries in the Analytic Polynomial-Time Hierarchy. ( Nr. 178). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR178, address = {Department of Computer Science}, author = {Baier, Herbert and Wagner, Klaus W.}, keywords = {myown}, month = {08}, number = 178, title = {Bounding Queries in the Analytic Polynomial-Time Hierarchy.}, type = {Technical Report}, year = 1997 }
• 
  Vollmer, Heribert: Relating Polynomial Time to Constant Depth. ( Nr. 179). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR179, address = {Department of Computer Science}, author = {Vollmer, Heribert}, keywords = {myown}, month = {08}, number = 179, title = {Relating Polynomial Time to Constant Depth.}, type = {Technical Report}, year = 1997 }
• 
  Tutschku, Kurt: Demand-based Radio Network Planning of Cellular Mobile Communication Systems. ( Nr. 177). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR177, address = {Department of Computer Science}, author = {Tutschku, Kurt}, keywords = {myown}, month = {07}, number = 177, title = {Demand-based Radio Network Planning of Cellular Mobile Communication Systems.}, type = {Technical Report}, year = 1997 }
• 
  Rose, Oliver: A Memory Markov Chain Model For VBR Traffic With Strong Positive Correlations. ( Nr. 176). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR176, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {06}, number = 176, title = {A Memory Markov Chain Model For VBR Traffic With Strong Positive Correlations.}, type = {Technical Report}, year = 1997 }
• 
  Kosub, Sven ; Schmitz, Heinz ; Vollmer, Heribert: Uniformly Defining Complexity Classes of Functions. ( Nr. 183). Department of Computer Science, 1997
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR183, address = {Department of Computer Science}, author = {Kosub, Sven and Schmitz, Heinz and Vollmer, Heribert}, keywords = {myown}, month = {09}, number = 183, title = {Uniformly Defining Complexity Classes of Functions.}, type = {Technical Report}, year = 1997 }

• 
  Vollmer, Heribert: A Note on the Power of Quasipolynomial Size Circuits. ( Nr. 140). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR140, address = {Department of Computer Science}, author = {Vollmer, Heribert}, keywords = {myown}, month = {06}, number = 140, title = {A Note on the Power of Quasipolynomial Size Circuits.}, type = {Technical Report}, year = 1996 }
• 
  Mandjes, M. ; Tutschku, Kurt: Efficient call handling procedures in cellular mobile networks. ( Nr. 144). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR144, address = {Department of Computer Science}, author = {Mandjes, M. and Tutschku, Kurt}, keywords = {myown}, month = {07}, number = 144, title = {Efficient call handling procedures in cellular mobile networks.}, type = {Technical Report}, year = 1996 }
• 
  Gerlich, Notker ; Tran-Gia, Phuoc ; Elsayed, K.: Performance Analysis of Link Carrying Capacity in CDMA Systems. ( Nr. 145). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR145, address = {Department of Computer Science}, author = {Gerlich, Notker and Tran-Gia, Phuoc and Elsayed, K.}, keywords = {myown}, month = {07}, number = 145, title = {Performance Analysis of Link Carrying Capacity in CDMA Systems.}, type = {Technical Report}, year = 1996 }
• 
  Leibnitz, Kenji ; Tutschku, Kurt ; Rothaug, U.: Künstliche Neuronale Netze für die Wegoptimierung in ATG Leiterplattentestern. ( Nr. 146). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR146, address = {Department of Computer Science}, author = {Leibnitz, Kenji and Tutschku, Kurt and Rothaug, U.}, keywords = {myown}, month = {07}, number = 146, title = {Künstliche Neuronale Netze für die Wegoptimierung in ATG Leiterplattentestern.}, type = {Technical Report}, year = 1996 }
• 
  Karch, O.: A Sharper Complexity Bound for the Robot Localization Problem. ( Nr. 139). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR139, address = {Department of Computer Science}, author = {Karch, O.}, keywords = {myown}, month = {06}, number = 139, title = {A Sharper Complexity Bound for the Robot Localization Problem.}, type = {Technical Report}, year = 1996 }
• 
  Ritter, Michael: Analysis of a Rate-Based Control Policy with Delayed Feedback and Variable Bandwidth Availability. ( Nr. 133). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR133, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = {01}, number = 133, title = {Analysis of a Rate-Based Control Policy with Delayed Feedback and Variable Bandwidth Availability.}, type = {Technical Report}, year = 1996 }
• 
  Luo, Y.: Distributed Implementation of PROLOG on Workstation Clusters. ( Nr. 136). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR136, address = {Department of Computer Science}, author = {Luo, Y.}, keywords = {myown}, month = {02}, number = 136, title = {Distributed Implementation of PROLOG on Workstation Clusters.}, type = {Technical Report}, year = 1996 }
• 
  Rose, Oliver: Estimation of the Hurst Parameter of Long-Range Dependent Time Series. ( Nr. 137). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR137, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {02}, number = 137, title = {Estimation of the Hurst Parameter of Long-Range Dependent Time Series.}, type = {Technical Report}, year = 1996 }
• 
  Albert, Jürgen ; Räther, F. ; Patzner, K. ; Schoof, Jochen ; Zimmer, J.: Concepts For Optimizing Sinter Processes Using Evolutionary Algorithms. ( Nr. 138). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR138, address = {Department of Computer Science}, author = {Albert, Jürgen and Räther, F. and Patzner, K. and Schoof, Jochen and Zimmer, J.}, keywords = {myown}, month = {02}, number = 138, title = {Concepts For Optimizing Sinter Processes Using Evolutionary Algorithms.}, type = {Technical Report}, year = 1996 }
• 
  Verbarg, K. ; Hensel, A.: Hierarchical Motion Planning Using a Spatial Index. ( Nr. 135). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR135, address = {Department of Computer Science}, author = {Verbarg, K. and Hensel, A.}, keywords = {myown}, month = {01}, number = 135, title = {Hierarchical Motion Planning Using a Spatial Index.}, type = {Technical Report}, year = 1996 }
• 
  Tutschku, Kurt ; Leibnitz, Kenji: Fast Ray-Tracing for Field Strength Prediction in Cellular Mobile Network Planning. ( Nr. 134). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR134, address = {Department of Computer Science}, author = {Tutschku, Kurt and Leibnitz, Kenji}, keywords = {myown}, month = {01}, number = 134, title = {Fast Ray-Tracing for Field Strength Prediction in Cellular Mobile Network Planning.}, type = {Technical Report}, year = 1996 }
• 
  Tran-Gia, Phuoc ; Gerlich, Notker: Impact of Customer Clustering on Mobile Network Performance. ( Nr. 143). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR143, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc and Gerlich, Notker}, keywords = {myown}, month = {07}, number = 143, title = {Impact of Customer Clustering on Mobile Network Performance.}, type = {Technical Report}, year = 1996 }
• 
  Tran-Gia, Phuoc ; Mandjes, M.: Modeling of customer retrial phenomenon in cellular mobile networks. ( Nr. 142). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR142, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc and Mandjes, M.}, keywords = {myown}, month = {07}, number = 142, title = {Modeling of customer retrial phenomenon in cellular mobile networks.}, type = {Technical Report}, year = 1996 }
• 
  Mittler, Manfred: Two-Moment Analysis of Alternative Tool Models with Random Breakdowns. ( Nr. 141). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR141, address = {Department of Computer Science}, author = {Mittler, Manfred}, keywords = {myown}, month = {07}, number = 141, title = {Two-Moment Analysis of Alternative Tool Models with Random Breakdowns.}, type = {Technical Report}, year = 1996 }
• 
  Niemann, G.: On Weakly Growing Grammars. ( Nr. 155). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR155, address = {Department of Computer Science}, author = {Niemann, G.}, keywords = {myown}, month = 10, number = 155, title = {On Weakly Growing Grammars.}, type = {Technical Report}, year = 1996 }
• 
  Ritter, Michael: Congestion Detection Methods and their Impact on the Performance of the ABR Flow Control Mechanism. ( Nr. 147). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR147, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = {08}, number = 147, title = {Congestion Detection Methods and their Impact on the Performance of the ABR Flow Control Mechanism.}, type = {Technical Report}, year = 1996 }
• 
  Baier, Herbert: On the Approximability of the Selection Problem. ( Nr. 159). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR159, address = {Department of Computer Science}, author = {Baier, Herbert}, keywords = {myown}, month = 12, number = 159, title = {On the Approximability of the Selection Problem.}, type = {Technical Report}, year = 1996 }
• 
  Wastl, R.: Lifting the Well-Founded Semantics to Disjunctive, Normal Databases. ( Nr. 157). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR157, address = {Department of Computer Science}, author = {Wastl, R.}, keywords = {myown}, month = 11, number = 157, title = {Lifting the Well-Founded Semantics to Disjunctive, Normal Databases.}, type = {Technical Report}, year = 1996 }
• 
  Vollmer, Heribert: Succinct Inputs, Lindström Quantifiers, and a General Complexity Theoretic Operator Concept. ( Nr. 158). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR158, address = {Department of Computer Science}, author = {Vollmer, Heribert}, keywords = {myown}, month = 11, number = 158, title = {Succinct Inputs, Lindström Quantifiers, and a General Complexity Theoretic Operator Concept.}, type = {Technical Report}, year = 1996 }
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  Wastl, R.: A Unified Semantical Framework for Deductive Databases. ( Nr. 153). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR153, address = {Department of Computer Science}, author = {Wastl, R.}, keywords = {myown}, month = 10, number = 153, title = {A Unified Semantical Framework for Deductive Databases.}, type = {Technical Report}, year = 1996 }
• 
  Nöth, Winfried ; Hinsberger, Uwe ; Kolla, Reiner: TROY - A Tree Oriented Approach to Logic Synthesis and Technology Mapping. ( Nr. 156). Department of Computer Science, 1996
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The problem of provable optimal synthesis of boolean functions for a given technology is still unsolved. In this paper we present a new approach to the synthesis of combinational circuits and the mapping of standard cells with arbitrary number of inputs. Our method is based on the provable optimal synthesis of the fanoutfree regions of a circuit, represented as Normal AND-OR-Trees. This representation enables TROY to rebalance the regions with respect to delay without sacrifying area and result in a larger search space than that used by Tree Matching. Fast heuristics derived from the optimal approach yield significantly better results than SIS on many standard benchmark circuits.

