On Channel Estimation for Group-Connected Beyond Diagonal RIS Assisted Multi-User MIMO Communication

2026-02-24

AI Summary

This work addresses the high channel estimation overhead in group-connected block-diagonal reconfigurable intelligent surface (BD-RIS)-assisted multi-user MIMO systems. It reveals that the cascaded channels within each RIS group exhibit a proportional structure, and leverages this property to propose a low-overhead, high-accuracy two-stage channel estimation protocol. In the first stage, reference cascaded channels for each group are estimated in parallel; in the second stage, the proportionality coefficients of the remaining antennas are recovered. By exploiting this structural insight, the proposed method substantially reduces the effective estimation dimensionality, achieving significantly lower pilot overhead while simultaneously enhancing channel estimation accuracy compared to existing approaches.

Technology Category

• Intelligent Robots: State Estimation
• Machine Learning: Multi-instance/Multi-view Learning
• Multiagent Systems: Coordination and Collaboration

Application Category

• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Security and Privacy: Large-scale security measurements

Abstract

Beyond diagonal reconfigurable intelligent surface (BD-RIS) architectures offer superior beamforming gain over conventional diagonal RISs. However, the channel estimation overhead is the main hurdle for reaping the above gain in practice. This letter addresses this issue for group-connected BDRIS aided uplink communication from multiple multi-antenna users to one multi-antenna base station (BS). We first reveal that within each BD-RIS group, the cascaded channel associated with one user antenna and one BD-RIS element is a scaled version of that associated with any other user antenna and BD-RIS element due to the common RIS-BS channel. This insight drastically reduces the dimensionality of the channel estimation problem. Building on this property, we propose an efficient two-phase channel estimation protocol. In the first phase, the reference cascaded channels for all groups are estimated in parallel based on common received signals while determining the scaling coefficients for a single reference antenna. In the second phase, the scaling coefficients for all remaining user antennas are estimated. Numerical results demonstrate that our proposed framework achieves substantially lower estimation error with fewer pilot signals compared to state-of-the-art benchmark schemes.

Problem

• Channel Estimation
• Reconfigurable Intelligent Surface
• Multi-User MIMO
• BD-RIS
• Pilot Overhead

Innovation

• Beyond Diagonal RIS
• Channel Estimation
• Group-Connected Architecture
• Multi-User MIMO
• Pilot Efficiency