Date Added: May 2013
Wi-Fi signals are typically information carriers between a transmitter and a receiver. In this paper, the authors show that Wi-Fi can also extend their senses, enabling there to see moving objects through walls and behind closed doors. In particular, they can use such signals to identify the number of people in a closed room and their relative locations. They can also identify simple gestures made behind a wall, and combine a sequence of gestures to communicate messages to a wireless receiver without carrying any transmitting device.