  @techreport{TR156, abstract = {The problem of provable optimal synthesis of boolean functions for a given technology is still unsolved. In this paper we present a new approach to the synthesis of combinational circuits and the mapping of standard cells with arbitrary number of inputs. Our method is based on the provable optimal synthesis of the fanoutfree regions of a circuit, represented as Normal AND-OR-Trees. This representation enables TROY to rebalance the regions with respect to delay without sacrifying area and result in a larger search space than that used by Tree Matching. Fast heuristics derived from the optimal approach yield significantly better results than SIS on many standard benchmark circuits.}, address = {Department of Computer Science}, author = {Nöth, Winfried and Hinsberger, Uwe and Kolla, Reiner}, keywords = {myown}, month = 11, number = 156, title = {TROY - A Tree Oriented Approach to Logic Synthesis and Technology Mapping.}, type = {Technical Report}, year = 1996 }
• 
  Noltemeier, Hartmut ; Krumke, S.O.: 30. Workshop Komplexitätstheorie, Datenstrukturen und effiziente Algorithmen. ( Nr. 152). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR152, address = {Department of Computer Science}, author = {Noltemeier, Hartmut and Krumke, S.O.}, keywords = {myown}, month = 10, number = 152, title = {30. Workshop Komplexitätstheorie, Datenstrukturen und effiziente Algorithmen.}, type = {Technical Report}, year = 1996 }
• 
  Wastl, R.: A Vectorial Well-Founded Semantics for Disjunctive, Deductive Databases. ( Nr. 154). Department of Computer Science, 1996
  • [ BibTeX ]
  @techreport{TR154, address = {Department of Computer Science}, author = {Wastl, R.}, keywords = {myown}, month = 10, number = 154, title = {A Vectorial Well-Founded Semantics for Disjunctive, Deductive Databases.}, type = {Technical Report}, year = 1996 }
• 
  Rose, Oliver: Discrete-time Analysis of a Finite Buffer with VBR MPEG Video Traffic Input. ( Nr. 150). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR150, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {09}, number = 150, title = {Discrete-time Analysis of a Finite Buffer with VBR MPEG Video Traffic Input.}, type = {Technical Report}, year = 1996 }
• 
  Vollmer, Heribert ; Wagner, Klaus W.: Measure One Results in Computational Complexity Theory. ( Nr. 149). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR149, address = {Department of Computer Science}, author = {Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = {09}, number = 149, title = {Measure One Results in Computational Complexity Theory.}, type = {Technical Report}, year = 1996 }
• 
  Vicari, Norbert ; Tran-Gia, Phuoc: A Numerical Analysis of the Geo/D/N Queueing System. ( Nr. 151). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR151, address = {Department of Computer Science}, author = {Vicari, Norbert and Tran-Gia, Phuoc}, keywords = {myown}, month = {09}, number = 151, title = {A Numerical Analysis of the Geo/D/N Queueing System.}, type = {Technical Report}, year = 1996 }
• 
  Baier, Herbert ; Wagner, Klaus W.: The Analytic Polynomial Time Hierarchy. ( Nr. 148). Department of Computer Science, 1996
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR148, address = {Department of Computer Science}, author = {Baier, Herbert and Wagner, Klaus W.}, keywords = {myown}, month = {09}, number = 148, title = {The Analytic Polynomial Time Hierarchy.}, type = {Technical Report}, year = 1996 }

• 
  Schömig, Alexander ; Kahnt, M.: Vergleich zweier Analysemethoden zur Leistungsbewertung von Kanban Systemen. ( Nr. 105). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR105, address = {Department of Computer Science}, author = {Schömig, Alexander and Kahnt, M.}, keywords = {myown}, month = {02}, number = 105, title = {Vergleich zweier Analysemethoden zur Leistungsbewertung von Kanban Systemen.}, type = {Technical Report}, year = 1995 }
• 
  Mittler, Manfred ; Gerlich, Notker ; Schömig, Alexander: Reducing the Variance of Cycle Times in Semiconductor Manufacturing Systems. ( Nr. 109). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR109, address = {Department of Computer Science}, author = {Mittler, Manfred and Gerlich, Notker and Schömig, Alexander}, keywords = {myown}, month = {04}, number = 109, title = {Reducing the Variance of Cycle Times in Semiconductor Manufacturing Systems.}, type = {Technical Report}, year = 1995 }
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  Puppe, Frank ; Daniel, M. ; Seidel, G.: Qualifizierende Arbeitsgestaltung mit tutoriellen Expertensystemen für technische Diagnoseaufgaben. ( Nr. 111). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR111, address = {Department of Computer Science}, author = {Puppe, Frank and Daniel, M. and Seidel, G.}, keywords = {myown}, month = {04}, number = 111, title = {Qualifizierende Arbeitsgestaltung mit tutoriellen Expertensystemen für technische Diagnoseaufgaben.}, type = {Technical Report}, year = 1995 }
• 
  Schömig, Alexander ; Kahnt, M.: A note on the Application of Marie’s Method for Queueing Networks with Batch Servers. ( Nr. 110). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR110, address = {Department of Computer Science}, author = {Schömig, Alexander and Kahnt, M.}, keywords = {myown}, month = {04}, number = 110, title = {A note on the Application of Marie's Method for Queueing Networks with Batch Servers.}, type = {Technical Report}, year = 1995 }
• 
  Schömig, Alexander ; Kahnt, M.: Performance Modelling of Pull Manufacturing Systems with Batch Servers and Assembly-like Structure. ( Nr. 108). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR108, address = {Department of Computer Science}, author = {Schömig, Alexander and Kahnt, M.}, keywords = {myown}, month = {03}, number = 108, title = {Performance Modelling of Pull Manufacturing Systems with Batch Servers and Assembly-like Structure.}, type = {Technical Report}, year = 1995 }
• 
  Mittler, Manfred ; Purm, M. ; Gihr, O.: Set Management: Synchronization of Prefabricated Parts before Assembly. ( Nr. 106). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR106, address = {Department of Computer Science}, author = {Mittler, Manfred and Purm, M. and Gihr, O.}, keywords = {myown}, month = {03}, number = 106, title = {Set Management: Synchronization of Prefabricated Parts before Assembly.}, type = {Technical Report}, year = 1995 }
• 
  Schömig, Alexander ; Mittler, Manfred: Autocorrelation of Cycle Times in Semiconductor Manufacturing Systems. ( Nr. 107). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR107, address = {Department of Computer Science}, author = {Schömig, Alexander and Mittler, Manfred}, keywords = {myown}, month = {03}, number = 107, title = {Autocorrelation of Cycle Times in Semiconductor Manufacturing Systems.}, type = {Technical Report}, year = 1995 }
• 
  Rose, Oliver ; Ritter, Michael: A New Approach for the Dimensioning of Policing Functions for MPEG-Video Sources in ATM-Systems. ( Nr. 97). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR97, address = {Department of Computer Science}, author = {Rose, Oliver and Ritter, Michael}, keywords = {myown}, month = {01}, number = 97, title = {A New Approach for the Dimensioning of Policing Functions for MPEG-Video Sources in ATM-Systems.}, type = {Technical Report}, year = 1995 }
• 
  Gerlich, Notker ; Tangemann, Michael: Towards a Channel Allocation Scheme for SDMA-based Mobile Communication Systems. ( Nr. 104). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR104, address = {Department of Computer Science}, author = {Gerlich, Notker and Tangemann, Michael}, keywords = {myown}, month = {02}, number = 104, title = {Towards a Channel Allocation Scheme for SDMA-based Mobile Communication Systems.}, type = {Technical Report}, year = 1995 }
• 
  Rooß, D. ; Wagner, Klaus W.: On the Power of Bio-Computers. ( Nr. 103). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR103, address = {Department of Computer Science}, author = {Rooß, D. and Wagner, Klaus W.}, keywords = {myown}, month = {02}, number = 103, title = {On the Power of Bio-Computers.}, type = {Technical Report}, year = 1995 }
• 
  Mittler, Manfred ; Müller, R.: Moment Approximation in Product Form Queueing Networks. ( Nr. 102). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR102, address = {Department of Computer Science}, author = {Mittler, Manfred and Müller, R.}, keywords = {myown}, month = {02}, number = 102, title = {Moment Approximation in Product Form Queueing Networks.}, type = {Technical Report}, year = 1995 }
• 
  Dabs, T. ; Schoof, Jochen: A Graphical User Interface For Genetic Algorithms. ( Nr. 98). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR98, address = {Department of Computer Science}, author = {Dabs, T. and Schoof, Jochen}, keywords = {myown}, month = {02}, number = 98, title = {A Graphical User Interface For Genetic Algorithms.}, type = {Technical Report}, year = 1995 }
• 
  Buntrock, Gerhard ; Niemann, G.: Weak Growing Context-Sensitive Grammars. ( Nr. 112). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR112, address = {Department of Computer Science}, author = {Buntrock, Gerhard and Niemann, G.}, keywords = {myown}, month = {05}, number = 112, title = {Weak Growing Context-Sensitive Grammars.}, type = {Technical Report}, year = 1995 }
