Re: [Discuss-gnuradio] plateau detectors

[Marcus Müller]

Hi zs,
hm, there's basically three places (that I know of) that GR uses Schmidl & Cox:
the ofdm_chanest Channel estimator, the original S&C-based ofdm_sync_pn.py and the more robustness-optimized version in ofdm_sync_pnac.py.
I suspect you're referring to one of the two ofdm_sync_pn*.py , but they differ a bit in how they deal with the peaks. Thus:
Which implementation are you referring to exactly?

Generally, Schmidl & Cox [1] states that
"The timing metric reaches a plateau [...] For the AWGN channel, there is a window with a length of the guard interval where the metric reaches a maximum, and the start of the frame can be taken to be anywhere within this window without a loss in the received  SNR."
Thus, without having really read throu ofdm_sync_pn.py in depth, if using the original approach, you shouldn't even care where the plateau is converted to a 1.

Greetings,
Marcus

[1] http://scholar.google.de/scholar?cluster=3934179950738780116&hl=en&as_sdt=0,5&as_vis=1

On 11/22/2014 02:04 PM, swx z wrote:

Hello all:
              I have read the code of "Schmidl & Cox synchronisation".And I
find the code use the plateau detectors.It shows that the code will output
1 at the middle of the plateau.Why not in the first place of the plateau
instead of in the middle of the plateau?
             Thank you very much.
Best regards,
zs

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