Vital-sign detection based on a passive WiFi radar

This paper presents a passive radar to detect human vital signs with ambient WiFi signals. The proposed radar does not contain a transmitting source. Instead, it captures WiFi signals produced by a far IEEE 802.11b/g/n access point and utilizes those signals to perform vital-sign detection according to Doppler effects. The reliability of detection depends on the conditions of WiFi connection, such as downloading or non-downloading states and signal strength, which is the focus of this study.