Abstract: Carrier Frequency Offset（CFO） mitigation is critical for Orthogonal Frequency Division Multiplexing（OFDM） because even small CFO per-transmitter may lead to serious performance loss.Making use of the character of all-phase OFDM frame，this paper proposes the correlation algorithm for frequency estimation in time domain.It is accomplished in one frame period with the advantage of fast convergence.Phase error can not affect the algorithm.This paper also proposes the frequency estimation algorithm based on all-phase FFT.The difference between FFT and all-phase FFT is used in it.Moreover，the relationship between the signal group delay and frequency is used，too.Finally，the paper obtains the accurate signal frequency.It is robust in fast fading channel and lightly impacted by frequency offset.

Key words: Orthogonal Frequency Division Multiplexing（OFDM）, all-phase OFDM, correlation algorithm in time domain, all-phase frequency estimator, Fast Fourier Transform（FFT）, all-phase FFT

摘要： 在正交频分复用（OFDM）系统中，载波频率偏移会导致系统性能严重下降。充分利用全相位OFDM系统的数据帧自我复制的特点，提出了时域自相关频率偏移估计算法。该算法能够在一帧数据周期内完成，收敛速度快，且不受相位偏差的影响。也提出了基于全相位FFT的频率估计算法，该算法利用全相位FFT和FFT在频域的信号相位差异以及信号群时延与频率之间的关系，准确地得到了信号频率。该算法在快衰落信道表现稳健，而且受频偏的影响非常小。

关键词: 正文频分复用（OFDM）, 全相位OFDM, 时域自相关算法, 全相位频率估计器, 快速傅里叶交换（FFT）, 全相位FFT