Researchers at the University of California, Santa Barbara have found an unusual use for Wi-Fi. As it turned out, by measuring the level of fluctuations in the signals from the router, it is possible to determine with great accuracy the number of people in the adjacent room.
It turns out that Wi-Fi acts as a kind of indoor radar: the transmitter emits a wireless signal through the wall, the level of which is measured by the receiver. According to the magnitude of the signal, it quantifies those inside the room. At the moment, the system is capable of counting up to 20 people.
When it was created, a mathematical model was used that provides the router with the ability to "see" people through the wall, measuring the change in signal strength. Bodies of people and objects absorb Wi-Fi signals as they move around the room, which allows them to be tracked in space. The measurement accuracy is plus / minus 2 people. At the moment, the system cannot display their position in space - by eliminating this problem, scientists will make it more efficient.