A novel network coded relay-assisted Hybrid-ARQ scheme

In conventional relay-assisted HARQ schemes, source is always in anidle state during the retransmission phase.In this paper, we proposed a relay-assisted HARQ scheme which makes use of the basic idea of network coding. We simply adopt a remapping modulation method to combine new codewords and the ones to be retransmittedas the network coding. Source will transmit the superposition symbols during retransmission phase. Thus a virtual MIMO (Multiple In Multiple Out) system can be created and diversity and multiplexing can be gained. A corresponding MMSE (Minimum Mean Square Error) MIMO receiver and a soft demodulation method are proposed to recover two data streams. The proposed scheme can enhance the reliability and at the same time, throughput can be also improved due to the double-amount retransmission. Simulation results show that proposed scheme can greatly balance the reliability and the efficiency.