How to capture raw signal from a wireless router?

Question

Now I have seen several projects that extract new spatial information from radio data collected from a typical wireless router:

http://wisee.cs.washington.edu/

http://www.extremetech.com/extreme/133936-using-wifi-to-see-through-walls

The idea of ​​using a wireless router as a kind of passive radar is fantastic.

I’m very interested in experimenting with the data collected from the wireless router, but there is little information on how to actually interact with the wireless router and get the raw stream of information collected by the device. Similar questions have been asked here before, but I have not yet found a satisfactory answer.

I do not have the reference points needed to link to other questions, but see:

'Capturing the original signal from a WiFi card, like a sound card'

raw wifi access data

I am looking for a solution that will allow me to use an inexpensive device, for example, such a common wireless router WRT54G. If your answer includes custom radio equipment, you need not worry about publishing.

Answer 1

As far as I know, the only hardware use option is to use an Intel 5300 Wifi card. You can get complex CSI (information about the amplitude and phase in it) from three antennas on it from a subcarrier sample (OFDM). You can look at this site:

http://dhalperi.imtqy.com/linux-80211n-csitool/

Answer 2

If you read the wisee research article , you will find the platform they use for the system, it is USRP N210 from the Ettus plus GNU radio software. So this is not your regular WiFi AP, which they use, but the SDR solution also hints at this issue .

WiFi devices are built to work with the physical layer in silicon, and monitor mode is the best you can get without switching to the SDR path. You can get quite a lot of information from it - the heading of the radio source contains, for example, the level of the received signal and information about the receiving antenna. But if you really want to study the physical level of Wi-Fi, then commercial equipment is not going to reduce it.