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seemoo-lab / nexmon_csi

Channel State Information Extraction on Various Broadcom Wi-Fi Chips
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read CSI value from bytes on ASUS router #134

Open yujianyuanhaha opened 4 years ago

yujianyuanhaha commented 4 years ago

greetings,

Recently I plan to write a bit my own code to convert these bytes (extract using Wireshark tools instead of nexmon matlab codes) to CSI value. It is clear to me how to convert the data into Csi value on NEXUS phone by description analyzing-the-csi.

However, it is not clear to me on ASUS router. The description said " The bcm4358 and bcm4366c0 return values in a floating point format with one bit sign of the following nine or twelve bits of a real part and the same for an imaginary part, followed by an exponent of five or six bits."

My understanding is it should be "The bcm4358 and bcm4366c0 return values in a floating point format with one bit sign of the following nine or ten bits of a real part and the same for an imaginary part, followed by an exponent of six or five bits." in this way number of bit is exact 32 per complex value, in form of (1+9+6)x2 or (1+10+5)x2.

Let me know if I get it wrong @DanielAW @schmittner @zeros @mzakharo @zeroby0

Best

zeroby0 commented 4 years ago

The example matlab code in utils folder might help.

yujianyuanhaha commented 4 years ago

@zeroby0 thanks. I have to read csi from byte cuz I have to deal with new format .pcap using the path in CSI with RSSI on ASUS router, which nexmon matlab code does NOT work

Deltaaaaaaaaaa commented 4 years ago

@yujianyuanhaha Hi ! By observing the HEX code, I found the complex float is packed as follow. 2bits 0, 1bit real sign, 11bits real, 1bit img sign, 11bits img, 6bits exp Where exp is a integer consisted of 1bit sign and 5bits digits, the real and imag parts should be multiplied by (2^exp). However, unless you are required to process the data in other languages( e.g. python), I don't recommand you to write your own unpack code, since the official matlab code is highly effiecient (much more efficient compared to the python code I wrote). Modifying the readpacp.m file (somewhere around line 57) would be a better way to get your work done. Good luck!

yujianyuanhaha commented 3 years ago

@Deltaaaaaaaaaa thanks a lot, however, the RSSI I get is in 2 bytes only, detail explain here ....

The RSSI does not need imaginary part since it should be alway real number, what does each bit represent then @jlinktu

Best.