Performance of time-difference-of-arrival ultra wideband indoor localisation

Ultra wideband (UWB) is a good candidate for indoor positioning, thanks to its ability to resolve multipath and penetrate through walls. This study investigates the performance of UWB-based time difference of arrival (TDOA) positioning for indoor environment, where one or more blind nodes are to be localised with the aid of a number of anchor nodes. The positions of the blind nodes are estimated using the previously proposed iterative localisation method. The achievable positioning accuracy is analysed in terms of Cramer-Rao lower bound (CRLB), which is a theoretical lower bound on the variance of the positions of blind nodes. The range errors are modelled as distance independent (DI) and distance dependent (DD) for line-of-sight (LOS) and non-line-of-sight (NLOS) cases. Closed-form expressions of CRLB for TDOA localisation are derived and the theoretical analyses have been verified by experimental results.