Scan-then-Localize UAV Trajectory Design for Wireless Sensor Localization

This paper proposes a novel scan-then-Iocalize scheme for the unmanned aerial vehicle (UAV) to localize a wireless sensor (WS). In both of the scan and the localizing phases, the UAV estimates its range and/or radial speed to the WS, by exploiting the orthogonal frequency division multiplexing (OFDM) sensing signal. We first derive the UAV's maximally allowable sensing radius to the WS to assure a sufficiently high correct estimation probability. Next, in the scan phase, we design the UAV's scan trajectory along a series of waypoints, where the number of the waypoints and their locations are found by solving the classic region least circle coverage problem. The scan phase ends when the UAV's estimated horizontal range to the WS becomes no larger than the maximally allowable sensing radius. The UAV then begins the localizing phase, where unlike the traditional three-measurement based localization, we propose that only two measurements of the UAV's range and radial speed to the WS are sufficient to localize the WS, but may generate a falsely-found ghost WS. By further identifying the UAV's improper flight angles that generate the ghost WSs, we newly propose the two-measurement based accurate localization algorithm. Finally, various simulation results are provided to validate the localizing performance of our proposed scheme.