Communication in millimeter wave (mmWave) and even terahertz (THz) frequency bands is ushering in a new era of wireless communications. Beam management, namely initial access and beam tracking, has been recognized as an essential technique to ensure robust mmWave/THz communications, especially for mobile scenarios. However, narrow beams at higher carrier frequency lead to huge beam measurement overhead, which has a negative impact on beam acquisition and tracking. In addition, the beam management process is further complicated by the fluctuation of mmWave/THz channels, the random movement patterns of users, and the dynamic changes in the environment. For mmWave and THz communications toward 6G, we have witnessed a substantial increase in research and industrial attention on artificial intelligence (AI), reconfigurable intelligent surface (RIS), and integrated sensing and communications (ISAC). The introduction of these enabling technologies presents both open opportunities and unique challenges for beam management. In this paper, we present a comprehensive survey on mmWave and THz beam management. Further, we give some insights on technical challenges and future research directions in this promising area.

翻译：毫米波乃至太赫兹频段的通信正开启无线通信的新纪元。波束管理（即初始接入与波束跟踪）已被公认为确保稳健的毫米波/太赫兹通信的关键技术，尤其在移动场景中。然而，更高载波频率下的窄波束导致巨大的波束测量开销，对波束获取与跟踪产生负面影响。此外，毫米波/太赫兹信道的波动、用户随机移动模式及环境的动态变化进一步增加了波束管理过程的复杂性。针对面向6G的毫米波与太赫兹通信，我们观察到人工智能、可重构智能超表面及通感一体化在研究与工业领域获得了显著关注。这些使能技术的引入为波束管理带来了开放机遇与独特挑战。本文对毫米波与太赫兹波束管理进行了全面综述，并针对该前景广阔领域的技术挑战与未来研究方向提出见解。