TDOA-Based Localization for Semi-Static Targets in NLOS Environments

We study the problem of locating semi-static targets in non-line-of-sight (NLOS) environments using multiple sets of time-difference-of-arrival (TDOA) measurements. Specific focus is placed on the correlation between TDOA measurements caused by NLOS errors. We propose an algorithm which takes this correlation into account when fusing the available TDOA measurements and achieves high accuracy in estimating both the position and the associated uncertainty. In addition, a statistical ranging error model for NLOS environments is proposed based on empirical ranging data, which substantially improves the positioning accuracy. The proposed approach is verified experimentally in an aircraft cabin and achieves seat-level accuracy for 99% of the nodes.