Though GPS technology is widely used with ease to track position but its not a good option for finding path indoor like: airport, museum, or mall. Also, it wouldn’t be a smart way if you need not to ask wi-fi password in cafe or restaurant? Why bother when your network could determine your exact position with more accuracy than GPS (Global Positioning System)?
MIT engineers have developed a new tool called “Chronos” which can calculate the user location from network signal to within just inches. Localizer system built by team from MIT’s Computer Science and Artificial Intelligence Lab (CSAIL) led by Professor Dina Katabi enables locating users within tens of centimeters range with the use of single access point.
Current Wi-Fi localization system require more than 4 access points to locate the devices as they don’t possess enough bandwidth to measure time-of-flight (data to travel from the user to an access point) but Chronos can calculate both angle distance from user and the access point. This eliminates the need of multiple access points to locate using existing system.
The system can have wide range of applications from drones to home automation. The demonstration shows that Chornos system can enable drone to maintain safe distance with a margin of minor error of about four centimeters.
It can detect the location of wifi users in public places like restaurant, museum, airport which could eliminate the need of wifi password. The service provider can easily determine whether the wifi user is the customers sitting just inside or is outside the door with 97% accuracy. For small businesses, it could help to prevent the non-customers from stealing their WiFi signals. 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. Chronos can also be implemented in home automation system including other indoor localization systems.
How it works?
Chronos needs two Wi-Fi devices: transmitter & receiver for operation and hop between all 35 frequency bands (current Wi-Fi system allows hopping on multiple frequency bands) in the 2.4 to 5.8 GHz range. The transmitter skips between the bands every 2 to 3 microseconds and receiver compares the phase differences at each step which then calculates the time of flight of signals and ultimately the distance between the devices by multiplying the time-of-flight by the speed of light. If one of the devices has multiple Wi-Fi antennas which most modern smart devices have, Chronos can even calculate the angle between the two devices, and locate them easily.
“Knowing both the distance and the angle allows you to compute the user’s position using just one access point,” said Deepak Vasisht, an MIT Ph.D. student. Chronos can determine the actual distance from user to the access point.
Chronos can run on existing Wi-Fi devices using just an app or by upgrading device firwware but need to undergo a one-time distance calibration. But if the network devices are moving relative to one another during the initial setup, accuracy may degrade as Chronos takes around one-tenth of a second to sweep all the Wi-Fi bands. But it can handle drone whose speed can be detected & controlled.
Chronos was tested on an AscTec Hummingbird quadcopter drone with with Intel 5300 Wi-Fi card and a Go-Pro camera and it was able to manage distance of just 4 cm of its programmed value.
As the system can track the user location with higher precision, if you are that much paranoid, its probably a better idea to not using public wi-fi?