High SNR Analysis of RIS-Aided MIMO Broadcast Channels

TL;DR

This paper investigates how reconfigurable intelligent surfaces (RIS) affect MIMO broadcast channels at high SNR, revealing fundamental limits and comparing advanced coding schemes to linear precoding.

Contribution

It provides a high SNR analysis of RIS-aided MIMO channels, connecting channel eigenvalues with RIS properties and comparing DPC and linear precoding performance.

Findings

RIS can improve channel rank and eigenvalues in high SNR.

Fundamental limits are derived for LOS scenarios between BS and RIS.

Performance gap between DPC and linear precoding can vanish under certain conditions.

Abstract

We analyze the influence of a reconfigurable intelligent surface (RIS) on the Gram channel eigenvalues in a high signal-to-noise ratio (SNR) scenario. This allows to connect specific channel properties with the rank improvement capabilities of the RIS. In particular, fundamental limits due to a possible line of sight (LOS) setup between the base station (BS) and the RIS are derived. Furthermore, dirty paper coding (DPC) based schemes are compared to linear precoding in such a scenario and it is shown that under certain channel conditions, the performance gap between DPC and linear precoding vanishes.