In this letter, a cooperative underlay cognitive non-orthogonal multiple access (NOMA)-based coordinated direct and relay transmission is investigated. Specifically, exact closed-form expressions for the outage probabilities (OPs) of the primary and SNs are derived, based on which the respective asymptotic analysis are carried out. Our results show the superiority of the proposed system when compared with conventional cooperative schemes. Also, it is shown that there exists an optimal point where the transmit powers of the primary and STs can be set in order to ensure a good performance for both networks.

中文翻译：

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基于底层基于认知NOMA的协调直接和中继传输

在这封信中，研究了基于合作式认知非正交多址（NOMA）的协调直接和中继传输。具体而言，得出主要和SN的停机概率（OP）的精确封闭式表达式，基于此表达式进行相应的渐近分析。我们的结果表明，与传统的协作方案相比，所提出的系统具有优越性。而且，示出了存在最佳点，在该最佳点处可以设置主站和ST的发射功率，以确保两个网络的良好性能。