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Re: [Discuss-gnuradio] 802.11b Headers

From: Teun
Subject: Re: [Discuss-gnuradio] 802.11b Headers
Date: Fri, 29 Jun 2007 09:39:06 -0700 (PDT)

Hi Dan,

thanks for your quick reply. The information i'm looking for is exactly the
packet length and the data rate of a packet. I'm using this information to
do some sort of wireless environment characterization.

If you can point me to the right places in the code, that would be awesome.



Daniel Sumorok wrote:
> 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.
>    -Dan
> 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
>>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.
>>when I compare it to my laptop, equipped with a packet sniffer, the
>>packets match perfectly. However, the code decodes packets with a data
>>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
>>difficulties in doing so?
>>Any comments are really useful.
>>Thanks again,
>>View this message in context: 
>>Sent from the GnuRadio mailing list archive at Nabble.com.
>>Discuss-gnuradio mailing list
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