Energy-Efficient UAV Relaying in Dual Communication Mode

Full abstract

Read the full abstract

In scenarios with intensive communication demands, heavy ground user (GU) traffic places significant pressure on ground base stations (BSs). Unmanned aerial vehicle (UAV)-assisted cellular communication offers a promising opportunity to enhance regional capacity and quality of service (QoS) by relaying GU data to neighboring underutilized BSs. In this paper, we propose an energy-efficient UAV-assisted relay communication system operating in a dual communication mode (cellular mode and UAV relay mode). Under UAV energy budget constraints, we jointly optimize users’ connection scheduling, bandwidth allocation, and UAV trajectory to maximize the long-term throughput of all GUs. The resulting mixed-integer nonlinear non-convex problem is difficult to solve. To address this, we decompose the proposed problem into two subproblems. Specifically, the path discretization technique, successive convex approximation (SCA) method, and difference-of-convex (DC) method are employed to handle trajectory design and variable service durations. The user connection scheduling and bandwidth resource allocation problems are solved via a penalty-DC framework. Simulation results demonstrate that the proposed algorithm achieves higher mean regional communication capacity than the benchmark schemes, while also revealing critical trade-offs between UAV trajectory, onboard energy limits, and user QoS requirements.