Re: [Discuss-gnuradio] 802.11b Headers

[Teun]

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.

Thanks, 

Teun



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
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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>>
>>
>>
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> 
> 
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