A novel ARQ protocol for OFDMA relay system based on network coding

Network coding is a prominent technique to efficiently utilize system resources and improve throughput of wireless networks. In this paper, we design a network coded cooperative scheme in OFDMA based single relay system. By exploiting retransmission request from the destination, the relay has capacity of forwarding XOR-code between source information transmitted in different transmission periods, which combines the new source information and the required retransmission information. In our scheme, it is not necessary to allocate extra system resource (time slot or bandwidth) for retransmission. A mathematical model is established to analyze the system outage probability. The system throughput is compared between our approach and other two traditional ARQ protocols. Simulation results show that the proposed protocol is much more efficient to utilize the available bandwidth.