Coded modulation using superimposed binary codes

• Published in: IEEE transactions on information theory Vol. 50; no. 12; pp. 3331 - 3343
• Main Authors: Ma, X., Ping, L.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2004; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Applied sciences; AWGN; Binary codes; Channel capacity; Coded modulation; Codes; Coding, codes; coding/shaping scheme; Exact sciences and technology; Gaussian processes; Information, signal and communications theory; Iterative algorithms; Iterative decoding; iterative decoding/demapping algorithm; iterative multistage decoding; Modulation coding; multilevel coding; Quadrature amplitude modulation; sigma-mapping; Signal and communications theory; Signal mapping; soft-input-soft-output (SISO) demapping algorithm; Telecommunications and information theory; Transmitters; coding/shaping scheme; Iterative method; Decoding; multilevel coding; Algorithm; Binary code; Coded modulation; soft-input-soft-output (SISO) demapping algorithm; iterative decoding/demapping algorithm; sigma-mapping; iterative multistage decoding; Modulation coding; Mutual information; Information theory
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2004.838104

In this correspondence, we investigate in a comprehensive fashion a one-layer coding/shaping scheme resembling a perfectly cooperated multiple-access system. At the transmitter, binary data are encoded by either single-level or multilevel codes. The coded bits are first randomly interleaved and then entered into a signal mapper. At each time, the signal mapper accepts as input multiple binary digits and delivers as output an amplitude signal, where the input are first independently mapped into 2-PAM signals (possibly having different amplitudes) and then superimposed to form the output. The receiver consists of an iterative decoding/demapping algorithm with an entropy-based stopping criterion. In the special cases when all the 2-PAM signals have equal amplitudes, based on an irregular trellis, we propose an optimal soft-input-soft-output (SISO) demapping algorithm with quadratic rather than exponential complexity. In the general cases, when multilevel codes are employed, we propose power-allocation strategies to facilitate the iterative decoding/dempaping algorithm. Using the unequal power-allocations and the Gaussian-approximation-based suboptimal demapping algorithm (with linear complexity), coded modulation with high bandwidth efficiency can be implemented.