Re: [Discuss-gnuradio] How many preambles uesd in ofdm example for frame synchronization, 10 short preambles ?

[Martin Braun (CEL)]

On Sun, Apr 07, 2013 at 11:49:14AM +0800, Yingjie Chen wrote:
> Thanks for your reply. I still have one question. I try to plot the peak
> detection data to observe the the shape of the peak, which seems like
> a plateau(square wave).I have done a simulation before in matlab.  If only
> one preamble exist, when the 1st half of the preamble correlate with 2nd
> half, the shape of peak should be much sharper(like a triangle), because
> the repeated pattern is not enough.
> My question is :
> If gunradio only use one preamble with 2 repeated pattern, the shape of the
> peak should look like a triangle rather than a plateau, is that right?

No, the plateau is correct. Since your correlation window is 2x half of
1 symbol, the cyclic prefix will increase your peak (in AWGN channels to
the length of the cyclic prefix).

MB

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