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Re: [Discuss-gnuradio] Cyclic Prefixer Rolloff Samples


From: Martin Braun (CEL)
Subject: Re: [Discuss-gnuradio] Cyclic Prefixer Rolloff Samples
Date: Fri, 30 Aug 2013 10:18:36 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

On Fri, Aug 23, 2013 at 01:50:14PM +0200, Bastian Bloessl wrote:
> >Only we're not filtering--we're adding a tapering window in time domain.
> >At the beginning of the symbol, we can simply multiply the samples with
> >the up-ramp of our tapering window (we use a raised cosine flank).
> >
> >So what happens at the end? We could do the same: Multiply the last few
> >samples with the down-ramp. But then we're simply throwing away energy.
> >It would be much nicer if the down-ramp came *after* the symbol, during
> >the up-ramp of the following symbol. This is achieved by adding samples
> >from the beginning of the symbol (think of it as a "cyclic postfix") and
> >multiply those with the down-ramp of the tapering window.
> 
> Ah OK, I see, taking the samples from the end is indeed stupid -.-
> Thanks for your explanation!

Hi Bastian,

just a quick follow-up: Did you have any problems with the rolloff
spectrum, or what caused you to change the code?
I checked the output, and it seemed correct--although I didn't
have the theoretical values here to compare the results to those.

MB

-- 
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

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Fax: +49 721 608-46071
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