a communications system which utilizes an m - ary qam signal constellation suitable for non - linear applications . the communications system includes a modulator for utilizing the m - ary constellation to implement the modulation . the m - ary constellation is a circular constellation which provides a simplified amplitude predistortion by utilizing the subject m - ary constellations , enabling more efficient communications can then be achieved through a peak - power - limited non - linear channel . such non - linear channels are more power efficient at creating rf energy from dc energy .