Symbol timing recovery in digital subscriber loops in the presence of residual echo and impulsive noise

In this paper, a general analysis is presented for the jitter performance of a common type of Symbol Timing Recovery (STR) system employed in a Digital Subscriber Loop (DSL) transceiver with adaptive echo cancellation for high-speed digital communications typical of evolving Integrated Service Digital Networks (ISDN´s). Exact analytical expressions for the mean and variance of the timing wave and for the r.m.s. phase jitter are derived as a function of the system parameters representing a particular DSL and its noise environment, including such effects as residual-echo and Impulsive Noise (IN). Numerical results, obtained for an experimental study of a 144 kbits/s SDL timing recovery system, show that the presence of these disturbing signals can substantially degrade the STR performance