15 June 2014

MIT perfects cheap, accurate through-wall movement and heartbeat detection with WiFi

MIT WiZ antenna setup
MIT’s rather fabulous Computer Science and Artificial Intelligence Laboratory (CSAIL), after using humble WiFi waves to sense movement behind a wall, has now improved its technology to the point that it can remotely from behind a wall in another room can detect heart rate and respiration. MIT has successfully used this technology to non-invasively check a sleeping baby’s breathing and pulse, and even to track the breathing of two adults simultaneously. Yes, there are videos of both feats embedded below.

This time last year it was Wi-Vi and now, with some further refinements, MIT is now calling it WiZ (which might be a play on “Wi-See,” but it isn’t clear). While Wi-Vi and other similar technologies could detect movement in general, WiZ can use radio waves to accurately (within a few centimeters) locate up to four people in a room. WiZ can also locate static people by detecting the motions caused by breathing and yes, from these minute movements, they can work out your heart rate with 99% accuracy.

“It has traditionally been very difficult to capture such minute motions that occur at the rate of mere millimeters per second,” says MIT’s Dina Katabi who co-authored the recent research paper. “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.”

MIT's WiZ, showing how it focuses on four different people, even if they're behind one another
MIT’s WiZ, showing how it focuses on four different people, even if they’re behind one another

To create WiZ, MIT uses a custom-made (but fairly inexpensive) setup consisting of a bunch of antennas that output specially constructed frequency-modulated carrier waves (FMCW). I won’t go into the exact maths of it, but these FMCWs allow the software to work out accurate time-of-flight for reflected radio waves much in the same way that Kinect 2.0 uses reflected infrared light to gather 3D time-of-flight data (infrared light and radio waves are ultimately both just different frequencies of electromagnetic radiation, so it makes sense that a similar approach can be used). Technologically speaking, the most impressive feat here is using the same radio waves to detect multiple people who may be in front of each other. There’s a lot of impressive maths going on behind the scenes.

Fancy maths aside, it’s the possible applications for WiZ that gets me truly excited. As you can see in the videos, at the very least we could be looking at a gadget that cheaply and easily monitors your child’s vital signs while they sleep. There could also be applications in military and law enforcement.

Perhaps most significantly, though, with the world moving towards wearable computers and ubiquitous sensor networks, WiZ could play a role in tracking your movement and vital signs without having to wear a Fitbit or smartwatch. It’s quite easy to imagine a wide-scale radio-based sensor network that tracks the movements of everyone through a given area and then using some kind of beacon system (say, if your smartphone broadcast your identity) that sensor data could be correlated to each person. It would be equal parts great news for people wanting to keep track of their health and activity levels, and modern-day governments that just love to surveil their populace.

Courtesy Extremetech


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