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OFDM time and frequency synchronization by spread spectrum pilot technique

Correct time and frequency synchronization is important for the performance of orthogonal frequency division multiplex (OFDM) systems. We evaluate a system where a pseudonoise sequence (PN-sequence) is used for estimation of these synchronization parameters. The PN-sequence is superimposed on the OFDM signal. The system is evaluated by means of the variance of the frequency estimation error and the probability for correct timing synchronization. Both theoretical and simulated results are presented. The proposed technique is very flexible and works also at low signal to noise ratios. The frequency offset range has been significantly increased compared to conventional OFDM synchronizer schemes.