In this letter, we investigate the energy efficiency (EE) and spectral efficiency (SE) tradeoff problem in intelligent reflecting surface (IRS)-assisted downlink millimeter wave (mmWave) non-orthogonal multiple access (NOMA) systems, where a quality of service (QoS) requirement-based decoding strategy is proposed to address the decoding uncertainty due to the impact of the IRS on channel gains. The EE-SE tradeoff problem is formulated as a multi-objective optimization problem through jointly optimizing power allocation, active precoding, and passive precoding. To handle the intractable problem, we first adopt the weighted-sum method to transform the original problem into a single objective problem. Then, we propose an iterative alternating optimization algorithm (IAOA) to effectively solve the single objective problem, as shown in simulation results. Moreover, the proof of the convergence and the complexity analysis of IAOA algorithm are given.

中文翻译：

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IRS 辅助下行链路毫米波 NOMA 系统中的能源效率和频谱效率权衡


在这封信中，我们研究了智能反射表面（IRS）辅助的下行链路毫米波（mmWave）非正交多址（NOMA）系统中的能源效率（EE）和频谱效率（SE）权衡问题，其中服务质量提出了基于需求（QoS）的解码策略来解决由于IRS对信道增益的影响而导致的解码不确定性。通过联合优化功率分配、主动预编码和被动预编码，将EE-SE权衡问题表述为多目标优化问题。为了解决这个棘手的问题，我们首先采用加权和方法将原始问题转化为单一目标问题。然后，我们提出了一种迭代交替优化算法（IAOA）来有效解决单目标问题，如仿真结果所示。此外，还给出了IAOA算法的收敛性证明和复杂度分析。