Re: [Discuss-gnuradio] 802.11b Headers

[Daniel Sumorok]

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 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,
>
> Teun
> --
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> http://www.nabble.com/802.11b-Headers-tf3999092.html#a11357744
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>
>
>
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