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ＯＦＤＭ对栽频偏差是很敏感的，因此不仅在同步的捕获阶段，而且在同步的跟踪阶段，精确的频偏估计是很重要的。文献［３］提出了一种简化的相干判决反馈的迭代算法来估计同步跟踪阶段的载频偏差，对于１２８个子载波、ＱＰＳＫ调制的ＯＦＤＭ系统，在多径衰落信道下，当频偏小于子载波间隔的１５％时，频偏估计的标准方差小于１％，但是这个结果是在假设信道频率响应、定时偏差、载波相位等参数已知的条件下取得的，而当这些参数的估计存在误差时，由仿真结果可看出，频偏估计性能恶化了，因此，提出了采用差分判决反馈的频偏估计算法，虽然只能估计小于子载波间隔 ８％的频偏，但差分判决反馈算法不需要知道信道的参数，由于在同步跟踪阶段，频偏一般都较小，因此采用差分判决反馈算法可以很好地估计出同步跟踪阶段的频率偏差。
OFDM is very sensitive to crop frequency deviation, so accurate frequency offset estimation is important not only in the synchronization acquisition phase but also in the synchronization tracking phase. Literature [3] proposed a simplified iterative algorithm for coherent decision feedback to estimate the carrier frequency offset in the synchronization tracking phase. For 128 sub-carriers and QPSK-modulated OFDM systems, when the frequency offset is less than The standard deviation of the frequency offset estimation is less than 1% at 15% of the carrier spacing, but this result is obtained assuming that the channel frequency response, timing offset, carrier phase and other parameters are known, and when the estimation of these parameters is in error , We can see from the simulation results that the performance of the frequency offset estimation deteriorates. Therefore, a frequency offset estimation algorithm using differential decision feedback is proposed. Although only the frequency offset smaller than 8% of the subcarrier spacing can be estimated, the differential decision feedback algorithm Need to know the parameters of the channel, due to the synchronization tracking phase, the frequency offset is generally small, so the use of differential decision feedback algorithm can be very good estimate of the synchronization tracking phase frequency deviation.