Hybrid non-orthogonal multiple access (NOMA) has recently received significant research interest due to its ability to efficiently use resources from different domains and also its compatibility with various orthogonal multiple access (OMA) based legacy networks. Unlike existing studies on hybrid NOMA that focus on combining NOMA with time-division multiple access (TDMA), this work considers hybrid NOMA assisted orthogonal frequency-division multiple access (OFDMA). In particular, the impact of a unique feature of hybrid NOMA assisted OFDMA, i.e., the availability of users' dynamic channel state information, on the system performance is analyzed from the following two perspectives. From the optimization perspective, analytical results are developed which show that with hybrid NOMA assisted OFDMA, the pure OMA mode is rarely adopted by the users, and the pure NOMA mode could be optimal for minimizing the users' energy consumption, which differs from the hybrid TDMA case. From the statistical perspective, two new performance metrics, namely the power outage probability and the power diversity gain, are developed to quantitatively measure the performance gain of hybrid NOMA over OMA. The developed analytical results also demonstrate the ability of hybrid NOMA to meet the users' diverse energy profiles.

翻译：混合非正交多址接入（NOMA）技术因其能够高效利用来自不同域的资源，以及与各种基于正交多址接入（OMA）的现有网络的兼容性，近来受到了广泛的研究关注。与现有主要关注将NOMA与时分多址接入（TDMA）相结合的混合NOMA研究不同，本文研究了混合NOMA辅助的正交频分多址接入（OFDMA）。特别地，本文从以下两个角度分析了混合NOMA辅助OFDMA的一个独特特征——用户动态信道状态信息的可用性——对系统性能的影响。从优化角度出发，推导的分析结果表明，在混合NOMA辅助的OFDMA中，用户很少采用纯OMA模式，而纯NOMA模式对于最小化用户能耗可能是最优的，这与混合TDMA的情况不同。从统计角度出发，本文提出了两个新的性能指标，即功率中断概率和功率分集增益，以定量衡量混合NOMA相对于OMA的性能增益。所推导的分析结果也证明了混合NOMA满足用户多样化能量需求的能力。