Statistical Characterization and Mitigation of NLOS Bias in UWB Localization Systems

Propagation in non-line-of-sight (NLOS) conditions is one of the major impairments in ultrawideband (UWB) wireless localization systems based on time-of-arrival (TOA) measurements. In this paper the problem of the joint statistical characterization of the NLOS bias and of the most representative features of LOS/NLOS UWB waveforms is investigated. In addition, the performance of various maximum-likelihood (ML) estimators for joint localization and NLOS bias mitigation is assessed. Our numerical results evidence that the accuracy of all the considered estimators is appreciably influenced by the LOS/NLOS conditions of the propagation environment and that a statistical knowledge of multiple signal features can be exploited to mitigate the NLOS bias, reducing the overall localization error.