Analysis of the joint network LDPC codes over orthogonal multi-access relay channel

The capacity approaching behavior of the joint network LDPC code is analyzed in this paper. We first derive the upper bound of the sum capacity of the orthogonal multiaccess relay channel where two sources communicate with one destination in the presence of one relay. Then, a new generalized Gaussian approximation method is designed to predict the decoding threshold of the joint network LDPC code. Results show that under the symmetric channel, the gap between the upper bound of the sum capacity and the decoding threshold ranges from 0.3 dB to 0.6 dB.