Spectral Efficient Half Duplex Relaying for Fountain Code with Wireless Network Coding

In this paper, we present a novel spectral efficient relaying scheme for a random linear fountain code with two half duplex relay nodes at which simple network coding, which consists of an XOR operation, is performed. Only the destination node will have a fountain decoder. At the relay nodes, the received packets will be CRC decoded¹ and randomly XOR with the earlier correctly CRC decoded packets which are stored in the relays´ buffers. If the received packets cannot be correctly CRC decoded, the relays will just randomly XOR the packets in their respective buffers and forward the newly network coded packet to the destination. The theoretical upper bound for the outage probability of this proposed scheme is derived. Our simulation results show that the upper bound is tight and the proposed scheme outperforms existing schemes. It is also shown that with wireless network coding, 1-2 dB performance gains and faster fountain decoding especially for low SNR can be achieved.