Wireless communication at the terahertz (THz) frequency bands (0.1–10 THz) is viewed as one of the cornerstones of tomorrow’s 6G wireless systems. Owing to the large amount of available bandwidth, if properly deployed, THz frequencies can potentially provide significant wireless capacity performance gains and enable high-resolution environment sensing. However, operating a wireless system at high-frequency bands such as THz is limited by a highly uncertain and dynamic channel. Effectively, these channel limitations lead to unreliable intermittent links as a result of an inherently short communication range, and a high susceptibility to blockage and molecular absorption. Consequently, such impediments could disrupt the THz band’s promise of high-rate communications and high-resolution sensing capabilities. In this context, this paper panoramically examines the steps needed to efficiently and reliably deploy and operate next-generation THz wireless systems that will synergistically support a fellowship of communication and sensing services. For this purpose, we first set the stage by describing the fundamentals of the THz frequency band. Based on these fundamentals, we characterize and comprehensively investigate seven unique defining features of THz wireless systems: 1) Quasi-opticality of the band, 2) THz-tailored wireless architectures, 3) Synergy with lower frequency bands, 4) Joint sensing and communication systems, 5) PHY-layer procedures, 6) Spectrum access techniques, and 7) Real-time network optimization. These seven defining features allow us to shed light on how to re-engineer wireless systems as we know them today so as to make them ready to support THz bands and their unique environments. On the one hand, THz systems benefit from their quasi-opticality and can turn every communication challenge into a sensing opportunity, thus contributing to a new generation of versatile wireless systems that can perform multiple functions beyond basic communications. On the other hand, THz systems can capitalize on the role of intelligent surfaces, lower frequency bands, and machine learning (ML) tools to guarantee a robust system performance. We conclude our exposition by presenting the key THz 6G use cases along with their associated major challenges and open problems. Ultimately, the goal of this article is to chart a forward-looking roadmap that exposes the necessary solutions and milestones for enabling THz frequencies to realize their potential as a game changer for next-generation wireless systems.

中文翻译：

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太赫兹 (THz) 无线系统的七个定义特征：通信与传感联谊


太赫兹 (THz) 频段（0.1-10 THz）的无线通信被视为未来 6G 无线系统的基石之一。由于可用带宽大量，如果部署得当，太赫兹频率可以提供显着的无线容量性能增益并实现高分辨率环境感测。然而，在太赫兹等高频段运行无线系统受到高度不确定和动态信道的限制。实际上，由于固有的短通信范围以及对阻塞和分子吸收的高度敏感性，这些通道限制导致不可靠的间歇性链路。因此，这些障碍可能会破坏太赫兹频段的高速率通信和高分辨率传感能力的承诺。在此背景下，本文全面研究了高效、可靠地部署和操作下一代太赫兹无线系统所需的步骤，该系统将协同支持通信和传感服务的联谊。为此，我们首先通过描述太赫兹频段的基本原理来做好准备。基于这些基本原理，我们描述并全面研究了太赫兹无线系统的七个独特的定义特征：1）频段的准光学性，2）太赫兹定制的无线架构，3）与较低频段的协同作用，4）联合传感和通信系统，5) PHY 层程序，6) 频谱接入技术，以及 7) 实时网络优化。这七个定义性特征使我们能够阐明如何重新设计我们今天所知道的无线系统，以便使它们做好支持太赫兹频段及其独特环境的准备。 一方面，太赫兹系统受益于其准光学性，可以将每一个通信挑战转化为传感机会，从而有助于新一代多功能无线系统，可以执行基本通信之外的多种功能。另一方面，太赫兹系统可以利用智能表面、较低频段和机器学习 (ML) 工具的作用来保证强大的系统性能。我们通过介绍关键的太赫兹 6G 用例及其相关的主要挑战和悬而未决的问题来结束我们的阐述。最终，本文的目标是绘制一个前瞻性的路线图，揭示必要的解决方案和里程碑，使太赫兹频率能够发挥其作为下一代无线系统游戏规则改变者的潜力。