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In this paper, a blind time-parameters estimation scheme for OFDM is proposed based on correlation property between useful symbol and cyclic prefix (CP) of an OFDM symbol. Without any prior information (including symbol rate and SNR level), the proposed scheme estimates "useful time" and symbol duration by two especially designed correlation algorithms, and then "guard time" can be worked out. The theoretical arguments and simulations show that the proposed time-parameters estimation algorithms for OFDM can obtain good performances in low SNR and multi-path channel conditions, and are robust in the presence of phase and frequency offsets.

An accurate bandwidth estimation scheme based on wavelet transform (WT) is proposed for OFDM, which estimates OFDM bandwidth using wavelet decomposition, signal reconstruction, moving covariance calculation and statistic histogram method in turn. Without requiring information about incoming signal and SNR level, the proposed scheme can estimate bandwidth parameter automatically and accurately even at low SNRs. Performance of the proposed scheme is shown by the theoretical arguments and simulations.

In the multi-stage symbol synchronization strategy for DVB-T COFDM, we proposed a low complexity and good performance coarse symbol synchronization (CSS) algorithm and an accurate fine symbol synchronization (FSS) algorithm. The new CSS algorithm is based on the autocorrelation property of the OFDM signal and estimates the symbol start position by measuring partial cyclic prefix (CP) correlation results. It has lower complexity and better performance (in multipath channel) compared with the conventional maximum likelihood (ML) method. The proposed FSS algorithm is based on pilots and estimates the residual symbol deviation by all-pilots in an OFDM symbol, including continual pilots and scattered pilots. It can acquire more accurate estimation results than the conventional algorithm only using scattered pilots. The analysis and simulations show the improved performance of the CSS algorithm and the FSS algorithm proposed in this paper.