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:尽管非正交多址技术 (NOMA) 可以提高频谱利用效率,但由于连续干扰消除 (SIC) 导致的接收端复杂度,其能效问题需要更加深入的研究。以往的 NOMA 能效研究忽视了 SIC 开销,并依赖于简单的功耗模型 (PCM) 。为了填补这一空白,本文首先引入 PCM-$\kappa$ 来考虑与 SIC 相关的功耗支出,其中 $\kappa$ 表示每个 SIC 层的平均功耗。然后,为了研究 NOMA 和联合传输 (JT)-CoMP NOMA 的能效问题,我们针对最大化能效制定了功率分配问题,并提出了在一个集中实体和基站上运行的局部算法。我们使用 PCM-$\kappa$ 和文献中常用的两种 PCM 来评估能效。数值分析表明,使用简单的 PCM 会导致能效被高估数个数量级,特别是当接收端的速率需求较低时。尽管 JT-CoMP NOMA 相对于传统 NOMA 具有更好的功率分配效果,但其能效差距仅仅是微小的。此外,当传统 NOMA 可行时,JT-CoMP NOMA 的最优解会收敛到传统 NOMA 上,而 NOMA 方案会偏向于信道质量更好的用户。