Superposition modulation with reliability-based hybrid detection

In this paper, an advanced modulation scheme called superposition modulation (SM) and its applications in bit-interleaved coded modulation (BICM) is studied. The maximum a posteriori (MAP) detector and the probabilistic data association detector with Gaussian approximation (PDA-GA) are investigated using the extrinsic information transfer (EXIT) chart technique. It is demonstrated that the performance loss of the PDA-GA detector is due to an inaccuracy of the Gaussian approximation at high SNRs. Additionally, a reliability-based hybrid detector is proposed, which approximates the probability density function (pdf) of residual interference by applying the Gaussian approximation on more reliable interfering symbols, while calculating the exact pdfs of unreliable interfering symbols. By adjusting the number of interfering symbols employing the Gaussian approximation, this hybrid scheme provides a flexible solution to compromise between performance and complexity.