Pulse Rate Monitoring Using Narrowband Received Signal Strength Measurements

Radio frequency (RF) solutions for human vital sign monitoring have gained importance due to their low device cost and non-contact sensing. However, most systems are quite heavy users of RF spectrum, e.g., transmitting hundreds of WiFi packets per second, which then interferes with wireless communications. In this paper, we present a narrowband RF-based pulse rate monitoring system which uses orders of magnitudes less spectrum and remains low-cost and non-contact. To achieve this, we use received signal strength (RSS) measurements, which then impose challenges due to the very low signal-to-noise ratio and the use of a single-dimensional measurement of the channel. We apply a combination of linear and non-linear filtering, and a new estimator to address these challenges. We report experimental results showing an error of 1.6 beats/min (bpm), similar to the state-of-the-art, but using three orders of magnitude less bandwidth.