改进CAZAC序列的OFDM时频同步算法

针对先前一些算法存在定时模糊以及存在较大干扰峰干扰的问题，提出了一种基于加权CAZAC序列的OFDM系统同步方案。利用训练序列共轭对称特性进行符号定时和频偏估计。利用训练序列延迟相关和对称相关的特点进行定时和粗频偏估计，能够有效抑制干扰从而得到更好的估计性能。利用循环前缀的冗余信息进行小数倍频偏精细估计。此外分析了整数倍频偏对时域CAZAC序列的影响。采用时域循环移位进行整数倍频偏估计。通过与其他算法的仿真对比可以得出，多径衰落信道下所提算法能够取得较高的定时准确率和频偏估计精度。

OFDM timing and frequency synchronization algorithm based on weighted CAZAC sequence

In this paper, a novel preamble structure based on weighted CAZAC （Constant Amplitude Zero Auto Correlation） sequence is designed to solve timing ambiguity and high interference peak. The conjugate symmetry of training sequence is used for symbol timing and frequency offset estimation. Then with the redundancy of the cyclic prefix, the fine fractional frequency offset is completed. Finally, the cyclic shifting operation in time domain is adopted to estimate the integer frequency offset. Analysis and computer simulation results show that the proposed method achieves high timing and frequency offset estimation accuracy compared with other algorithm, and solves the problem of synchronization inaccuracy under multipath fading channel. The proposed method has important significance for improving the performance of OFDM system under multipath fading channel environment.