NOMA-enabled D2D adaptive relaying and transmission in cellular networks

With the aim of improving the spectrum efficiency, we propose a two-phase cellular non-orthogonal and device-to-device (D2D) non-orthogonal (CNDN) transmission scheme, wherein a base station (BS) can transmit data to a near-user and a far-user simultaneously assisted by two D2D users. Either the D2D transmitter or the D2D receiver can adaptively forward the BS data to the far-user according to their decoding statuses. When the D2D transmitter forwards the cellular data, it also transmits its own data to the D2D receiver simultaneously. The superposition coding technique is adopted for the non-orthogonal transmission and the opportunistic interference cancelation is performed for the data decoding. Taking into account the adaptive operations of cellular and D2D users, we analyze the throughput of both cellular and D2D systems. Extensive simulations show that the proposed CNDN scheme greatly outperforms the cellular orthogonal and D2D non-orthogonal (CODN) transmission scheme in terms of throughput.