In millimeter wave (mmWave) systems, the advanced lens antenna array can effectively reduce the radio frequency chains cost. However, the mmWave signal is still vulnerable to blocking obstacles and suffers from severe path loss. To address this problem, we propose an intelligent reflect surface (IRS) enhanced multi-user mmWave communication system with lens antenna array. Moreover, we attempt to optimize energy efficiency in the proposed system. An energy efficiency maximization problem is formulated where the transmit beamforming at base station and the reflect beamforming at IRSs are jointly considered. To solve this non-convex problem, we propose an algorithm based on the alternating optimization technique. In the proposed algorithm, the transmit beamforming is handled by the sequential convex approximation method and the reflect beamforming is optimized based on the quadratic transform method. Our simulation results show that the proposed algorithm can achieve significant energy efficiency improvement under various scenarios.

中文翻译：

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带透镜天线阵列的 IRS 增强型毫米波系统的能效优化

在毫米波（mmWave）系统中，先进的透镜天线阵列可以有效降低射频链成本。然而，毫米波信号仍然容易被障碍物阻挡并遭受严重的路径损耗。为了解决这个问题，我们提出了一种带有透镜天线阵列的智能反射面 (IRS) 增强型多用户毫米波通信系统。此外，我们试图优化所提议系统的能源效率。一个能量效率最大化问题被公式化，其中基站的发射波束成形和 IRS 的反射波束成形被联合考虑。为了解决这个非凸问题，我们提出了一种基于交替优化技术的算法。在提出的算法中，发射波束成形采用顺序凸逼近法处理，反射波束成形采用二次变换法优化。我们的仿真结果表明，所提出的算法可以在各种场景下实现显着的能效提升。