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arXiv · 2512.15441

Semi-Blind Joint Channel and Symbol Estimation for Beyond Diagonal Reconfigurable Surfaces

Gilderlan Tavares de Araújo·André L. F. de Almeida·Buno Sokal·Gabor Fodor
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Abstract

The beyond-diagonal reconfigurable intelligent surface (BD-RIS) is a recent architecture in which scattering elements are interconnected to enhance the degrees of freedom for wave control, yielding performance gains over traditional single-connected RISs. For BD-RIS, channel estimation, which is well studied for conventional RIS, becomes more challenging due to complex connections and a larger number of coefficients. Prior works have relied on pilot-assisted estimation followed by data decoding. This paper introduces a semi-blind tensor-based approach to joint channel and symbol estimation that reduces the need for dedicated training sequences by directly leveraging data symbols. We consider a practical scenario with time-varying user terminal-RIS channels under mobility. By reformulating the received signal from a tensor decomposition perspective, we develop two semi-blind receivers: a two-stage method that transforms the fourth-order PARATUCK model into a third-order PARAFAC model, and a single-stage iterative process based on the fourth-order TUCKER decomposition. Identifiability conditions for reliable joint recovery are derived, and numerical results demonstrate the performance advantages and trade-offs of the proposed schemes over existing solutions.

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Gilderlan Tavares de Araújo, André L. F. de Almeida, Buno Sokal, Gabor Fodor. 2025-12-17. Semi-Blind Joint Channel and Symbol Estimation for Beyond Diagonal Reconfigurable Surfaces. https://arxiv.org/abs/2512.15441

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