Statistical CSI-Based Design for RIS-Assisted Communication Systems

Reconfigurable intelligent surfaces (RISs) have attracted considerable attention over the past years. A RIS can smartly adjust phase of incident wavefronts and create anomalous reflections towards desired directions. In this letter, we consider a RIS-assisted large antenna system investigate ergodic spectral efficiency (SE). By considering finite dimensional channel, derive an upper bound on SE. Based bound, propose optimal shift design by exploiting statistical channel state information. Specifically, develop semidefinite relaxation technique Gaussian randomization procedure for continous design. Furthermore, alternating optimization algorithm is applied to discrete case. Numerical results verify tightness effectiveness our Considering hardware limitations, find that 2-bit adjustable elements achieves same SE as architecture.