New Technology Uses Low-Power Wi-Fi Signal To Track Moving Humans - Even Behind Walls

New Technology Uses Low-Power Wi-Fi Signal To Track Moving Humans - Even Behind Walls

Two years ago, Massachusetts Institute of Technology researchers used Wi-Fi signals to see through walls and track a person's activities. The same group has now come up with a new innovation that's not only able to recognize a person's shadow through walls but can also make out different individuals. 

The  team declared  they have refined their system to be even more exact by changing to radio signals. The system, known as “WiTrack,” works with the assistance of four antennae. One transmits a signal and the other three take in signals that bounce back. Based on how long it takes a signal to return, WiTrack can calculate an object’s distance from the antennae and map movement.  

Chronos that can exactly identify the position of a person or object inside a room within tens of centimeters, using WiFi signals only and without any sensors.

"It has traditionally been very difficult to capture such minute motions that occur at the rate of mere millimeters per second," writes Dina Katabi professor of electrical engineering and computer science at MIT in the research paper. She also directs the Wireless Center. "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."

"Knowing both the distance and the angle allows you to compute the user's position using just one access point," Ph.D. student Deepak Vasisht, who helped author a paper about the new technology, said in a statement.

Chronos works without the guide of any secondary sensors just utilizing a technology called time-of-flight calculation that measures the time it takes data to travel from the WiFi access point to the user's device. 

The researchers said Chronos is 20 times more exact than the current WiFi-based tracking systems. This can be used to give Wi-Fi access to folks in one area, whereas keeping those outside the specified location of the network. It may also be used on drones in the future to help them maintain a safe distance from people. Researchers say that Chronos was 94 percent successful in identifying which room a person is currently in, and 97 percent effective in figuring out whether if a shop's customer was inside or outside the store.

"From developing drones that are safer for people to be around, to tracking where family members are in your house, Chronos could open up new avenues for using WiFi in robotics, home automation and more," Vasisht said. "Designing a system that enables one WiFi node to locate another is an important step for wireless technology."

Wi-Fi can enter walls, but not very well as anyone who has had to set up a signal repeater knows. Things can block the signal, like stucco walls and paints. Even when it does enter, the signal can be spoiled by other objects, so the team had to create technology to cancel out insignificant reflections.
Eventually, the team hopes to enhance the technology to the point it can produce outlines of the people and detect emotions and feelings.

"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," says Katabi. "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."

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