Improvement on Approximate Point In Triangle (APIT) Localization Algorithm in Large-scale Wireless Sensor Networks

Abstract

In wireless sensor networks, the location of sensor nodes that generate information in application such as target tracking, geographic routing , environmental monitoring and forest fire monitoring are very essential. Localization techniques are used to estimate the locations of the unknown nodes in a network using the available few anchors in network and inter-sensor measurements such as time different of arrival, angle of arrival and connectivity, and of which the three are categorized under range based localization algorithm and the last one is under range free localization algorithm. In localization of unknown sensor nodes in wireless sensor networks, the straight forward solution is installing the GPS in every sensor nodes. But it is infeasible due to lack of line-of-sight in indoor applications, high network cost because of energy consumption and hardware cost. In the localization algorithms, the range based algorithms are better in location accuracy but they need additional hardware requirement and energy which is the tradeoffs. In the case of range free localization algorithms, they are cost and energy efficient but with less localization accuracy. Since most of the wireless sensor network applications need coarse localization accuracy, range free localization algorithms are more effective than the range based ones, taking into consideration the tradeoffs. Among range free localization algorithms APIT, DV-hop and Centroid localization algorithms are the popular ones. In this thesis, we proposed improved APIT localization algorithm by developing novel and simple Point in triangle test to minimize the probability of wrong judgement of whether the unknown sensor node is inside triangle formed by the three anchor nodes or outside the triangle. We have evaluated the performance of both the improved APIT and the original APIT based on the localization error, and the simulation experiment result show that improved APIT localization algorithm has better performance than the original APIT. Accordingly localization error rate of improved APIT localization algorithm is 26%, while localization error rate of APIT localization algorithm is 31% when anchor node percentage is 25% of the total sensor nodes.