End-to-End Mutual Coupling Aware Communication Model for Reconfigurable Intelligent Surfaces: An Electromagnetic-Compliant Approach Based on Mutual Impedances

Gabriele Gradoni,Marco Di Renzo

doi:10.1109/lwc.2021.3050826

Abstract

Reconfigurable intelligent surfaces (RISs) are an emerging technology for application to wireless networks. We introduce a physics and electromagnetic (EM) compliant communication model for analyzing and optimizing RIS-assisted wireless systems. The proposed model has four main notable attributes: (i) it is end-to-end, i.e., it is formulated in terms of an equivalent channel that yields a one-to-one mapping between the voltages fed into the ports of a transmitter and the voltages measured at the ports of a receiver; (ii) it is EM-compliant, i.e., it accounts for the generation and propagation of the EM fields; (iii) it is mutual coupling aware, i.e., it accounts for the mutual coupling among the sub-wavelength unit cells of the RIS; and (iv) it is unit cell aware, i.e., it accounts for the intertwinement between the amplitude and phase response of the unit cells of the RIS.

Highlights

Reconfigurable intelligent surfaces (RISs) are an emerging and promising software-defined technology for enhancing the performance of wireless networks at a low cost, power, and complexity [1], [2]
We prove that the impact of (i) the incident EM fields; (ii) the voltage generators at the transmitter and the load impedances at the receiver; and (iii) the tunable load impedances that control the passive scatterers of the RIS is jointly taken into account, and is explicitly unfolded and individually observable in the proposed end-to-end communication model
END-TO-END COMMUNICATION MODEL based on the enabling results proved in Lemmas 3 and 4, we introduce an end-to-end communication model for RIS-assisted communications that accounts for an arbitrary number of coupled antenna elements at the transmitter and receiver, and passive scatterers at the RIS

Summary

Introduction

Reconfigurable intelligent surfaces (RISs) are an emerging and promising software-defined technology for enhancing the performance of wireless networks at a low cost, power, and complexity [1], [2]. For analyzing and optimizing RIS-aided wireless systems, sufficiently realistic and accurate yet tractable communication models that account for the physics and electromagnetic (EM) properties of the scattering elements of the RIS are needed. This is an open research issue, and only a few EM-compliant models for RIS-assisted wireless systems are available to date [4]-[7]. In [4], an experimentally-validated path-loss model for a non-homogenizable RIS is proposed. In [5], a path-loss model for a homogenizable RIS is introduced by using the vector theory of scattering. In [7], the mutual coupling among the active radiating elements of a large surface is investigated

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Conclusion