CRH: A Contactless Respiration and Heartbeat Monitoring System with COTS RFID Tags

Monitoring respiration and heartbeat contributes to disease prediction, sub-health diagnosis, exercise and sleep quality analysis, fatigue warning, and even emotion estimation. There is a compelling need for contactless, easy-to-deploy and long-term respiration and heartbeat monitoring. In this paper, we present CRH, an RFID-based contactless respiration and heartbeat monitoring system. The key insight is that the RFID signal fluctuation induced by the chest motion is synchronous with respiration and heartbeat. Therefore, CRH collects the temporal phase information from the tag array near or on body to extract respiration and heartbeat signals using a sequence of signal processing techniques. We propose a signal separation method based on multi-tag empirical mode decomposition (EMD) to obtain respiration rate and heart rate after preprocessing. Furthermore, CRH can also detect intense motions and abnormal respiration. We implement and evaluate CRH using Commercial Off-The-Shelf (COTS) RFID devices. Extensive experimental results in different scenarios show that CRH can achieve high accuracy for monitoring multi-user respiration and heart rates, validating its wide applicability and high reliability for contactless fine-grained respiration and heartbeat monitoring.