New system uses low-power Wi-Fi signal to track moving humans — even behind walls

MIT.edu ^ | June 28, 2013

[BenLurkin]

The system, called “Wi-Vi,” is based on a concept similar to radar and sonar imaging. But in contrast to radar and sonar, it transmits a low-power Wi-Fi signal and uses its reflections to track moving humans. It can do so even if the humans are in closed rooms or hiding behind a wall.

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.

Motion detector

To do this, the system uses two transmit antennas and a single receiver. The two antennas transmit almost identical signals, except that the signal from the second antenna is the inverse of the first. As a result, the two signals interfere with each other in such a way as to cancel each other out. Since any static objects that the signals hit — including the wall — create identical reflections, they too are cancelled out by this nulling effect.

[i_robot73]

and the Warriors of the WoD will herald the shredding of the 4th even more.

[NormsRevenge]

Uses technology similar to the old see thru walls glasses,, they always fogged up. :-)

[Pearls Before Swine]

LOL...but the Patriots do have this kind of technology...it’s called Tim Tebow! :)

I was roundly laughed at here for suggesting that, as a joke, when the police first started looking at Hernandez. Since then, I've seen some articles on the sports blogs suggesting the very same thing--Tebow is big, he's strong, he did the full combine and scored higher than most tight ends, etc. I don't think that will happen, though, outside of some trick plays.

[BenLurkin]

Thx!