Hybrid non-orthogonal multiple access (NOMA), which organically combines pure NOMA and conventional OMA, has recently received significant attention to be a promising multiple access framework for future wireless communication networks. However, most of the literatures on hybrid NOMA only consider fixed order of successive interference cancellation (SIC), namely FSIC, for the NOMA transmission phase of hybrid NOMA, resulting in limited performance. Differently, this paper aims to reveal the potential of applying hybrid SIC (HSIC) to improve the energy efficiency of hybrid NOMA. Specifically, a HSIC aided hybrid NOMA scheme is proposed, which can be treated as a simple add-on to the legacy orthogonal multiple access (OMA) based network. The proposed scheme offers some users (termed ``opportunistic users'') to have more chances to transmit by transparently sharing legacy users' time slots. For a fair comparison, a power reducing coefficient $\beta$ is introduced to ensure that the energy consumption of the proposed scheme is less than conventional OMA. Given $\beta$, the probability for the event that the achievable rate of the proposed HSIC aided hybrid NOMA scheme cannot outperform its OMA counterpart is obtained in closed-form, by considering impact of user pairing. Furthermore, asymptotic analysis shows that the aforementioned probability can approach zero under some given conditions in the SNR regime, indicating that the energy efficiency of the proposed scheme is almost surely higher than that of OMA for these given conditions. Numerical results are presented to verify the analysis and also demonstrate the benefit of applying HSIC compared to FSIC.

翻译：混合非正交多址接入（NOMA）通过有机结合纯NOMA与传统正交多址接入（OMA），近年来作为未来无线通信网络中一种极具前景的多址接入框架受到广泛关注。然而，现有关于混合NOMA的研究大多仅考虑在混合NOMA的NOMA传输阶段采用固定顺序的连续干扰消除（SIC），即FSIC，导致性能受限。与此不同，本文旨在揭示应用混合SIC（HSIC）提升混合NOMA能效的潜力。具体而言，本文提出一种HSIC辅助的混合NOMA方案，该方案可作为对现有基于传统OMA网络的简易附加模块。所提方案使部分用户（称为“机会用户”）能够通过透明共享传统用户的时隙获得更多传输机会。为公平比较，引入功率缩减系数$\beta$以确保所提方案的能耗低于传统OMA。在给定$\beta$的条件下，通过考虑用户配对的影响，推导出所提HSIC辅助混合NOMA方案可达速率无法超越对应OMA方案这一事件的闭式概率表达式。进一步，渐近分析表明在特定给定条件下，当信噪比趋于无穷大时，上述概率可趋近于零，这意味着在这些条件下所提方案的能效几乎必然高于OMA。数值结果验证了理论分析，并展示了相较于FSIC，应用HSIC所带来的性能优势。