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From: Laron on 19 Mar 2010 20:09
>Could you specify which OFDM system is interested for you? Wimax, LTE,
IEEE
>802.11 a/g, DVB? Each system has a unique design to implement the
>synchronization.
>
>Frank
>
>>
Wimax, Thanks.
From: Frank_os on 20 Mar 2010 03:37
>>Could you specify which OFDM system is interested for you? Wimax, LTE,
>IEEE
>>802.11 a/g, DVB? Each system has a unique design to implement the
>>synchronization.
>>
>>Frank
>>
>>>
>Wimax, Thanks.
>

To get the timing/Frame synchronization, it is need to perform the preamble
detection in time domain (before FFT) by making use of conjugate symmetry
and repetition property; to get the frequency synchronization, it is need
to correlate the signal with its CP counterpart for each symbol after
timing synchronization.
From: robo on 20 Mar 2010 10:36
>>>Could you specify which OFDM system is interested for you? Wimax, LTE,
>>IEEE
>>>802.11 a/g, DVB? Each system has a unique design to implement the
>>>synchronization.
>>>
>>>Frank
>>>
>>>>
>>Wimax, Thanks.
>>
>
>To get the timing/Frame synchronization, it is need to perform the
preamble
>detection in time domain (before FFT) by making use of conjugate symmetry
>and repetition property; to get the frequency synchronization, it is need
>to correlate the signal with its CP counterpart for each symbol after
>timing synchronization.

I' really glad I found this thread as I was just going to create a similar
one. I'm implementing (generic) OFDM system in Matlab and use Schmidl-Cox
synchronization algorithm. The problem I have is that the M(d) (Schmidl-Cox
timing metric) away from the synchronization symbol has very strong peaks,
with the strongest ones following in the data frame just after second
synchronization symbol. Please see a plot of it here:
http://img718.imageshack.us/img718/5716/34169742.jpg
(horizontal is for sample number and vertical is timing metric). The
correlation of the synchronization symbols is seen at the very beginning
and around x=130 and it is exactly equal to 1 (ideal channel) and length 5
samples. In this example two frames were transmitted, each contained 2 SC
synchronization symbols (c1 and c2) and 8 data symbols.

At the moment I'm using 8 QAM4 sub-carriers, cyclic prefix length is 5
samples and nothing else (thus resulting OFDM symbol length is 13 samples).
The synchronization symbol is created as described in SC paper, i.e. points
are chosen from QAM64 constellation.

Thanks for any clues on what might be causing this problem and what can be
done about this.


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