Capacity Enhancement for D2D-Assisted Cooperative NOMA Systems

In this paper, a novel device-to-device (D2D)-assisted cooperative non-orthogonal multiple access (NOMA) model with a two-stage transmission scenario is proposed, which consists of 1) partial decoding and forwarding from the transmitter to relay nodes; 2) transmission from relay nodes to the receivers. A sum-rate maximization problem is formulated, which is decoupled into subchannel selection and two-stage channel link power allocation. A joint optimization algorithm based on game theory and successive convex approximation (JOAGS) is proposed, which can efficiently utilize network resources and increase spectrum efficiency. The algorithm proposed in this paper has been validated through simulation results, demonstrating its substantial capability to amplify system capacity, diminish the outage probability of the communication link, and extend the communication distance. The findings reveal that when compared to the existing scheme, the system’s sum-rate is augmented by 10.8%, and the outage probability registers a notable reduction of 23.6%.