---------- Forwarded message ---------- From: Karan Talasila <[email protected]> Date: Thu, Apr 18, 2013 at 2:48 PM Subject: Re: [Discuss-gnuradio] ofdm demodulation To: Brian Padalino <[email protected]>
I understand the intuitive way in which first the phase offset is found. from that you can find finefrequency offset and timing offset. But I am looking at how all this is done in the code using appropriate equations, especially how coarse frequency offset is found using the math. The paper says there will be a factor of 2z/T that you should consider when the offset is greater than half the subcarrier spacing. i.e. integer frequency offset. Hopefully a page on how the sync is being implemented in the code would help. I have to blame my poor c++ skills for all this pain. On Thu, Apr 18, 2013 at 1:44 AM, Brian Padalino <[email protected]> wrote: > On Wed, Apr 17, 2013 at 6:30 AM, Karan Talasila <[email protected]>wrote: > >> Hi, >> >> >> I am trying to understand ofdm demodulation using schmidl and cox paper. >> Can anybody explain how a pn sequence on even frequencies and 0 on odd >> frequencies help in the estimation of timing and frequency offset. >> >> > Hi Karan, > > I haven't read the paper, but here is what I know from the description of > the scenario. Someone who has more OFDM experience can probably speak with > a little more authority. > > If you skip every other bin in the frequency domain, the time domain > signal is actually repeated during the whole OFDM symbol. Since the time > domain information is repeated, you can perform a correlation with a > delayed version of the symbol coming in for some rough synchronization of > the preamble. Also, the phase difference of that result will be the > average frequency offset over that number of samples, giving you a decent > frequency offset estimate as well. > > At least, that's what I think would be useful. > > Does that make sense to you? > > Brian > > >> -- >> Regards >> Karan Talasila >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected] >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > -- Regards Karan Talasila -- Regards Karan Talasila
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