A timing recovery criterion derived from the tap weights of a decision feedback equalizer for QAM digital subscriber line systems

In this paper a timing recovery criterion is derived from the optimum feedforward coefficients of an adaptive symbol-spaced complex-valued decision feedback equalizer (DFE). The criterion is deduced by evaluating the relationship of sampling phase and corresponding, in the minimum mean square error (MMSE) sense optimum, equalizer tap weights exemplarily for a typical digital subscriber line (DSL) scenario. It turns out that a linear combination of the real and imaginary parts of the precursor and cursor coefficient can be applied as timing recovery criterion suitable for digital implementation.