Problem in Implementing Autocorrelation on Stratix II EP2S60 DSP Development Board

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I am basically using OFDM kinda thing for Spatial Modulation. I am transmitting a sinusoid of say freq f1 for synchronization and subsequently of freq f2 for data and will be performing correlation with sinusoid of freq f1 on the receiver side. I expect to get a peak of approx 1 for auto-correlation which will trigger my receiver to collect data. The problem I have is that I am using 128 data length for each symbol and I am using altera blockset (simulink) and I am totally confused about what blocks to use for performing the correlation thing.

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In direct spread spectrum (DSS) systems like CDMA, base stations transmit PRBS codes for synchronization. I have not looked into OFDM, so I am not familiar with their technique. However, your description does not sound correct, perhaps you really mean different 'carriers' for modulated data.

Can you please provide a reference for OFDM where they discuss synchronization.

Altera has some application notes on OFDM, so how do they synchronize?

Cheers,

Dave

thanks for the reply Dave.I really appreciate your interest.

I am basically using OFDM kinda thing for Spatial Modulation. I am transmitting a sinusoid of say freq f1 for synchronization and subsequently of freq f2 for data and will be performing correlation with sinusoid of freq f1 on the receiver side. I expect to get a peak of approx 1 for auto-correlation which will trigger my receiver to collect data. The problem I have is that I am using 128 data length for each symbol and I am using altera blockset (simulink) and I am totally confused about what blocks to use for performing the correlation thing.

thanks...

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I am trying to synchronize the transmitted signal with the receiver by energy detection. The transmitted signal is a sine wave and I plan to autocorrelate it to obtain the peak and then transmitting the data. Could you please help me in implementing the autocorrelation using Stratix II.

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If the transmitted signal is a sinusoid, then the autocorrelation is a cosine. Auto-correlation not help you synchronize, cross-correlation does; you correlate a reference signal to the incoming signal and try to 'find' the start of the transmitted signal. Since the peaks of the cross-correlation of two sinusoids repeat every period, the synchronization is ambiguous, so it won't work very well.

Synchronization based on autocorrelation typically uses pseudo-random binary sequences (PRBS), since the auto-correlation, or really the cross-correlation of a PRBS at the receiver, with the incoming PRBS has a peak. When you move the peak to the zeroth lag, you are synchronized to the transmitter. Radar and sonar systems use FM chirp pulses (linear FM), Barker codes, and other signals with sharp autocorrelation peaks.

There is no peak in your scheme, so it won't work.

Why don't you explain what you are trying to do. Can you change the transmit signal?

Cheers,

Dave