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.