Scientists develop Low power Wi-Fi that can ‘see’ people through walls and doors

Bradley Wint
By: - 2nd Jul 2013
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A scientist at MIT has come up with a way to use Wi-Fi signals to ‘see’ through walls and closed doors.

Dina Katabi, a professor in MIT’s Department of Electrical Engineering and Computer Science is developing  a very low-cost, low-powered, and portable Wi-Fi transmitter/receiver that can effectively detect a human’s presence in another room and display where they are.

While ‘Wi-Vi” as it’s being called won’t allow you to see what they look like (like in the Superman comics), the system can draw an outline and where they are in the next room.

As a Wi-Fi signal is transmitted at a wall, a portion of the signal penetrates through it, reflecting off any humans on the other side. However, only a tiny fraction of the signal makes it through to the other room, with the rest being reflected by the wall, or by other objects. “So we had to come up with a technology that could cancel out all these other reflections, and keep only those from the moving human body,” Katabi says.

Wi-Vi works by filtering out signal reflections from static objects, thus pinpointing those that are in motion. To do this, two transmitters and only one receiver were installed on the unit with each transmitter sending a signal that is inverse of the other. As a result, the inverse signals cause interference and have a cancelling effect because there is only one receiver and because the reflection times are the same. This means that it can filter out static objects like walls, doors, furniture, and so on, and track the movement of humans or anything else in motion. When objects move, the two transmitted signals have different reflection times, allowing the receiving antenna to track both signals, revealing an approximate location. The software would then be able to generate an outline indicating where someone is in a different room.

MIT is has hopes that it can be used for personal safety or for disaster recovery, but then there is the flip side where it can be used for negative such as spying on others.

[Cover Photo: nSeika/Flickr]

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