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mobisys2018_nexmon_channel_state_information_extractor
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Update README.md

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@ -6,9 +6,29 @@ This projects allows you to extract channel state information (CSI) of OFDM-modu
Wi-Fi frames (802.11a/(g)/n/ac) on a per frame basis with up to 80 MHz bandwidth
using BCM4339 Wi-Fi chips installed, for example, in Nexus 5 smartphones.
After following the getting stated guide below, you can do the following to capture
raw CSI data on a per frame basis. As the extraction of CSI information takes some
time, we install a filter that compares the first 16 bytes of a Wi-Fi frame. In our
example, we consider beacon frames from an access point with MAC address
`00:11:22:33:44:55`, running on Wi-Fi channel 100 with a bandwidth of 20 MHz: `64d0`.
By using a channel in the 5 GHz band, we make sure that it uses OFDM-modulated frames.
The following command can be used to prepare a base64-encoded payload for ioctl 500 to
set the channel, activate CSI extraction and set the frame filter:
```
echo "64d0010080000000ffffffffffff001122334455" | xxd -r -p | base64
```
We can then send the resulting string to our patched Wi-Fi firmware:
```
nexutil -s500 -l20 -b -vZNABAIAAAAD///////8AESIzRFU=
```
After activating monitor mode, we can capture the filtered frames, followed by a
broadcasted UDP frame that includes the CSI information:
```
nexutil -m1
tcpdump -i wlan0 -xxx
```
Soon, we will publish a MATLAB script to analyze those raw CSI dumps.
# Extract from our License