Joint Beamforming and Reflecting Design in Reconfigurable Intelligent Surface-Aided Multi-User Communication Systems

Reconfigurable intelligent surface (RIS) provides a promising way to build the programmable wireless transmission environments in future. Owing large number of reflecting elements used at RIS, joint optimization for active beamforming transmitter and passive reflector RIS is usually complicated time-consuming. To address this problem, article proposes low-complexity algorithm based on fractional programing (FP). Specifically, we first consider RIS-aided multi-user communication system with perfect channel state information (CSI) formulate an problem maximize sum rate all users. Since nonconvex, decompose original into three disjoint subproblems. By introducing favorable auxiliary variables, derive closed-form expressions vectors matrix each subproblem, leading low complexity. We then extend our approach handle case when transmitter-RIS RIS-receiver channels are not develop corresponding practical estimation. Simulation results have verified effectiveness proposed algorithms as compared various benchmark schemes.