This paper investigates a non-orthogonal multiple access (NOMA) technique by employing device-to-device (D2D) transmission in small-cell networks. More specifically, the D2D transmission combines the relay selection model from a group of macro base stations (MBS) with the D2D mode in in small-cell network to form a D2D-NOMA system. Such D2D transmission needs assistance from multiple MBS and the small-cell base station (SBS) using decode-and-forward (DF) techniques. In this context, full-duplex (FD) is adopted at intermediate nodes. Furthermore, there are two possible scenarios in practice including perfect channel state information (CSI) and imperfect CSI that need to be studied to examine performance degradation in such considered network. To evaluate system performance, we derive expressions of outage probability for D2D user. Our study results show that the proposed network with more MBSs selection can improve the outage performance compared to the conventional orthogonal multiple access (OMA) scheme. Finally, numerical results confirms the accuracy of the derived expressions.

本文研究了在小型蜂窝网络中采用设备到设备（D2D）传输的非正交多址（NOMA）技术。更具体地，在小小区网络中，D2D传输将来自一组宏基站（MBS）的中继选择模型与D2D模式相结合，以形成D2D-NOMA系统。这种D2D传输需要使用解码和转发（DF）技术的多个MBS和小型基站（SBS）的协助。在这种情况下，中间节点采用全双工（FD）。此外，实践中存在两种可能的情况，包括完美信道状态信息（CSI）和不完善CSI，需要进行研究以检查这种考虑的网络中的性能下降。为了评估系统性能，我们导出了D2D用户中断概率的表达式。我们的研究结果表明，与传统的正交多址（OMA）方案相比，所建议的具有更多MBS选择的网络可以改善中断性能。最后，数值结果证实了导出表达式的准确性。