Radio waves can 'see' terrorists, hostages through walls

The system could help police, firefighters and others nab intruders, and rescue hostages, fire victims and elderly people. It also might help retail marketing and border control.

The method uses radio tomographic imaging (RTI), which can "see", locate and track moving people or objects in an area surrounded by inexpensive radio transceivers that send and receive signals. People don't need to wear radio-transmitting ID tags.

RTI is different and much cheaper than radar, in which radar or radio signals are bounced off targets and the returning echoes or reflections provide the target's location and speed. RTI instead measures "shadows" in radio waves created when they pass through a moving person or object.

"By showing the locations of people within a building during hostage situations, fires or other emergencies, radio tomography can help law enforcement and emergency responders to know where they should focus their attention," say study authors Joey Wilson and Neal Patwari of the University of Utah (U-U).

Both researchers are in the U-U department of electrical and computer engineering - Patwari as an assistant professor and Wilson as a doctoral student.

The study involved placing a wireless network of 28 low cost radio transceivers - called nodes - around a square-shaped portion of the atrium and a similar part of the lawn, says an U-U release.