Robust multi-person vital-sign sensing in indoor environments using FMCW MIMO radar

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Abstract

Contactless monitoring of respiration and heart rate in shared indoor spaces-such as hospital wards, eldercare facilities, and sleep labs-demands solutions that are unobtrusive, privacy-preserving, and robust to static reflections, multipath, and inter-subject interference. This paper presents a complete millimetre-wave frequency-modulated continuous-wave (FMCW) technology - multiple-input multiple- output (MIMO) radar framework for multi-subject vital-sign sensing with three key contributions: (i) clutter-robust target discovery to stabilize detections in realistic indoor scenes; (ii) high-resolution spatial separation to suppress inter-subject leakage; and (iii) hybrid time–frequency decomposition to improve heartbeat isolation by mitigating respiration harmonics and noise. Experiments on single-, two-, and three-subject datasets achieve Mean Absolute Error/ Root Mean Squared Error (MAE/RMSE) of 2.81/4.13 Beats Per Minute (BPM) for respiration and 2.43/3.61 BPM for heart rate. Compared with filtering-, Ensemble Empirical Mode Decomposition (EEMD), Compressive Sensing - Orthogonal Matching Pursuit (CS-OMP), and mmRH-Millimetre-wave radar heart-rate (mmRH) based baselines, the proposed framework yields substantially lower heart-rate errors while maintaining reliable multi-subject operation in shared indoor environments.

Keywords

FMCW radar / vital signs monitoring / respiration rate / heart rate / multi-subject separation

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