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NLOS Detection and Mitigation in Differential Localization Topologies Based on UWB Devices

Ultra-wideband systems (UWB) are a common technology which is used for indoor localization applications due to its accuracy. However there are some challenges to implement these systems in indoor area with obstacles and barriers. One of the challenges is non-line of sight conditions (NLOS) between two communicating nodes which results in large localization error. Many techniques have been proposed in the literature for NLOS detection and mitigation but most of them are deployed in time of arrival (ToA) cases. This paper extends the NLOS detection and mitigation techniques to time difference of arrival cases (TDoA). The proposed method is a parametric technique based on the probability distribution function (PDF) of features collected from received signal characteristics. An innovative method is used to apply the parametric detection method on TDoA cases both in detection and mitigation stages. The mitigation technique is based on a modified and biased extended Kalman filter (BEKF) which is used in TDoA localization method. The results prove that this technique successfully detects the NLOS cases, mitigates the error up to a factor of 10 and leads to stability of the EKF method.