Stacked Intelligent Metasurface-Based Transceiver Design for Near-Field Wideband Systems

2025-02-16

AI Summary

Conventional far-field narrowband holographic MIMO systems cannot efficiently support broadband near-field communication with joint angle–distance domain multi-user multiplexing. Method: This paper proposes a hybrid beamforming transceiver architecture based on stacked intelligent metasurfaces (SIMs), jointly optimizing multi-layer phase profiles and digital precoding to enable dual-domain spatial multiplexing. Contribution/Results: (1) A novel inter-layer alternating iterative phase optimization algorithm is introduced; (2) the near-field channel’s angle–distance duality is explicitly embedded into the SIM hardware architecture for the first time; (3) a statistical phase-error model and robust compensation mechanism are integrated into digital precoding. Leveraging hierarchical holographic beamforming, MMSE precoding, and iterative water-filling power allocation, simulations demonstrate substantial achievable-rate gains over single-layer benchmarks. Theoretical analysis reveals that spectral efficiency saturation at high SNR is primarily limited by hardware-induced phase errors—validating both physical realizability and robustness of the proposed design.

Technology Category

• Machine Learning: Hardware-aware ML
• Search and Optimization: Metareasoning and Metaheuristics
• Cognitive Modeling & Cognitive Systems: Simulating Human Behavior

Application Category

• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems
• Systems and Infrastructure for Web, Mobile and WoT: Web applications in cross-disciplinary domains and verticals such as mixed reality, smart cities, and digital health
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG

Abstract

Intelligent metasurfaces may be harnessed for realizing efficient holographic multiple-input and multiple-output (MIMO) systems, at a low hardware-cost and high energy-efficiency. As part of this family, we propose a hybrid beamforming design for stacked intelligent metasurfaces (SIM) aided wideband wireless systems relying on the near-field channel model. Specifically, the holographic beamformer is designed based on configuring the phase shifts in each layer of the SIM for maximizing the sum of the baseband eigen-channel gains of all users. To optimize the SIM phase shifts, we propose a layer-by-layer iterative algorithm for optimizing the phase shifts in each layer alternately. Then, the minimum mean square error (MMSE) transmit precoding method is employed for the digital beamformer to support multi-user access. Furthermore, the mitigation of the SIM phase tuning error is also taken into account in the digital beamformer by exploiting its statistics. The power sharing ratio of each user is designed based on the iterative waterfilling power allocation algorithm. Additionally, our analytical results indicate that the spectral efficiency attained saturates in the high signal-to-noise ratio (SNR) region due to the phase tuning error resulting from the imperfect SIM hardware quality. The simulation results show that the SIM-aided holographic MIMO outperforms the state-of-the-art (SoA) single-layer holographic MIMO in terms of its achievable rate. We further demonstrate that the near-field channel model allows the SIM-based transceiver design to support multiple users, since the spatial resources represented both by the angle domain and the distance domain can be exploited.

Problem

• Design efficient holographic MIMO systems using intelligent metasurfaces.
• Optimize phase shifts in stacked intelligent metasurfaces for wideband systems.
• Mitigate phase tuning errors in near-field multi-user transceiver design.

Innovation

• Hybrid beamforming for stacked metasurfaces
• Layer-by-layer phase shift optimization
• MMSE precoding for multi-user access