An Integration Method for Wireless Location Using Built-in Sensors of Mobile Phones and TDOA Landmarks

Abstract

Non-line-of-sight (NLOS) signal propagation is the major source of error in wireless Time Difference of Arrival (TDOA) indoor systems. Even if enough landmarks (LMs) can be deployed by the service providers or system designers, the existing methods experience the location accuracy problem when few line-of-sight (LOS) measurements can be detected. Under the condition that the total number of TDOA measurements satisfies the minimum triangulation requirements (≥ 3), this paper proposes a new integrated location method. The proposed method integrates the user's step length and count from the built-in sensors of mobile phone into the wireless TDOA location systems. Firstly, it detects LOS/NLOS measurements using the user's step length and count. Secondly, it integrates the previous location and step length as supplementary LM and measurement to estimate the location, when two LOS measurements are detected. Simulation results show that the proposed method detects LOS/NLOS measurements at a higher ratio. Performance of location errors depends on the number of detected LOS measurements. The proposed method achieves lower location errors when two LOS measurements are detected.