Flexible Intelligent Layered Metasurfaces for Downlink Multi-user MISO Communications

2025-10-28

AI Summary

Conventional stacked intelligent metasurfaces (SIMs) suffer from severe power attenuation due to uniform inter-layer spacing and deep structural stacking. Method: This paper proposes a reconfigurable, transmissive, dual-layer flexible intelligent metasurface architecture for multi-user MISO communication systems. By jointly optimizing the electromagnetic phase response and physical deformation of two flexible metasurface layers, the architecture dynamically enhances channel matching—eliminating reliance on high layer counts and fixed spacing. A dynamically tunable transmission coefficient matrix is introduced to preserve beamforming capability while significantly reducing hardware complexity and signal loss. An alternating optimization algorithm jointly solves closed-form phase updates and gradient-descent-based deformation control, integrated with channel fitting modeling and sum-rate upper-bound analysis. Results: Simulations demonstrate over 200% sum-rate improvement and more than 7 dB BER gain compared to a seven-layer conventional SIM.

Technology Category

• Search and Optimization: Metareasoning and Metaheuristics
• Intelligent Robots: Multi-Robot Systems
• Machine Learning: Hardware-aware ML

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

Stacked intelligent metasurfaces (SIMs) have recently gained attention as a paradigm for wave-domain signal processing with reduced reliance on costly radio-frequency (RF) chains. However, conventional SIMs rely on uniform inter-layer spacing and require deep stacking to ensure processing capability, resulting in severe power attenuation in practice. To address this issue, we propose a flexible intelligent layered metasurface (FILM) architecture consisting of two shape-controllable flexible metasurface layers. By replacing rigid metasurfaces with flexible ones in both layers, the transmission coefficient matrix can be dynamically adjusted, significantly decreasing the number of required layers while maintaining signal processing performance. Firstly, we develop a two-layer FILM-assisted multi-user multiple-input single-output (MU-MISO) system, wherein we formulate a channel fitting problem aimed at reducing the difference between the FILM-induced and target channels. Then, we solve this non-convex problem by employing an alternating optimization (AO) method, featuring closed-form phase shift updates and a gradient descent-based shape optimization. Furthermore, we analyze the upper bound on sum-rate and the complexity of computation to provide insights into design trade-offs. Finally, simulation results demonstrated that the proposed transmissive FILM architecture achieves over 200% improvement in sum-rate and more than 7 dB bit-error rate (BER) gain compared to the conventional seven-layer SIMs.

Problem

• Reducing power attenuation in stacked metasurface communications
• Optimizing flexible metasurface layers for dynamic channel adjustment
• Enhancing multi-user MISO system performance with fewer layers

Innovation

• Flexible metasurface layers replace rigid uniform design
• Dynamic shape control reduces required layer count
• Alternating optimization method solves channel fitting problem