Seven Defining Features of Terahertz (THz) Wireless Systems: A Fellowship of Communication and Sensing

Abstract

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 highrate 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) THztailored wireless architectures, 3) Synergy with lower frequency bands, 4) Joint sensing and communication systems, 5) PHYlayer 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

How Crucial Is It for 6G Networks to Be Autonomous?

“…There are a number of applications, e.g. holographic communications, that are bandwidth intensive and thus require opening up new and wider spectrum such as terahertz (THz) bands [9]. On the other hand, other use cases involve communications between multiple small devices that mainly work on batteries set the trend for energy sustainability.…”

“…Facilitating the 6G high-rate highmobility use cases (e.g. autonomous vehicles), mmWave is considered to be one of the 6G enabling technologies [9]. MmWave communications, ranging from 24 GHz to 300 GHz, will be one of the leading candidate systems for future wireless communications [10].…”

“…The 0.275 to 3 terahertz band spectrum is the main part of the THz band, which ranges from 0.1 to 10 terahertz, to be used for cellular communications, according to International Telecommunication Union Radio Communication Sector (ITU-R) guidelines [17]. Such abundance in spectrum portend to offer extremely high data rates [9].…”

Learning-based Prediction, Rendering and Transmission for Interactive Virtual Reality in RIS-Assisted Terahertz Networks

“…In [26], the network architecture and spectrum access of AI-enabled Internet of Things in 5G and 6G networks were proposed. In [27], a comprehensive roadmap outlining the seven defining features of THz wireless systems that guarantee a successful deployment in future wireless generations was proposed. In [28] and [29], a novel hybrid beamforming scheme for multi-hop RISassisted communication networks was proposed to improve the coverage range of THz networks.…”

Indoor Propagation Measurements with Sekisui Transparent Reflectors at 28/39/120/144 GHz

“…M illimeter wave (mmWave) and Terahertz bands are crucial enablers of beyond 5G (B5G)/6G wireless communications. In particular, the THz communication is recognized as one of the nine key communication technology enablers [1], due to its large bandwidth and its support of new possibilities ranging from augmented/virtual reality to highresolution positioning and autonomous driving [2]. One of the numerous challenges in a THz/mmWave network, is the requirement of the line of sight (LoS) or at least a strong first-order reflected non-LoS (NLoS) path to form a link, as diffraction is not significant at these frequencies.…”