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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
Kaiserstraße 12
Building 05.01
76131 Karlsruhe
Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu
KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association
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