Channel-Aware Mode Switching Enhanced RDARS-Aided Downlink MmWave MIMO Systems

Distributed antenna system (DAS) has been extensively applied in millimeter-wave (mmWave) communications due to its geographically dispersed and cooperating antennas. Incorporating reconfigurable intelligent surfaces (RISs) into DAS is a promising and effective approach to reducing hardware costs and energy consumption while simultaneously maintaining the benefits of distributed gains. Recently, an innovative architecture named reconfigurable distributed antenna and reflecting surface (RDARS) has attracted significant attention as each element can be flexibly switched between the connection and the reflection modes. This dynamic mode switching offers substantial gains by providing an additional degree of freedom (DoF) in system design. In this paper, we investigate the weighted sum rate (WSR) optimization problem in the RDARS-aided downlink mmWave multi-user system and propose a penalty item-based weighted minimum mean square error (PWM) algorithm to jointly optimize the passive phase coefficients, the mode switching, and the active beamforming for the base station and the RDARS elements in the connection mode. Numerical results demonstrate the superiority of the RDARS structure in improving WSR and verify the effectiveness of the proposed PWM algorithm.