  Good quality sleep is essential for good health and sleep monitoring becomes
a vital research topic. This paper provides a low cost, continuous and
contactless WiFi-based vital signs (breathing and heart rate) monitoring
method. In particular, we set up the antennas based on Fresnel diffraction
model and signal propagation theory, which enhances the detection of weak
breathing/heartbeat motion. We implement a prototype system using the off-shelf
devices and a real-time processing system to monitor vital signs in real time.
The experimental results indicate the accurate breathing rate and heart rate
detection performance. To the best of our knowledge, this is the first work to
use a pair of WiFi devices and omnidirectional antennas to achieve real-time
individual breathing rate and heart rate monitoring in different sleeping
postures.
