Network coding gain in device-to-device underlaying primary communications

Direct device-to-device (D2D) communication between cellular equipments is proposed to increase data-rate and extend conventional cellular coverage, by introducing underlaying communications with cellular network in cognitive fashion. For enhancing D2D coverage and reliability, we consider advanced relaying techniques. We study D2D communications over more than one hop using relay nodes, i.e., we study utilization of idle devices in connecting the D2D Tx and Rx playing the role of relays. This relaying technique can be implemented using network coding (NC) to provide extra redundancy in the network. With the help of Monte Carlo simulations, we investigate the network performance by comparing the sum rate of the D2D underlaying cellular network achieved with and without NC. It is shown that the physical network coding protocol outperforms the traditional routing scheme, while the digital network coding lies between the performance of both thus offering a good compromise. Finally we show that by considering the best case relay selection can significantly increase the system performance.