In-Vehicle Breathing Rate Monitoring Based on WiFi Signals

In this work, we propose in-vehicle breathing rate monitoring by exploiting channel state information (CSI) available in WiFi signals. The system uses CSI phase and amplitude extracted from a commercial-off-the-shelf (COTS) network interface card (NIC). We provide a simple two-path radio signal propagation model to explain the complementary relation between CSI phase and amplitude. Analyzing CSI phase and amplitude separately, we estimate the breathing rate of a person in a stationary vehicle. We conduct measurements using different antenna positions and with single and multiple antennas at the receiver. Verifying the measurement results with real-time counting of the breathing rate, we show that using multiple antennas significantly improve the performance of the system.