A new time-frequency synchronisation algorithm based on preamble sequence in OFDM system

Aiming at the problems of high computational complexity in the timing synchronisation phase and poor frequency offset estimation performance of existing time-frequency synchronisation algorithms, this paper proposes an improved time-frequency synchronisation algorithm based on preamble sequence for OFDM systems. The preamble sequence is designed by using the property that the cross-correlation value of the Constant Amplitude Zero Auto Correlation (CAZAC) sequence with different root values is close to zero. Based on its features, a timing metric function and the frequency offset estimation function are designed. The frequency offset estimation function is used to obtain the coarse fractional frequency offset, and the fine fractional frequency offset is obtained by combining Cyclic Prefix (CP) and Cyclic Suffix (CS). Then, the time domain sliding correlation between receiving sequence and the local preamble sequence is used to estimate the integer frequency offset. The results indicate that the proposed method has better synchronisation capability than existing algorithms.