WiFi-based through-the-wall presence detection of stationary and moving humans analyzing the doppler spectrum

Through-the-wall (TTW) sensing is relevant in several scenarios. In particular, a system able to detect the presence of a noncollaborative person behind a wall could be used by law enforcement for better planning actions in case of standoffs and hostage situations. For emergency situations, first responders could use such a system to detect the presence of people through rubble and collapsed structures. Traditionally, these types of systems have been designed using a radar approach. In particular, ultrawideband systems (2 GHz of bandwidth) have been proposed for detecting human presence by using radio frequency (RF) signals [1], [2]. These systems usually require a large power source and big antennas. Recently, to reduce the power and complexity of these devices, the use of opportunity signals, such as WiFi signals, has been considered [3]-[6].