Beyond-Diagonal RIS: Adversarial Channels and Optimality of Low-Complexity Architectures

Fuente: arXiv
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Main Authors: Iivanainen, Atso, Rajamäki, Robin, Koivunen, Visa
Format: Preprint
Published: 2025
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author Iivanainen, Atso
Rajamäki, Robin
Koivunen, Visa
author_facet Iivanainen, Atso
Rajamäki, Robin
Koivunen, Visa
contents Beyond-diagonal reconfigurable intelligent surfaces (BD-RISs) have recently gained attention as an enhancement to conventional RISs. BD-RISs allow optimizing not only the phase, but also the amplitude responses of their discrete surface elements by introducing adjustable inter-element couplings. Various BD-RIS architectures have been proposed to optimally trade off between average performance and complexity of the architecture. However, little attention has been paid to worst-case performance. This paper characterizes novel sets of adversarial channels for which certain low-complexity BD-RIS architectures have suboptimal performance in terms of received signal power at an intended communications user. Specifically, we consider two recent BD-RIS models: the so-called group-connected and tree-connected architecture. The derived adversarial channel sets reveal new surprising connections between the two architectures. We validate our analytical results numerically, demonstrating that adversarial channels can cause a significant performance loss. Our results pave the way towards efficient BD-RIS designs that are robust to adversarial propagation conditions and malicious attacks.
format Preprint
id arxiv_https___arxiv_org_abs_2508_19000
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Beyond-Diagonal RIS: Adversarial Channels and Optimality of Low-Complexity Architectures
Iivanainen, Atso
Rajamäki, Robin
Koivunen, Visa
Signal Processing
Beyond-diagonal reconfigurable intelligent surfaces (BD-RISs) have recently gained attention as an enhancement to conventional RISs. BD-RISs allow optimizing not only the phase, but also the amplitude responses of their discrete surface elements by introducing adjustable inter-element couplings. Various BD-RIS architectures have been proposed to optimally trade off between average performance and complexity of the architecture. However, little attention has been paid to worst-case performance. This paper characterizes novel sets of adversarial channels for which certain low-complexity BD-RIS architectures have suboptimal performance in terms of received signal power at an intended communications user. Specifically, we consider two recent BD-RIS models: the so-called group-connected and tree-connected architecture. The derived adversarial channel sets reveal new surprising connections between the two architectures. We validate our analytical results numerically, demonstrating that adversarial channels can cause a significant performance loss. Our results pave the way towards efficient BD-RIS designs that are robust to adversarial propagation conditions and malicious attacks.
title Beyond-Diagonal RIS: Adversarial Channels and Optimality of Low-Complexity Architectures
topic Signal Processing
url https://arxiv.org/abs/2508.19000