Research And Implementation Of Range-Free Localization In Wireless Sensor Network

Wireless Sensor Networks (WSN), which integrates sensor techniques, embedded computation, low-power electronic techniques and wireless communication technologies, is a novel technique on acquiring and processing data information. WSN has a wide application in national defence, environmental supervision, outer space exploration, medical treatment, precision agriculture, transportation, counter-terrorism and disaster retrieval. Self-localization, which has been focused as a basic problem, is the precondition of many applications of WSN, such as target identification, surveillance and tracking. Thus, localization has become one of the indispensable supporting techniques in WSN.For the constraints in power, cost and size of sensor nodes, the self-localization techniques meet new requirements and challenges. With basic accuracy requirement, the localization algorithm must be practicable, straightforward and with low-power. This thesis focuses on the problem of self-localization in WSN and makes thorough discussion and research of it. The concrete content is as follows:1. The problem of self-localiztion in WSN and its significance are illustrated. The characteristics, architecture, key technologies and application fields of WSN are summarized exhaustively. The research status of self-localization techniques are discussed and presented based on the study of a great deal of related literatures and research results.2. The fundamental principles of the self-localization techniques of WSN are studied and the distance measurement methods are analysed. The evaluation criterion of self-localization algorithm and system are described comprehensively. And the taxonomy for self-localization algorithm are presented in consideration of measurement technologies, mode, performance and cost. 3. Range-free localization algorithms and technologies are discussed thoroughly. The measurement techniques of connectivity and hop are presented and the implementation princple are analyzed. The principles and performances of several representative range-free localization approaches are studied and compared in detail.4. Based on the existing algorithms, a range-free self-localization algorithm, called Efficient Localization Measurement (ELM), is proposed. To those nodes that can communicate with beacons directly, ELM takes full advantage of beacons to positioning them at first hand. A method to validate the positioning result is included in the ELM and the simulation results show that it has the good positioning accuracy and coverage.5. The sensor node for experiment is designed to further validate the practicability of the algorithm. The LPC2138 embedded microprocessor from Philips and the CC1100 multi-channel RF transceiver from Chipcon are adopted to design the experiment node. The project design of the positioning system is described. TinyOS is transplanted to the experiment node and the self-localization algorithm ELM is programed by using nesC. In the end, the self-localization algorithm is tested with the experiment node.