The non-orthogonal multiple access (NOMA) approach enables a number of users to share the same resource via superposition coding in the transmitter and successive detection in the receiver. In this study a power allocation (PA) approach based on the proportional fair division technique is proposed. In this regard, power is assigned to users such that it ensures the fairness of NOMA follows that of orthogonal multiple access. A straight forward approach that achieves this objective is stated and is followed by proposing three different algorithms. These algorithms loosen the strict proportionality criterion to fulfil the data rate of a specific user. Also, a new fairness index for NOMA based on data rate ratios is defined. Afterwards, a low-complexity strategy based on water filling (WF) for PA amongst resources is proposed. This second PA stage aims at improving the data rate of users. The proposed approaches are applied to NOMA systems with different pairing strategies and results are compared. Results show that the proposed approaches improve the fairness of NOMA and WF increases the total system rate.

中文翻译：

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非正交多路访问系统公平分配功率

非正交多址访问（NOMA）方法使许多用户可以通过发射机中的叠加编码和接收机中的连续检测来共享同一资源。在这项研究中，提出了一种基于比例公平分配技术的功率分配（PA）方法。在这方面，功率被分配给用户，从而确保了NOMA的公平性遵循正交多址访问的公平性。陈述了实现此目标的简单方法，然后提出了三种不同的算法。这些算法放宽了严格的比例标准，以满足特定用户的数据速率。此外，基于数据速率比率，为NOMA定义了新的公平性指标。然后，提出了一种基于水填充（WF）的资源间低复杂度策略。第二个PA阶段旨在提高用户的数据速率。所提出的方法应用于具有不同配对策略的NOMA系统，并比较了结果。结果表明，所提出的方法提高了NOMA的公平性，并且WF提高了总系统速率。