Enabling Smart Radio Environments in the Frequency Domain With Movable Signals

2025-11-12

AI Summary

The commercialization of smart radio environments (SREs) is hindered by the high cost and low robustness of reconfigurable intelligent surfaces (RISs) and mechanically tunable devices. Method: This paper proposes, for the first time, the “frequency-domain movable signal” paradigm—dynamically shifting the spectral position of the transmitted signal to synergize with fixed-impedance intelligent surfaces (FISs) for environmental intelligence, eliminating the need for electronic reconfiguration or physical movement. Contribution/Results: Theoretical analysis and MISO-case validation demonstrate that, under non-line-of-sight conditions, the proposed scheme achieves up to a 4× improvement in received power over conventional fixed-frequency RIS systems. It circumvents fundamental bandwidth and phase-response constraints inherent to RISs, thereby enabling low-cost, high-robustness SREs. This paradigm establishes a novel, hardware-efficient pathway toward practical SRE deployment.

Technology Category

• Intelligent Robots: Multi-Robot Systems
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Search and Retrieval-Augmented AI: Personalized, context-aware and across-device search
• Security and Privacy: Large-scale security measurements

Abstract

Smart radio environments (SREs) enhance wireless communications by allowing control over the channel. They have been enabled through surfaces with reconfigurable electromagnetic (EM) properties, known as reconfigurable intelligent surfaces (RISs), and through flexible antennas, which can be viewed as realizations of SREs in the EM domain and space domain, respectively. However, these technologies rely on electronically reconfigurable or movable components, introducing implementation challenges that could hinder commercialization. To overcome these challenges, we propose a new domain to enable SREs, the frequency domain, through the concept of movable signals, where the signal spectrum can be dynamically moved along the frequency axis. We first analyze movable signals in multiple-input single-output (MISO) systems under line-of-sight (LoS) conditions, showing that they can achieve higher average received power than quantized equal gain transmission (EGT). We then study movable signals under non-line-of-sight (NLoS) conditions, showing that they remain effective by leveraging reflections from surfaces made of uniformly spaced elements with fixed EM properties, denoted as fixed intelligent surfaces (FISs). Analytical results reveal that a FIS-aided system using movable signals can achieve up to four times the received power of a RIS-aided system using fixed-frequency signals.

Problem

• Overcoming implementation challenges of reconfigurable intelligent surfaces and flexible antennas
• Enabling smart radio environments through dynamic signal spectrum movement in frequency domain
• Achieving higher received power using movable signals with fixed intelligent surfaces

Innovation

• Movable signals dynamically shift spectrum along frequency axis
• Frequency domain approach replaces reconfigurable hardware components
• Fixed intelligent surfaces enhance signals using static reflectors