RF-RES: Respiration Monitoring With COTS RFID Tags by Dopplershift

In health assessment and disease prevention, vital signs such as breathing rate, heartbeat rate, blood pressure and posturography play a critical role. Not only the elderly, but also young people need to pay attention to vital signs monitoring because more and more young people die of sudden diseases, such as sudden death and myocardial infarction. Traditional vital signs monitoring methods are invasive and inconvenient to use, especially for the elderly because these methods usually require users to wear some dedicated sensors. In recent years, some non-invasive vital signs monitoring methods based on wireless sensing have been proposed. Usually, these methods need the user to remain still. When the user walks around, these methods cannot work well. One of the challenges of mobile people breathing monitoring is that the small body chest displacement caused by breathing is disturbed by people’s walking. In this paper, we propose RF-RES, which is an accurate continuous breathing monitoring method based on RFID technology and uses a pair of tags to eliminate the influence of the user’s body movement. We merge the data of the tag pairs to eliminate the influence of the user’s entire body movement and propose an algorithm based on doppler frequency shift to track the user’s displacement during exercise. We conduct practical experiments to evaluate the performance with Impinj R420 and passive tags. The results show that RF-RES achieves accurate respiratory rate monitoring when estimating the respiratory rate of different users, with an average error of 0.54 BPM.