Researchand Design Of Localization System In Wireless Sensor Networks

Recently, with the development of technology in wireless communication, sensor technology and embedded technology, it is possible to deploy the large scale wireless sensor networks (WSN), and so it is applicable in military and civilian fields. Since location information plays an important role in wireless sensor networks, the problem of designing the efficient localization algorithm and system has become an hot research topic.Localization algorithm plays an important role in wireless sensor networks Based on the analysis of the existing algorithms, we conclude some technical difficulties in design of systems. Therefore, some interesting problems are presented as follows: First, how to design a higher location accuracy algorithm without increasing the communication burden, and the designed algorithm can satisfy the need of most localization system in WSN; Second, how to provide a higher scalability algorithm in the changeable topology of network; Third, how to design a robust algorithm for the noise environment. In this thesis, main results have been obtained for the aforementioned problems and are listed as follows:Firstly, the node location models, including system model, ranging model and error model, are established.Secondly, two factors, which influence the location accuracy, including the distance between beacons and unknown nodes, and the colinearity of beacons, are analyzed. Then a new selection scheme for the best beacon group is proposed.Thirdly, the extended Kalman model for node localization is investigated. By its iterative refinement process, the measure noise is successfully suppressed, and the location accuracy of unknown nodes is improved.Fourthly, based on the best beacon group, a new BBG-EKF algorithm is proposed, and the designed algorithm has the advantage of low complexity, low communication overhead and high accuracy.Finally, a localization system, including hardware platform and software platform, is designed in wireless sensor networks. The hardware platform mainly contains the design of sensor nodes and sink nodes. To extend the application of this localization system, two ranging ways, which include RSSI and ultrasonic, are proposed. The software platform mainly contains the realization of BBG-EKF algorithm, the software of nodes and monitoring center.