A comparison of different blind equalization techniques for xDSL-transceivers

In this paper blind equalization techniques based on the constant modulus algorithm (CMA) are compared for single carrier modulation (SCM) transceivers in typical digital subscriber line (DSL) environments. The considered algorithms can be implemented with low computational effort and they are shown to converge for the two most commonly employed equalization techniques for SCM systems, namely feedforward equalization (FFE) and decision feedback equalization (DFE). In both cases the equalizer´s feedforward filter (FFF) can be spaced at symbol-rate T or by a fraction of it. The considered algorithms are employed in two scenarios. The first one is limited by intersymbol interference (ISI) the second by far end crosstalk (FEXT) noise. In all cases, the considered techniques lead to a signal-to-interference plus noise ratio (SINR) close to the theoretical optimum.