Non-Line of Sight mitigation using a range and location filtering algorithm

This paper considers a problem arising in ultrasonic location systems due to non-line of sight between base stations and mobile devices, which leads to significant location errors. Herein, a dual Kalman filtering method is proposed to mitigate NLOS effects, using a-priori partial knowledge of the ultrasonic signals. In the proposed method, a first filter provides a set of filtered range estimates that mitigate the NLOS ranging error, while a second filter provides positioning filtering that mitigates the overall location error. The method is shown to reduce location errors providing a maximum error in location of 9 cm in simulation.