Classification and weighting techniques for NLOS mitigation in TOA-based radiolocation.

摘要

The need for localization of mobile stations is increasing rapidly in cellular systems and sensor networks. One of the main problems facing an accurate location using Time-of-Arrival (TOA) measurements in wireless communication systems is Non-Line-of-Sight (NLOS) propagation. Different NLOS mitigation approaches are available in the literature. The two most important approaches are classification and weighting. Classification attempts to identify and localize with only LOS base stations. Weighting localizes with all NLOS and LOS measurements, but provides weighting or scaling to minimize the effects of the NLOS bias.;This thesis studies the impact of the NLOS propagation in TOA-based radiolocation systems and implements some mitigation techniques. The impact of the NLOS base stations layout and NLOS environments on the radiolocation performance is investigated. Two mitigation techniques are implemented and investigated. These techniques are the Residual Test (RT) which is based on the classification approach and the Range Scale Algorithm (RSA) that is based on the weighting approach. Two modified algorithms based on the RT and the RSA proposed in this thesis are presented and tested under different conditions (i.e., number of NLOS BSs and different NLOS models). Simulation results demonstrate that the two proposed algorithms are significantly more efficient in radiolocation accuracy than the RSA and the RT, even under highly NLOS conditions.