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radar-self-csi.md

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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
./wgd.sh
./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.