

Counting people with WiFi - vinchuco
http://phys.org/news/2015-06-people-wifi.html

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acd
A bit similar to WiSee that controlling devices with Wifi using your hands,
though not counting people
[http://wisee.cs.washington.edu/](http://wisee.cs.washington.edu/)

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sehugg
I noticed this effect when I was working with Zigbee mesh networks (which
usually operate on 2.4 GHz like wifi). You could clearly see the S/N ratio
change between working and non-working hours as people in the office came and
went. I always thought it could be used as an occupancy sensor for home or
building automation (I'm surprised they aren't doing this already for hotels
and other commercial buildings)

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zhte415
Fascinating

> 'Our approach can estimate the number of people walking in an area, based on
> only the received power measurements of a WiFi link,' said Mostofi, a
> professor of electrical and computer engineering. This approach does not
> require people to carry WiFi-enabled telecommunications devices for them to
> be counted, Mostofi emphasized.

So completely passive (as long as WiFi is on and seeking a connection).

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chrismcb
I'm not sure what you mean by passive, but one wifi card needs to send a
signal to the other. Seems more active than passive.

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zhte415
Correct. A passive action by the user, who often just leaves WiFi on seeking
mode when on the move from convenience (walking between home, work, Starbucks,
Subway, friend's house, etc).

Passive of the user not taking action, I don't mean passive of the device.

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filleokus
I wonder if enterprise grade AP/wifi-systems expose signal levels in such a
way that is easily implementable. Would be a fun project to try at my
university campus, which is crowded with AP's everywhere.

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captn3m0
Any particular reason for using WiFi, instead of relying on better tech (such
as ultrasonic, radar etc)? I'm guessing that this is a solved problem in those
areas.

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icebraining
Well, one advantage is that WiFi can be used through walls, as the article
points out.

There's also the plausible deniability if you're trying to apply this
technique without being noticed by someone with detection capabilities - a
WiFi hotspot blends in better than most other alternatives.

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madaxe_again
This has been done before, with Bluetooth - and it really pissed people off.

[http://www.theguardian.com/news/blog/2008/jul/21/bluetoothbl...](http://www.theguardian.com/news/blog/2008/jul/21/bluetoothblog)

[http://www.cityware.org.uk/](http://www.cityware.org.uk/)

[http://www.bbc.co.uk/news/technology-23665490](http://www.bbc.co.uk/news/technology-23665490)

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abandonliberty
Not the same thing at all. These are all intrusive and dependent on the user
having a device.

This article is using wifi as a sort of radar by measuring signal
attenuation/interference from meatbags.

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jkot
It is pretty impresive field. Some device can detect heart beat behind 10 feet
of rocks.

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hammock
Sounds like radar... but with wifi.

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weavie
Seeing as I always switch off my wifi when out of the house, this might not
always be that accurate.

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egeozcan
> This approach does not require people to carry WiFi-enabled
> telecommunications devices for them to be counted, Mostofi emphasized

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weavie
Darn it. Remind me to never comment on something I don't read properly. So
easy to jump to assumptions when just skimming.

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rogeryu
Never comment on something you don't read properly!

