Analysis of Frequency Error on Feed-Forward Timing

For the purpose of studying the influence of residual carrier frequency error on NDA feed-forward timing estimators, a symmetrical feed-forward timing scheme (SFT) is deduced on the basis of ML rule. It is shown that the O&M estimator is just a limit case of SFT. Through the acquired SFT general formula, it is also proved in the frequency domain that SFT estimator is not influenced by frequency error when the bandwidth of the pre-filter is wide enough. In the end, the timing variances of O&M and SFT has been simulated under different carrier frequency errors and roll-off factors on additive white Gaussian noise channel in the case of QPSK modulation. The result testifies that the SFT estimator has a better performance and can be applied to the symbol timing for burst PSK signals.