Unmanned aerial vehicles (UAVs) fill coverage holes as wireless relays during emergency situations. Fixed-wing UAVs offer longer flight duration and larger coverage in such situations than rotary-wing counterparts. Maximizing the effectiveness of fixed-wing UAV relay systems requires careful tuning of system and flight parameters. This process is challenging because factors including flight trajectory, timeshare, and user scheduling are not easily optimized. In this paper, we propose an optimization for UAV-based wireless relaying networks based on a setup which is applicable to arbitrary spatial user positions. In the setup, a fixed-wing UAV flies over a circular trajectory and relays data from ground users in a coverage hole to a distant base station (BS). Our optimization iteratively maximizes the average achievable spectral efficiency (SE) for the UAV trajectory, user scheduling, and relay timeshare. The simulation results show that our optimization is effective for varying user distributions and that it performs especially well on distributions with a high standard deviation.

翻译：在紧急情况下，无人机作为无线中继填补覆盖空洞。相较于旋转翼无人机，固定翼无人机在此类场景中可提供更长的飞行时长与更广的覆盖范围。为最大化固定翼无人机中继系统的效能，需精确调整系统与飞行参数。由于飞行轨迹、时分方案及用户调度等因素难以优化，这一过程充满挑战。本文针对任意空间用户位置场景，提出一种基于特定配置的无人机无线中继网络优化方案。在该配置中，固定翼无人机沿圆形轨迹飞行，将覆盖空洞内的地面用户数据中继至远端基站。所提优化方法通过迭代方式最大化无人机轨迹、用户调度与中继时分的平均可达频谱效率。仿真结果表明，该优化方法对不同用户分布均有效，尤其在高标准差分布中性能表现优异。