• 
  Rose, Oliver: Statistical Properties of MPEG Video Traffic and their Impact on Traffic Modeling in ATM Systems. ( Nr. 101). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR101, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {02}, number = 101, title = {Statistical Properties of MPEG Video Traffic and their Impact on Traffic Modeling in ATM Systems.}, type = {Technical Report}, year = 1995 }
• 
  Frater, M.R. ; Rose, Oliver: Cell Loss Analysis of Broadband Switching Systems Carrying VBR Video. ( Nr. 99). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR99, address = {Department of Computer Science}, author = {Frater, M.R. and Rose, Oliver}, keywords = {myown}, month = {02}, number = 99, title = {Cell Loss Analysis of Broadband Switching Systems Carrying VBR Video.}, type = {Technical Report}, year = 1995 }
• 
  Hertrampf, Ulrich ; Vollmer, Heribert ; Wagner, Klaus W.: On the Power of Number-Theoretic Operations with Respect to Counting. ( Nr. 100). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR100, address = {Department of Computer Science}, author = {Hertrampf, Ulrich and Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = {01}, number = 100, title = {On the Power of Number-Theoretic Operations with Respect to Counting.}, type = {Technical Report}, year = 1995 }
• 
  Verbarg, K.: Approximate Center Points in Dense Point Sets. ( Nr. 117). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR117, address = {Department of Computer Science}, author = {Verbarg, K.}, keywords = {myown}, month = {05}, number = 117, title = {Approximate Center Points in Dense Point Sets.}, type = {Technical Report}, year = 1995 }
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  Krumke, S.O. ; Valenta, J.: Finding Tree-2-Spanners. ( Nr. 131). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR131, address = {Department of Computer Science}, author = {Krumke, S.O. and Valenta, J.}, keywords = {myown}, month = 12, number = 131, title = {Finding Tree-2-Spanners.}, type = {Technical Report}, year = 1995 }
• 
  Garcia, J. ; Ritter, Michael: Determination of Traffic Parameters for VPs Carrying Delay-Sensitive Traffic. ( Nr. 113). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR113, address = {Department of Computer Science}, author = {Garcia, J. and Ritter, Michael}, keywords = {myown}, month = {05}, number = 113, title = {Determination of Traffic Parameters for VPs Carrying Delay-Sensitive Traffic.}, type = {Technical Report}, year = 1995 }
• 
  Mittler, Manfred ; Gerlich, Notker ; Schömig, Alexander: On Cycle Times and Interdeparture Times in Semiconductor Manufacturing. ( Nr. 124). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR124, address = {Department of Computer Science}, author = {Mittler, Manfred and Gerlich, Notker and Schömig, Alexander}, keywords = {myown}, month = {09}, number = 124, title = {On Cycle Times and Interdeparture Times in Semiconductor Manufacturing.}, type = {Technical Report}, year = 1995 }
• 
  Ritter, Michael: Steady-State Analysis of the Rate-Based Congestion Control Mechanism for ABR Services in ATM Networks. ( Nr. 114). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR114, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = {05}, number = 114, title = {Steady-State Analysis of the Rate-Based Congestion Control Mechanism for ABR Services in ATM Networks.}, type = {Technical Report}, year = 1995 }
• 
  Wolfrath, M.: Results on Fat Objects with a Low Intersection Proportion. ( Nr. 130). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR130, address = {Department of Computer Science}, author = {Wolfrath, M.}, keywords = {myown}, month = 12, number = 130, title = {Results on Fat Objects with a Low Intersection Proportion.}, type = {Technical Report}, year = 1995 }
• 
  Hafner, U.: Asymmetric Coding in (m)-WFA Image Compression. ( Nr. 132). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR132, address = {Department of Computer Science}, author = {Hafner, U.}, keywords = {myown}, month = 12, number = 132, title = {Asymmetric Coding in (m)-WFA Image Compression.}, type = {Technical Report}, year = 1995 }
• 
  Gerlich, Notker: A Toolkit of Octave Functions for Discrete-Time Analysis of Queuing Systems. ( Nr. 128). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR128, address = {Department of Computer Science}, author = {Gerlich, Notker}, keywords = {myown}, month = 12, number = 128, title = {A Toolkit of Octave Functions for Discrete-Time Analysis of Queuing Systems.}, type = {Technical Report}, year = 1995 }
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  Mittler, Manfred ; Ono-Tesfaye, T. ; Schömig, Alexander: On the Approximation of Higher Moments in Open and Closed Fork/Join Primitives with Limited Buffers. ( Nr. 126). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR126, address = {Department of Computer Science}, author = {Mittler, Manfred and Ono-Tesfaye, T. and Schömig, Alexander}, keywords = {myown}, month = 11, number = 126, title = {On the Approximation of Higher Moments in Open and Closed Fork/Join Primitives with Limited Buffers.}, type = {Technical Report}, year = 1995 }
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  Mittler, Manfred ; Kern, Christoph: Discrete-Time Approximation of the Machine Repairman Model with Generally Distributed Failure, Repair, and Walking Times. ( Nr. 127). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR127, address = {Department of Computer Science}, author = {Mittler, Manfred and Kern, Christoph}, keywords = {myown}, month = 11, number = 127, title = {Discrete-Time Approximation of the Machine Repairman Model with Generally Distributed Failure, Repair, and Walking Times.}, type = {Technical Report}, year = 1995 }
• 
  von Gudenberg, Jürgen Wolff: Hardware Support for Interval Arithmetic - Extended Version. ( Nr. 125). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR125, address = {Department of Computer Science}, author = {von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = 10, number = 125, title = {Hardware Support for Interval Arithmetic - Extended Version.}, type = {Technical Report}, year = 1995 }
• 
  Ritter, Michael: Network Buffer Requirements of the Rate-Based Control Mechanism for ABR Services. ( Nr. 129). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR129, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = 12, number = 129, title = {Network Buffer Requirements of the Rate-Based Control Mechanism for ABR Services.}, type = {Technical Report}, year = 1995 }
• 
  Book, R.V. ; Vollmer, Heribert ; Wagner, Klaus W.: On Type-2 Probabilistic Quantifiers. ( Nr. 123). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR123, address = {Department of Computer Science}, author = {Book, R.V. and Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = {08}, number = 123, title = {On Type-2 Probabilistic Quantifiers.}, type = {Technical Report}, year = 1995 }
• 
  Rhein-Desel, U.: Eine ¨Übersicht¨ über medizinische Informationssysteme: Krankenhausinformationssysteme, Patientenaktensysteme und Kritiksysteme. ( Nr. 119). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR119, address = {Department of Computer Science}, author = {Rhein-Desel, U.}, keywords = {myown}, month = {07}, number = 119, title = {Eine ¨Übersicht¨ über medizinische Informationssysteme: Krankenhausinformationssysteme, Patientenaktensysteme und Kritiksysteme.}, type = {Technical Report}, year = 1995 }
• 
  Schömig, Alexander: On Transfer Blocking and Minimal Blocking in Serial Manufacturing Systems - The Impact of Buffer Allocation. ( Nr. 121). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR121, address = {Department of Computer Science}, author = {Schömig, Alexander}, keywords = {myown}, month = {07}, number = 121, title = {On Transfer Blocking and Minimal Blocking in Serial Manufacturing Systems - The Impact of Buffer Allocation.}, type = {Technical Report}, year = 1995 }
• 
  Rose, Oliver: Simple and Efficient Models for Variable Bit Rate MPEG Video Traffic. ( Nr. 120). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR120, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {07}, number = 120, title = {Simple and Efficient Models for Variable Bit Rate MPEG Video Traffic.}, type = {Technical Report}, year = 1995 }
• 
  Tutschku, Kurt: Recurrent Multilayer Perceptrons for Identification and Control: The Road to Applications. ( Nr. 118). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR118, address = {Department of Computer Science}, author = {Tutschku, Kurt}, keywords = {myown}, month = {06}, number = 118, title = {Recurrent Multilayer Perceptrons for Identification and Control: The Road to Applications.}, type = {Technical Report}, year = 1995 }
• 
  Graefe, Holger: Konzepte für ein zuverlässiges Message-Passing-System auf der Basis von UDP. ( Nr. 115). Department of Computer Science, 1995
  • [ BibTeX ]
  @techreport{TR115, address = {Department of Computer Science}, author = {Graefe, Holger}, keywords = {myown}, month = {05}, number = 115, title = {Konzepte für ein zuverlässiges Message-Passing-System auf der Basis von UDP.}, type = {Technical Report}, year = 1995 }
