Sum-Rate Maximization for IRS-Assisted UAV OFDMA Communication Systems

In this paper, we propose the use of intelligent reflecting surface (IRS) in unmanned aerial vehicle (UAV)- based orthogonal frequency division multiple access (OFDMA) communication systems. The proposed scheme exploits both the rich beamforming gain brought by the IRS and the high mobility of UAV for improving the system sum-rate. The joint design of UAV's trajectory, IRS scheduling, and communication resource allocation for the proposed system is formulated as a non-convex optimization problem to maximize the system sum-rate. The existence of an IRS introduces both frequencyselectivity and spatial-selectivity in the fading of the composite channel from the UAV to ground users. To facilitate the design, we first derive the expression of the composite channel gain and propose a parametric approximation approach to establish a lower bound for the formulated problem. An alternating optimization algorithm is devised to handle the lower bound optimization problem. Simulation results unveil the promising sum-rate gain achieved by the deployment of an IRS in UAVbased communication systems.