openwifi/doc/app_notes/radar-self-csi.md

One super power of the openwifi platform is "Full Duplex" which means that openwifi baseband can receive its own TX signal. Just like a radar! This brings a unique capability of "joint radar and communication" to openwifi. For instance, put two directional antennas to openwifi TX and RX, and the CSI (Channel State Information) of the self-TX signal will refect the change of the target object.

Quick start

• Power on the SDR board.

• Connect a computer to the SDR board via Ethernet cable. The computer should have static IP 192.168.10.1. Open a terminal on the computer, and then in the terminal:

  ssh root@192.168.10.122
  (password: openwifi)
  cd openwifi
  ./fosdem.sh
  (After the AP started by above command, you can connect a WiFi client to this openwifi AP)
  (Or setup other scenario according to your requirement)
  ifconfig
  (Write down the openwifi AP MAC address. For example 66:55:44:33:22:5a)
  insmod side_ch.ko num_eq_init=0
  ./side_ch_ctl wh1h4001
  ./side_ch_ctl wh7h4433225a
  (Above two commands ensure receiving CSI only from XX:XX:44:33:22:5a. In this case, it is the openwifi self-TX)
  ./sdrctl dev sdr0 set reg xpu 1 1
  (Above unmute the baseband self-receiving to receive openwifi own TX signal/packet)
  ./side_ch_ctl g0
  

  You should see on board outputs like:

  loop 64 side info count 4
  loop 128 side info count 5
  ...
  

  If the second number (4, 5, ...) keeps increasing, that means the CSI is going to the computer smoothly.

• On your computer (NOT ssh onboard!), run:

  cd openwifi/user_space/side_ch_ctl_src
  python3 side_info_display.py 0
  

  The python script needs "matplotlib.pyplot" and "numpy" packages installed. Now you should see figures showing run-time CSI and frequency offset. Meanwhile the python script prints the timestamp.

  While running, all CSI data is also stored into a file side_info.txt. A matlab script test_side_info_file_display.m is offered to help you do CSI analysis offline. In this case, run test_side_info_file_display(0) in Matlab.

  The following picture is generated by data processing on the captured openwifi CSI while people move in front of two directional antennas (Tx/Rx antenna).

Please learn the python and Matlab script for CSI data structure per packet according to your requirement.

Do read the normal CSI app note to understand the basic implementation architecture.