Decentralized Cooperative Localization With LoS and NLoS UWB Inter-Agent Ranging

This paper develops an infrastructure-free global cooperative localization solution for a group of communicating mobile agents (e.g., first responders or exploring robots) via an ultra-wideband (UWB) inter-agent ranging aided dead-reckoning. UWB offers a decimeter level accuracy in line-of-sight (LoS). Still, its accuracy degrades significantly in non-line-of-sight (NLoS) due to the significant unknown positive bias in the measurements. Instead of identifying and excluding the NLoS measurements, this paper proposes a framework to use the NLoS measurements. The method includes (a) proposing a bias compensation method to process NLoS measurements; (b) taking into account the probabilistic nature of the NLoS identifiers and casting the UWB measurements by a probabilistic bi-modal model; (c) using an interacting multiple model estimator to process the bi-modal UWB measurements. Our cooperative localization's effectiveness is demonstrated via a set of two experiments for a group of pedestrians who use UWB relative range measurements among themselves to improve their shoe-mounted INS geolocation.