How to track movement without a wearable device

New wireless technology out of MIT measures movements as subtle as breathing and heart rate from a distance, without any wearable sensors.


From smart watches and sensor-laden shirts to electronic tattoos and rings synced to smartphones , wearable technology feels ubiquitous these days. What if instead of wearable sensors that track movement and monitor your health, these same devices could work without being on you at all?

New wireless technology out of MIT can measure movements as slight as heart rate and breathing through a wall. They call their system Wi-Vi -- seeing with Wi-Fi signals -- and it could be useful for health tracking apps, baby monitoring (pictured below), and search-and-rescue operations.

Developed by a team from the Computer Science and Artificial intelligence Laboratory (CSAIL), the system can detect gestures as subtle as the rise and fall of your chest, from as far as another room away -- no device on the other side of the wall is necessary. From those measurements, the system can determine heart rate with 99 percent accuracy.

  • Wi-Vi transmits a low-power wireless signal and uses its reflections to track the movement of up to four people in a closed room.
  • As the signal is transmitted, a portion penetrates through the wall and reflects off the people on the other side.
  • As the person moves (however slightly), that tiny change in distance leads to a difference in timing of the reflected signal.
  • The technology cancels out irrelevant reflections to limit signal interference from stationary objects.

"It has traditionally been very difficult to capture such minute motions that occur at the rate of mere millimeters per second," MIT's Dina Katabi says in a news release. "Being able to do so with a low-cost, accessible technology opens up the possibilities for people to be able to track their vital signs on their own."

Wi-Vi was presented at the ACM Sigcomm conference in Hong Kong last year. Here's their latest report [pdf] and you can watch videos of the technology in action: monitoring baby breathing and heart rate and multiple adults in a room.

[MIT News Office]

Image: Christine Daniloff/MIT (top) & MIT (middle)

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