Re: [Discuss-gnuradio] guard band

[Johannes Demel]

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Hi Sara,

it seems like there is some confusion between time and frequency domain.
In an OFDM system you have subcarriers next to each other in the
frequency domain. You will most likely add new subcarriers by putting
non-zero values on your vector in the frequency domain. In order to
realize a guard band you just put zeros on this vector in the
frequency domain.
The cyclic prefix, CP, is a guard time. It is a time domain concept.
It provides protection between each OFDM symbol.

I hope this cleared things up a little

happy hacking
Johannes

On 22.05.2014 11:29, Sara Chérif wrote:
> In ofdm transmitter , I want to add 6 subcarriers as a guard band 
> between symbols , so that each symbol is fft + cp + guard band ..
> How to add this guard band ? is there a block which add zeros ? I
> think I can make guard band included in CP , I can make cp longer
> by 6 then multiplying symbols by a window (multipling fft and
> actual cp by ones & multipling last 6 subcarriers by zeros ) . Is
> there a window or time domain filter in GNU Radio ? Thanks.
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