Phase Difference of Arrival Aided Downlink Time Difference of Arrival Ultra-Wide Band Positioning System

Kurzfassung

Currently there is a growing demand for accurate and reliable positioning indoors or in other environments, where Global Navigation Satellite Systems (GNSS) are unavailable. The precise positioning is required for example by autonomous vehicles used in the industry, safety anti-collision systems or for tracking of goods. Ultra-Wide Band (UWB) positioning systems provide precise location information and are therefore often utilized in such scenarios. The GNSS-like Downlink Time Difference of Arrival (TDoA) method is well suited for these problems, enabling unlimited number of simultaneous users. The addition of independent measurements is often sought for improved precision and robustness of the position estimates. So far, only time-based measurements were available, however, UWB boards capable of Phase Difference of Arrival (PDoA) and thus Angle of Arrival measurements have been introduced recently. In this article we leverage UWB-PDoA board with two Qorvo DW1000 transceivers that share a common clock. Its position is estimated by fusing the TDoA and PDoA by Extended Kalman Filter (EKF) in downlink-based system. The EKF tracks the clock bias between the two chips; consequently, prior calibration is unnecessary, as it is done online. Moreover, precise localization is enabled through the algorithm that resolves the ambiguity of PDoA measurements. The positioning performance evaluation shows improvement in accuracy with respect to the TDoA-only solution. The root-mean-square error decreased from 16.38 cm to 15.09 cm, i.e., 8 %, when evaluated among all test points. In the best case, reduction from 14.79 cm to 10.14 cm, i.e., 35 % was observed.