This paper investigates outage and throughput performance of non-orthogonal multiple access (NOMA) based underlay cognitive radio (i.e., CR-NOMA) network under partial relay selection (PRS) scheme. Here NOMA is used in the secondary network, where K half duplex, decode-and-forward (DF) relays are available for assisting the secondary base station (SBS) to deliver information to the secondary users (SUs). We derive analytical expressions for the outage probabilities experienced by the SUs under imperfect successive interference cancellation (i-SIC) conditions. The interference threshold constraint of the primary receiver and the maximum transmit power constraint of the secondary nodes are considered for the analysis. To provide more insights on the outage performance, we obtain expressions for the asymptotic outage probabilities of the SUs in the high transmit power region. Next, we derive analytical expressions for the optimal power allocation (OPA) factors at the SBS and at the selected relay that independently maximize the delay limited throughput of the secondary network in CR-NOMA system. We also determine the jointly optimal power allocation factors that maximize the throughput. We use numerical and simulation investigations to establish that the outage probabilities of the SUs reduce significantly while the throughput improves under the considered PRS scheme, compared to random relay selection and fixed relaying strategies. Further, it is established that the proposed OPA factors can significantly reduce the outage probabilities experienced by the SUs and improve the system throughput compared to equal/random power allocation schemes.

中文翻译：

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具有部分中继选择的基于 NOMA 的底层认知无线电网络的性能分析


本文研究了部分中继选择（PRS）方案下基于非正交多址（NOMA）的底层认知无线电（即CR-NOMA）网络的中断和吞吐量性能。这里，NOMA用于辅助网络，其中K个半双工、解码转发(DF)中继可用于辅助辅助基站(SBS)向辅助用户(SU)传递信息。我们推导了 SU 在不完美的连续干扰消除 (i-SIC) 条件下经历的中断概率的解析表达式。分析时考虑了主接收机的干扰阈值约束和辅节点的最大发射功率约束。为了提供有关中断性能的更多见解，我们获得了 SU 在高发射功率区域的渐近中断概率的表达式。接下来，我们推导出 SBS 和所选中继处的最佳功率分配 (OPA) 因子的解析表达式，这些表达式独立地最大化 CR-NOMA 系统中辅助网络的延迟有限吞吐量。我们还确定了最大化吞吐量的联合最佳功率分配因子。我们使用数值和模拟研究来确定，与随机中继选择和固定中继策略相比，在所考虑的 PRS 方案下，SU 的中断概率显着降低，而吞吐量提高。此外，与等/随机功率分配方案相比，所提出的 OPA 因子可以显着降低 SU 经历的中断概率并提高系统吞吐量。