Research On Node Localization Algorithm Based On APIT In Wireless Sensor Networks

Wireless sensor networks can be used for testing,sensing,collecting and Processing information of monitored objects and transferring the processed information to users. Therefore it has very broad application prospects. And node localization technology is one of the main supporting technologies in a wireless sensor network. The correct positioning of the node itself is the premise of providing monitoring information. Node localization problems are that on the basis of a small number of known location nodes, according to a positioning mechanism, unknown node can define their own positions. Approximate Point-In-Triangulation test (APIT) is one of the node localization algorithms. It has unique advantages of lower requirements on communication cost and node density, so it is extremely useful in resource-constrained wireless sensor networks. In this paper, node localization algorithms in wireless sensor networks are researched, the traditional APIT algorithm is improved, and some meaningful results are obtained .Main tasks are summarized as follows:1. The characteristics of wireless sensor networks are studied and node localization mechanisms are investigated, including: node localization methods, algorithm performance evaluation standards and classifications. The localization program used in the main stage and its possible impact in results are comparatively analyzed. Principles and characteristics of representative algorithms in the Range-free localization mechanism are focused. And the advantages and disadvantages existed in algorithms are analyzed. 2. Approximate Point-In-Triangulation test (APIT), one localization algorithm in Range-free location technology is deeply analyzed. Theory and performance of the algorithm are analyzed and simulated. The reasons of the error are discussed.3. A new algorithm which has better performance is put forward in this paper. Three improvements are proposed: comparison of received signal strength is added before the APIT test ;and position calculation method is improved ; according to set conditions,part of the located Unknown nodes are upgraded as anchor nodes in order to enhance the coverage ratio. Simulation Results show that it has the better positioning accuracy and coverage, but low communication overhead and computational amount.