Wi-Fi-based positioning improves access point security

High-accuracy indoor localization, along with password-free Wi-Fi, is now a possibility with new access point technology.

cuba elgan at hotspot
Amira Elgan

Imagine if your router could detect a user’s location to within a few inches? For one thing, hotspot password protection becomes redundant because geographic authentication takes over—the router can be configured to only allow access from within a location, an apartment, say. In-café users could be allowed access without passwords, yet freeloaders on the street get blocked.

Researchers think they’ve worked out how to do it.

The system “locates users by calculating the ‘time-of-flight’ that it takes for data to travel from the user to an access point,” says Adam Conner-Simons in a recent MIT News article. And it does it with a single access point. That’s unlike other setups that require four or five access points for triangulation-like measuring. One access point determining a user’s position means costs should be lower, and individuals or small businesses can take advantage of the tech.

Chronos, as the new MIT invention is called in a paper, calculates angles relative to a person’s position. That’s the same method as existing location services—which do it from multiple spots to figure the rough location. However, Chronos also uses time of flight multiplied by the speed of light to find distance.

“Knowing both the distance and the angle allows you to compute the user’s position using just one access point,” says Deepak Vasisht, one of the paper’s authors, on the MIT website. In other words, the access point finds the user.

That’s a big deal not only because of the aforementioned wireless hotspot password issue, but for a myriad of other purposes you could use it for:

“Imagine having a system like this at home that can continuously adapt the heating and cooling depending on the number of people in the home and where they are,” lead researcher Dina Katabi explains in the article.

“You could follow a person around a house, for example,” says Victoria Woollaston in her Mailonline article. That’s in addition to “blocking outsiders, such as your neighbors, from stealing your Wi-Fi,” the story points out.

Another use could be in drone collision avoidance—a red hot subject right now. A drone could operate at “a safe distance from its user with a margin of error of about four centimeters,” the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) scientists say on the MIT website.

“The system is 20 times more accurate than existing systems, computing time-of-flight with an average error of 0.47 nanoseconds,” MIT says.

The accuracy comes from an ingenious exploitation of how Wi-Fi works. While you wouldn’t be able to measure time-of-flight constantly—it’s too bandwidth-intensive—you can do it by hopping from channel to channel and grabbing a time of flight measurement.

“Chronos then automatically ‘stitches’ together these measurements to determine the distance,” MIT explains.

Delays exist, they say, but for the most, part they can be eliminated. One problem is that the signals can bounce off walls and furniture. With algorithms, those errors can be minimized.

The ability to channel hop quickly, a method devised by the scientists, cuts out the need for multiple triangulating access points.

“This is encouraging news for the many small businesses and consumers that don’t have the luxury of owning several access points,” Vasisht adds.

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