Smartphones: 3D Indoor Localization Using Wi-Fi RTT

This letter proposes a 3D indoor localization algorithm for smartphones using wireless fidelity (WiFi) round-trip time (RTT). In the proposed algorithm, the weighted centroid (WC) algorithm is utilized to estimate the rough two-dimensional (2D) position due to its easy implementation and low complexity. The coarse target altitude is acquired according to pedestrian activity. Then, the coarse altitude and 2D position combine into a rough 3D position, which is regarded as the initial position of the standard particle swarm optimization (SPSO) algorithm. The SPSO algorithm aims to estimate a more accurate 3D location on the basis of the cursory 3D position of the smartphone. To reduce the computation, we use the density-based spatial clustering of applications with noise (DBSCAN) algorithm to assist in updating the SPSO particles. Experimental results show that the proposed positioning algorithm has better 3D accuracy than WC and Least-squares (LS) algorithms, with a 2D accuracy of 1.147 meters and an altitude precision of 0.305 meters.