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Re: [Discuss-gnuradio] BBN 802.11 bbn_80211b_rx.py
From: |
yyzhuang |
Subject: |
Re: [Discuss-gnuradio] BBN 802.11 bbn_80211b_rx.py |
Date: |
Mon, 28 Jul 2008 09:28:24 -0700 (PDT) |
What does "combination of the LO in the front end and the digital
downconverter" mean please?
Eric Blossom wrote:
>
> On Fri, Jul 25, 2008 at 10:11:34AM -0700, Y. Zhuang wrote:
>> http://en.wikipedia.org/wiki/List_of_WLAN_channels
>>
>> Is it because the channel for 802.11 in 2.432G there, so the front end
>> was tuned to 2.432G? But there is 2.437G as well.
>> Or the font end is just picking the strongest channel it finds? Thanks
>>
>> Y
>
> None of the above. I'm just decoding the details of how the usrp was
> tuned using a combination of the LO in the front end and the digital
> downconverter. The command line shows -f 2.437G. See the excellent
> USRP FAQ for additional info. http://gnuradio.org/trac/wiki/UsrpFAQ
>
> Eric
>
>
>>
>> 2008/7/25 Eric Blossom <address@hidden>:
>> > On Fri, Jul 25, 2008 at 07:46:58AM -0400, Greg Troxel wrote:
>> >> BTW, what does that guy mean "Not sure when you updated, but we have
>> changed
>> >> the checked in code to default to 2437, and run it like this (as a
>> NetBSD
>> >> rc.d start script)", following the above link?
>> >>
>> >> details if you care, but surely they have little to do with your
>> issues.
>> >>
>> >> http://www.netbsd.org/docs/guide/en/chap-rc.html
>> >>
>> >> about your output:
>> >>
>> >> ./bbn_80211b_rx.py -f 2.437G -v -b
>> >> Bits Per Encoded Sample = 8
>> >> adc frequency = 64000000
>> >> decimation frequency = 16
>> >> input_rate = 4000000
>> >> gain = 45.0
>> >> desired freq = 2437000000.0
>> >> baseband frequency 2432000000.0
>> >> dxc frequency -5000000.0
>> >> Samples per data bit = 8
>> >> >>> gr_fir_ccf: using SSE
>> >>
>> >> 2.432G is used instead of 2.437G. Also the dxc frequency is
>> negative. And
>> >> no packets get printed out.
>> >>
>> >> I am unclear on dxc.
>> >
>> > That part is fine. dxc = digital down converter (DDC) or DUC depending
>> on the context.
>> > In this case he wanted 2.437G. The front end was tuned to 2.432G, thus
>> > the DDC needed to be set to -5M to get the desired frequency translated
>> > to 0 Hz in the complex baseband.
>> >
>> > Eric
>> >
>
>
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