Cutoff rate and constellation design for the companding channel

Abstract

In modern voiceband data communication the received signal is subject t o nonlinear quantization noise due t o companding. Under certain conditions this quantization noise m a y become dominant and cause serious degradation in performance. In this work w e first calculate the c u t 0 8 rate and t h e n use these results t o design n e w "optimal" signal constellations f o r the companding channel. These n e w constellations are computed assuming a signal dependent non-circular Gaussian channel transition density.