the adverse effects of rf and baseband circuits are mitigated using a post - compensation method wherein a transfer function that would un - distort or complement a distorted waveform is parameterized to a relatively small number of degrees of freedom ; and the parameters are estimated in a feedback loop . the error function of the feedback loop is generated by comparing some relatively low - order statistics that are known a priori or can be computed with relative certainty from the decided output waveform — to the statistics of the corrected signal .