Abstract: By combining multiple information copies from different source nodes at the destination node in a cooperative relay network, we propose a joint irregular repeat accumulate (IRA) code and network coding modified decoding (JI-NMD) algorithm. We first demodulate the modulation information with soft demodulation information of each link, and extract the information copies from the relay node at the destination. This is done according to the functional relationships between the network coding at relay node and the original information in the direct link. We then update the soft demodulation information
of the two copies from the direct and cooperative links in the IRA decoder, and construct a new decoding decision method. We further obtain a simplified log-likelihood ratio (LLR)method. Finally, we analyze the outage probability and spectral efficiency. Simulationresults show that the JI-NMD algorithm has lower bit error rate for QPSK and 16QAM.