Two-Layer Coding Rate Optimization in Relay-Aided Systems

We consider a three-node transmission system, where a source node conveys a data block to a destination node with the help of a half-duplex decode and-forward (DF) relay node. The whole data block is transmitted as a sequence of packets. For reliable transmission in the three-node system, a two-layer coding scheme is proposed, where physical layer channel coding is utilized within each packet for error-correction and random network coding is applied on top of channel coding for network error-control. There is a natural tradeoff between the physical layer coding rate and the network coding rate given different system performance requirements. For different objectives, two optimization problems are formulated and solutions are presented. One is to minimize the outage probability given the efficiency requirement, while the other one is to maximize the transmission efficiency given the outage probability requirement. Numerical results are also provided to show the optimized physical layer coding and network coding rate pairs in different system scenarios.