Channel Coding Design to Support Asynchronous Physical Layer Network Coding

In this paper, we discuss the channel coding design to support the two-phase physical-layer network coding (PLNC) under a typical three-node network coding scenario. We prove, even two source nodes could use different channel codes, the error correction capability at the relay node is bounded by that of the weaker one, i.e. the code with a smaller minimum distance. Therefore, we propose to use the same channel code at two source nodes, which can also provide potential to simplify the joint PLNC-channel decoding procedure (PLNC-DEC) at the relay node. Moreover, we propose a channel coding scheme based on linear convolutional codes to relax the strict synchronization requirement, which is difficult to achieve in some real applications. The proposed coding scheme is robust to the synchronization error between two source nodes and enables the relay node to perform the PLNC-DEC with only one Viterbi decoding procedure. Compared to the three-phase network coding scheme, the proposed scheme reduces the decoding/demodulation complexity of the relay node almost by half and achieves significant throughput gain.