Design of Optimal LDPC Code for the System of MDPSK Concatenated with LDPC Codes

The combined demodulating and decoding algorithm of the system of M-ary Differential Phase-Shift Keying (MDPSK) concatenated with Low-Density Parity Check Codes in AWGN channels is analyzed in this paper. Concentrating on the above algorithm, we propose a design method of optimal LDPC code based on Extrinsic Information Transfer Chart. Meanwhile, as an example, degree distribution of LDPC code at a rate of one-half bit per channel is given for both MDPSK and pi/4 DQPSK system concatenated with Low-Density Parity Check Codes.