Performance Characterization of Continuous Reconfigurable Intelligent Surfaces

TL;DR

This paper analyzes a continuous reconfigurable intelligent surface (RIS) that can implement seamless phase shifts, deriving optimal designs and performance bounds for single-user scenarios with line-of-sight and Rayleigh fading.

Contribution

It introduces the concept of a continuous RIS, deriving optimal configurations and performance metrics, advancing the understanding of RIS design beyond discrete element implementations.

Findings

Optimal RIS design for single-user scenarios with LoS and Rayleigh fading.

Derived bounds on spectral efficiency and SNR outage probability.

Insights into channel hardening effects for continuous RIS.

Abstract

We consider a reconfigurable intelligent surface (RIS) that can implement a phase rotation continuously over the whole surface rather than via a finite number of discrete elements. Such an RIS can be considered a design for future systems where advances in metamaterials make such an implementation feasible or as the limiting case where the number of elements in a traditional RIS increases in a given area. We derive the optimal RIS design for the single-user (SU) scenario assuming a line-of-sight (LoS) from the RIS to the base station (BS) and correlated Rayleigh fading for the other links. We also derive the associated optimal signal-to-noise ratio (SNR) and its mean, a bound on the mean spectral efficiency (SE), an approximation to the SNR outage probability and an approximation to the coefficient of variation for the investigation of channel hardening.