The position accuracy of range free localization is a fundamental problem in Wireless Sensor Networks (WSNs). The accuracy of the localization algorithm greatly depends on the distance estimation between an anchor node and a sensor node, which impacts the performance of the localization dependent protocols and applications, such as routing and storage. In this paper we propose a novel scheme called Detour Path Angular Information (DPAI) based range free sensor localization with single hop Received Signal Strength Indication (RSSI) measurement based distance calculation, which can greatly reduce the localization error in the irregular deployment areas. We estimate the average hop distance by selecting the middle of the transmission path between every two anchor pairs one by one. Then the estimated hop distance is adjusted by the angle between the anchor pairs to that selected middle point. The anchor node also uses RSSI distance to finally adjust the average hop distance. The method of calculation of angle of the detour path is totally conducted in the anchor nodes. Based on the angle of the detoured path, our algorithm determines whether the path is isotropic or detoured by anisotropic factors. Our proposed algorithm does not require any global knowledge of network topology to tolerate the network anisotropy. Also it does not require the high sensor node density for higher localization accuracy. The simulation results show that DPAI achieves significant improvement in localization accuracy both in isotropic and anisotropic WSNs even with few anchor nodes such as 10 of total nodes.
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