Performance of High Order QAM under Transmit Nonlinearities

High data rate demands of new generations of communication systems necessitate the use of higher and higher order QAM schemes. However, the nonlinearities in various stages of the transmitter may hinder the performance of higher order QAM and limit the transmission rate enhancements. As observed in many studies in the literature, outermost constellation points are usually more adversely affected by nonlinearities and larger regions of uncertainty form around them. We focus on nonuniform error vector magnitude (EVM) values of QAM symbols in this paper and present achievable rates. Furthermore, we propose a simplified receiver that considers the unequal EVM distribution by splitting the constellation into multiple regions and compare the performance of the receiver to that of a conventional receiver taking into account average EVM.