Terahertz (THz) communications are celebrated as key enablers for converged localization and sensing in future sixth-generation (6G) wireless communication systems and beyond. Instead of being a byproduct of the communication system, localization in 6G is indispensable for location-aware communications. Towards this end, we aim to identify the prospects, challenges, and requirements of THz localization techniques. We first review the history and trends of localization methods and discuss their objectives, constraints, and applications in contemporary communication systems. We then detail the latest advances in THz communications and introduce THz-specific channel and system models. Afterward, we formulate THz-band localization as a 3D position/orientation estimation problem, detailing geometry-based localization techniques and describing potential THz localization and sensing extensions. We further formulate the offline design and online optimization of THz localization systems, provide numerical simulation results, and conclude by providing lessons learned and future research directions. Preliminary results illustrate that under the same transmission power and array footprint, THz-based localization outperforms millimeter wave-based localization. In other words, the same level of localization performance can be achieved at THz-band with less transmission power or a smaller footprint.

中文翻译：

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6G 通信系统太赫兹频段定位教程


太赫兹 (THz) 通信被誉为未来第六代 (6G) 无线通信系统及其他系统中融合定位和传感的关键推动者。 6G 中的定位不是通信系统的副产品，而是位置感知通信所不可或缺的。为此，我们的目标是确定太赫兹定位技术的前景、挑战和要求。我们首先回顾本地化方法的历史和趋势，并讨论它们的目标、限制以及在当代通信系统中的应用。然后，我们详细介绍了太赫兹通信的最新进展，并介绍了太赫兹特定的信道和系统模型。随后，我们将太赫兹波段定位表述为 3D 位置/方向估计问题，详细介绍基于几何的定位技术并描述潜在的太赫兹定位和传感扩展。我们进一步制定了太赫兹定位系统的离线设计和在线优化，提供数值模拟结果，并总结经验教训和未来的研究方向。初步结果表明，在相同的传输功率和阵列占用空间下，基于太赫兹的定位优于基于毫米波的定位。换句话说，可以在太赫兹频段以更低的传输功率或更小的占地面积实现相同水平的定位性能。