Reimagining Wireless Connectivity: The FAS-RIS Synergy for 6G Smart Cities

TL;DR

This paper proposes an integrated FAS-RIS architecture for 6G smart cities, combining reconfigurable antennas and intelligent surfaces to enhance wireless connectivity, diversity, and environmental control.

Contribution

It introduces a novel FAS-RIS integrated framework with five key applications, including new RIS paradigms and a two-timescale control mechanism for future smart city networks.

Findings

Simulation results show improved robustness and system effectiveness.

The proposed architecture enhances spatial diversity and beamforming capabilities.

New RIS paradigms enable reconfigurable and active environmental shaping.

Abstract

Fluid antenna system (FAS) represents the concept of treating antenna as a reconfigurable physical-layer resource to broaden system design and network optimization and inspire next-generation reconfigurable antennas. FAS can unleash new degree of freedom (DoF) via antenna reconfigurations for novel spatial diversity. Reconfigurable intelligent surfaces (RISs) on the other hand can reshape wireless propagation environments but often face limitations from double path-loss and minimal signal processing capability when operating independently. This article envisions a transformative FAS-RIS integrated architecture for future smart city networks, uniting the adaptability of FAS with the environmental control of RIS. The proposed framework has five key applications: FAS-enabled base stations (BSs) for large-scale beamforming, FAS-equipped user devices with finest spatial diversity, and three novel RIS paradigms -- fluid RIS (FRIS) with reconfigurable elements, FAS-embedded RIS as active relays, and enormous FAS (E-FAS) exploiting surface waves on facades to re-establish line-of-sight (LoS) communication. A two-timescale control mechanism coordinates network-level beamforming with rapid, device-level adaptation. Applications spanning from simultaneous wireless information and power transfer (SWIPT) to integrated sensing and communications (ISAC), with challenges in co-design, channel modeling, and optimization, are discussed. This article concludes with simulation results demonstrating the robustness and effectiveness of the FAS-RIS system.