A comparison of the performance of hard and soft-decision turbo coded Orthogonal Frequency Division Multiplexing (OFDM) systems with Quadrature Phase Shift Keying (QPSK) and 16-Quadrature Amplitude Modulation (16-QAM) is considered in the first section of this paper. The results show that the soft-decision method greatly outperforms the hard-decision method. The complexity of the demapper is reduced with the use of simplified algorithm for 16-QAM demapping. In the later part of the paper, the authors consider the transmission of data over Additive White class A Noise (AWAN) channel, using turbo coded QPSK and 16-QAM systems. They propose a novel turbo decoding scheme for AWAN channel.