In this letter, a downlink intelligent reflecting surface (IRS) enhanced millimeter-wave (mmWave) non-orthogonal multiple access (NOMA) system is considered. A joint optimization problem over active beamforming, passive beamforming and power allocation is formulated. Due to the highly coupled variables, the formulated optimization problem is non-convex. To solve this problem, an alternative optimization and successive convex approximation based iterative algorithm is proposed. Numerical results illustrate that: 1) the proposed scheme offers significant sum-rate gains, which confirms the effectiveness of introducing IRS for mmWave-NOMA systems; 2) the proposed algorithm with discrete phase shifts can achieve close performance to that of continuous phase shifts.

中文翻译：

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智能反射面增强型毫米波 NOMA 系统

在这封信中，考虑了下行链路智能反射面 (IRS) 增强型毫米波 (mmWave) 非正交多址 (NOMA) 系统。制定了主动波束成形、被动波束成形和功率分配的联合优化问题。由于高度耦合的变量，公式化的优化问题是非凸的。为了解决这个问题，提出了一种基于替代优化和连续凸逼近的迭代算法。数值结果表明：1）所提出的方案提供了显着的总速率增益，这证实了为mmWave-NOMA系统引入IRS的有效性；2）所提出的离散相移算法可以实现与连续相移接近的性能。