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arXiv · 2605.22360

Low-Complexity Tensor Beamforming for RIS-Aided Multiuser Multistream MIMO Systems

Bruno Sokal·André L. F. de Almeida·Martin Haardt
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Abstract

We address joint active and passive beamforming for uplink RIS-assisted multi-user multi-stream MIMO systems with joint detection. The coupled design of the receive combiner, block-diagonal user precoders, and RIS phase vector is formulated through a third-order composite channel tensor. Exploiting this multilinear structure, we propose a multi-stream tensor alternating optimization method that updates the combiner, user precoders, and RIS coefficients via low-dimensional tensor projections. Simulations show that the proposed method approaches a multi-start alternating-optimization benchmark while reducing computational complexity and improving large-RIS scaling.

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Bruno Sokal, André L. F. de Almeida, Martin Haardt. 2026-05-21. Low-Complexity Tensor Beamforming for RIS-Aided Multiuser Multistream MIMO Systems. https://arxiv.org/abs/2605.22360

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