Joint Channel-Network Coding in Unequally Error Protected Multi-way Wireless Relay Systems

Abstract

Joint-channel physical layer network coding (JCPNC) has attracted much attention recently as a promising technique to achieve a good trade-off between the error performance and the spectral efficiency in multi-way wireless relay systems. However, in most of the practical multi-way relay systems, the channels between the nodes and the relay are heterogeneous. In particular, some channels can be of relatively poorer quality than the other channels which require a higher error protection. Meanwhile, providing the same high level of error protection in high-quality channels results in a poor spectral efficiency. Thus, in this paper, we propose a novel unequal error protection scheme in order to achieve a better trade-off between the error performance and spectral efficiency. In the proposed scheme, low-quality channels are provided higher protection using a full-length low density parity check (LDPC) channel code, while high-quality channels are given lower protection using punctured LDPC codes. We also develop a novel joint LDPC decoding and network coding algorithm to be employed at the relay. As demonstrated by the simulation results, the proposed error protection scheme together with the joint decoding algorithm provides an excellent spectral efficiency-error performance trade-off in practical multi-way wireless relay systems.