We develop accurate and robust one-dimensional EXIT chart methods to design Raptor codes with binary and higher-order modulations on AWGN channels.
Global Design Methods for Raptor Codes Using Binary and Higher-Order Modulations
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We develop accurate and robust one-dimensional EXIT chart methods to design Raptor codes with binary and higher-order modulations on AWGN channels. We formulate the checknode degree distribution optimization as a linear program that directly accounts for the pre-code error correction capability and simultaneously optimizes over any desired range of rate operating points. The throughput curves predicted by the analysis are easily compared across different pre-code rates and pre-code error-correcting capabilities. For higher-order modulations we employ BICM on a standard Gray-mapped 16-QAM constellation. We further enhance the optimization by applying separate check-node degree distributions to the mapped MSBs and LSBs, which results in significant gains compared to a single check-node degree distribution.