Respiration Monitoring of Multiple People using Multi-site FMCW SISO Radar Systems

TL;DR

This paper introduces a contactless multi-site SISO radar system for monitoring multiple people's respiration, overcoming resolution and synchronization challenges with a novel physiological-feature-assisted technique.

Contribution

It proposes a non-coherent multi-site SISO radar system that eliminates synchronization needs and employs a new method to distinguish true targets from ghost artifacts.

Findings

Accurately resolves two subjects less than 20 cm apart.

Achieves respiration rate estimation with 0.7 bpm RMSE.

Surpasses traditional MIMO array resolution limits.

Abstract

Continuous contactless respiration monitoring of co-sleeping subjects faces a dilemma: conventional single-site multiple-input multiple-output (MIMO) radars struggle with limited angular resolution for closely spaced individuals, while distributed radar networks typically require complex hardware synchronization. To address these limitations, this paper proposes non-coherent multi-site single-input-single-output (SISO) radar systems that completely eliminate the need for physical synchronization cables or common reference clocks. The fundamental challenge of ghost target ambiguity in such non-coherent multilateration is resolved through a novel physiological-feature-assisted suppression technique. By exploiting the inherent statistical independence of individual respiratory rhythms, true target locations are robustly distinguished from ghosts via cross-correlation analysis. Experimental validation demonstrates that the proposed system can accurately resolve two subjects spaced less than 20 cm apart, surpassing the resolution limits of traditional compact MIMO arrays, while achieving a respiration rate estimation accuracy of 0.7 bpm root mean square error (RMSE) compared to contact-based ground truth.