Reconfigurable Intelligent Surfaces assisted Communications with Limited Phase Shifts: How Many Phase Shifts Are Enough?

TL;DR

This paper analyzes how limited phase shifts in reconfigurable intelligent surfaces affect uplink communication performance, deriving the minimum number of phase shifts needed to maintain data rate quality.

Contribution

It provides an approximation of data rate performance and determines the required number of phase shifts to limit degradation in RIS-assisted systems.

Findings

Derived the relationship between phase shifts and data rate.

Identified the minimum number of phase shifts for performance preservation.

Validated analysis with numerical simulations.

Abstract

Reconfigurable intelligent surface~(RIS) has drawn a great attention worldwide as it can create favorable propagation conditions by controlling the phase shifts of the reflected signals at the surface to enhance the communication quality. However, the practical RIS only has limited phase shifts, which will lead to the performance degradation. In this letter, we evaluate the performance of an uplink RIS assisted communication system by giving an approximation of the achievable data rate, and investigate the effect of limited phase shifts on the data rate. In particular, we derive the required number of phase shifts under a data rate degradation constraint. Numerical results verify our analysis.