A Survey on Stacked Intelligent Metasurfaces: Fundamentals, Recent Advances, and Challenges

2026-03-05

AI Summary

Conventional single-layer reconfigurable intelligent surfaces (RISs) offer limited electromagnetic control, insufficient to meet 6G’s demand for high-dimensional and flexible signal processing. This work presents a systematic review of stacked intelligent metasurfaces (SIMs), establishing— for the first time—a theoretical framework that positions SIMs as programmable electromagnetic processors. It introduces a novel wave-domain signal processing paradigm grounded in cascaded wave–matter interactions. By leveraging cascaded operator modeling, multi-port impedance analysis, and learning-driven control strategies, the study reveals the potential of SIMs in near-field communications, broadband transmission, and integrated sensing and communication. Furthermore, it identifies key research directions, including cross-layer co-design and network-level integration, thereby providing a comprehensive technical roadmap for programmable electromagnetic front-ends in 6G systems.

Technology Category

• Search and Optimization: Metareasoning and Metaheuristics
• Intelligent Robots: Multi-Robot Systems
• Cognitive Modeling & Cognitive Systems: Simulating Human Behavior

Application Category

• 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
• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems

Abstract

Reconfigurable intelligent surfaces (RISs) enable programmable control of wireless propagation. Beyond environmental deployments, integrating metasurfaces at the antenna front end allows direct manipulation of the radiated electromagnetic field and enables wave-domain signal processing. In this context, stacked intelligent metasurfaces (SIMs) have recently been proposed as an advanced architecture in which multiple programmable metasurface layers interact through wave propagation, enabling richer and more flexible electromagnetic transformations than conventional single-layer designs. By leveraging cascaded wave-matter interactions at the transmitter or receiver front end, SIMs substantially expand the design space of programmable wireless systems. This survey provides a comprehensive overview of SIMs technologies from the electromagnetic processing perspective, covering their physical principles, modeling frameworks, hardware realizations, and emerging architectural designs. We review existing modeling approaches based on cascaded operators, multiport impedance formulations, and network parameter representations, and discuss their implications for scalable optimization and system design. The survey further examines key communication functionalities enabled by front-end metasurface processing, including communication performance optimization, near-field and wideband transmission, learning-driven control, integrated sensing and communications, and emerging architectures such as cell-free and non-terrestrial networks. Finally, we identify open research problems related to physical modeling, scalability, hardware-algorithm co-design, and network integration, and outline promising directions toward realizing SIM-based antenna front ends as fully programmable electromagnetic processors for future sixth-generation (6G) wireless systems.

Problem

• Stacked Intelligent Metasurfaces
• Reconfigurable Intelligent Surfaces
• Electromagnetic Processing
• Antenna Front End
• 6G Wireless Systems

Innovation

• Stacked Intelligent Metasurfaces
• Wave-domain Signal Processing
• Cascaded Wave-Matter Interaction
• Programmable Antenna Front End
• Electromagnetic Processing