Joint Beamforming Design Combined with Reconfigurable Intelligent Surface Selection

This paper studies a scheme of joint beamforming design combined with reconfigurable intelligent surface (RIS) selection to maximize the received signal-to-noise ratio (SNR) at the user. Specifically, we consider a communication system, in which multiple RISs are employed to assist the transmission from the base station (BS) to UE. To enhance the communication quality more effectively, the optimal RIS is selected based on the received SNR at UE. In this process, the joint beamforming at the BS and any RIS is optimized separately to maximize the received SNR at UE. Since the line of sight (LOS) propagation may be obstructed or suffer from severe power attenuation, this paper considers two scenarios that the direct link exists and is blocked. Simulation results show that the proposed RIS selection scheme is able to improve the received SNR more significantly than the counterparts without RIS selection.