Energy-Efficient Fixed-Wing UAV Relay With Considerations of Airframe Shadowing

Owing to their high energy efficiency, fixed-wing unmanned aerial vehicles (UAVs) can operate as aerial relays to provide long periods of uninterrupted connectivity. In such systems, however, airframe shadowing may occur (i.e. the blockage of a UAV communication link by the UAV’s own airframe) and can significantly degrade the communications performance. In this work, we propose a novel approach to optimize the trajectory of a fixed-wing UAV operating as a relay between a ground user (GU) and a ground base station (BS) to maximize the relay efficiency (defined as the ratio of the amount of relayed data to the consumed energy). We use the aerodynamic equations of the fixed-wing UAV to derive a semi-deterministic airframe shadowing model for loitering trajectories. Analytical expressions and simulation results illustrate the dependence of the airframe shadowing on the UAV’s attitude and speed.