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Re: [Discuss-gnuradio] FTW IEEE802.11a/g/p OFDM Frame Encoder


From: Ashutosh Grewal
Subject: Re: [Discuss-gnuradio] FTW IEEE802.11a/g/p OFDM Frame Encoder
Date: Mon, 21 Feb 2011 20:15:13 -0500

Hi Guanbo,

You're running the script fine. If you look into theftw_packet_utils.py script, you'll find that the encoder just prepends a static MAC header -Source Mac is00:20:d6:01:3c:f1 (a quick web search will show thatMAC Addresses which begin with00:20:d6 belong toBREEZECOM). Similarly you' can find thedestinationMAC and BSSID. The packet will be decoded as amac-layer service data unit (MSDU).

I'm not sure if you've done this already but make sure you set up your wireshark correctly byselecting "802.11" as the "Link-layer header type" in the "Capture Options"to receive 802.11 packets (http://wiki.wireshark.org/CaptureSetup/WLAN)

Let me know how it goes.

Thanks,
Ashu

On 21 February 2011 18:36, Guanbo ZHENG <address@hidden> wrote:
The frequency band is correct. Just now, I re-install the repository from the CGRAN, and tried again using:
sudo python ftw_ofdm_tx.py -f 2.462G -i 5 --regime=8 --payload="Here are some test messages from WiSeR" -r 10000
So the only question is, I have NOT updated my firmware. I will try that as well.

By the way, what does the USRP2 generated packet look like in Wireshark at another laptop?

Thanks,
Guanbo


On Sun, Feb 20, 2011 at 11:32 PM, Ashutosh Grewal <address@hidden> wrote:
Hi Guanbo,

Thanks for your reply.

I've some good news regarding the FTW OFDM encoder - we were able to decode 802.11 a/g packets using kismet/wireshark later in the day. It seems that we'll have toset the OFDM coderegime option as 6 or 7 or 8 (I'm not sure about 8 but 6 definitely worked). The version information of our test system is same as that as what is used here - https://www.cgran.org/wiki/ftw80211ofdmtx but our USRP2 HW revision number is different and we used the latest firmware.

Regarding BBN USRP2Version - I'll try that and get back to you in case I face any difficulties.

Thanks,

Ashu

On 21 February 2011 00:07, Guanbo ZHENG <address@hidden> wrote:
Regarding to BBN, you may try to the high interpolation and decimation rate, as well as proper gain. I was able to decode it on RX (Ubuntu 9.10+gnuradio 3.2.2)

For FTW OFDM code, I was able to decode the 802.11g packet as well at Wireshark using an Atheros 802.11a/b/g NIC in monitor mode, where I have saved the TCPdump file. But recently I tried to re-conduct the experiment, I can not get it anymore. :(
I am still trying to figure out what problem there is.

Guanbo

On Sun, Feb 20, 2011 at 3:13 PM, Sankalp Nimbhorkar <address@hidden> wrote:
Dear All,
We tried using this encoder to transmit frames with USRP2 XCVR 2450 daughter-card on Ubuntu 9.10. We confirmed transmission with a WiSpy dongle. But we cannot receive the frames on a receiver. The receiver we are using is an Atheros 802.11 a/b/g NIC in monitor mode with Mad WiFi driver. We have tried almost all the channels in 802.11a and 802.11g, but could not receive a single packet on receiver. In the project description we came to know that 802.11a frames were successfully received with a Ralinc NIC. Has anyone tried out this project? If so, please tell us the procedure to receive these frames with an NIC? Or at least some way to confirm that the frame was actually received by the NIC? (We even tried Kismet configured to report frames even if CRC check fails). Any help would be appreciated.

Thank you.
Sankalp Nimbhorkar
CSC Graduate Student
North Carolina State University

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Brian

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