WiRainbow: Single-Antenna Direction-Aware Wi-Fi Sensing via Dispersion Effect

2025-11-14

AI Summary

To address the high cost and deployment complexity of multi-antenna arrays in Wi-Fi sensing, this paper proposes a novel single-antenna directional sensing paradigm. The core innovation leverages the dispersive property of a frequency-scanning antenna, enabling inherent spatial beam steering across OFDM subcarriers—thus achieving subcarrier-level angular separation. We further design a coupled-resonator antenna architecture to significantly widen the field of view and develop a signal processing framework driven by signal-to-noise ratio (SNR) optimization for robust azimuth estimation in multipath environments. Experimental evaluation on a prototype system demonstrates sub-10° direction-of-arrival (DoA) accuracy in realistic indoor scenarios. The approach achieves low hardware cost, strong robustness against multipath interference, and straightforward deployment. By eliminating the need for antenna arrays while preserving high angular resolution, this work establishes a scalable, practical pathway for contactless Wi-Fi sensing.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Application Domains: Internet of Things, Sensor Networks & Smart Cities
• Intelligent Robots: Multimodal Perception & Sensor Fusion

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web
• Security and Privacy: Large-scale security measurements

Abstract

Recently, Wi-Fi signals have emerged as a powerful tool for contactless sensing. During the sensing process, obtaining target direction information can provide valuable contextual insights for various applications. Existing direction estimation methods typically rely on antenna arrays, which are costly and complex to deploy in real-world scenarios. In this paper, we present WiRainbow, a novel approach that enables single-antenna-based direction awareness for Wi-Fi sensing by leveraging the dispersion effect of frequency-scanning antennas (FSAs), which can naturally steer Wi-Fi subcarriers toward distinct angles during signal transmission. To address key challenges in antenna design and signal processing, we propose a coupled-resonator-based antenna architecture that significantly expands the narrow Field-of-View inherent in conventional FSAs, improving sensing coverage. Additionally, we develop a sensing signal-to-noise-ratio-based signal processing framework that reliably estimates target direction in multipath-rich environments. We prototype WiRainbow and evaluate its performance through benchmark experiments and real-world case studies, demonstrating its ability to achieve accurate, robust, and cost-effective direction awareness for diverse Wi-Fi sensing applications.

Problem

• Enables single-antenna direction-aware Wi-Fi sensing using dispersion effect
• Expands narrow Field-of-View via coupled-resonator antenna design
• Estimates target direction reliably in multipath-rich environments

Innovation

• Single-antenna direction sensing via dispersion effect
• Coupled-resonator antenna expands narrow Field-of-View
• SNR-based processing for direction estimation in multipath