Study Of Nodes Localization's Key Technique In Wireless Sensor Network

With advances in Micro-Electro-Mechanical System, wireless communication and low power embedded technology, have brought wireless senser network develops quickly in low power, small size, wireless communication and so on, which makes wireless sensor network can be widely used. Localization technology which is one of the key techniques takes great significance on the efficiency of the application of wireless sensor network.The corresponding action can be taken only when the position information of the event is known, which can be implemented by knowing the position information of all the sensor nodes.This thesis introduces the background and the significance of the localization in wireless sensor network, gives an overview on the current state of the art, and introduces some classical range-free localization algorithms and systems based on reading a large amount literature at home and abroad.The error of the unknown nodes is large by using the average hop distance which is computed by taking some of beacon nodes into account in traditional DV-Hop algorithm. Furthermore, it may make the localization of some unknown nodes out-of-scope. For the problems in traditional DV-Hop introduced above, an improved algorithm named BHDV-Hop (Beacon-modify Hopsize DV-Hop) is proposed. BHDV-Hop takes improvements over DV-Hop from the following aspects: firstly, average hop distance is calculated by taking all the beacon nodes into consideration. Secondly, the position information of unknown nodes is amended by utilizing average hop error of beacon nodes. Finally, the position information of the node whose coordinate is out-of-scope is corrected by taking boundary coordinates as its position information.In traditional DV-Hop algorithm, average hop distance is computed without considering the difference of the path between different beacon nodes, which makes the error very large. Another improved algorithm named WHDV-Hop (Weighted Hopsize DV-Hop) is proposed by combining the proposed strategies in BHDV-Hop with the difference between various routes. WHDV-Hop uses weighted average hop distance instead of average hop distance. In order to verify the efficiency of the improved algorithm, the beacon nodes are distributed randomly, centrally and marginally respectively to compare with the traditional DV-Hop algorithm and BHDV-Hop algorithm.To compare the efficiency of the presented improved algorithms, scientific tools Omnet++ and Matlab are adopted for simulation. The results of experiment indicate that the accuracy of two improved algorithm is higher than DV-Hop, especially when the beacon nodes are distributed marginally in the network, which can fulfil the demand of practical applications.