Cutoff rate and constellation design for the companding channel

摘要

In modern voiceband data communication the received signal is subject to nonlinear quantization noise due to companding. Under certain conditions this quantization noise may become dominant and cause serious degradation in performance. We first calculate the cutoff rate and then use these results to design new "optimal" signal constellations for the companding channel. These new constellations are computed assuming a signal dependent non-circular Gaussian channel transition density.