Performance of a Coded Non-Square Quadrature Amplitude Modulation Scheme over Fading Channels

It is shown that a non-square (NS) 2-ary quadrature amplitude modulation (QAM) can be decomposed into a single-parity-check (SPC) block encoder and a memoryless modulator with independent in-phase (I) and quadrature (Q) symbol mapping. When NS-2-QAM is concatenated with a forward-errorcorrecting (FEC) code, iterative demodulation and decoding of the FEC code and the inherent SPC code of NS-2-QAM exploits the modulation’s inherent memory and its independent Iand Q-channel mapping and demapping. The capacity and the bit-/symbol-error-rate (BER/SER) performance of coded and uncoded NS-2-QAM systems are given for both additive white Gaussian noise (AWGN) channels and Rayleigh fading channels and are compared to those of other conventional 2-ary systems. Simulation results show that, with iterative demodulation and decoding, coded NS-8QAM outperforms three conventional 8-ary systems by at least 0.65 dB on AWGN channels and by at least 0.57 dB on Rayleigh fading channels at BER = 10−5, when the FEC code is a concatenation of (15,11) Hamming codes with rate-1 accumulator codes, while coded NS-32QAM outperforms standard 32QAM by about 0.45 dB on AWGN channels and by about 0.27 dB on Rayleigh fading channels.