Re: [Discuss-gnuradio] BBN 802.11 bbn_80211b_rx.py

[Eric Blossom]

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
> >