Single Antenna Precise Angle Estimation by Exploiting Doppler Shift and its Application in Pedestrian Positioning

Pedestrian-to-vehicle (P2V) communication helps prevent pedestrian accidents, and its effect largely depends on the pedestrian’s positioning precision. But in urban canyons, GPS positioning performance may be significantly degraded. Noticing that 1) vehicles tend to have higher positioning precision than pedestrians by using more sensors and 2) position information is exchanged among nearby vehicles by vehicle-to-vehicle (V2V) communication, in our previous work, a pedestrian positioning method was proposed, which uses vehicles as anchors besides satellites. In addition to distances from vehicles, a pedestrian device also measures angles with respect to vehicles by an antenna array. Its performance, however, relies on the number of antennas which is limited by the device size, and is affected by the orientation error of a pedestrian device. To solve these problems, in this paper, we propose a new method, Single Antenna Precise Angle Estimation (SAPAE), to precisely estimate the angle of a pedestrian with respect to a vehicle and use it for high precision pedestrian positioning. Specifically, it leverages the Doppler shift, uses the phase difference caused by vehicle movement, and works regardless of the number of antennas. Extensive evaluations by 3D ray tracing simulation confirm that the proposed method with a single antenna can reduce the angle estimation error from 15 degrees to 5.7 degrees and reduce the positioning error from 6.42 m to 3.49 m, compared to the base method that uses a linear array of 6 antennas.