MIT system lets Wi-Fi locate users within tens of centimeters

April 04, 2016 // By Graham Prophet
A system designed by MIT’s Computer Science and Artificial Intelligence Lab (Cambridge, MA) enables a single WiFi access point that can locate users within tens of centimetres; the team offers the prospect of safer drones, smarter homes, and password-free WiFi.

We've all been there (the MIT statement says), impatiently twiddling our thumbs while trying to locate a Wi-Fi signal. But what if, instead, the Wi-Fi could locate us? In a new paper, a research team led by Professor Dina Katabi present a system called Chronos that enables a single Wi-Fi access point to locate users to within tens of centimetres, without any external sensors.

The team demonstrated the system in an apartment and a cafe, while also showing off a drone that maintains a safe distance from its user with a margin of error of about four centimeters.

"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 Wi-Fi in robotics, home automation and more," says PhD student Deepak Vasisht, who is first author on the paper alongside Katabi and former PhD student Swarun Kumar, who is now an assistant professor at Carnegie Mellon University. "Designing a system that enables one Wi-Fi node to locate another is an important step for wireless technology."

Experiments conducted in a two-bedroom apartment with four occupants show that Chronos can correctly identify which room a resident is in 94% of the time. For the cafe demo, the system was 97% accurate in distinguishing in-store customers from out-of-store intruders - meaning it could be used by small businesses to prevent non-customers from stealing their Wi-Fi. (32% of Americans have confessed to this cyber-crime.)

Chronos locates users by calculating the "time-of-flight" that it takes for data to travel from the user to an access point. The system is 20 times more accurate than existing systems, computing time-of-flight with an average error of 0.47 nsec. Vasisht presented the paper at this month's USENIX Symposium on Networked Systems Design and Implementation (NSDI '16).

Eliminates triangulation

Existing localisation methods have required four or five Wi-Fi access points. This is because today's