• 
  Schömig, Alexander ; Rau, H.: A Petri Net Approach for the Performance Analysis of Business Processes. ( Nr. 116). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR116, address = {Department of Computer Science}, author = {Schömig, Alexander and Rau, H.}, keywords = {myown}, month = {05}, number = 116, title = {A Petri Net Approach for the Performance Analysis of Business Processes.}, type = {Technical Report}, year = 1995 }
• 
  Fritsch, Thomas ; Tutschku, Kurt ; Leibnitz, Kenji: Field Strength Prediction by Ray-Tracing for Adaptive Base Station Positioning in Mobile Communication Networks. ( Nr. 122). Department of Computer Science, 1995
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR122, address = {Department of Computer Science}, author = {Fritsch, Thomas and Tutschku, Kurt and Leibnitz, Kenji}, keywords = {myown}, month = {08}, number = 122, title = {Field Strength Prediction by Ray-Tracing for Adaptive Base Station Positioning in Mobile Communication Networks.}, type = {Technical Report}, year = 1995 }

• 
  Rose, Oliver: Approximate Analysis of an ATM Multiplexer with MPEG Video Input. ( Nr. 79). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR79, address = {Department of Computer Science}, author = {Rose, Oliver}, keywords = {myown}, month = {01}, number = 79, title = {Approximate Analysis of an ATM Multiplexer with MPEG Video Input.}, type = {Technical Report}, year = 1994 }
• 
  Hertrampf, Ulrich ; Vollmer, Heribert ; Wagner, Klaus W.: On Balanced vs. Unbalanced Computation Trees. ( Nr. 82). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR82, address = {Department of Computer Science}, author = {Hertrampf, Ulrich and Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = {05}, number = 82, title = {On Balanced vs. Unbalanced Computation Trees.}, type = {Technical Report}, year = 1994 }
• 
  Ritter, Michael ; Kornprobst, S. ; Hübner, Frank: Performance Analysis of Source Policing Architectures in ATM Systems. ( Nr. 81). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR81, address = {Department of Computer Science}, author = {Ritter, Michael and Kornprobst, S. and Hübner, Frank}, keywords = {myown}, month = {04}, number = 81, title = {Performance Analysis of Source Policing Architectures in ATM Systems.}, type = {Technical Report}, year = 1994 }
• 
  Schömig, Alexander: Using Kanban in a Semiconductor Fabrication Environment - a Simulation Study. ( Nr. 80). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR80, address = {Department of Computer Science}, author = {Schömig, Alexander}, keywords = {myown}, month = {03}, number = 80, title = {Using Kanban in a Semiconductor Fabrication Environment - a Simulation Study.}, type = {Technical Report}, year = 1994 }
• 
  Cronauer, K.: A Criterion to Separate Complexity Classes by Oracles. ( Nr. 76). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR76, address = {Department of Computer Science}, author = {Cronauer, K.}, keywords = {myown}, month = {01}, number = 76, title = {A Criterion to Separate Complexity Classes by Oracles.}, type = {Technical Report}, year = 1994 }
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  Poeck, K. ; Fensel, D. ; Landes, D. ; Angele, J.: Combining KARL and Configurable Role Limiting Methods for Configuring Elevator Systems. ( Nr. 78). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR78, address = {Department of Computer Science}, author = {Poeck, K. and Fensel, D. and Landes, D. and Angele, J.}, keywords = {myown}, month = {01}, number = 78, title = {Combining KARL and Configurable Role Limiting Methods for Configuring Elevator Systems.}, type = {Technical Report}, year = 1994 }
• 
  Ritter, Michael: Analysis of the Generic Cell Rate Algorithm Monitoring ON/OFF-Traffic. ( Nr. 77). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR77, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = {01}, number = 77, title = {Analysis of the Generic Cell Rate Algorithm Monitoring ON/OFF-Traffic.}, type = {Technical Report}, year = 1994 }
• 
  Hübner, Frank: Output Process Analysis of the Peak Cell Rate Monitor Algorithm. ( Nr. 75). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR75, address = {Department of Computer Science}, author = {Hübner, Frank}, keywords = {myown}, month = {01}, number = 75, title = {Output Process Analysis of the Peak Cell Rate Monitor Algorithm.}, type = {Technical Report}, year = 1994 }
• 
  Hertrampf, Ulrich: Complexity Classes Defined via k-valued Functions. ( Nr. 84). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR84, address = {Department of Computer Science}, author = {Hertrampf, Ulrich}, keywords = {myown}, month = {07}, number = 84, title = {Complexity Classes Defined via k-valued Functions.}, type = {Technical Report}, year = 1994 }
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  Mittler, Manfred ; Schömig, Alexander: Entwicklung von ¨Due-Date¨-Warteschlangendisziplinen zur Optimierung von Produktionssystemen. ( Nr. 83). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR83, address = {Department of Computer Science}, author = {Mittler, Manfred and Schömig, Alexander}, keywords = {myown}, month = {05}, number = 83, title = {Entwicklung von ¨Due-Date¨-Warteschlangendisziplinen zur Optimierung von Produktionssystemen.}, type = {Technical Report}, year = 1994 }
• 
  Hertrampf, Ulrich: On Simple Closure Properties of #P. ( Nr. 90). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR90, address = {Department of Computer Science}, author = {Hertrampf, Ulrich}, keywords = {myown}, month = 10, number = 90, title = {On Simple Closure Properties of #P.}, type = {Technical Report}, year = 1994 }
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  Hertrampf, Ulrich: Locally Definable Acceptance: Closure Properties, Associativity, Finiteness. ( Nr. 85). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR85, address = {Department of Computer Science}, author = {Hertrampf, Ulrich}, keywords = {myown}, month = {07}, number = 85, title = {Locally Definable Acceptance: Closure Properties, Associativity, Finiteness.}, type = {Technical Report}, year = 1994 }
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  Mittler, Manfred ; Müller, R.: Sojourn Time Distribution of the Asymmetric M/M/1//N - System with LCFS-PR Service. ( Nr. 94). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR94, address = {Department of Computer Science}, author = {Mittler, Manfred and Müller, R.}, keywords = {myown}, month = 11, number = 94, title = {Sojourn Time Distribution of the Asymmetric M/M/1//N - System with LCFS-PR Service.}, type = {Technical Report}, year = 1994 }
• 
  Beaudry, M.: Recognition of Nonregular Languages by Finite Groupoids. ( Nr. 96). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR96, address = {Department of Computer Science}, author = {Beaudry, M.}, keywords = {myown}, month = 12, number = 96, title = {Recognition of Nonregular Languages by Finite Groupoids.}, type = {Technical Report}, year = 1994 }
• 
  Rose, Oliver ; Frater, M.R.: Delivery of MPEG Video Services over ATM . ( Nr. 86). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR86, address = {Department of Computer Science}, author = {Rose, Oliver and Frater, M.R.}, keywords = {myown}, month = {08}, number = 86, title = {Delivery of MPEG Video Services over ATM .}, type = {Technical Report}, year = 1994 }
• 
  Ritter, Michael: Performance Analysis of the Dual Cell Spacer in ATM Systems. ( Nr. 95). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR95, address = {Department of Computer Science}, author = {Ritter, Michael}, keywords = {myown}, month = 11, number = 95, title = {Performance Analysis of the Dual Cell Spacer in ATM Systems.}, type = {Technical Report}, year = 1994 }
• 
  Vollmer, Heribert ; Wagner, Klaus W.: Recursion Theoretic Characterizations of Complexity Classes of Counting Functions. ( Nr. 91). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR91, address = {Department of Computer Science}, author = {Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = 11, number = 91, title = {Recursion Theoretic Characterizations of Complexity Classes of Counting Functions.}, type = {Technical Report}, year = 1994 }
• 
  Nöth, Winfried ; Kolla, Reiner: Optimal Synthesis of Fanoutfree Functions. ( Nr. 93). Department of Computer Science, 1994
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  The problem of provable optimal synthesis of boolean functions for a given technology is still unsolved. In this paper we study the problem for the small class of fanoutfree functions. Every fanoutfree function can be uniquely represented by a Normal AND-OR-Tree. Based on this representation, we introduce algorithms for provable optimal synthesis of any n-input fanoutfree function over a given library of gates implementing the functions AND, OR, NAND and NOR with 2...k inputs. The synthesis yields a complete time-area tradeoff of the optimal fanoutfree implementations of the function. Since in worst case our algorithms have exponential run time, we show their feasibility on realistic examples of fanout free zones of circuits. Finally, ideas are outlined for the integration of complex gates into the synthesis process.

