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

TL;DR

WiRainbow tackles the need for direction-aware Wi-Fi sensing without antenna arrays by leveraging a dispersion-enabled frequency-scanning antenna (FSA). It introduces a coupled-resonator antenna design to substantially widen the FoV and a SSNR-based signal-processing pipeline to robustly identify target directions in multipath environments. The system is prototyped and validated through benchmark experiments and case studies, demonstrating accurate angle estimation (typically within a few degrees) and interference-resistant multi-target sensing, with applications such as walking-area detection and respiration monitoring. The work offers a low-cost, scalable path toward single-antenna direction awareness in Wi-Fi sensing, with potential extensions to higher bands and other wireless modalities.

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.

Figures (18)

• Figure 1: Using FSAs for direction-aware Wi-Fi sensing.
• Figure 2: Principle of Wi-Fi sensing.
• Figure 3: Principle of frequency-scanning antennas.
• Figure 4: Illustration of the proposed antenna design.
• Figure 5: Principle of resonator-based architecture.