Research And Improvement Of Wireless Sensor Networks Range-based Positioning Algorithm

In wireless sensor networks (WSN), localization information of sensor nodes are essential for WSN monitoring, sensed data is always meaningless without relating to its physical location. In addition, some middle ware services such as location aided routing need localization information. Therefore, it is very important to gain localization of sensor node automatically.Generally positioning algorithm is divided into range-based algorithm and range-free algorithm according to whether it needs physical measurement to obtain the information about the distance between the nodes or not. The thesis focuses on the range-based algorithm of RSSI-based positioning algorithm and DV-Distance positioning algorithm. First, the thesis summarizes node positioning technology of the WSN, and then mainly introduces node positioning-related concepts and terminology, classification and the basic principles of measurement edge positioning.Secondly, the RSSI algorithm is deeply discussed and simulation analyzed in this thesis. The algorithm requires low node hardware and its implement is simple. However, the algorithm is vulnerable to the impact of the sparse anchor nodes, ranging error and communication power, which resulted positioning coverage and positioning accuracy not ideal. So this thesis proposes a hierarchical iterative cooperative positioning algorithm. The improved algorithm uses cooperative method to improve positioning coverage and adopts position optimization strategy of the anchor nodes and grading sets the threshold of neighbor number to reduce positioning error. MATLAB simulation shows that the improved algorithm has a higher positioning coverage and positioning precision than the traditional RSSI algorithm.Thirdly, the DV-Distance positioning algorithm is further studied and simulation analyzed. Due to the algorithm adopts multi-hop distance instead of inter-node Euclidean distance, it results biggish positioning error. In order to solve this problem, the thesis proposes an improved DV-Distance algorithm, which refines initial positioning results by iteration calculation. Compared with the traditional DV-Distance algorithm, positioning performance results show that the improved algorithm improves positioning accuracy, inherits the traditional DV-Distance algorithm excellent positioning coverage, and also better to adapt to the anisotropy of the network structure. However, communication overhead and computation of the improved algorithm should be improved.Finally, the work of this thesis is concluded and future research work is prospected.