Optimal Design of the Joint Network LDPC Codes for Half-Duplex Cooperative Multi-access Relay Channel

Optimization of degree distribution of the joint network LDPC code for orthogonal multiple-access relay channel (MARC) is investigated in this paper. We first calculated the code capacity of the source-destination link of orthogonal MARC based on a Gaussian approximation, where two sources communicate with one destination in the presence of one relay. Then, a new generalized differential evolution algorithm is developed to iteratively improve the degree distribution of the joint network LDPC code. Simulation results show that, the gap between bit error rate (BER) performance of our designed codes and the decoding threshold is about 0.4dB, and that between the capacity limit and decoding threshold is less than 0.7dB at BER = 10-6.