Improved Non-Data-Aided Feedforward Symbol Timing Estimator for Low-Rate Sampling Systems

This letter investigates a non-data-aided feedforward timing estimator at low-rate sampling systems. Conventional symbol timing estimator uses the cyclic correlation of oversampled signal. Despite its benefit, the performance of conventional estimators is severely degraded because they use only one cyclic correlation. To mitigate this degradation, we propose the phase rotated estimator for low-rate sampling systems. The proposed estimator is designed to exploit the cyclic correlations at timing lag zero and one. In this context, we first generalize the timing estimator using the modified cyclic correlations. To prevent an aliasing effect, we further obtain the cyclic correlation of a low-pass filtered signal instead of original one. The low-pass filtered signal enables to estimate a timing offset even when the number of samples per symbol is more than one. Simulation results show that the proposed estimator can significantly improve the MSE compared to conventional estimators.