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

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.