Joint Trajectory Design and Resource Allocation for IRS-Assisted UAV Multipair Communications

Unmanned aerial vehicles (UAVs) have played an integral part in emergency communications due to their excellent maneuverability. In this paper, we propose an intelligent reflecting surface (IRS)-assisted UAV multipair communication system, in which the IRS establishes a communication link between each pair of base stations (BSs) and users. Our goal is to maximize the minimum transmission rate by using relaxation and successive convex approximation (SCA) techniques. The optimization problem is nonconvex and difficult to address due to the presence of binary and coupled variables. Therefore, we relax the binary variables into continuous variables and decompose the problem into three subproblems for iterative optimization, leading to the derivation of the optimal solution. Initially, we address the optimization of resource allocation and IRS phase shift variables. Subsequently, we apply the SCA technique to resolve the UAV trajectory optimization problem. Finally, the above three subproblems are iterated until the algorithm converges. Numerical results indicate that the minimum transmission rate is effectively enhanced by employing the proposed algorithm.