While non-orthogonal multiple access (NOMA) improves spectral efficiency, it results in a complexity at the receivers due to successive interference cancellation (SIC). Prior studies on the energy efficiency of NOMA overlook the SIC overhead and rely on simplistic power consumption models (PCM). To fill this gap, we first introduce PCM-$\kappa$ that accounts for SIC-related power expenditure, where $\kappa$ represents the average power consumption per SIC layer. Then, to investigate the energy efficiency of NOMA and joint transmission (JT)-CoMP NOMA, we formulate a power allocation problem for maximizing the energy efficiency and consequently propose a global approach running at a centralized entity and a local algorithm running at a base station. We evaluate the energy efficiency using PCM-$\kappa$ and two PCMs commonly used in the literature. Numerical analysis suggests that using simplistic PCMs leads to a few orders of magnitude overestimation of energy efficiency, especially when the receivers have low rate requirements. Despite the superiority of JT-CoMP NOMA over conventional NOMA in finding a feasible power allocation, the difference in their energy efficiency is only marginal. Moreover, when conventional NOMA is feasible, the optimal solution for JT-CoMP NOMA converges to conventional NOMA and NOMA schemes favour the users with the best channel quality.

翻译：尽管非正交多址接入(NOMA)提升了频谱效率，但因采用逐次干扰消除(SIC)技术，接收端复杂度随之增加。现有NOMA能效研究未考虑SIC开销，且依赖简化的功耗模型(PCM)。为弥补这一不足，我们首先提出PCM-$\kappa$模型，该模型考虑了SIC相关功耗，其中$\kappa$表示每层SIC的平均功耗。随后，为研究NOMA与联合传输(JT)-CoMP NOMA的能效，我们构建了以最大化能效为目标的功率分配问题，并分别提出运行于集中式实体的全局算法与运行于基站的本地算法。我们采用PCM-$\kappa$及文献中常用的两种PCM评估能效。数值分析表明，使用简化PCM会导致能效被高估数个数量级，尤其当接收端具有低速率需求时。尽管JT-CoMP NOMA在寻找可行功率分配方面优于传统NOMA，但两者能效差异甚微。此外，当传统NOMA可行时，JT-CoMP NOMA的最优解会收敛至传统NOMA方案，且NOMA方案更偏好信道质量最优的用户。