Decoding Algorithms of LDPC Coded Superposition Modulation

This paper is concerned with the design of decoding algorithms for superposition modulation systems in which all levels are coded with an identical binary low-density parity-check (LDPC) code. First, we present a computing-based iterative multistage decoding algorithm (CB-IMSDA). Then, we show that the considered system can be treated as a nonbinary LDPC (NB-LDPC) coded modulation system. Based on this, a joint decoding algorithm (JDA) is proposed. As a by-product, we propose a time-varying signaling scheme for the JDA. Numerical results show that 1) both the CB-IMSDA and JDA perform better than the standard iterative multistage decoding algorithm, and 2) extra coding gain can be obtained when the time-varying signaling scheme is employed.