Mutual Coupling in RIS-Aided Communication: Model Training and Experimental Validation

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Main Authors: Zheng, Pinjun, Wang, Ruiqi, Shamim, Atif, Al-Naffouri, Tareq Y.
Format: Preprint
Published: 2023
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_version_ 1866913408591331328
author Zheng, Pinjun
Wang, Ruiqi
Shamim, Atif
Al-Naffouri, Tareq Y.
author_facet Zheng, Pinjun
Wang, Ruiqi
Shamim, Atif
Al-Naffouri, Tareq Y.
contents Mutual coupling is increasingly important in reconfigurable intelligent surface (RIS)-aided communications, particularly when RIS elements are densely integrated in applications such as holographic communications. This paper experimentally investigates the mutual coupling effect among RIS elements using a mutual coupling-aware communication model based on scattering matrices. Utilizing a fabricated 1-bit quasi-passive RIS prototype operating in the mmWave band, we propose a practical model training approach based on a single 3D full-wave simulation of the RIS radiation pattern, which enables the estimation of the scattering matrix among RIS unit cells. The formulated estimation problem is rigorously convex with a limited number of unknowns un-scaling with RIS size. The trained model is validated through both full-wave simulations and experimental measurements on the fabricated RIS prototype. Compared to the conventional communication model that does not account for mutual coupling in RIS, the mutual coupling-aware model incorporating trained scattering parameters demonstrates improved prediction accuracy. Benchmarked against the full-wave simulated RIS radiation pattern, the trained model can reduce prediction error by up to approximately 10.7%. Meanwhile, the S-parameter between the Tx and Rx antennas is measured, validating that the trained model exhibits closer alignment with the experimental measurements. These results affirm the accuracy of the adopted model and the effectiveness of the proposed model training method.
format Preprint
id arxiv_https___arxiv_org_abs_2311_10544
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Mutual Coupling in RIS-Aided Communication: Model Training and Experimental Validation
Zheng, Pinjun
Wang, Ruiqi
Shamim, Atif
Al-Naffouri, Tareq Y.
Signal Processing
Mutual coupling is increasingly important in reconfigurable intelligent surface (RIS)-aided communications, particularly when RIS elements are densely integrated in applications such as holographic communications. This paper experimentally investigates the mutual coupling effect among RIS elements using a mutual coupling-aware communication model based on scattering matrices. Utilizing a fabricated 1-bit quasi-passive RIS prototype operating in the mmWave band, we propose a practical model training approach based on a single 3D full-wave simulation of the RIS radiation pattern, which enables the estimation of the scattering matrix among RIS unit cells. The formulated estimation problem is rigorously convex with a limited number of unknowns un-scaling with RIS size. The trained model is validated through both full-wave simulations and experimental measurements on the fabricated RIS prototype. Compared to the conventional communication model that does not account for mutual coupling in RIS, the mutual coupling-aware model incorporating trained scattering parameters demonstrates improved prediction accuracy. Benchmarked against the full-wave simulated RIS radiation pattern, the trained model can reduce prediction error by up to approximately 10.7%. Meanwhile, the S-parameter between the Tx and Rx antennas is measured, validating that the trained model exhibits closer alignment with the experimental measurements. These results affirm the accuracy of the adopted model and the effectiveness of the proposed model training method.
title Mutual Coupling in RIS-Aided Communication: Model Training and Experimental Validation
topic Signal Processing
url https://arxiv.org/abs/2311.10544