Regular network low density parity check codes for multiple-access relay channel

Regular network low density parity check (NLDPC) codes are proposed for the multiple-access relay channel with two sources, one relay and one destination. A three-layer Tanner graph is used to describe the code, where the coded bits from the two sources and the coded bits from the relay are separated into two different layers. This makes it possible to design the code more flexibly. A three-layer Gaussian approximation algorithm is developed to calculate the mean values of messages propagated between the layers during decoding iterations. The separation of coded bits from the sources and the relay, which produces the three-layer graph, makes the calculation more accurate. With threshold analysis, it is shown that the regular NLDPC codes are optimal when the degrees of the variable nodes in the middle layer and the lower layer are unitary.