Mobile location estimator with NLOS mitigation using Kalman filtering

Mobile location estimation has attracted much interest over the past few years. The most challenging issues, which render to reach the required accuracy for the time-based location system, are multipath and non line-of-sight (NLOS) problems. This paper suggests the simple but robust techniques using biased Kalman filter to smooth and mitigate the NLOS effect for TOA measurements. The processed TOAs are then used for DTOA formulation and provided for location estimation. The further tracking stage is shown not to improve the accuracy much but to be necessary to smooth the mobile trajectory. The better accuracy for mobile location is suggested for future work by using the geographical information through searching the match between the path loss measured at multiple BSs and that estimated by ray-tracing techniques.