  @techreport{TR93, abstract = {The problem of provable optimal synthesis of boolean functions for a given technology is still unsolved. In this paper we study the problem for the small class of fanoutfree functions. Every fanoutfree function can be uniquely represented by a Normal AND-OR-Tree. Based on this representation, we introduce algorithms for provable optimal synthesis of any n-input fanoutfree function over a given library of gates implementing the functions AND, OR, NAND and NOR with 2...k inputs. The synthesis yields a complete time-area tradeoff of the optimal fanoutfree implementations of the function. Since in worst case our algorithms have exponential run time, we show their feasibility on realistic examples of fanout free zones of circuits. Finally, ideas are outlined for the integration of complex gates into the synthesis process.}, address = {Department of Computer Science}, author = {Nöth, Winfried and Kolla, Reiner}, keywords = {myown}, month = 11, number = 93, title = {Optimal Synthesis of Fanoutfree Functions.}, type = {Technical Report}, year = 1994 }
• 
  Hinsberger, Uwe ; Kolla, Reiner: Optimal Technology Mapping for Single Output Cells. ( Nr. 92). Department of Computer Science, 1994
  • [ Abstract ]
  • [ BibTeX ]
  • [ URL ]
  This paper presents a new approach to technology mapping for arbitrary technologies with single output cells. It overcomes the restrictions of tree-mapping based methods. Optimal algorithms for special cases of DAG-mapping are presented: for minimum delay mapping and for duplication-free mapping under a class of simple cost functions (including area and delay). Heuristics for the general case and for computing AT-tradeoffs are developed and applied to LUT-based FPGAs.

  @techreport{TR92, abstract = {This paper presents a new approach to technology mapping for arbitrary technologies with single output cells. It overcomes the restrictions of tree-mapping based methods. Optimal algorithms for special cases of DAG-mapping are presented: for minimum delay mapping and for duplication-free mapping under a class of simple cost functions (including area and delay). Heuristics for the general case and for computing AT-tradeoffs are developed and applied to LUT-based FPGAs.}, address = {Department of Computer Science}, author = {Hinsberger, Uwe and Kolla, Reiner}, keywords = {myown}, month = 11, number = 92, title = {Optimal Technology Mapping for Single Output Cells.}, type = {Technical Report}, year = 1994 }
• 
  Hertrampf, Ulrich: Finite Acceptance Type Classes. ( Nr. 89). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR89, address = {Department of Computer Science}, author = {Hertrampf, Ulrich}, keywords = {myown}, month = 10, number = 89, title = {Finite Acceptance Type Classes.}, type = {Technical Report}, year = 1994 }
• 
  Rothaug, U. ; Yanenko, E. ; Leibnitz, Kenji: Artificial Neural Networks Used for Way Optimization in Multi-Head Systems in Application to Electrical Flying Probe Testers. ( Nr. 88). Department of Computer Science, 1994
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR88, address = {Department of Computer Science}, author = {Rothaug, U. and Yanenko, E. and Leibnitz, Kenji}, keywords = {myown}, month = {09}, number = 88, title = {Artificial Neural Networks Used for Way Optimization in Multi-Head Systems in Application to Electrical Flying Probe Testers.}, type = {Technical Report}, year = 1994 }
• 
  Reinhardt, B.: Kritik von Symptomerkennung in einem Hypertext-Dokument. ( Nr. 87). Department of Computer Science, 1994
  • [ BibTeX ]
  @techreport{TR87, address = {Department of Computer Science}, author = {Reinhardt, B.}, keywords = {myown}, month = {08}, number = 87, title = {Kritik von Symptomerkennung in einem Hypertext-Dokument.}, type = {Technical Report}, year = 1994 }

• 
  Öhring, S. ; Das, S.K.: Mapping Dynamic Data and Algorithm Structures on Product Networks. ( Nr. 65). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR65, address = {Department of Computer Science}, author = {Öhring, S. and Das, S.K.}, keywords = {myown}, month = {05}, number = 65, title = {Mapping Dynamic Data and Algorithm Structures on Product Networks.}, type = {Technical Report}, year = 1993 }
• 
  Vollmer, Heribert ; Wagner, Klaus W.: The complexity of finding middle elements. ( Nr. 53). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR53, address = {Department of Computer Science}, author = {Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = {01}, number = 53, title = {The complexity of finding middle elements.}, type = {Technical Report}, year = 1993 }
• 
  Gihr, O. ; Gold, Hermann ; Heilmann, S.: Analysis of machine breakdown models. ( Nr. 54). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR54, address = {Department of Computer Science}, author = {Gihr, O. and Gold, Hermann and Heilmann, S.}, keywords = {myown}, month = {01}, number = 54, title = {Analysis of machine breakdown models.}, type = {Technical Report}, year = 1993 }
• 
  Öhring, S.: Optimal dynamic embeddings of arbitrary trees in de Bruijn networks. ( Nr. 55). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR55, address = {Department of Computer Science}, author = {Öhring, S.}, keywords = {myown}, month = {02}, number = 55, title = {Optimal dynamic embeddings of arbitrary trees in de Bruijn networks.}, type = {Technical Report}, year = 1993 }
• 
  Hübner, Frank: Dimensioning of a peak cell rate monitor algorithm using discrete-time analysis. ( Nr. 59). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR59, address = {Department of Computer Science}, author = {Hübner, Frank}, keywords = {myown}, month = {03}, number = 59, title = {Dimensioning of a peak cell rate monitor algorithm using discrete-time analysis.}, type = {Technical Report}, year = 1993 }
• 
  Albert, Jürgen ; Duckstein, Franz ; Lautner, M. ; Menzel, Bernd: Message-passing auf transputer-systemen. ( Nr. 57). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR57, address = {Department of Computer Science}, author = {Albert, Jürgen and Duckstein, Franz and Lautner, M. and Menzel, Bernd}, keywords = {myown}, month = {03}, number = 57, title = {Message-passing auf transputer-systemen.}, type = {Technical Report}, year = 1993 }
• 
  Stock, Thomas ; Tran-Gia, Phuoc: Basic concepts and performance of high-speed protocols. ( Nr. 58). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR58, address = {Department of Computer Science}, author = {Stock, Thomas and Tran-Gia, Phuoc}, keywords = {myown}, month = {03}, number = 58, title = {Basic concepts and performance of high-speed protocols.}, type = {Technical Report}, year = 1993 }
• 
  Gold, Hermann ; Frötschl, Bernhard: Performance analysis of a batch service system working with a combined push/pull control. ( Nr. 61). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR61, address = {Department of Computer Science}, author = {Gold, Hermann and Frötschl, Bernhard}, keywords = {myown}, month = {04}, number = 61, title = {Performance analysis of a batch service system working with a combined push/pull control.}, type = {Technical Report}, year = 1993 }
• 
  Vollmer, Heribert: On different reducibility notions for function classes. ( Nr. 62). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR62, address = {Department of Computer Science}, author = {Vollmer, Heribert}, keywords = {myown}, month = {04}, number = 62, title = {On different reducibility notions for function classes.}, type = {Technical Report}, year = 1993 }
• 
  Buntrock, Gerhard ; Lorys, K.: The variable membership problem: Succinctness versus complexity. ( Nr. 60). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR60, address = {Department of Computer Science}, author = {Buntrock, Gerhard and Lorys, K.}, keywords = {myown}, month = {04}, number = 60, title = {The variable membership problem: Succinctness versus complexity.}, type = {Technical Report}, year = 1993 }
• 
  Mittler, Manfred: Analysis of two finite queues coupled by a triggering scheduler. ( Nr. 56). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR56, address = {Department of Computer Science}, author = {Mittler, Manfred}, keywords = {myown}, month = {03}, number = 56, title = {Analysis of two finite queues coupled by a triggering scheduler.}, type = {Technical Report}, year = 1993 }
• 
  Öhring, S. ; Das, S.K.: Incomplete Hypercubes: Embeddings of Tree-Related Networks. ( Nr. 64). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR64, address = {Department of Computer Science}, author = {Öhring, S. and Das, S.K.}, keywords = {myown}, month = {05}, number = 64, title = {Incomplete Hypercubes: Embeddings of Tree-Related Networks.}, type = {Technical Report}, year = 1993 }
• 
  Rose, Oliver ; Frater, M.R.: A Comparison of Models for VBR Video Traffic Sources in B-ISDN. ( Nr. 72). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR72, address = {Department of Computer Science}, author = {Rose, Oliver and Frater, M.R.}, keywords = {myown}, month = 10, number = 72, title = {A Comparison of Models for VBR Video Traffic Sources in B-ISDN.}, type = {Technical Report}, year = 1993 }
• 
