The Study of Features of Functioning of Channel with Memory and APSK-N-Signal. The Possibilities of Increasing its Spectral Efficiency

The features of functioning of a non-parametric, frequency-selective communication channel with memory utilizing by amplitude-phase-keying signals with N discrete states are studied. It should be noted that in this study, the decision rule of the receiver is based on the theory of resolution time. And therefore, special attention in this paper is given to the stability of "transparency windows" caused by intersymbol interference in the presence of destabilizing factors, as the presence of a frequency detuning and measurement errors of the envelope and phase introduced by the receiver. Based on the results of research, recommendations to spectral efficiency increasing were presented.