Wi-Vi lets smartphones see through walls

Jun 28, 2013
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Using WiFi to "see through walls" and track people when they're moving could be a new feature on your next smartphone, if MIT researchers have their way, with a low-cost method of tracking relying on the wireless connectivity cooked up in their labs. The project, dubbed Wi-Vi, repurposes WiFi in a similar manner to sonar or radar, pinging out radio waves and then tracking how they're bounced back. Since WiFi can pass through walls, so Wi-Vi can give a glimpse of what's happening through barriers, albeit with some limitations.

Biggest is probably the resolution that's currently supported. Right now, this isn't the stuff of superheroes: instead, Wi-Vi delivers a more basic perspective on moving objects, rather than allowing you to see details on who or what is there. "Simple gestures" are also trackable, the team behind the project, Fadel Adib and Dina Katabi, says.

In fact, Wi-Vi actually uses two WiFi pings to identify objects, not just one. The second is the inverse of the first WiFi signal: when they both hit stationary objects, they cancel each other out, but when the object is moving the slight offset between them can be picked up by the device. By using two transmitters and a single receiver, it's also possible to identify the direction of movement.

Although sonar and radar are nowhere near new, they're also expensive to add to a mobile device. In contrast, Wi-Vi relies on off-the-shelf hardware, simply 2.4GHz WiFi radios. That opens the door to integrating it into regular smartphones, which invariably already feature wireless support.

The MIT team behind the project have some big ambitions for Wi-Vi. The scanning technology could be used by law enforcement and emergency services personnel, to identify hiding suspects, potential hazards, and people trapped in wreckage or rubble. It could also have a role in smart homes, being used to track movement and activity to control lighting, heating, and other environmental features, or perhaps move A/V content around to follow the listener.

Meanwhile, although there are obviously privacy issues to be faced, the researchers argue that the relatively low resolution compared to a traditional camera could make the Wi-Vi system more palatable for monitoring situations such as keeping an eye on elderly relatives or in hospitals. Rather than an intrusive CCTV feed, the more generic Wi-Vi could be tracked to highlight people who haven't moved recently, and who may be suffering from ill-health.

For the rest of us, just as motion gaming technologies like Kinect and Wii have taken off, so the Wi-Vi team believes there's room for the scanning system in games and entertainment. That could include controllers that can see "through" other players, or that don't have full line-of sight.

VIA Computerworld


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