Joint Optimization of UAV Trajectory and User Scheduling in Intelligent Reflecting Surface-Aided Systems with Interfering Nodes

This paper focuses on maximizing the aggregate throughput in a downlink wireless communication system. The system involves collaboration between an unmanned aerial vehicle (UAV) and an intelligent reflecting surface (IRS) acting as a mobile relay between the base stations (BSs) and a set of users. The goal is to optimize the reflecting matrix of the IRS, user scheduling, and UAV trajectory to maintain strong links between the users and the serving BS while suppressing interference from other nodes. Depending on whether the amplitudes of reflecting elements are fixed, we consider both ideal and non-ideal IRS scenarios. To address the mixed-integer non-convex optimization problem with coupled variables, the original problem is decomposed into three sub-problems, and an alternating optimization algorithm is developed. For the ideal IRS case, the successive convex approximation (SCA) technique is employed to transform the problem into a convex one. In the non-ideal case, a novel algorithm utilizing the direction matrix is proposed to achieve a rank-one solution. Simulation results demonstrate the rapid convergence and improved sum rate performance of the proposed algorithm compared to traditional schemes.