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Re: [Discuss-gnuradio] 802.11b Headers

From: Daniel Sumorok
Subject: Re: [Discuss-gnuradio] 802.11b Headers
Date: Fri, 29 Jun 2007 09:11:27 -0400

Hello Teun,
There are two rates for the 802.11b physical headers - 1 Mbps, and 2 Mbps. Most likely, packets that use the CCK modulation (5.5 and 11 Mbps) use the 2 Mbps physical header. I never got the 2 Mbps header decoding working properly for some reason, although the code does try to decode 2 Mbps headers. (It could detect that a 2 Mbps header was there, and often got some of the bits correct...) By the way, these headers don't really contain that much more information than the packet length and the data rate - however if you want to debug this, I can point you to the appropriate places in the code.


At 05:51 AM 6/29/2007, Teun wrote:

Hi Guys,

First of all, thanks for all the help you have been giving me, it was really
helpful for me to understand the  USRP / GNU Radio package.

I'm hoping someone from the BBN group is reading this, or anyone else who
has an idea.
Within our research group we are interested in decoding 11b/(g?) packet
headers. I have installed the 802.11 BBN code, which runs really good. Even
when I compare it to my laptop, equipped with a packet sniffer, the detected
packets match perfectly. However, the code decodes packets with a data rate
of 1Mbit and occasionally a 2Mbit packets due to the USB limitations. We
would like to detect "all" packets, at least their headers containing the
useful information. Header files use a low modulation type, so I think we
should always be able to capture the header of a packet. Does anyone see any
difficulties in doing so?

Any comments are really useful.

Thanks again,

View this message in context: http://www.nabble.com/802.11b-Headers-tf3999092.html#a11357744
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