For downlink multi-user non-orthogonal multiple access (NOMA) systems with successive interference cancellation (SIC) receivers, and a base-station not possessing the instantaneous channel gains, the fundamental relationship between the target rates and power allocation is investigated. It is proven that the total interference from signals not removed by SIC has a fundamental upper limit which is a function of the target rates, and the outage probability equals one when exceeding this limit. The concept of well-behaved power allocation strategies is defined, and its properties are proven to be derived solely based on the target rates. The existence of power allocation strategies that enable NOMA to outperform OMA in per-user outage probability is proven, and are always well-behaved for the case when the outage probability performance of NOMA and OMA are equal for all users. The proposed SIC decoding order is then shown to be the most energy efficient. The derivation of well-behaved power allocation strategies that have improved outage probability performance over OMA for each user is outlined. Simulations validate the theoretical results, demonstrating that NOMA systems can always outperform OMA systems in outage probability performance, without relying on the exact channel gains.

中文翻译：

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具有目标速率的下行链路多用户 NOMA 的功率分配策略基础

对于具有连续干扰消除 (SIC) 接收机和不具有瞬时信道增益的基站的下行链路多用户非正交多址 (NOMA) 系统，研究了目标速率与功率分配之间的基本关系。事实证明，来自 SIC 未去除的信号的总干扰有一个基本上限，它是目标速率的函数，超过此限制时中断概率等于 1。定义了行为良好的功率分配策略的概念，并证明其特性仅基于目标速率推导出来。证明了存在使 NOMA 在每用户中断概率方面优于 OMA 的功率分配策略的存在，并且在所有用户的 NOMA 和 OMA 的中断概率性能相等的情况下始终表现良好。所提出的 SIC 解码顺序随后被证明是最节能的。概述了行为良好的功率分配策略的推导，这些策略在每个用户的 OMA 上提高了中断概率性能。仿真验证了理论结果，表明 NOMA 系统在中断概率性能方面始终优于 OMA 系统，而无需依赖于精确的信道增益。