MMHeart: An Efficient Heartbeat Monitoring System Based on MIMO mmWave Radar

Heart rate provides aln important reference for human physical conditions and psychological changes. MmWave-based heart rate estimation has increasingly attracted attention in recent years due to its non-intrusiveness and cost-effectiveness. However, when the subject locates far away from the mmWave radar and also deviates from it, the low accuracy of heart rate estimation becomes a major concern. This paper presents MMHeart, a new heart rate estimation and heartbeat waveform reconstruction system based on MIMO mmWave radar. In order to effectively improve the accuracy of heart rate estimation, MMHeart first calculates appropriate range bins based on positioning results, then estimates candidate heart rates in all channels, removes abnormal candidates based on spectrum kurtosis, and finally estimates the heart rate by clustering the remaining candidates. Then in order to reconstruct more accurate heartbeat waveform, MMHeart first segments the signal by trough detection, then resamples heartbeat waveform template, and finally fine-tunes the start and end points of each segment. Our extensive experiments show that in long-range and large-deviation scenarios, MMHeart can improve the accuracy of heart rate estimation by at least 54.1% compared to mmEGC and PiVimo, while it can improve the accuracy of cardiac cycle duration by 52.2% compared to mmEGC.