Analysis of equalizer-based baud-spaced timing recovery for digital subscriber line systems

This paper presents an analysis of symbol-spaced timing recovery algorithms which are based on the equalizer precursor tap weights of the equalizer. These algorithms break the coupling of conventional adaptive decision-directed timing recovery (based e.g. on the well known M&M algorithm) and the adaptive equalizer in the tracking mode, once acquisition has been reached. The performance and key characteristics of a precursor tap weight based timing recovery algorithm are evaluated exemplarily for a very high bit-rate digital subscriber line (VDSL) application and compared to conventional M&M timing recovery, dependent on the step size of the equalizer LMS adaptation algorithm of the equalizer and the parameters of the timing loop filter.