Abstract: Aiming at the problem of low localization accuracy for APIT localization algorithm in wireless sensor network, an improved APIT algorithm is proposed. The improved algorithm presents a new test method of points to overcome the shortcoming of low localization accuracy which is caused by InToOut and OutToIn errors. To further improve the positioning accuracy, the algorithm adopts the medium line to reduce the localization area of triangle in traditional APIT algorithm. The improved algorithm has low complexity and never requires any additional hardware support. Simulation results show that the proposed algorithm keeps high localization accuracy under different anchor density and communication radius. Therefore, it meets the needs for the most node positioning in wireless sensor networks.

Key words: Wireless Sensor Networks（WSNs）, Approximate Point-In-Triangulation test（APIT） algorithm, medium line, Received Signal Strength Indicator（RSSI） technology, signal strength

摘要： 针对无线传感器网络中APIT定位算法定位误差大的问题，提出了一种改进的APIT定位算法。该算法针对APIT测试易产生InToOut和OutToIn错误而影响定位精度的问题，提出了新的内点测试方法；算法进一步通过中位线来缩减传统APIT算法中的三角形定位区域，提高定位精度。改进算法复杂度低，不需要任何额外硬件的支持。仿真结果表明，改进算法在不同锚节点密度和通信半径的网络中都具有较高的定位精度，满足于大多数无线传感器网络的定位需求。

关键词: 无线传感器网络, 近似三角形内点测试法（APIT）算法, 中位线, 接收的信号强度指示（RSSI）技术, 信号强度