Mobile tracking using UKF, time measures and LOS-NLOS expert knowledge

The main difficulty for the location of terminals in wireless communications systems is the non line of sight (NLOS) situation caused by obstacles in the transmitted signal path, between the base stations and the user equipment. This NLOS situation biases TDOA measures, resulting in a biased final position. However, not all of the base stations may be in NLOS. Determining which base stations are in LOS can improve the accuracy of the system. It is feasible to estimate the reliability of the measures through the study of signal parameters like the delay spread, received power or previous position estimates. The objective of this paper is to analyze the improvements in positioning accuracy by tracking the terminal with an unscented Kalman filter (UKF) incorporating knowledge of NLOS-LOS situation. The evaluation of the approach has been carried out with measures taken in real scenarios.