You no longer have to rely on the number of connected smartphones in a given area to count the number of people present there. A new method developed by researchers at Santa Barbara is based solely on changes and fading in a WiFi signal.
On paper the idea is quite straightforward: analyse the variations in a wireless signal received in a particular area in order to count the number of people moving around there. Starting out from the principle that people alter the signal by their physical presence, the researchers from the University of California Santa Barbara have developed a mathematical model to estimate the number of individuals in a given area. Electrical and Computer Engineering Professor Yasamin Mostofi and her team placed two WiFi cards at opposite ends of a target area, a roughly 70 square metre space. They found that if a person crosses the direct line of sight between the WiFi cards, that will attenuate the signal, and that human bodies also scatter the signal even when they are not in the direct sight path. Having developed a probabilistic mathematical framework based on these two phenomena, the researchers were able to estimate the number of people present in real time, even if they were moving around.
A security tool?
This scientific discovery would seem to meet one particular need: working out how many people are taking part in a street demonstration or public gathering. The researchers claim that this approach, which provides real-time density data, could improve security at events. However, existing methods of counting based on mobile phone data already come close to meeting these objectives, and it should also be pointed out that the WiFi approach – notwithstanding its key advantage of being able to count people who are not carrying smartphones – is suitable only for smaller spaces than the areas generally covered by such happenings as political demonstrations.
Could WiFI help to make buildings greener and smarter?
Towards ‘smarter’ buildings
In fact there is another field in which Professor Mostofi’s work could make a real difference. The WiFi method could be used to help make buildings ‘smarter’. As she explains in a University bulletin: ‟Smart stores can benefit from counting the number of shoppers to improve their business planning.” Knowing exactly how many people there are in a given place, or the number of shoppers in a store, could moreover lead to more efficient energy consumption, and perhaps to new marketing opportunities. One idea is that advertising screens could be programmed to adapt to the number of people present in the vicinity.