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Optimization of degree-profile matching interleavers for LDPC-coded modulation
Yang, Hyun-koo,Yang, Kyeongcheol IEEE 2006 IEEE COMMUNICATIONS LETTERS Vol.10 No.12
<P>In this paper we introduce the concept of degree-profile matching interleavers (DPM-interleavers) and propose an LDPC-coded modulation scheme with a DPM-interleaver for 2<SUP>m</SUP>-PAM. One advantage of our scheme over conventional LDPC-coded modulation schemes is to support various modulation orders in a single coder/decoder by properly choosing DPM-interleavers according to each modulation order. Given the degree distribution for a good binary LDPC code, we present the optimized degree-profiles for DPM-interleavers by density evolution in the cases of 4-PAM and 8-PAM, respectively. Simulation results show that our proposed scheme provides compatible performance with those of conventional LDPC-coded modulation schemes</P>
Gallager's decoding algorithm Α over high order modulations
Hyun-Koo Yang,Myung-Kyu Lee,Kyeongcheol Yang IEEE 2009 IEEE communications letters Vol.13 No.5
<P>Gallager's decoding algorithm A (GDA) for low density parity check (LDPC) codes is of interest mainly due to its good performance with extremely low complexity. In this paper, we analyze GDA over 2<SUP>m</SUP>-ary pulse-amplitude modulation (2<SUP>m</SUP>-PAM). Firstly, we represent its average error probability by means of a recursion formula. We then define its threshold for additive white Gaussian noise (AWGN) channels and derive its stability condition. The bit-to-symbol mapping strategies have a strong influence on the performance of LDPC-coded modulation systems. Finally, we show that the bit-reliability mapping strategy proposed by Li and Ryan maximizes the threshold of the LDPC coded modulation system with GDA over Gray-mapped 2<SUP>m</SUP>-PAM in the AWGN channel.</P>