Seminar: Sensornetze (WS2012/13)

In dieser Einführungsveranstaltung werden einige, für das Seminar wesentliche Begriffe (z.B. Sensorknoten, Sensornetzwerk, ...) kurz erläutert, sowie die bereitgestellten Themen vorgestellt. Eine Themenreservierung ist ebenso möglich, wie die Erörterung des organisatorischen Ablaufs.

Abstract Environmental scientists frequently engage in "campaignstyle" deployments, where they visit a location for a relatively short period of time (several weeks to months) and intensively collect measurements with a combination of manual and automatic methods. We present K2, a mote-based system which brings high-quality automated monitoring to deployments of this nature. We identify key application requirements, describe the design and evolution of K2, and present performance results from two field deployments (the largest lasting ~ 5 weeks and including 50 sensing nodes). Our results indicate that K2 is a viable scientific tool, achieving data yield > 99% and producing accurately time-stamped data, even in the absence of a persistently available reliable clock source. These results point a path towards WSN deployments managed by non-CS specialists.

Abstract Wireless Sensor Network (WSN) in combination with image sensors opens plethora of opportunities in the wildlife tracking. It provides a glimpse into previously unseen, remote and inaccessible world of some of the most endangered species on earth. tigerCENSE is such an attempt to put sensor network technology in conserving one of the rarest and most elusive big cat species. The node, triggered by the Passive Infrared (PIR) sensor, captures the image of tiger using a CMOS image sensor and stores it in an external memory chip. To avoid any disturbance to animal, the node uses an Infrared (IR) flash, instead of white flash, to illuminate the target at night. The stored images get transferred to the base station via radio transceiver. This is transferred to the database server through Internet links for analysis by wildlife researchers. A solar energy harvesting system for recharging node's batteries is being added to avoid frequent human visit to change the batteries, making it highly non-intrusive system. 

Abstract We study the characteristics of the communication links of a wireless sensor network in a tropical cloud forest in Ecuador, in the context of a wildlife monitoring application. Thick vegetation and high humidity are in principle a challenge for the IEEE 802.15.4 radio we employed. We performed experiments with stationary-only nodes as well as in combination with mobile ones. Due to logistics, all the experiments were performed in isolation by the biologists on our team. In addition to discussing the characteristics of links in this previously unstudied environment, we also discuss the lessons we learned from operating under peculiar constraints in a peculiar deployment scenario.   

Abstract The computing department at Lancaster University are currently involved in the ongoing deployment of an advanced communications system designed to support the requirements of search and rescue teams. This system is based around the concept of using an all IP infrastructure to provide multi-functional data communications (such as group voice calling, live video streaming and location updates) to highly mobile vehicles and personnel in challenging environments. In addition to these types of data communications there is also a requirement to reliably transmit different types of sensor data information from the individual rescue team members, their vehicles and the casualties they locate and rescue. In this paper we describe the work we have carried out to incorporate an IP based sensor networking approach into our existing communications system deployment that we have in place with the Morecambe Bay Search and Rescue Team, in order to support Mobile Sensor Networks. In addition, we present results from our experimentation with our deployment that is specifically focused on the issue of wireless interference that our Mobile Sensor Networking solution is potentially subjected to.

Abstract Over the last years Wireless Sensor Networks (WSN) have been becoming increasingly applicable for real world scenarios and now production ready solutions are available. In the same period the upcoming combination of Service-oriented Architectures and Web Service technology demonstrated a way to realize open standardized, flexible, service component based, loosely coupled and interoperable cross domain enterprise software solutions. But those solutions have been too resource-intensive and complex to be applicable for limited devices like wireless sensor nodes or small-sized embedded systems. Thus, more and more research investigations have been launched to bring the aspect of cross domain interoperability to the field of embedded battery powered devices. The proposed laboratory assistance solution in this paper demonstrates the benefits of Web Service enabled WSNs for process monitoring and disaster management by extending an existing system in the Life Science Automation domain. Especially, the capability to provide location based services in industrial automation environment represents a beneficial feature of the presented integration approach and results in high-quality information delivery bundled with specific data about the locational origin of the capturing sensor.   

