Study On Range-free Localization Method Of Wireless Sensor Networks

With the development of wireless sensor network, the application of the wireless sensor network become more and more wider,such as in military affairs, medical treatment, environment-monitor and industrial and agricultural production,etc. The node localization of wireless sensor networks is the basis of many applications of wireless sensor networks, of which location accuracy is one of critical index. The data information measured by the sensor node is closely related to position information. Currently, node localization algorithms are still in the stage of theory although there have been a large number of them proposed. It is a challenging and difficult problem for node localization automatically. Under the consideration of node energy, low cost and volume, it’s focus and difficult to design low power,low cost, low complexity and high location accuracy.This thesis introduces the background and significance of the research of the wireless sensor network technology, and the domestic and foreign research present situation, elaborate performance evaluation criteria for the location algorithms. This thesis focuses on the wireless sensor network node positioning technology of based on non-distance measurement. In this kind of technique, the most widely used algorithm is DV-Hop algorithm. Its advantages are very simple,easy to realize, the disadvantages are using hop-distance to replace the real distance will lead to larger error.The localization algorithm named connectivity differences distance vector-hop algorithm, referred to as CDA DV-HOP algorithm, could improve the positioning accuracy of the algorithm.But the complexity of the algorithm is high. Base on the CDA DV-HOP algorithm,the ICDA DV-Hop algorithm is presented in this thesis. The algorithm could reduce the errors caused by uneven distribution of anchor nodes by limiting the flooding and the anchor node selection strategy. And the ultimate estimated position is chosen from the candidate positions in which the connectivity difference value is the smallest. The simulation results show that the ICDA DV-Hop algorithm can reduce the complexity of the algorithm and the overhead of network communication. In order to solve the DV-Hop algorithm’s poor positioning accuracy by the ranging error, this thesis using AEPSO to optimize DV-Hop algorithm, the MSE(mean square error) between estimated distance and measured distance was used as the optimization fitness function, the ideas of adaptive weighting and natural selection were introduced into the PSO algorithm. This algorithm could balance the global and local search capability and has better convergence, the simulation results show that the algorithm reduce the positioning error effectively. In the end of this thesis, Use the good performance of AEPSO algorithm and combined with the ICDA DV-Hop. The simulation shows that the improved algorithm has better convergence speed and positioning accuracy is higher.