Respiratory Rate Estimation Based on WiFi Frame Capture

TL;DR

This paper introduces a novel WiFi frame capture method that estimates respiratory rates by analyzing beamforming feedback matrices, achieving high accuracy without specialized hardware.

Contribution

It proposes a new approach using unencrypted beamforming feedback matrices from WiFi frames for vital sign sensing, eliminating the need for specialized firmware or chips.

Findings

Estimation error is lower than 3.2 breaths/minute.

The method works with standard WiFi hardware and unencrypted frames.

Effective for respiratory rate monitoring using WiFi signals.

Abstract

This paper presents a method that estimates the respiratory rate based on the frame capturing of wireless local area networks. The method uses beamforming feedback matrices (BFMs) contained in the captured frames, which is a rotation matrix of channel state information (CSI). BFMs are transmitted unencrypted and easily obtained using frame capturing, requiring no specific firmware or WiFi chipsets, unlike the methods that use CSI. Such properties of BFMs allow us to apply frame capturing to various sensing tasks, e.g., vital sensing. In the proposed method, principal component analysis is applied to BFMs to isolate the effect of the chest movement of the subject, and then, discrete Fourier transform is performed to extract respiratory rates in a frequency domain. Experimental evaluation results confirm that the frame-capture-based respiratory rate estimation can achieve estimation error lower than 3.2 breaths/minute.