Multi-User Wireless Communications with Holographic MIMO Surfaces: A Convenient Channel Model and Spectral Efficiency Analysis

TL;DR

This paper models electromagnetic channels for multi-user holographic MIMO surfaces using Fourier plane wave representation, devises a Zero-Forcing precoding scheme, and analyzes spectral efficiency, showing improved performance with more antennas and larger spacing.

Contribution

It introduces a tractable electromagnetic channel model for MU-HMIMOS in the wavenumber domain and provides a spectral efficiency analysis with a robust theoretical framework.

Findings

Spectral efficiency improves with more patch antennas and larger spacing.

The proposed model accurately predicts performance even in highly correlated scenarios.

The analytical expressions closely match simulation results, validating the approach.

Abstract

The multi-user Holographic Multiple-Input and Multiple-Output Surface (MU-HMIMOS) paradigm, which is capable of realizing large continuous apertures with minimal power consumption and of shaping radio wave propagation at will, has been recently considered as an energy-efficient solution for future wireless networks. The tractable channel modeling of MU-HMIMOS signal propagation is one of the most critical challenges, mainly due to the coupling effect induced by the excessively large number of closely spaced patch antennas. In this paper, we focus on this challenge for downlink communications and model the electromagnetic channel in the wavenumber domain using the Fourier plane wave representation. Based on the proposed model, we devise a Zero-Forcing (ZF) precoding scheme, capitalizing on the sampled channel variance that depends on the number and spacing of the HMIMOS patch antennas, and perform a spectral efficiency analysis. Our simulation results showcase that the more patch antennas and the larger their spacing is, the performance of the considered MU-HMIMOS system improves. In addition, it is demonstrated that our theoretical performance expressions approximate sufficiently well the simulated spectral efficiency, even for the highly correlated cases, thus verifying the effectiveness and robustness of the presented analytical framework.