Optimal Channel Estimation with Timing Synchronization

To achieve the highest possible BER performance in OFDM systems, the receiver and transmitter must be fully time synchronized. The channel estimation is never going to be at its best without temporal synchronization. Both timing synchronization and optimum channel estimation are the essential requirements to maximize the performance of the system. To maximize the throughput of OFDM systems it is required to minimize the number of pilots. This requires the knowledge of the number of channel taps.

In the OFDM signal received over any multipath channel, the samples corresponding to the cyclic prefix are correlated with the same number of last samples in the symbol frame. All the other samples are uncorrelated. The number of such correlated samples is equal to the sum of the number of samples in the cyclic prefix and channel delay spread. From the first sample in the cyclic prefix, the amount of correlation of these samples increases to a maximum and decreases to zero.