Sum-Rate Maximization for D2D and Cellular Hybrid Networks Enhanced by NOMA

Non-Orthogonal Multiple Access (NOMA) has recently been conceived as a promising technology for the fifth-generation mobile communication system. In this paper, we apply NOMA into the device-to-device (D2D) and cellular hybrid networks to improve the data rate of the D2D links. Specifically, we formulate a D2D transmission rate maximization problem by jointly considering user pairing and power control under the constraints of the decoding threshold of cellular users. To solve the formulated problem, we first analyze the optimal transmission power of the D2D users. According to the obtained power control strategy, the user pairing problem is transformed into a bipartite graph matching problem, which can be solved optimally by the Hungarian algorithm. Simulation results demonstrate that our algorithm outperforms the existing schemes in terms of data rate.