Reconfigurable Intelligent Surface-Assisted Coordinated Multi-UAV Communications

This paper explores the application of reconfigurable intelligent surfaces (RISs) in coordinated multi-UAV communications to optimize the signal-To-noise ratio (SNR). A collaborative group of UAVs, supported by the surrounding multiple RISs, aims to enhance signal quality for a ground user. The joint design problem of UAV beamforming and RIS passive beamforming is known to be non-convex and complex. To over-come this challenge, we propose a novel approach that combines maximum ratio transmission (MRT) for UAV beamforming with a semi-definite relaxation (SDR)-based method to determine finite resolution phases of the RISs, thereby maximizing the user's SNR. Our numerical results demonstrate the effectiveness of the proposed joint design method, which surpasses the performance of other compared methods.