Two drones see through walls in 3D using WiFi signals

Transmit and receive drones perform 3D imaging through walls using WiFi (credit: Chitra R. Karanam and Yasamin Mostofi/ACM) Researchers at the University of California Santa Barbara have demonstrated the first three-dimensional imaging of objects through walls using an ordinary wireless signal. Applications could include emergency search-and-rescue, archaeological discovery, and structural monitoring, according to the researchers. Other applications could include military and law-enforcement surveillance. In the research, two octo-copters (drones) took off and flew outside an enclosed, four-sided brick structure whose interior was unknown to the drones. One drone continuously transmitted a WiFi signal; the other drone (located on a different side of the structure) received that signal and transmitted the changes in received signal strength ("RSSI") during the flight to a computer, which then calculated 3D high-resolution images of the objects inside (which do not need to move). Interestingly, the equipment is all commercially available: two drones with "yagi" antenna, WiFi router, Tango tablet (for real-time localization), and Raspberry Pi computer with network interface to record measurements.