| Rapid advances in micro-electronic technology, embedded system and wireless communication technology have enabled to develop low cost wireless sensor network (WSN), where each sensor node individually senses the environment but collaboratively achieves complex information gathering and dissemination tasks. Wireless sensor network is a promising technique for many applications, such as target tracking, intrusion detection, wildlife habitat monitoring and real-time traffic monitoring.The location of nodes in WSN plays an important role in the most application fields. The information that is collected by the sensor nodes makes sense only when it is combined with the location information of the sensor nodes. In addition, knowing the relative locations of sensors allows use of location-based addressing and routing protocols. Therefore, positioning technology which draws more attention becomes one of the key technologies in wireless sensor networks and has been widely studied.The research of this thesis is based on the analysis of a great deal of recent technical reports and research results on WSN. Centroid algorithm, TDOA ranging method and the application of positioning technology on robot football program are described. In Centroid algorithm, high density of beacon nodes is required and the effect beacon nodes have on the unknown nodes is not reflected. In this paper, a novel distributed positioning algorithm, referred to as TDOA-Centroid algorithm (TCA), is presented and simulated. Distance between two nodes is computed through TDOA ranging method. The influence factor which is computed according to the distance between beacon node and unknown node is used to measure the position of unknown node. Moreover, the iterative approach is utilized to improve the density of anchor nodes. Localized nodes transfer to beacon nodes and help other unknown nodes. The results show that it has better positioning accuracy than Centroid algorithm, especially when density of beacon nodes is low. |
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