  Tran-Gia, Phuoc: Discrete-Time Analysis Technique and Application to Usage Parameter Control Modelling in ATM Systems. ( Nr. 74). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR74, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc}, keywords = {myown}, month = 11, number = 74, title = {Discrete-Time Analysis Technique and Application to Usage Parameter Control Modelling in ATM Systems.}, type = {Technical Report}, year = 1993 }
• 
  Mittler, Manfred ; Gerlich, Notker: Reducing the Variance of Sojourn Times in Queueing Networks with Overtaking. ( Nr. 73). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR73, address = {Department of Computer Science}, author = {Mittler, Manfred and Gerlich, Notker}, keywords = {myown}, month = 11, number = 73, title = {Reducing the Variance of Sojourn Times in Queueing Networks with Overtaking.}, type = {Technical Report}, year = 1993 }
• 
  Öhring, S. ; Das, S.K.: Optimal Communication Primitives on the Folded Petersen Networks. ( Nr. 71). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR71, address = {Department of Computer Science}, author = {Öhring, S. and Das, S.K.}, keywords = {myown}, month = 10, number = 71, title = {Optimal Communication Primitives on the Folded Petersen Networks.}, type = {Technical Report}, year = 1993 }
• 
  Öhring, S. ; Das, S.K.: Folded Petersen Cube Networks: New Competitors for the Hyepercubes. ( Nr. 63). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR63, address = {Department of Computer Science}, author = {Öhring, S. and Das, S.K.}, keywords = {myown}, month = {05}, number = 63, title = {Folded Petersen Cube Networks: New Competitors for the Hyepercubes.}, type = {Technical Report}, year = 1993 }
• 
  Öhring, S. ; Das, S.K.: Embeddings of Tree-Related Topologies in Hyper Petersen Networks. ( Nr. 70). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR70, address = {Department of Computer Science}, author = {Öhring, S. and Das, S.K.}, keywords = {myown}, month = 10, number = 70, title = {Embeddings of Tree-Related Topologies in Hyper Petersen Networks.}, type = {Technical Report}, year = 1993 }
• 
  Buntrock, Gerhard: Growing Context-Sensitive Languages and Automata. ( Nr. 69). Department of Computer Science, 1993
  • [ BibTeX ]
  @techreport{TR69, address = {Department of Computer Science}, author = {Buntrock, Gerhard}, keywords = {myown}, month = {09}, number = 69, title = {Growing Context-Sensitive Languages and Automata.}, type = {Technical Report}, year = 1993 }
• 
  Frisch, M. ; Jucht, K.: Pascalli-P. ( Nr. 68). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR68, address = {Department of Computer Science}, author = {Frisch, M. and Jucht, K.}, keywords = {myown}, month = {08}, number = 68, title = {Pascalli-P.}, type = {Technical Report}, year = 1993 }
• 
  Dittmann, Rainer ; Hübner, Frank: Discrete-Time Analysis of a Cyclic Service System with Gated Limited Service. ( Nr. 67). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR67, address = {Department of Computer Science}, author = {Dittmann, Rainer and Hübner, Frank}, keywords = {myown}, month = {06}, number = 67, title = {Discrete-Time Analysis of a Cyclic Service System with Gated Limited Service.}, type = {Technical Report}, year = 1993 }
• 
  Hübner, Frank ; Tran-Gia, Phuoc: A Discrete-Time Analysis of Cell Spacing in ATM Systems. ( Nr. 66). Department of Computer Science, 1993
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR66, address = {Department of Computer Science}, author = {Hübner, Frank and Tran-Gia, Phuoc}, keywords = {myown}, month = {06}, number = 66, title = {A Discrete-Time Analysis of Cell Spacing in ATM Systems.}, type = {Technical Report}, year = 1993 }

• 
  Buntrock, Gerhard ; Lorys, K.: On growing context-sensitive languages. ( Nr. 38). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR38, address = {Department of Computer Science}, author = {Buntrock, Gerhard and Lorys, K.}, keywords = {myown}, month = {01}, number = 38, title = {On growing context-sensitive languages.}, type = {Technical Report}, year = 1992 }
• 
  Wagner, Klaus W.: Alternating machines using partially defined ``AND’’ and ``OR’’ . ( Nr. 39). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR39, address = {Department of Computer Science}, author = {Wagner, Klaus W.}, keywords = {myown}, month = {01}, number = 39, title = {Alternating machines using partially defined ``AND'' and ``OR'' .}, type = {Technical Report}, year = 1992 }
• 
  Hübner, Frank ; Tran-Gia, Phuoc: An analysis of multi-service systems with trunk reservation mechanisms. ( Nr. 40). Department of Computer Science, 1992
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  @techreport{TR40, address = {Department of Computer Science}, author = {Hübner, Frank and Tran-Gia, Phuoc}, keywords = {myown}, month = {04}, number = 40, title = {An analysis of multi-service systems with trunk reservation mechanisms.}, type = {Technical Report}, year = 1992 }
• 
  Huckenbeck, Ulrich: Cost-bounded paths in networks of pipes with valves. ( Nr. 42). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR42, address = {Department of Computer Science}, author = {Huckenbeck, Ulrich}, keywords = {myown}, month = {05}, number = 42, title = {Cost-bounded paths in networks of pipes with valves.}, type = {Technical Report}, year = 1992 }
• 
  Huckenbeck, Ulrich: On a generalization of the bellman-ford-algorithm for acyclic graphs. ( Nr. 41). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR41, address = {Department of Computer Science}, author = {Huckenbeck, Ulrich}, keywords = {myown}, month = {05}, number = 41, title = {On a generalization of the bellman-ford-algorithm for acyclic graphs.}, type = {Technical Report}, year = 1992 }
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  Hübner, Frank: Autocorrelation and power density spectrum of ATM multiplexer output processes. ( Nr. 43). Department of Computer Science, 1992
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR43, address = {Department of Computer Science}, author = {Hübner, Frank}, keywords = {myown}, month = {09}, number = 43, title = {Autocorrelation and power density spectrum of ATM multiplexer output processes.}, type = {Technical Report}, year = 1992 }
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  Hübner, Frank ; Ritter, Michael: Multi-service broadband systems with CBR and VBR input traffic. ( Nr. 44). Department of Computer Science, 1992
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR44, address = {Department of Computer Science}, author = {Hübner, Frank and Ritter, Michael}, keywords = {myown}, month = 10, number = 44, title = {Multi-service broadband systems with CBR and VBR input traffic.}, type = {Technical Report}, year = 1992 }
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  Mittler, Manfred ; Tran-Gia, Phuoc: Performance of a neural net scheduler used in packet switching interconnection networks. ( Nr. 45). Department of Computer Science, 1992
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR45, address = {Department of Computer Science}, author = {Mittler, Manfred and Tran-Gia, Phuoc}, keywords = {myown}, month = 10, number = 45, title = {Performance of a neural net scheduler used in packet switching interconnection networks.}, type = {Technical Report}, year = 1992 }
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  Kowaluk, M. ; Wagner, Klaus W.: Vector language: Simple description of hard instances. ( Nr. 46). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR46, address = {Department of Computer Science}, author = {Kowaluk, M. and Wagner, Klaus W.}, keywords = {myown}, month = 10, number = 46, title = {Vector language: Simple description of hard instances.}, type = {Technical Report}, year = 1992 }
• 
  Öhring, S.: On dynamic and modular embeddings into hyper de Bruijn networks. ( Nr. 49). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR49, address = {Department of Computer Science}, author = {Öhring, S.}, keywords = {myown}, month = 11, number = 49, title = {On dynamic and modular embeddings into hyper de Bruijn networks.}, type = {Technical Report}, year = 1992 }
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  Menzel, Bernd ; von Gudenberg, Jürgen Wolff: Kommentierte Syntaxdiagramme für C++. ( Nr. 47). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR47, address = {Department of Computer Science}, author = {Menzel, Bernd and von Gudenberg, Jürgen Wolff}, keywords = {myown}, month = 11, number = 47, title = {Kommentierte Syntaxdiagramme für C++.}, type = {Technical Report}, year = 1992 }
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  Emme, D.: A kernel for function definable classes and its relations to lowness. ( Nr. 48). Department of Computer Science, 1992
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR48, address = {Department of Computer Science}, author = {Emme, D.}, keywords = {myown}, month = 11, number = 48, title = {A kernel for function definable classes and its relations to lowness.}, type = {Technical Report}, year = 1992 }
• 
