Guest Editorial Advanced Signal Processing for Terahertz Communications in 6G and Beyond Networks

Terahertz (THz) communications has been envisioned as an enabling and highly promising technology for the sixth generation (6G) and beyond wireless networks which aim to provide full and unlimited wireless connectivity for the ubiquitous intelligent information society of 2030 and beyond. In particular, the ultra-wide THz band from 0.1 to 10 THz offers enormous potential to alleviate the spectrum scarcity and break the capacity limitation of emerging wireless systems, such as the fifth generation (5G) wireless networks. This will undoubtedly support epoch-making wireless applications that demand ultra-high quality of service requirements and multi-terabits/s data transmission in the 6G and beyond era, such as holographic communications, immersive extended reality, ultra-fast backhaul and wireless local area networks, and wireless high-bandwidth secure transmission. Moreover, THz transceivers and antennas boast an incredibly compact size, reaching sub-millimetric dimensions. This miniaturization enables the seamless integration of extremely small radios into various environments, giving rise to ground-breaking applications, e.g., the Internet of Nano-Things and wireless networks-on-chip. Furthermore, the utilization of the THz band extends beyond traditional radar and localization, opening doors to novel wireless sensing capabilities and underpinning cutting-edge applications such as healthcare nano-bio-sensing. Due to the aforementioned advantages, an unprecedented amount of spectrum within the 0.275–0.45 THz band was opened for land mobile and fixed service in 6G after World Radio Conference 2019. Additionally, the IEEE 802.15.3 d standard has been established as the first wireless standard in the sub-THz band (specifically, 253–322 GHz) to support data rates of 100 gigabit/s and above.