User Selection in Reconfigurable Intelligent Surface Assisted Communication Systems

This letter presents a detailed investigation on the performance of reconfigurable intelligent surface (RIS)-assisted communication system with user scheduling. Depending availability channel state information (CSI) at RIS, two separate scenarios are considered, namely without CSI and CSI. Closed-form expressions derived for ergodic capacity in both scenarios. It is found that has significant impact system. Without CSI, RIS provides an array gain N, where N number reflecting elements, scheduling multi-user $\log \log \text {M}$ , M users. With notation="LaTeX">$\text {N}^{2}$ while no diversity can be obtained.