Hierarchical modulated channel and network coding scheme in the multiple-access relay system

In this paper, we consider a multiple-access relay system with two sources, one relay, and one destination. The relay combines the information received from these two sources, and then sends the combining information to the destination. For the information combing at the relay, a traditional network coding scheme, based on XOR-operation does not show good error protection capability and becomes less effective. In this paper, we propose a hierarchical modulated network coding scheme to enhance the spectrum efficiency, where the hierarchical modulation is proposed to enhance the transmission at both sources, and an joint channel coding and network coding is presented to resist the interference and fading at the relay. Simulation results show that the proposed scheme substantially improves the bit-error probability and even achieves high spectral efficiency compared to traditional scheme.