3D Outdoor Positioning Based on RSSI

As a key feature of wireless sensor networks, location-based services find wide applications in social networks, e.g., emergency, navigation and marketing. However, most positioning algorithms aim at two-dimensional indoor applications and few have focused on three-dimensional (3D) outdoor applications. To fill in this gap, this paper develops two 3D positioning algorithms based on received signal strength indicator (RSSI). In particular, after obtaining coarse estimates of user position based on least squares (LS) algorithm, the weighted centroid algorithm (WCA) or particle swarm optimization (PSO) is further exploited to refine the estimate. Monte-Carlo simulation and field test results demonstrate that the LS-PSO algorithm outperforms the LS-WCA, with the accuracy of positioning no worse than 5 meters and the relative error in each spatial dimension smaller than 2%.