NLoS error suppression algorithm based on two-step Kalman filtering

In order to solve the problem of non-line-of-sight propagation error which affects the positioning accuracy in ultra wide band (UWB) positioning, a secondary elimination method of non line of sight (NLoS) error based on kalman filtering is proposed. This method makes use of the mutual independence between the NLoS error and the measurement error, separates the NLoS error from the total error with the help of Kalman filter, estimates it in real time, and uses the estimated value of the NLoS error as the basis for NLoS error identification and distance measurement correction. Time of arrival (TOA) ranging accuracy is improved by secondary estimation, discrimination and correction of TOA ranging value through Kalman filtering, thus accurate real-time positioning of UWB in indoor complex environment is realized. The simulation results show that this method can not only track and estimate NLoS errors, but also has strong sensitivity to the transition of line-of-sight (LoS)/NLoS environment. The location performance of NLoS error measurements after applying this method is close to the ideal state in LoS environment.