Researchers from MIT's Computer Science and Artificial Intelligence Laboratory have developed what could be a low-cost, X-ray vision system. The system, known as "Wi-Vi," is based on a concept similar to radar and sonar, but instead of using high-powered signals, it uses reflected Wi-Fi signals. This way, it can track people's movements behind walls and closed doors.
When a Wi-Fi is transmitted through a wall, a portion of that signal penetrates and bounces off of any people in the other room. Since only a small amount of the signal gets through the wall, while the rest is reflected, the researchers had to devise a technology that could cancel out the spurious reflections and keep only those that reflected people's movement.
Dina Katabi, a professor in MIT's Department of Electrical Engineering and Computer Science, and her graduate student Fadel Adib have developed a system that uses two transmitting antennas and a single receiver. The two antennas transmit nearly identical signals, except that the signal from the second antenna is the reverse of the first. The reversed signals result in interference.
This interference causes the signals to cancel each other out. If the signals encounter stationary objects, they create identical reflections, and thus cancel each other out. If the reflections do not cancel each other out, then the researchers know that there are moving objects behind the wall, since the signals bounce back to the receiver.
The new technology is very low-cost. Wi-Vi could be used in everything from disaster recovery (you know, searching for people in earthquakes) to gaming. Because the device can detect any action behind a wall, the system could be used as a gesture-based technology that controls devices or lighting.
Mr. Venkat Padmanabhan, principal researcher at Microsoft Research, says that Wi-Vi technology could be easily used for gaming since it does not require line-of-sight between the user and the device itself.
