Hyun-Koo Yang

Optimization of degree-profile matching interleavers for LDPC-coded modulation

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 2m-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

Gallager's decoding algorithm Α over high order modulations

Gallagers 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 2m-ary pulse-amplitude modulation (2m-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 2m-PAM in the AWGN channel.