Students at the University of California at Santa Barbara have come up with a way to use Wi-Fi signals to count the number of people in a given area, even if not all of the individuals are carrying a digital device. “Our approach can estimate the number of people walking in an area, based on only the received power measurements of a Wi-Fi link,” noted Yasmin Mostofi, a professor of electrical and computer engineering at Santa Barbara, in a press release.
People affect Wi-Fi signals in two ways. First, when you cross the line-of-sight of a signal, its power drops dramatically. Second, even if a person is not crossing the line-of-sight, his/her physical presence scatters the signal, acting as a multi-path fader. The students, along with Professor Mostofi, figured out how to relate the results of both of these phenomena to the number of people inhabiting a certain space. Future applications could include automatically adjusting heating and cooling in building, depending on the number of people inside, while stores could use the information to better service their customers.