University of California Santa Barbara researchers have demonstrated a system for two unmanned vehicles to see through thick concrete walls using only WiFi signals - fully discovering what is on the other side with high accuracy. The objects on the other side don’t have to move to be detected. Potential applications include search and rescue operations and surveillance. One robot measures the wireless transmissions of the other robot that is in the broadcast mode. Each wireless transmission passes through the unknown area and the objects attenuate the signal depending on their material properties and locations. By devising a framework based on proper wave propagation modeling and sparse signal processing, the researchers have shown that it is possible for the two unmanned vehicles to image the entire area, with a high targeted resolution, and see through highly-attenuating walls. They used directional antennas in order to increase the imaging resolution.