NLOS aware TOF positioning in WLAN

Time-based Wireless Local Area Network (WLAN) positioning, particularly in indoor environments, faces the challenge that Non-Line-of-Sight (NLOS) signals enlarge the measured value of Time-of-Flight (TOF) and lead to positioning errors. It is feasible to improve the performance of time-based positioning by recognizing and eliminating NLOS signals. Unfortunately, existing NLOS recognition approaches require complex devices and algorithms and aren´t suitable for WLAN positioning. In this paper, we propose an efficient NLOS recognition algorithm based on the comparison between TOF and RSSI. The NLOS probability of a certain measured TOF could be evaluated according to the relationship between the measured TOF and Received Signal Strength Indicator (RSSI). Then the collected TOF values which correspond to NLOS signal with high probability are discarded so that the positions of clients could be estimated more accurately. In the simulation, we evaluate the NLOS aware TOF positioning algorithm in indoor environments. The results show that the proposed algorithm improved the positioning accuracy without any additional equipments or calibrations.