Hybrid beamforming for Terahertz (THz) ultra-massive multiple-input multiple-output (UM-MIMO) systems is a promising technology for 6G space-air-ground integrated networks, which can overcome huge propagation loss and offer unprecedented data rates. With ultra-wide bandwidth and ultra-large-scale antennas array in THz band, the beam squint becomes one of the critical problems which could reduce the array gain and degrade the data rate substantially. However, the traditional phase-shifters-based hybrid beamforming architectures cannot tackle this issue due to the frequency-flat property of the phase shifters. In this paper, to combat the beam squint while keeping high energy efficiency, a novel dynamic-subarray with fixed true-time-delay (DS-FTTD) architecture is proposed. Compared to the existing studies which use the complicated adjustable TTDs, the DS-FTTD architecture has lower power consumption and hardware complexity, thanks to the low-cost FTTDs. Furthermore, a low-complexity row-decomposition (RD) algorithm is proposed to design hybrid beamforming matrices for the DS-FTTD architecture. Extensive simulation results show that, by using the RD algorithm, the DS-FTTD architecture achieves near-optimal array gain and significantly higher energy efficiency than the existing architectures. Moreover, the spectral efficiency of DS-FTTD architecture with the RD algorithm is robust to the imperfect channel state information.

中文翻译：

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用于太赫兹宽带混合波束成形的具有固定真时延设计的节能动态子阵列

用于太赫兹 (THz) 超大规模多输入多输出 (UM-MIMO) 系统的混合波束成形是 6G 空地一体网络的一项有前途的技术，可以克服巨大的传播损耗并提供前所未有的数据速率。随着太赫兹频段的超宽带宽和超大规模天线阵列，波束斜视成为可能降低阵列增益和大幅降低数据速率的关键问题之一。然而，由于移相器的频率平坦特性，传统的基于移相器的混合波束成形架构无法解决这个问题。在本文中，为了在保持高能效的同时对抗光束斜视，提出了一种具有固定真实时延（DS-FTTD）架构的新型动态子阵列。与使用复杂可调 TTD 的现有研究相比，得益于低成本的 FTTD，DS-FTTD 架构具有更低的功耗和硬件复杂性。此外，提出了一种低复杂度行分解 (RD) 算法来设计用于 DS-FTTD 架构的混合波束成形矩阵。大量仿真结果表明，通过使用 RD 算法，DS-FTTD 架构实现了接近最优的阵列增益和显着高于现有架构的能效。此外，具有RD算法的DS-FTTD架构的频谱效率对不完善的信道状态信息具有鲁棒性。大量仿真结果表明，通过使用 RD 算法，DS-FTTD 架构实现了接近最优的阵列增益和显着高于现有架构的能效。此外，具有RD算法的DS-FTTD架构的频谱效率对不完善的信道状态信息具有鲁棒性。大量仿真结果表明，通过使用 RD 算法，DS-FTTD 架构实现了接近最优的阵列增益和显着高于现有架构的能效。此外，具有RD算法的DS-FTTD架构的频谱效率对不完善的信道状态信息具有鲁棒性。