CSI capture and Extraction

[Mweme]

Hello team,
I'm new to the channel thing, but currently is the place I'm working my research.
I have installed nexmon in RPi and was successful and I have configured another RPi to work as AP.
But I would like to have guidance on the following:-

How do I capture CSI frames?
How do I visualize these frames?
Which file do these CSI frames are kept in Rx?
How analysis has been done?
Any assistance will be much appreciated.

[zeroby0]

I know it isn't much detailed, I'm a bit busy these day, but here are some quick pointers.

How do I capture CSI frames?

Set your transmitter Pi to transmit in channel 36 at 40 MHz, then use makecsiparams and generate a configuration string.
makecsiparams -c 36/40 -C 1 -N 1

makecsiparams has to be compiled with make, it's in utils/makecsiparams.

makecsiparams -c 36/40 -C 1 -N 1 captures CSI of ALL packets going on channel 36, to capture only packets from your Pi, use the -m flag with transmitter Pi's mac address (usage in readme)

This tries to capture all packets coming from your transmitter Pi, if you need only some packets, use the -b flag and filter by frames first byte

Then follow the readme and setup CSI collection. Use tcpdump to collect packets, the packets contain CSI in them, and store them as pcap.

I have a script that does most of the work for you, and some documentation here: https://github.com/nexmonster/nexmon_csi/tree/pi-5.4.51

How do I visualize these frames?

There is a matlab script in the utils folder, but if you want to use Python, use this: https://github.com/nexmonster/nexmon_csi/tree/feature/python/utils/python

I'm planning to release it as a separate tool, but till then, you can use this. You can also use CSIkit by @Gi-z.

Which file do these CSI frames are kept in Rx?

Whichever file you write to with tcpdump -o

How analysis has been done?

Depends on how you want to use the CSI values. You will probably have to figure this out on your own.

Make sure you're using a supported kernel version. The latest version is not supported yet, so if you download the latest raspberry os, it won't work. Link to the latest raspberry os with a supported kernel is in my fork: https://github.com/nexmonster/nexmon_csi/tree/pi-5.4.51