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OFDM synchronization question

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Antonio_Magma

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ofdm sync

Guys, i have a doubt which i hope u guys can help me.

I've read & studied about OFDM symbol synchronization, either through the use of cyclic prefix or preamble sequences.

However there is 1 part i do not understand. My OFDM simulation in Simulink produces a real valued output before transmission (Complex symmetry at IFFT). Thus my transmitting signal is real. But at synchronization, after a certain delay of T i'm suppose to perform complex conjugate before correlation with the original signal. How do i perform the conjugation when the incoming signal is real? Am i suppose to perform some IQ demodulation to turn it into complex?
 

Gandharva

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simulink ofdm synchronization

yes, you need to take the complex conjugate before correlating with the original signal.
Well, you might be thinking why should one take complex conjugate of a real signal. Think in this way: Your signal is real at the Tx end, this signal is multiplied by a complex phasor when it passes through a channel, this will result in reception of a complex signal at the receiver end.

Now, if you are not introducing a channel between your Tx and Rx you can safely ignore the complex conjugation operation.

hope this answers your Q
 

Antonio_Magma

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ofdm synchronization 2009

Haven't seen in you quite a while Gandharva :) Good to see you again...

Ok, so do i just perform simple conjugation then? or none? Coz to perform correlation i need to have conjugation right?

To give you an idea of what i'm trying to do with the synchronization. HomePlug, the standard for power line communications uses preambles for synchronization 6 SYNCP symbols and 1 SYNCM symbols (which is the reverse of SYNCP). However, i do not know what is SYNCP and SYNCM thus i'm using the PN sequence generator in Simulink.

I'm trying to implement a double correlation system, where:
1) coarse sync forms a plateau where the incoming signal is autocorrelated with a delayed version of itself and
2) fine sync produces peaks when crosscorrelated with the known preamble

Then the result of the 2 is compared and synchronization is obtained.

Added after 23 minutes:

Another thing, for autocorrelation before the conjugation there is a delay. How much should i set for this delay/lag?
 

prince24

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ofdm synchronization matlab

Please refer "Robust Frequency and timing synchronizatrion for OFdm " By Schmidle and c.cox IEEE paper for clearing your concepts regarding your problem.
 

yanghui_1231

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matlab ofdm sync

you could download the papers to see,it's easy!
 

ahmedseu

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ofdm synchonisation

Check this link, it contains a very good dissertation in OFDM synchronization.
 

bingo369

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ofdm synchronization

I have the same problem too, but deos anyone can tell me how to find Matlab codeing for OFDM synchronization?
 

Sadaf Iqbal

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ofdm synchronization correlation

hello every one
m new member of edaboard
can any one help me regarding cyclic prefix
how i will add it to my data in matlab???
 

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