Exploiting Phase Difference of Arrival of V2X Signals for Pedestrian Positioning: Key Methods and Simulation Evaluation

Pedestrian-to-vehicle communication helps to prevent pedestrian accidents by disseminating position information of a pedestrian to nearby vehicles. This is especially useful when a pedestrian is in the blind spot of vehicles. In urban canyons, roadside buildings obstruct satellite signals, which may cause an outage in pedestrian positioning. Using vehicles and roadside units as positioning anchors helps to solve this problem. But the performance of distance estimation, based on the attenuation property of wireless signals, is degraded by multipath propagation. To address this issue, this paper exploits phase information of V2X signals, instead of signal strength, for distance estimation. The signal transmitted by a pedestrian device is simultaneously received by several anchors, and the phase difference of arrival (PDoA) is used to compute the distance difference. Using the OFDM structure, phase information of multiple subcarriers can be computed efficiently. Potential problems like inter-symbol interference, synchronization error and phase ambiguity are addressed and the accuracy of distance estimation is further improved by combining phase information of multiple subcarriers before fixing the phase ambiguity. The effectiveness of the proposed method is verified by simulation evaluations, using 3D map and ray-tracing.