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Re: [Discuss-gnuradio] Some basic questions


From: Martin Braun
Subject: Re: [Discuss-gnuradio] Some basic questions
Date: Tue, 8 Jun 2010 18:26:47 +0200
User-agent: Mutt/1.5.20 (2009-06-14)

On Mon, May 03, 2010 at 09:25:56PM +0000, jack william wrote:
> Hi,
> Could someone please answer following questions of mine :
> 1) In
> pkt = ofdm_packet_utils.make_packet(payload, 1, 1, self._pad_for_usrp,
> whitening=True)
> 
> what is whitening?

It scrambles up your bits (makes them white in a stochastic sense).

> 
> 2) In gr.fft_vcc(fft_size,forward, window, shift=false)
>      What is window vector?

A tapering window applied before the actual FFT (like a Hamming window)


> 3) in ofdm_mod there is a portion of code having comments:
> Use freq domain to get doubled-up known symbol for correlation in time domain

This is part of OFDM timing synchronisation. You probably want to read
up on that topic if your interested (e.g., the paper on OFDM synch by
Schmidl & Cox).

Cheers
MB


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

Dipl.-Ing. Martin Braun
Research Associate

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Building 05.01
76131 Karlsruhe

Phone: +49 721 608-3790
Fax: +49 721 608-6071
www.cel.kit.edu

KIT -- University of the State of Baden-W├╝rttemberg and
National Laboratory of the Helmholtz Association

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