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

[Yingjie Chen]

Thanks for your reply, Martin. I still have one question. I have done the simulation for PN peak normalization process in matlab. I try to plot the P(refer to correlation result between 1st half and 2nd half) and R(refer to the power of 2nd half symbol) . However, when I plot the P and R in the same picture using gr_plot_float in gnuradio, the curve seems different my simulation result. The R curve seems to be up-side-down against P curve. Please check the attached file for reference. Thank you again.

2013/4/8 Martin Braun (CEL) <address@hidden>

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

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

Dipl.-Ing. Martin Braun
Research Associate

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KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

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