Do not fidget! WiFi will depend you

Credit score: CC0 Public Area

Researchers in UC Santa Barbara professor Yasamin Mostofi’s lab have enabled, for the primary time, counting a stationary seated crowd utilizing WiFi indicators, and with out counting on folks to hold a tool. The method, which additionally counts via partitions, wants solely a wi-fi transmitter and receiver exterior the world of curiosity the place the group is seated. It has quite a lot of functions, together with sensible power administration, controlling the group measurement throughout a pandemic, enterprise planning and safety.

“Our proposed strategy makes it doable to estimate the variety of seated folks in an space from exterior,” stated Mostofi, a professor {of electrical} and pc engineering at UCSB. “This strategy makes use of solely the obtained energy measurements of 1 WiFi hyperlink, doesn’t depend on folks to hold a tool and works via partitions.”

The proposed methodology and experimental outcomes appeared within the latest nineteenth ACM Worldwide Convention on Cellular Methods, Purposes, and Providers (MobiSys).

Within the crew’s experiments, one WiFi transmitter and one WiFi receiver (each off-the-shelf) are in an space the place quite a few persons are seated. The transmitter sends a wi-fi sign whose obtained energy is measured by the receiver. Through the use of solely such obtained sign energy measurements, the receiver estimates how many individuals are current—an estimate that intently matches the precise quantity.






Credit score: College of California – Santa Barbara

This innovation builds on earlier work within the Mostofi Lab, which has pioneered sensing with on a regular basis radio frequency indicators comparable to WiFi since 2009. As an illustration, their 2018 paper confirmed how WiFi can depend a crowd of cell folks. Nevertheless, folks needed to transfer round to be counted.

“Counting a stationary seated crowd is a significantly difficult downside as a result of lack of main physique movement,” stated Mostofi. Her lab’s success on this endeavor is as a result of new proposed methodology they developed.

“Whereas the folks within the crowd are stationary, i.e., with no main physique movement besides respiration, they don’t keep nonetheless for an extended time period and often interact in small in-place pure physique motions known as fidgets,” Mostofi defined. “As an illustration, they could alter their seating place, cross their legs, verify their telephones, stretch, or cough, amongst others.”

The researchers have proposed that the combination collective pure fidgeting and in-place motions of a seated crowd carry essential info on the group depend, and have proven, for the primary time, how you can extract the combination fidgets and depend the whole variety of folks primarily based on them.

“Take into account the Crowd Fidgeting Durations (CFPs), which we outline because the time durations during which at the very least one individual within the WiFi space is fidgeting, in addition to the Crowd Silent Durations (CSPs), which we outline because the time durations during which not one of the persons are fidgeting. These intervals are simply extractable from the obtained WiFi indicators,”stated Belal Korany, the principle Ph.D. pupil on the mission. “Intuitively talking, the higher the variety of folks, the upper the prospect that CFPs are longer and the CSPs are shorter. Thus, these intervals implicitly carry info on the whole variety of folks.”

The researchers then developed a brand new mathematical mannequin that statistically describes the collective fidgeting habits of a stationary crowd, i.e., the CFPs and CSPs, and explicitly relates them to the whole variety of seated folks.

In growing their mathematical formulation, they first reveal how this downside resembles a a number of decades-old queuing principle downside, a seemingly unrelated downside from a totally totally different area. “Queuing principle is a department of arithmetic that research ready strains in methods that contain the arrival of consumers, who require a service from an entity that features quite a few servers,” stated Mostofi. They then present how the CSPs are much like the instances when no buyer is at a queue that has infinite servers, whereas the CFPs resemble the instances when at the very least one buyer is being served at such a queue. This then permits them to borrow mathematical instruments from queuing principle to develop a totally new method for counting the whole variety of stationary folks.

“We’ve got examined this expertise extensively in numerous areas, and with totally different numbers of individuals in a number of totally different seating configurations,” stated Korany. The lab has examined their new expertise with 47 experiments in 4 totally different environments (together with through-wall settings), during which as much as and together with 10 persons are seated and behaving usually, whereas a pair of WiFi transceivers make WiFi measurements. Their experiments embody varied events, comparable to attending a lecture/presentation, watching a film or studying in a library.

Their analysis outcomes present a really excessive counting accuracy, with the estimated variety of folks being zero or one individual off from the true variety of folks 96.3% of the time in non-through-wall settings, and 90% of the time in through-wall settings. Total, their outcomes present the potential of this new expertise for crowd-counting in real-world eventualities, comparable to for limiting the whole variety of folks in a crowd throughout a pandemic.


Crowd counting via partitions, with WiFi


Extra info:
Outcomes: net.ece.ucsb.edu/~ymostofi/CountingStationaryCrowd

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College of California – Santa Barbara


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Do not fidget! WiFi will depend you (2021, September 13)
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