Design of joint network-low density parity check codes based on the EXIT charts

For the multiple-access relay network where two sources communicate with one destination in the presence of one relay, a practical joint network-low density parity check code is designed to help the relay jointly re-encode the messages from both sources. A bilayer extrinsic information transfer chart is developed based on which a design methodology is proposed to iteratively improve the degree distribution of the proposed code. Simulations illustrate that the gap between the convergence threshold and the performance of the coding scheme is less than 0.6dB at BER=10^-5.