Combined equalization and nonlinear distortion cancellation for transmission of QAM signal in fixed wireless channel

Abstract

In this paper, we consider combined equalization and nonlinear distortion cancellation for transmission of QAM signals in fixed wireless channel with nonlinear distortion. To reduce nonlinear intersymbol interference (ISI) due to the use of high power amplifiers in the transmitter, we design a nonlinear equalization scheme by approximating the Volterra series model for the nonlinear distortion. The proposed equalization scheme employs two memoryless nonlinear modules, one at the input of the feedback filter and the other at the input of the decision device of the conventional minimum mean-squared-error decision-feedback equalizer (MMSE-DFE). The performance of the proposed scheme is analyzed in terms of the symbol error rate and verified by computer simulation. The SNR gain of the proposed scheme over the conventional MMSE-DFE increases as the QAM constellation size and/or the roll-off factor of the transmit and receive filters increase, enabling the transmission of high-level QAM signals in fixed wireless channel.