  Poeck, K. ; Tins, M.: An intelligent tutoring system for classification problem solving. ( Nr. 50). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR50, address = {Department of Computer Science}, author = {Poeck, K. and Tins, M.}, keywords = {myown}, month = 11, number = 50, title = {An intelligent tutoring system for classification problem solving.}, type = {Technical Report}, year = 1992 }
• 
  Fritsch, Thomas ; Mittler, Manfred ; Tran-Gia, Phuoc: Artificial neural net applications in telecommunication systems. ( Nr. 52). Department of Computer Science, 1992
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR52, address = {Department of Computer Science}, author = {Fritsch, Thomas and Mittler, Manfred and Tran-Gia, Phuoc}, keywords = {myown}, month = 12, number = 52, title = {Artificial neural net applications in telecommunication systems.}, type = {Technical Report}, year = 1992 }
• 
  Poeck, K. ; Puppe, Frank: COKE: Efficient solving of complex assignment problems with the propose-and-exchange method. ( Nr. 51). Department of Computer Science, 1992
  • [ BibTeX ]
  @techreport{TR51, address = {Department of Computer Science}, author = {Poeck, K. and Puppe, Frank}, keywords = {myown}, month = 11, number = 51, title = {COKE: Efficient solving of complex assignment problems with the propose-and-exchange method.}, type = {Technical Report}, year = 1992 }

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  Fritsch, Thomas ; Mandel, Wolfgang: Communication network routing using neural nets - numerical aspects and alternative approaches. ( Nr. 30). Department of Computer Science, 1991
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  • [ URL ]
  @techreport{TR30, address = {Department of Computer Science}, author = {Fritsch, Thomas and Mandel, Wolfgang}, keywords = {myown}, month = {07}, number = 30, title = {Communication network routing using neural nets - numerical aspects and alternative approaches.}, type = {Technical Report}, year = 1991 }
• 
  Wrathall, C.: Confluence of one-rule Thue systems. ( Nr. 24). Department of Computer Science, 1991
  • [ BibTeX ]
  @techreport{TR24, address = {Department of Computer Science}, author = {Wrathall, C.}, keywords = {myown}, month = {01}, number = 24, title = {Confluence of one-rule Thue systems.}, type = {Technical Report}, year = 1991 }
• 
  Gihr, O. ; Tran-Gia, Phuoc: A layered description of ATM cell traffic streams and correlation analysis. ( Nr. 25). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR25, address = {Department of Computer Science}, author = {Gihr, O. and Tran-Gia, Phuoc}, keywords = {myown}, month = {01}, number = 25, title = {A layered description of ATM cell traffic streams and correlation analysis.}, type = {Technical Report}, year = 1991 }
• 
  Gold, Hermann ; Hübner, Frank: Multi server batch service systems in push and pull operating mode - a performance comparison. ( Nr. 26). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR26, address = {Department of Computer Science}, author = {Gold, Hermann and Hübner, Frank}, keywords = {myown}, month = {06}, number = 26, title = {Multi server batch service systems in push and pull operating mode - a performance comparison.}, type = {Technical Report}, year = 1991 }
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  Gold, Hermann ; Grob, Heidrun: Performance analysis of a batch service system operating in pull mode. ( Nr. 27). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR27, address = {Department of Computer Science}, author = {Gold, Hermann and Grob, Heidrun}, keywords = {myown}, month = {07}, number = 27, title = {Performance analysis of a batch service system operating in pull mode.}, type = {Technical Report}, year = 1991 }
• 
  Hertrampf, Ulrich: Locally definable acceptance types-the three valued case. ( Nr. 28). Department of Computer Science, 1991
  • [ BibTeX ]
  @techreport{TR28, address = {Department of Computer Science}, author = {Hertrampf, Ulrich}, keywords = {myown}, month = {07}, number = 28, title = {Locally definable acceptance types-the three valued case.}, type = {Technical Report}, year = 1991 }
• 
  Vollmer, Heribert ; Wagner, Klaus W.: Classes of counting functions and complexity theoretic operators. ( Nr. 31). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR31, address = {Department of Computer Science}, author = {Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = {08}, number = 31, title = {Classes of counting functions and complexity theoretic operators.}, type = {Technical Report}, year = 1991 }
• 
  Hertrampf, Ulrich: Locally definable acceptance types for polynomial time machines. ( Nr. 29). Department of Computer Science, 1991
  • [ BibTeX ]
  @techreport{TR29, address = {Department of Computer Science}, author = {Hertrampf, Ulrich}, keywords = {myown}, month = {07}, number = 29, title = {Locally definable acceptance types for polynomial time machines.}, type = {Technical Report}, year = 1991 }
• 
  Hübner, Frank: Queueing analysis of resource dispatching and scheduling in multi-media systems. ( Nr. 33). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR33, address = {Department of Computer Science}, author = {Hübner, Frank}, keywords = {myown}, month = {09}, number = 33, title = {Queueing analysis of resource dispatching and scheduling in multi-media systems.}, type = {Technical Report}, year = 1991 }
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  Gold, Hermann ; Bleckert, Gabriele: Analysis of a batch service system with two heterogeneous servers. ( Nr. 34). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR34, address = {Department of Computer Science}, author = {Gold, Hermann and Bleckert, Gabriele}, keywords = {myown}, month = {09}, number = 34, title = {Analysis of a batch service system with two heterogeneous servers.}, type = {Technical Report}, year = 1991 }
• 
  Vollmer, Heribert ; Wagner, Klaus W.: Complexity of functions versus complexity of sets. ( Nr. 35). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR35, address = {Department of Computer Science}, author = {Vollmer, Heribert and Wagner, Klaus W.}, keywords = {myown}, month = 10, number = 35, title = {Complexity of functions versus complexity of sets.}, type = {Technical Report}, year = 1991 }
• 
  Tran-Gia, Phuoc ; Gropp, O.: Structure and performance of neural nets in broadband system admission control. ( Nr. 37). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR37, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc and Gropp, O.}, keywords = {myown}, month = 11, number = 37, title = {Structure and performance of neural nets in broadband system admission control.}, type = {Technical Report}, year = 1991 }
• 
  Hübner, Frank: Discrete-time analysis of the output process of an ATM multiplexer with periodic input. ( Nr. 36). Department of Computer Science, 1991
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR36, address = {Department of Computer Science}, author = {Hübner, Frank}, keywords = {myown}, month = 11, number = 36, title = {Discrete-time analysis of the output process of an ATM multiplexer with periodic input.}, type = {Technical Report}, year = 1991 }
• 
  Book, R.V. ; Lutz, J.H. ; Wagner, Klaus W.: On complexity classes and algorithmically random languages. ( Nr. 32). Department of Computer Science, 1991
  • [ BibTeX ]
  @techreport{TR32, address = {Department of Computer Science}, author = {Book, R.V. and Lutz, J.H. and Wagner, Klaus W.}, keywords = {myown}, month = {08}, number = 32, title = {On complexity classes and algorithmically random languages.}, type = {Technical Report}, year = 1991 }

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  Hübner, Frank: Analysis of a finite capacity a synchronous multiplexer with periodic sources. ( Nr. 14). Department of Computer Science, 1990
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR14, address = {Department of Computer Science}, author = {Hübner, Frank}, keywords = {myown}, month = {07}, number = 14, title = {Analysis of a finite capacity a synchronous multiplexer with periodic sources.}, type = {Technical Report}, year = 1990 }
• 
  Gutbrod, Roger: A transformation system for chain code picture languages: Properties and algorithms. ( Nr. 10). Department of Computer Science, 1990
  • [ BibTeX ]
  @techreport{TR10, address = {Department of Computer Science}, author = {Gutbrod, Roger}, keywords = {myown}, month = {01}, number = 10, title = {A transformation system for chain code picture languages: Properties and algorithms.}, type = {Technical Report}, year = 1990 }
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  Stock, Thomas ; Tran-Gia, Phuoc: A discrete-time analysis of the DQDB access protocol with general input traffic. ( Nr. 11). Department of Computer Science, 1990
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  • [ URL ]
  @techreport{TR11, address = {Department of Computer Science}, author = {Stock, Thomas and Tran-Gia, Phuoc}, keywords = {myown}, month = {02}, number = 11, title = {A discrete-time analysis of the DQDB access protocol with general input traffic.}, type = {Technical Report}, year = 1990 }
• 
  Allender, E.W. ; Hertrampf, Ulrich: On the power of uniform families of constant depth threshold circuits. ( Nr. 12). Department of Computer Science, 1990
