# Can We Monitor Breathing During Sleep via Wi-Fi on Smartphone?

## TL;DR

This study demonstrates that smartphones can detect breathing during sleep by analyzing Wi-Fi channel state information, achieving high correlation with contact sensors, thus enabling contactless sleep monitoring.

## Contribution

The paper introduces a novel method for smartphone-based sleep breathing detection using Wi-Fi CSI, eliminating the need for additional sensors.

## Key findings

- Achieved mean correlation coefficient of 0.85 between Wi-Fi CSI and ground truth signals.
- Mean absolute difference in respiratory rate estimation is 0.39 breaths per epoch.
- Feasibility shown across different sleep postures and body mass indices.

## Abstract

Over the last decade there has been high interest in home sleep monitoring among research community and society. Smartphone-based sleep monitoring seems to be especially attractive. However, smartphone should be able to register physiological processes for that, such as breathing or heartbeats. In this study, we tried to detect breathing based on the analysis of channel state information (CSI) of Wi-Fi connection between a smartphone and an access point. We collected data of 5 subjects with different body mass index (17-33) in base sleep postures: prone, supine, and side. The obtained CSI-based respiratory signal was compared with ground truth from a contact belt sensor. The mean correlation coefficient between the signals of 0.85 was achieved. The mean absolute difference between respiratory rates (breaths per epoch) is 0.39. The results show that it is possible to use smartphones without additional sensors for registering breathing based on CSI and potentially for sleep monitoring.