Terahertz (THz) communications are envisioned as a key technology for sixth generation (6G) wireless systems. The study of underlying THz wireless propagation channels provides the foundations for the development of reliable THz communication systems and their applications. This article provides a comprehensive overview of the study of THz wireless channels. First, the three most popular THz channel measurement methodologies, namely, frequency-domain channel measurement based on a vector network analyzer (VNA), time-domain channel measurement based on sliding correlation, and time-domain channel measurement based on THz pulses from time-domain spectroscopy (THz-TDS), are introduced and compared. Current channel measurement systems and measurement campaigns are reviewed. Then, existing channel modeling methodologies are categorized into deterministic, stochastic, and hybrid approaches. State-of-the-art THz channel models are analyzed, and the channel simulators that are based on them are introduced. Next, an in-depth review of channel characteristics in the THz band is presented. Finally, open problems and future research directions for research studies on THz wireless channels for 6G are elaborated.
翻译:Terahertz(Thz)通信被认为是第六代(6G)无线系统的一项关键技术,对Thz无线传播基本渠道的研究为开发可靠的Thz通信系统及其应用奠定了基础,本条款全面概述了对Thz无线频道的研究。首先,三种最受欢迎的Thz频道测量方法,即基于矢量网络分析仪的频率-多域频道测量、基于滑动相关性的时空信道测量和基于时空光谱仪(THz-TDS)的Thz脉冲的时间-多域频道测量,引入和比较。最后,对现有频道测量系统和测量运动进行审查,然后将现有的频道模型方法分类为确定性、随机性和混合方法。分析了Thz频道的状态模型,并采用了基于这些模型的频道模拟器。接着,介绍了对Thz频带的频道特征的深入审查。最后,为6G无线频道研究提出了公开的问题和未来研究方向。