  • [ BibTeX ]
  @techreport{TR12, address = {Department of Computer Science}, author = {Allender, E.W. and Hertrampf, Ulrich}, keywords = {myown}, month = {02}, number = 12, title = {On the power of uniform families of constant depth threshold circuits.}, type = {Technical Report}, year = 1990 }
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  Buntrock, Gerhard ; Hemachandra, L.A. ; Siefkes, D.: Using inductive counting to simulate nondeterministic computation. ( Nr. 13). Department of Computer Science, 1990
  • [ BibTeX ]
  @techreport{TR13, address = {Department of Computer Science}, author = {Buntrock, Gerhard and Hemachandra, L.A. and Siefkes, D.}, keywords = {myown}, month = {04}, number = 13, title = {Using inductive counting to simulate nondeterministic computation.}, type = {Technical Report}, year = 1990 }
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  Gold, Hermann ; Tran-Gia, Phuoc: Performance analysis of a batch service queue arising out of manufacturing systems modeling. ( Nr. 16). Department of Computer Science, 1990
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR16, address = {Department of Computer Science}, author = {Gold, Hermann and Tran-Gia, Phuoc}, keywords = {myown}, month = {07}, number = 16, title = {Performance analysis of a batch service queue arising out of manufacturing systems modeling.}, type = {Technical Report}, year = 1990 }
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  Hübner, Frank ; Tran-Gia, Phuoc: Quasi-stationary analysis of a finite capacity asynchronous multiplexer with modulated deterministic input. ( Nr. 17). Department of Computer Science, 1990
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR17, address = {Department of Computer Science}, author = {Hübner, Frank and Tran-Gia, Phuoc}, keywords = {myown}, month = {07}, number = 17, title = {Quasi-stationary analysis of a finite capacity asynchronous multiplexer with modulated deterministic input.}, type = {Technical Report}, year = 1990 }
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  Buntrock, Gerhard ; Damm, C. ; Hertrampf, Ulrich ; Meinel, C.: Structure and importance of logspace- MOD -classes. ( Nr. 15). Department of Computer Science, 1990
  • [ BibTeX ]
  @techreport{TR15, address = {Department of Computer Science}, author = {Buntrock, Gerhard and Damm, C. and Hertrampf, Ulrich and Meinel, C.}, keywords = {myown}, month = {07}, number = 15, title = {Structure and importance of logspace- MOD -classes.}, type = {Technical Report}, year = 1990 }
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  Tran-Gia, Phuoc: Analysis of polling systems with general input process and finite capacity. ( Nr. 19). Department of Computer Science, 1990
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR19, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc}, keywords = {myown}, month = {08}, number = 19, title = {Analysis of polling systems with general input process and finite capacity.}, type = {Technical Report}, year = 1990 }
• 
  Huckenbeck, Ulrich: Complexity and approximation theoretical properties of rational functions which map two intervals into two other ones. ( Nr. 18). Department of Computer Science, 1990
  • [ BibTeX ]
  @techreport{TR18, address = {Department of Computer Science}, author = {Huckenbeck, Ulrich}, keywords = {myown}, month = {08}, number = 18, title = {Complexity and approximation theoretical properties of rational functions which map two intervals into two other ones.}, type = {Technical Report}, year = 1990 }
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  Friedewald, Conny ; Hieronymus, Andreas ; Menzel, Bernd: WUMPS Würzburger message passing system. ( Nr. 20). Department of Computer Science, 1990
  • [ BibTeX ]
  @techreport{TR20, address = {Department of Computer Science}, author = {Friedewald, Conny and Hieronymus, Andreas and Menzel, Bernd}, keywords = {myown}, month = 10, number = 20, title = {WUMPS Würzburger message passing system.}, type = {Technical Report}, year = 1990 }
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  Stock, Thomas: Influences of multiple priorities on DQDB protocol performance. ( Nr. 22). Department of Computer Science, 1990
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR22, address = {Department of Computer Science}, author = {Stock, Thomas}, keywords = {myown}, month = 11, number = 22, title = {Influences of multiple priorities on DQDB protocol performance.}, type = {Technical Report}, year = 1990 }
• 
  Book, R.V.: On random oracle separations. ( Nr. 21). Department of Computer Science, 1990
  • [ BibTeX ]
  @techreport{TR21, address = {Department of Computer Science}, author = {Book, R.V.}, keywords = {myown}, month = 11, number = 21, title = {On random oracle separations.}, type = {Technical Report}, year = 1990 }
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  Tran-Gia, Phuoc ; Dittmann, Rainer: Performance analysis of the CRMA-protocol in high-speed networks. ( Nr. 23). Department of Computer Science, 1990
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR23, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc and Dittmann, Rainer}, keywords = {myown}, month = 12, number = 23, title = {Performance analysis of the CRMA-protocol in high-speed networks.}, type = {Technical Report}, year = 1990 }

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  Wagner, Klaus W.: 9. Workshop über Komplexitätstheorie, effiziente Algorithmen und Datenstrukturen. ( Nr. 9). Department of Computer Science, 1989
  • [ BibTeX ]
  @techreport{TR9, address = {Department of Computer Science}, author = {Wagner, Klaus W.}, keywords = {myown}, month = 11, number = 9, title = {9. Workshop über Komplexitätstheorie, effiziente Algorithmen und Datenstrukturen.}, type = {Technical Report}, year = 1989 }
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  Kowaluk, M. ; Wagner, Klaus W.: Die Vektor-Sprache: Einfachste Mittel zur kompakten Beschreibung endlicher Objekte. ( Nr. 7). Department of Computer Science, 1989
  • [ BibTeX ]
  @techreport{TR7, address = {Department of Computer Science}, author = {Kowaluk, M. and Wagner, Klaus W.}, keywords = {myown}, month = {08}, number = 7, title = {Die Vektor-Sprache: Einfachste Mittel zur kompakten Beschreibung endlicher Objekte.}, type = {Technical Report}, year = 1989 }
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  Kowaluk, M. ; Wagner, Klaus W.: Vektor-Reduzierbarkeit. ( Nr. 8). Department of Computer Science, 1989
  • [ BibTeX ]
  @techreport{TR8, address = {Department of Computer Science}, author = {Kowaluk, M. and Wagner, Klaus W.}, keywords = {myown}, month = {08}, number = 8, title = {Vektor-Reduzierbarkeit.}, type = {Technical Report}, year = 1989 }
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  Tran-Gia, Phuoc ; Stock, Thomas: Approximate performance analysis of the DQDB access protocol. ( Nr. 6). Department of Computer Science, 1989
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR6, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc and Stock, Thomas}, keywords = {myown}, month = {08}, number = 6, title = {Approximate performance analysis of the DQDB access protocol.}, type = {Technical Report}, year = 1989 }
• 
  Allender, E.W.: A note on the power of threshold circuits. ( Nr. 5). Department of Computer Science, 1989
  • [ BibTeX ]
  @techreport{TR5, address = {Department of Computer Science}, author = {Allender, E.W.}, keywords = {myown}, month = {07}, number = 5, title = {A note on the power of threshold circuits.}, type = {Technical Report}, year = 1989 }
• 
  Wagner, Klaus W.: Bounded query classes. ( Nr. 1). Department of Computer Science, 1989
  • [ BibTeX ]
  @techreport{TR1, address = {Department of Computer Science}, author = {Wagner, Klaus W.}, keywords = {myown}, month = {02}, number = 1, title = {Bounded query classes.}, type = {Technical Report}, year = 1989 }
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  Wagner, Klaus W.: Number-of-query hierarchies. ( Nr. 4). Department of Computer Science, 1989
  • [ BibTeX ]
  @techreport{TR4, address = {Department of Computer Science}, author = {Wagner, Klaus W.}, keywords = {myown}, month = {02}, number = 4, title = {Number-of-query hierarchies.}, type = {Technical Report}, year = 1989 }
• 
  Tran-Gia, Phuoc: Application of the discrete transforms in performance modeling and analysis. ( Nr. 2). Department of Computer Science, 1989
  • [ BibTeX ]
  • [ URL ]
  @techreport{TR2, address = {Department of Computer Science}, author = {Tran-Gia, Phuoc}, keywords = {myown}, month = {02}, number = 2, title = {Application of the discrete transforms in performance modeling and analysis.}, type = {Technical Report}, year = 1989 }
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  Hertrampf, Ulrich: Relations among mod-classes. ( Nr. 3). Department of Computer Science, 1989
  • [ BibTeX ]
  @techreport{TR3, address = {Department of Computer Science}, author = {Hertrampf, Ulrich}, keywords = {myown}, month = {02}, number = 3, title = {Relations among mod-classes.}, type = {Technical Report}, year = 1989 }