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A New Role for WiFi-enabled Mobile Devices: Counting People
We already knew Wi-Fi was a versatile technology. But it may be even more powerful than we realize. Researchers at the University of California, Santa Barbara (UCSB) are using Wi-Fi to estimate the number of people walking in an area – and according to the researchers, the people don't even have to be connected to Wi-Fi for it to work.
"Our approach can estimate the number of people walking in an area, based on only the received power measurements of a WiFi link," said Prof. Yasamin Mostofi, a professor of electrical and computer engineering, , in an interview with UC Santa Barbara's The Current. "This approach does not require people to carry WiFi-enabled telecommunications devices for them to be counted."
To do this, research team members placed two WiFi cards at opposite ends of a targeted area measuring about 70 square meters. By tracking measurements of power between the two WiFi cards, the research team was able to estimate the number of people walking in that area.
As people walk past the linked WiFi cards, changes in the power of wireless signals received by the researchers in part enabled them to come up with their estimates of people walking by. Human bodies cut the WiFi signal when they walk past the line-of-sight. Human bodies not in direct line-of-sight also scatter the signals – a phenomenon known as multi-path fading, The Current's Sonia Fernandez reports.
Based on these two phenomena, the research team developed a probabilistic model that produces estimates of the numbers of people passing by.
New Role for WiFi: Counting People
Thus far, Mostofi and his team have successfully tested this method in indoor and outdoor settings with as many as nine people in the area. "This is about counting walking people, which is very challenging," Mostofi added. "Counting this many people in such a small area with only WiFi power measurements of one link is a hard problem, and the main motivation for this work."
Mostofi and his research team envision a number of applications for their methodology. "Stores can benefit from counting the number of shoppers for better business planning," Mostofi said. Security and search-and-rescue operations are other potential application areas.
Previously, Mostofi and lab members investigated the use of WiFi signals to image stationary objects and human beings through walls. Mostofi intends to combine the two projects in future.
Additional information about the Wi-Fi people counting project is available on the research group's project page.