Opportunistic-Reconfigurable Intelligent Surface Aided SDMA/TDMA Grouping in Multiuser Uplink

This paper investigates the use of reconfigurable intelligent surface (RIS) to enhance the performance of mixed space-division multiple access (SDMA) and time-division multiple access (TDMA) in multiuser uplink scenarios. Specifically, we introduce an opportunistic phase-shift tuning approach to help group multiple user equipment (UE(s)) in the time domain and improve spatial-multiplexing capability in the spatial domain. This method significantly reduces the implementation complexity of operating the RIS while achieving a notable gain. Simulation results demonstrate that our proposed approach successfully increases the average achievable rate (AR).