In this article, we evaluate the overall outage probability (OOP) of pairwise Non-orthogonal Multiple Access (NOMA) for both uplink and downlink. We also propose a dynamic decoding order (DDO) together with a fixed pairwise power allocation (FPPA) scheme, in which the optimal decoding order is decided based on the instantaneous channel gains, and thereafter, a pair of power levels is assigned in accordance with the selected decoding order. Exact closed-form expressions of the OOPs for both uplink and downlink pairwise NOMA considering all proposed decoding orders over Nakagami- $m$ fading are derived. Further, we find the optimal fixed power levels for different power allocation strategies so that the OOPs are minimized. Moreover, we investigate the influence of the distances between the source nodes and the access point (AP), the target transfer rates and the path-loss exponents on the OOPs for all cases of decoding orders. In addition, we benchmark our proposed DDO against other decoding orders in terms of the OOP. The results show that assigning optimal fixed power levels which takes the instantaneous decoding order into account not only improves the communication reliability, but also reduces the complexity and computational load at the AP.

中文翻译：

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成对NOMA的中断性能，允许动态解码顺序和最佳功率电平对

在本文中，我们评估了上行链路和下行链路的成对非正交多路访问（NOMA）的总体中断概率（OOP）。我们还提出了动态解码顺序（DDO）和固定的成对功率分配（FPPA）方案，其中基于瞬时信道增益确定最佳解码顺序，然后根据所选的解码顺序。考虑到Nakagami-上所有建议的解码顺序，上行和下行成对NOMA的OOP的精确闭式表达式 $ m $ 淡入淡出。此外，我们找到了针对不同功率分配策略的最佳固定功率水平，从而使OOP最小化。此外，我们研究了在所有解码顺序情况下，源节点与接入点（AP）之间的距离，目标传输速率和路径损耗指数对OOP的影响。此外，根据OOP，我们针对其他解码顺序对建议的DDO进行了基准测试。结果表明，分配考虑瞬时解码顺序的最佳固定功率电平不仅可以提高通信可靠性，而且可以降低AP的复杂性和计算量。