Improved Least Median of Squares Localization for Non-Line-of-Sight Mitigation

Non-line-of-sight (NLOS) propagation is one of the major problems that cause errors in localization systems. There exist many algorithms to reduce NLOS caused errors. Most of these algorithms require a priori information about the NLOS links, which limits their application. The least median of squares (LMedS) method is an exception and is thus attractive for its simplicity. LMedS selects only a subset of the anchors with the smallest residue for location calculation, but it tends to discard more range measurements than necessary. Its performance can be improved significantly, particularly when the percentage of NLOS links is not high. In this paper, we present an improved LMedS method, which maximizes the subset of reliable anchors to be used. We show via simulation that, compared with the existing LMedS method, the proposed algorithm has significantly higher localization accuracy and is more stable.