Re: [Discuss-gnuradio] OFDM cyclic prefixer

[Martin Braun]

On 14.05.2014 04:36, Ron Economos wrote:
> If you're sending packets, then Length Tag Key should be
> set to the packet length you're using. If you're sending
> a stream (like DVB-T), then this field is not used (and
> left blank).

It needs an empty string, in this case.

> The OFDM cyclic prefixer is used after the (reverse)
> FFT block. The FFT Length in the OFDM Cyclic Prefixer
> block should match the FFT Size in the FFT block.

That's right. The block doesn't check if the input is actually OFDM.

Martin
> Ron
>
> On 5/13/2014 6:06 PM, Yuri P.M wrote:
> > Hello,
> >
> > My name is Yuri.
> > ​ I very new to GNU Radio, and I'm using GRC 3.7.1.​
> >
> >
> > I am doing a research, and I need to modulate specific signal in OFDM.
> > I would like to insert cyclic prefix (or guard interval in my project,
> > the same thing with a different name).
> >
> > I looked at the examples
> > ​under gr-digital
> > ​/examples/ofdm, and I've also read some papers about OFDM technics.
> >
> > My doubt is: what is the parameter "Length Tag Key"? I've seen it
> > working in the examples located in the folder above, I've tried to do
> > the same in my project, but it states a message that this parameter is
> > missing.
> >
> > By chance, does this cyclic prefixer block only works with other
> > blocks of the same category? I mean, do I need to use OFDM carrier
> > allocator before it, or something like that?
> >
> > Thank you for your attention,
> >
> > Yuri.
>
>
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