Stacked Intelligent Metasurfaces for 6G Wireless Networks: Principles, Applications, and Research Directions

TL;DR

This paper reviews the use of stacked intelligent metasurfaces (SIMs) in 6G wireless networks, highlighting their potential to enhance electromagnetic control, interference management, and security in distributed architectures.

Contribution

It provides a comprehensive overview of SIM integration in 6G networks, including system architectures, signal processing challenges, and future research directions.

Findings

SIMs enable advanced wave-domain operations.

Case studies show significant performance improvements.

Future directions include AI integration and hardware design.

Abstract

The sixth-generation (6G) wireless networks are expected to deliver ubiquitous connectivity, resilient coverage, and intelligence-driven services in highly dynamic environments. To achieve these goals, distributed wireless architectures such as cell-free massive multiple-input multiple-output (MIMO) have attracted significant attention due to their scalability and fairness. Recently, stacked intelligent metasurfaces (SIMs) have emerged as a promising evolution of reconfigurable intelligent surfaces, offering multi-layer electromagnetic domain processing with enhanced controllability and spatial degrees of freedom. By integrating SIMs into distributed wireless networks, advanced wave-domain operations can be realized, enabling efficient interference management, improved energy and spectral efficiency, and robust physical-layer security. This article provides a comprehensive overview of SIM-aided distributed wireless networks, including their application scenarios, classification, and system architectures. Key signal processing challenges, such as hierarchical frameworks, user association, and joint precoding, are discussed, followed by case studies demonstrating significant performance gains. Finally, future research directions in hardware design, energy consumption modeling, algorithm development, and artificial intelligence integration are highlighted, aiming to pave the way for scalable and intelligent 6G distributed wireless networks.