Performance Analysis of Uplink MISO Systems with RIS Selections and MRC/SC Configurations

This paper analyses the performance of the uplink multiple-input single-output (MISO) reconfigurable intelligence surface (RIS)-based system. Aiming to improve the user’s uplink channel quality, we consider the scenario of deploying the maximal-ratio-combining (MRC) or selection-combining (SC) at the base station and selecting one optimal RIS among a set of distributed RISs. In particular, we derive the closed-form and asymptotic expressions for the outage probability (OP) under two scenarios of RIS with random phase-shift (RPS) and optimal phase-shift (OPS). Numerical results showed that by employing MRC and configuring OPS, the system achieves the best performance. For a small number of antenna settings, the SC-OPS scheme can provide better outage performance when compared to the MRC-RPS one. Finally, we provide Monte-Carlo simulation results to validate the accuracy of the theoretical analyses.