MIT lets Wi-Fi router determine user location

Researchers at MIT have demonstrated a working way to locate a user using Wi-Fi signals. One of the applications is the exclusion of people who try to gain access to a network from ‘outside’.

This is an existing concept that has already been demonstrated by the Computer Science and Artificial Intelligence lab of the renowned research institute. However, the scientists have now actually succeeded in building a working prototype of a Wi-Fi router with which position determination is possible. Chronos, as the technology is called, quickly switches through the 35 frequency bands in the spectrum between the 2.4GHz and 5.8GHz, at intervals of two to three milliseconds. Based on the phase difference of each of these signals, as shown below, a ‘time of flight’ is calculated, which allows the distance to the receiver to be determined. If a receiver has several WiFi chips on board, the location can even be determined in three dimensions.

Research from MIT shows that in 97 percent of the cases it was possible to determine whether a receiver was inside or outside the room. In an experiment in a four-room apartment, it was correctly determined in 94 percent of the cases which room a user was in. According to the researchers, Chronos has a precision of up to 65 centimeters, which makes the technology better than GPS.

Several applications have already been devised for Chronos. One of the most important would be to be able to exclude ‘outsiders’ from public places. In cafes, for example, visitors could be given a WiFi connection, while people standing outside the cafe would be denied access. The researchers also think they can use WiFi positioning for robots and drones; for example, these can be kept at a preset distance from the owner.

No special additional hardware is required to use Chronos; conventional, modern Wi-Fi chips that are used in smartphones, among other things, are sufficient to determine the position, the researchers say. This makes it relatively easy to use WiFi positioning in practice. However, it is still unclear when commercial applications will be introduced.