Downlink Energy Efficiency Maximization for RSMA-UAV Assisted Communications

In this letter, we propose a novel rate splitting multiple access-based unmanned aerial vehicle (RSMA-UAV) system to enhance ground communications. The RSMA-UAV acts as an aerial base station (BS) and serves ground users within its flight period. Our main objective is to maximize the downlink energy efficiency (EE) of the UAV. To achieve this, we formulate a non-convex joint optimization problem that considers communication scheduling, common rate, transmit power, and UAV trajectory. To solve this optimization problem, we employ the block coordinate descent method, which allows us to decompose the problem into four sub-problems. Each sub-problem can be efficiently solved using the Dinkelbach algorithm and successive convex approximation (SCA). By iteratively optimizing these sub-problems, we propose a joint optimization algorithm to solve the original optimization problem. Simulation results demonstrate that the RSMA-UAV scheme outperforms the orthogonal multiple access (OMA)-UAV scheme. Additionally, the RSMA-UAV scheme achieves better user fairness compared to the OMA-UAV scheme and non-orthogonal multiple access (NOMA)-UAV scheme.