Abstract We present a sensor network testbed that monitors a hallway. It consists of 120 load sensors and 29 passive infrared sensors (PIRs), connected to 30 wireless sensor nodes. There are also 29 LEDs and speakers installed, operating as actuators, and enabling a direct interaction between the testbed and passers-by. Beyond that, the network is heterogeneous, consisting of three different circuit boards—each with its specific responsibility. The design of the load sensors is of extremely low cost compared to industrial solutions and easily transferred to other settings. The network is used for in-network data processing algorithms, offering possibilities to develop, for instance, distributed target-tracking algorithms. Special features of our installation are highly correlated sensor data and the availability of miscellaneous sensor types.  

Abstract The sensor data are used by end users using various IT applications. The typical application for monitoring, querying and controlling the deployed Wireless Sensor Network is complex in nature from application development point of view, owing to various resource limitations. Post-deployment nuances like firmware update, addition of new nodes or replacement of others are not so easy task, either. In recent past, efforts have been made to minimize the complexity of end user through desktop and web-based application. However, so far, instant messaging has not been tried for communication between an end user and physical mote, where an individual sensor node (or group of them) appearing as a buddy in the instant messaging contact list and one can talk to it. In this paper we are describing a system that we developed recently with the name senSebuddy, based on instant messaging technique to monitor, query and control the deployed WSN applications. We also describe the functionality of the prototype implementation of the system with Smack XMPP API and Openfire XMPP server. We have carried out series of experiments to prove that one can chat with sensor mote like a normal human being, and mote can be programmed using gtalk without experiencing any delay. 

Abstract This paper presents a self-organizing Medium Access Control (MAC) protocol framework for distributed sensor networks with arbitrary mesh topologies. The novelty of the proposed In-band Self-Organized MAC (ISOMAC) protocol lies in its in-band control mechanism for exchanging Time-Division Multiple Access (TDMA) slot information with distributed MAC scheduling. A fixed-length bitmap vector is used in each packet header for exchanging relative slot timing information across immediate and up to two-hop neighbors. It is shown that, by avoiding explicit timing information exchange, ISOMAC can work without networkwide time synchronization, which can be prohibitive for severely cost-constrained sensor nodes in very large networks. A slot-clustering effect, caused by in-band bitmap constraints, enables ISOMAC to offer better spatial channel reuse compared to traditional distributed TDMA protocols. ISOMAC employs a partial node wake-up and header-only transmission strategy to adjust energy expenditure based on the instantaneous nodal data rate. Both analytical and simulation models have been developed for characterizing the proposed protocol. Results demonstrate that, with in-band bitmap vectors of moderate length, ISOMAC converges reasonably quickly, that is, approximately within a four to eight TDMA frame duration. Also, if the bitmap header duration is restricted within 10 percent of packet duration, then the energy penalty of the in-band information is quite negligible. It is also shown that ISOMAC can be implemented in the presence of network time synchronization, although its performance without synchronization is just marginally worse than that with synchronization.

Abstract This paper contributes to understanding and solving several important scheduling problems associated with hybrid protocols based on the assumption of periodic operation. If we assume the nodes in these networks are multi-rate and inhomogeneous, close to optimal scheduling can be determined as a dynamic process by considering a limited number of transmission periods. We describe the Periodic-MAC algorithm, which utilizes this property by iteratively running through a set of solutions that have previously resulted in successful transmissions. However, to simplify the analysis of a network with periodic operation, we will assume that the nodes can only store one such solution. We also look at possible improvements of the algorithm.

Abstract We extend the artificial force field concept to multi-hop networks. We begin by applying DWARF directly to a simple multi-hop topology and indicate how the algorithm fails on such a topology. Then, we propose two simple but elegant resolutions to extend DWARF for multi-hop networks. We further explain the algorithm that applies such resolutions. Then, we evaluate and compare our algorithm to other algorithms. We also propose the optimization to reduce communication overhead and present the robustness to message loss of the algorithm. 

Abstract The present study investigates a Medium Access Control (MAC) protocol for reliable inter-vehicle communications (IVC) to support safe driving with the goal of reducing road traffic accidents. A number of studies have evaluated the performance of the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. However, the communication quality provided by the CSMA/CA protocol is degraded seriously by the hidden terminal problem in IVC. Therefore, we propose a new MAC protocol, referred to as Periodic Broadcast- Timing Reservation Multiple Access (PB-TRMA), which can autonomously control transmission timing and avoid packet collisions by enhancing the Network Allocation Vector (NAV) for periodic broadcast communications. The simulation results show that the proposed protocol can resolve the hidden terminal roblem and mitigate data packet collisions. Moreover, the behavior of PB-TRMA is similar to that of Time-Division Multiple Access (TDMA).