A Method for Non-line of Sight Identification and Delay Correction for UWB Indoor Positioning

UWB has a centimetre level of positioning accuracy in line of sight (LOS) environment, and is one of the most promoted indoor positioning technologies. However, when a wall or other objects block UWB signals, non-line of sight (NLOS) happens, which reduces the signal/noise ratio and causes signal transmission delay. As NLOS introduces large distance measurement error, UWB positioning accuracy is dramatically degraded. A new NLOS identification and distance correction method is introduced in this paper. The NLOS between a UWB anchor and a moving tag is identified by analysing the variance of the change of UWB measured distance in adjacent samples. The NLOS distance measurement error caused by walls is corrected by modelling the UWB signal transmission delay. Tests have been conducted to evaluate the new method performance for UWB indoor positioning. The results show that NLOS identification accuracy can reach more than 90%. The delay estimation model can effectively correct measurement errors and make positioning accuracy with NLOS appearance comparable to that in LOS.