Blind DFE with parametric entropy-based feedback

This paper considers the blind decision feedback equalizer for quadrature amplitude modulation (QAM) systems and proposes the optimization method of parametric stochastic gradient algorithms particularly derived for its entropy-based feedback filter. The optimization method is based on the fact that the “slope” of applied parametric complex-valued nonlinearity can be adjusted to the unknown probability distribution of an input intersymbol interference to respond with a maximum entropy output. The parametric optimization is achieved for 16-, 32- and 64-QAM signals.