An Electromagnetic Framework for the Deployment of Reconfigurable Intelligent Surfaces to Control Massive MIMO Channel Characteristics

TL;DR

This paper presents an electromagnetic framework using FDTD simulations to analyze how reconfigurable intelligent surfaces (RIS) with switchable FSS layers can control and customize the uplink channel characteristics of massive MIMO systems.

Contribution

It introduces a novel electromagnetic simulation approach to study RIS effects on massive MIMO channels, enabling deterministic control of channel eigenvalues.

Findings

RIS can selectively enhance or suppress channel eigenvalues.

Deployment of switchable FSS layers influences the MIMO channel eigenspace.

Electromagnetic control allows for deterministic channel customization.

Abstract

In this paper, we deploy a full-wave FDTD paradigm to investigate the effect of reconfigurable intelligent surface (RIS) -- switchable frequency-selective surfaces (FSS) -- on generic massive MIMO uplink channel's eigenspace structure. We place an RIS based on two switchable FSS layers in the vicinity of a 64-element massive MIMO base-station (BS) array, serving a cluster of four fixed user equipment (UE) units. Utilizing an electromagnetic tool based on time-averaged Poynting flow developed recently by the authors, we demonstrate how the illumination of BS-array aperture can be controlled by the intentional deployment of various switching states in the RIS placed near the BS. We show that such supplementary RIS structures may assist the wireless link engineer in deterministically "customizing" the uplink channel behaviour by selectively enhancing/suppressing certain channel eigenvalues.