Iterative demodulation, demapping, and decoding of coded non-square QAM

It is shown that a non-square (NS) 2²ⁿ⁺¹-ary quadrature amplitude modulation (QAM) can be decomposed into a single parity-check (SPC) block encoder and a memoryless modulator in such a way that the inherent block encoder has a recursive nature. When concatenated with a forward-error-correcting (FEC) code, iterative demodulation, demapping, and decoding of the FEC code and the inherent SPC code of NS-2²ⁿ⁺¹-QAM is then possible. Simulation results show that coded NS-8QAM performs nearly 2 dB better than standard 8QAM and star-8QAM, and nearly 1 dB better than 8-ary phase-shift keying when the FEC code is a rate-1/2, 16-state convolutional code, while coded NS-32QAM performs 0.75 dB better than standard 32QAM.