A Novel Cooperative Full Duplex Device to Device Communication Underlaying Cellular Networks

Full duplex (FD) communication and Device-to-Device (D2D) communication can greatly improve spectral efficiency. In this paper, a new cooperative mode is proposed, here it is named T-mode, in which two D2D users not only transmit signal to each other, but also act as relays to forward the signal from Base Station to two cellular users simultaneously. Thus the two D2D users share the same downlink spectrum resource with the two cellular users. In one timeslot, the system can finish the signal transmission between BS and two cellular users through D2D users' relaying as well as the data transmission between two D2D users when the non-orthogonal multiple access (NOMA) is considered at the D2D users. To optimize the performance of the cooperative model, an optimal power allocation is proposed under the minimum constraint of the transmission rate of D2D links and cellular user links. The optimization of power allocation is a non-convex problem. By loosening self-interference to a fixed value, the non-convex problem is converted into a solvable geometric programming problem. The system sum rate is given and compared with the conventional cooperative mode with three timeslots. The simulation results show that the pro-posed cooperative model with optimal power allocation outperforms the conventional cooperative mode.