Performance of nonuniform M-ary QAM constellation on nonlinear channels

This paper investigates the effects of the nonequiprobable distribution of a high bandwidth efficiency M-ary QAM signal constellation on the error performance for nonlinear channels. A simple nonlinear channel model where the phase and amplitude of the transmitted samples are distorted by a nonlinear function with additive white Gaussian noise (AWGN) in the downlink was simulated. Simulation results for binary turbo coded modulation (TCM) show a 3 dB improvement when the distribution of the signal constellation is nonequiprobable