Beam Selection for RIS-Aided Uplink mmWave MU-MIMO Systems

Conventional multi-antenna millimeter wave (mmWave) systems suffer from high hardware costs, high power consumption, and vulnerability to signal blockage. To address these issues, this letter investigates a reconfigurable intelligent surface (RIS)-aided mmWave multiuser multiple-input multiple-output (MU-MIMO) system incorporating beam selection, aiming to maximize the uplink sum-rate. An efficient algorithm based on the block coordinate descent (BCD) and weighted minimum mean square error (WMMSE) framework is proposed to jointly optimize the active beamforming at user terminals (UTs), the passive beamforming at the RIS, and the beam selection matrix at the base station (BS). Numerical results demonstrate that the proposed algorithm significantly outperforms existing baselines in sum-rate performance.