Mobile location tracking with NLOS error mitigation

We present a mobile location tracking method with non-line-of-sight (NLOS) error mitigation for network-based wireless location systems. Based on the reconstructed LOS time of arrival (TOA) results from NLOS propagation identification and correction, geometric location techniques are used to calculate the location estimate of a mobile station. General TOA geometric cases and positioning solutions are analyzed. The time sequence of location samples is processed by Kalman filtering for position tracking and velocity estimation. A post-Kalman filter smoothing method is also applied to improve the velocity estimation. It is shown that the location tracking error can be reduced by processing the reconstructed line-of-sight TOA measurements with Kalman filtering.