A Postfix Synchronization Method for OFDM and MIMO-OFDM Systems

This paper proposes a synchronization method that uses as preamble two identical training parts (Chu sequences) followed by a flipped postfix (FlP) for OFDM and MIMO-OFDM systems. The proposed method provides symbol timing and carrier frequency offset (CFO) estimators. By using this FlP-based preamble, the accuracy of the symbol timing estimator is highly improved without increasing the computation complexity. The time synchronization method includes both coarse and fine time synchronization. In particular, this paper indicates how to set up the threshold for the fine time synchronization. Performance evaluation of the proposed method, applied to MIMO-OFDM systems, with various diversity combining shows that receive diversity gives more gain than transmit diversity. The proposed method for both OFDM and MIMO-OFDM systems is also compared to various synchronization methods such as the Schmidl-Cox (SC) and Minn-Zeng-Bhargava (MZB)'s methods in time invariant and time-variant Rayleigh fading channels in terms of mean and variance of the timing and CFO estimators. Overall, it is seen that the proposed new method offers good advantages compared to existing synchronization methods.