Feedforward Timing Recovery Research Articles

Design of new digital blind feedforward timing recovery algorithm for linear modulations in digital communication receivers

Synchronisers are a significant part of digital communication receivers since they are used to estimate the received signal timing. Among these synchronisers, non-data-aided (NDA) or blind synchronisers are even more important due to bandwidth efficiency. In this study, a different approach is investigated to derive new feedforward NDA timing estimators based on Newton algorithm. Two novel estimators with four and two samples per symbol are presented and compared with traditional timing estimators, respectively. One of the main advantages of the second proposed estimator is the ability to control the loop gain automatically. This ability improves the convergence speed and robustness of the design. Simulation results show that the presented estimators outperform the conventional estimators over a noisy channel, especially at small excess bandwidth and low signal to noise ratio.

Impact of Self Noise on Tracking Performance of Non-Data-Aided Digital Timing Recovery

Non-data-aided feedforward timing recovery is preferred to non-data-aided feedback timing recovery in digital receivers because it does not suffer delay in the loop. However, while feedback timing recovery with optimized predetection filter is not affected by self noise, in this paper it is pointed out for the first time that, even if an optimized predetection filter is adopted, feedforward timing recovery is. The paper proposes an approximation to the power spectral density of self noise that leads to analytical performance evaluation, the accuracy of the approximation being confirmed by simulation results. Also, a comparative study of feedforward and feedback timing recovery is presented. The result of the comparison is that, for signal-to-noise ratio lower than 50 dB and realistic spectra of phase noise affecting the timing wave to be tracked, despite self noise, feedforward timing recovery outperforms feedback timing recovery.

On the Design of a Digital Blind Feedforward, Nearly Jitter-Free Timing-Recovery Scheme for Linear Modulations

This letter deals with the compensation of the self-noise (jitter) in a nondata-aided (blind) feedforward symbol-timing estimator using two samples per symbol for linearly modulated waveforms transmitted through additive white Gaussian noise channels. The main contribution of this letter is the derivation of an appropriate prefilter to achieve nearly jitter-free digital blind feedforward timing recovery. Computer simulations illustrate that the proposed prefiltering scheme improves significantly the performance at mid and high signal-to-noise ratios.