Almost jitter-free feedforward symbol timing recovery for GMSK modulations

A novel nondata-aided feedforward symbol timing estimator was recently proposed by Morelli and Vitetta for minimum-shift keying (MSK) modulations in S. J. Lee et al., May 2002. This estimator represents an approximate maximum likelihood (ML) method, and at low signal-to-noise ratios (SNRs) it approaches the Cramer-Rao bound (CRB). However, at medium and high SNRs, the performance of this estimator is far from CRB especially for partial response modulations. In this paper, a new prefilter is proposed to improve the medium and high SNR performance of this estimator by reducing its self-noise (jitter) and without compromising its good low SNR performance. An improved version of the timing recovery scheme introduced by Wu and Ng for GMSK modulations (Y. Wu et al., May 2001) is also proposed. Computer simulations are shown to illustrate the merits of the proposed prefilter based timing recovery schemes.