Self-localization Technology For Wireless Sensor Networks

Wireless sensor networks, which integrate technologies of micro-electro-mechanism, sensing, embedded computing, distributed information processing and wireless communication, lead to a new pattern of information gathering and processing. The fundamental problems of sensor networks are deployment and coverage, localization, and networking protocols. And localization, which has been focused as a basic problem, is the precondition of many applications of sensor networks, such as target identification, surveillance and tracking.In this thesis, we discuss the self-localization technology in detail. Since the nodes are restricted by size, cost, energy, and work under the environment that should not be accessed, the basic approach is to use beacons that aware of their positions as reference, and the other nodes compute their positions through the relationship of distance, angel, or network connectivity to the beacons.The DV-Hop algorithm uses the average hop size of the network and hops of the shortest path from an unknown node to every beacon to represent the distance between them approximately, and then the unknown node calculates its position using trilater-ation. In this thesis, we discuss the proper situation of using the algorithm, the factor of localization error, communication and computation cost, and whether the error can be forecasted. The simulation shows that the algorithm works fine with an isotropic network. The localization precision can be improved a lot by suitable deployment of beacons when the percentage of beacons is small. However, the precision improvement is very limited by increasing percentage of beacons for an isotropic network, but an average precision improvement of 10% can be expected by proper deployment of beacons.The most important problem of the localization algorithm with a mobile beacon is the problem how we choose the path of the mobile beacon, and when the beacon broadcasts its position. We propose a feasible scheme using virtual force, which assures the beacon's coverage of the surveillance area, and makes the beacon's path shortest.Finally, we implement the localization module for our sensor network simulator using DV-Hop algorithm.