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MIT Develops Accurate System For Tracking People, Objects Via WiFi (softpedia.com)
An anonymous reader writes: MIT's Computer Science and Artificial Intelligence Laboratory has created a new system called Chronos that can accurately detect the position of electronic devices in a room -- as well as the users who are carrying them -- within tens of centimeters using Wi-Fi signals only. "Chronos works without the aid of any secondary sensors, only using a technology called time-of-flight calculation, which measures the time it takes data to travel from the WiFi access point to the user's device," according to an article on Softpedia, citing a paper (PDF) that the researchers presented at a USENIX symposium in March. "MIT researchers say that by multiplying the time-in-flight value they receive from each user with the speed of light, they were able to detect each user's distance to the central Wi-Fi access point."
All of the major WiFi equipment vendors (Cisco, Aruba, etc.) have offered this for some time -- though they don't claim anywhere near the MIT Lab's level of accuracy. For instance, Aruba calls their offering "ALE" or Aruba Location Engine. It sits as a separate virtual appliance and communicates to the central WiFi controller (AirWave in their parlance) or to the individual APs if they are operating in autonomous mode. It gets signal strength indications for each WiFi and bluetooth antenna in range of the APs (note: *not* just those devices that are Associated with the WiFi networks served by said APs) and feeds that into ALE. From there, you can map out the devices. Both Cisco and Aruba's products have very extensive APIs to access this info. Maybe they can enhance their offerings with MIT's new technology and get the location resolution improved a bit. For now, in the wild, it's often difficult to get a station (i.e. device) location down to better than a range of 3-10 meters.
They're using a single MIMO AP with multiple antennas and sub decimetre ( than the accuracy, and the antennas are not perfectly in a single line (eg offset middle antenna), than you can effectively coarsely triangulate the signal using a single AP.