MIT researchers use Wi-Fi to track silhouettes through walls

Researchers at MIT have developed a Wi-Fi technology capable of seeing people through walls and other structures, which could have applications for powering virtual reality, smart homes and Hollywood film stages. The research is a follow-on to technology the researchers previously demonstrated that could help firefighters determine if there are living people in a burning building.

In a paper accepted to the SIGGRAPH Asia conference taking place next month, a team of researchers at MIT's Computer Science and Artificial Intelligence Lab (CSAIL) decribed a new technology called RF Capture that picks up wireless reflections off the human body to see the silhouette of a human standing behind a wall, according to MIT News.

By tracking the silhouette, the device can trace a person's hand as he writes in the air and even distinguish between 15 different people through a wall with nearly 90 percent accuracy. Researchers say the technology could have major implications for everything from gaming and filmmaking to emergency response and eldercare.

Regarding motion capture in movie production: "Today actors have to wear markers on their bodies and move in a specific room full of cameras," said PhD student Fadel Adib, who is lead author on the new paper. Other co-authors include MIT professor Frédo Durand, PhD student Chen-Yu Hsu and undergraduate intern Hongzi Mao. "RF Capture would enable motion capture without body sensors and could track actors' movements even if they are behind furniture or walls," Adib said.

The device's motion-capturing technology makes it equally valuable for smart homes, according to MIT professor and paper co-author Dina Katabi. "We're working to turn this technology into an in-home device that can call 911 if it detects that a family member has fallen unconscious," said Katabi, director of the [email protected] center. "You could also imagine it being used to operate your lights and TVs, or to adjust your heating by monitoring where you are in the house."

Future versions could be integrated into gaming interfaces, allowing users to interact with a game from different rooms or even trigger distinct actions based on which hand is moved.

The device works by transmitting wireless signals that traverse the wall and reflect off a person's body back to the device. (Researchers said the emitted radiation is approximately 1/10,000 the amount given off by a standard cellphone.) The device captures the reflections and analyzes them in order to see the person's silhouette.

Katabi said they can extract meaningful signals through a series of algorithms they developed that minimize the random noise produced by the reflections.

Last summer, a team of researchers at the University of California at Santa Barbara (UCSB) demonstrated that a Wi-Fi signal can be used to count the number of people in a given space when they are not carrying Wi-Fi devices, the idea being that having the ability to estimate the number of people in an area could help in emergency evacuation procedures or for heating and cooling a building.

For more:
- see this MIT News article

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