Performance Evaluation for Subarray-based Reconfigurable Intelligent Surface-Aided Wireless Communication Systems

TL;DR

This paper evaluates the impact of a subarray-based reconfigurable intelligent surface scheme on spectral and energy efficiency in wireless systems, proposing an optimal phase shift design and analyzing its performance benefits.

Contribution

It introduces a subarray-based RIS scheme with an optimal phase shift design and derives an upper bound for ergodic spectral efficiency, providing new insights into energy efficiency improvements.

Findings

The upper bound of ergodic spectral efficiency is tight and reliable.

The optimal phase shift design significantly enhances system performance.

The subarray-based scheme reduces power consumption while maintaining efficiency.

Abstract

Reconfigurable intelligent surfaces (RISs) have received extensive concern to improve the performance of wireless communication systems. In this paper, a subarray-based scheme is investigated in terms of its effects on ergodic spectral efficiency (SE) and energy efficiency (EE) in RIS-assisted systems. In this scheme, the adjacent elements divided into a subarray are controlled by one signal and share the same reflection coefficient. An upper bound of ergodic SE is derived and an optimal phase shift design is proposed for the subarray-based RIS. Based on the upper bound and optimal design, we obtain the maximum of the upper bound. In particular, we analytically evaluate the effect of the subarray-based RIS on EE since it reduces SE and power consumption simultaneously. Numerical results verify the tightness of the upper bound, demonstrate the effectiveness of the optimal phase shift design for the subarray-based RIS, and reveal the effects of the subarray-based scheme on SE and EE.