Passive Through-Wall Human Sensing with WiFi

Through-wall human sensing is of high interest to both the Defense Department in counter-terrorism applications and the Home Affairs Department for civilian law enforcement purposes, particularly in the modern highly urbanized environment. Conventional active radar sensors possess good performance, however, at the expense of high cost and complexity of the transmitter/receiver design. This talk demonstrates the effectiveness of a passive through-wall human sensing technique using the opportunistic WiFi signal. With a simple software defined radio (SDR) receiver, the position of indoor WiFi access point is accurately localized and the Doppler/micro-Doppler of human motions inside the room are clearly detected. It is demonstrated that the WiFi-based passive radar is capable of detecting not only major motions such as walking and waving hand, but also very small human motions such as finger typing and breathing.