MIT Develops Wi-Fi Device that can See Through Walls

A low-cost device that manipulates a Wi-Fi signal promises to grant its users with an ability straight out of superhero comics: X-ray vision.

Dina Katabi and her colleagues at MIT are developing a system that could enable its users to see through walls and closed doors.

The system is called "Wi-Vi" and is based on a similar concept to radar and sonar imaging; the device emits a low-power Wi-Fi signal and uses reflections of the signal to track the movement.

"We wanted to create a device that is low-power, portable and simple enough for anyone to use, to give people the ability to see through walls and closed doors," Katabi said in an MIT statement.

But getting the device to pick up the signal from a human body was no easy feat.

As a Wi-Fi signal travels towards a wall, only a portion of the signal passes through it, reflecting off any humans on the other side, but also any other static objects around. Katabi said her team had to come up with a technology that could cancel out all the other reflections and isolate the signals bounced back off the human body.

To achieve the desired results, the research team employed two transmit antennas and a single receiver. The antennas transmit almost identical signals; the second antenna transmits a signal that's the inverse of the first. The inverse signals cause them to mostly cancel each other out. Since any static objects the signals hit - including the wall - create identical reflections, they too are cancelled out. The receiver will only pick up the signal from a moving object, so any person walking behind the wall will be detected.

Potential applications for the device include search-and-rescue operations, police work and video games, the researchers report.

It could also be used for personal safety. "If you are walking at night and you have the feeling that someone is following you, then you could use it to check if there is someone behind the fence or behind a corner," Katabi said.