Research On Range-Free Localization Algorithm In Wireless Sensor Networks

With the advances of technology in wireless sensor network (WSN) in recent years, they have great prospect in many applications, such as military affairs, intelligent transportation system, medical treatment and public health, environmental protection, manufacturing industry, precision agriculture, and so on. As a novel technology of information acquiring and processing, wireless sensor network becomes a new research focus in communication and computer fields.The node localization of wireless sensor networks is the basis of many applications of wireless sensor networks, in which positioning accuracy is a of its key performance indicators. The position information in collected data of WSN is correlated to node position closely. At present, a lot of node localization algorithms have been proposed, but they are still far away from practical system and also challenge problems in these fields. It is a focus and difficultly of current research that how can design a special self-organizing network WSN which are confined by low cost, low complexity, energy effective and high localization accuracy.Based on the comparison of two positioning algorithms between based-range and range-free, the thesis mainly focuses on one of localization rang-free algorithm DV-hop.First of all, the state-of-art in WSN are reviewed on several aspects, such as research background, the progress in domestic and overseas, research significance, and so on; Then, the system structure of WSN, the network characteristic, and the key technology of WSN are summarized. Secondly, the classifications of the localization algorithm in WSN are provided; the methods of distance measurement and the principle and characteristics of the typical range-free positioning algorithm are introduced; then the performance evaluation criteria of the wireless sensor node localization are gave.Afterward, MyEDV-hop, an improved localization algorithm, are proposed based on the analysis of DV-hop localization algorithm, and improves from two stages when it estimates the average hop distance and solves the equations. In contrast to the several algorithms from three aspects:node localization error, coverage and computation, the simulation results show that MyEDV-hop is the best.In the end, the localization accuracy of MyEDV-hop is still not enough and susceptible to the constraints of environmental conditions in practical applications, although it improves the performance. Based on the analysis of advantages and disadvantages of the Taylor series, an improved positioning algorithm, referred to as MyEDV-hop+, is presented, which is combination of MyEDV-hop and Taylor series. MyEDV-hop+takes advantage of characteristics of high positioning precision and strong ability to adapt to the environment in the Taylor series, and take the high accuracy localization results of the MyEDV-hop as the initial value of Taylor series, therefore it solves the problem that it is hard to determine the initial value of Taylor series. Then, it is proved by simulation that the performance of MyEDV-hop+is better and it is more suitable for practical applications. Finally, conclusion for the thesis and prospect for the future research work are drawn at the end of the thesis.