The Evolution of Applications, Hardware Design, and Channel Modeling for Terahertz (THz) Band Communications and Sensing: Ready for 6G?

TL;DR

This roadmap outlines how terahertz hardware approaches (electronic, photonic, and plasmonic) and channel models have evolved toward 6G readiness, emphasizing ultra-wide bandwidths and highly directional THz links. It argues that no single THz channel model will fit all deployments; instead, environment- and use-case-specific models—accounting for near-field effects, molecular absorption, and mobility—are essential. A key contribution is the introduction of energy-efficiency metrics like the power-waste factor $W$ and Consumption Efficiency Factor $CEF$ to guide end-to-end THz system design. By detailing hardware progress, channel phenomena, and open research directions, the paper provides a practical framework for integrating THz communications and sensing into next-generation networks with cross-layer optimization. The work underscores that while THz systems are becoming feasible, achieving reliable, scalable 6G THz networks will require coordinated advances across devices, waveforms, beam management, and network protocols, all tailored to specific deployment scenarios.

Abstract

For decades, the terahertz (THz) frequency band had been primarily explored in the context of radar, imaging, and spectroscopy, where multi-gigahertz (GHz) and even THz-wide channels and the properties of terahertz photons offered attractive target accuracy, resolution, and classification capabilities. Meanwhile, the exploitation of the terahertz band for wireless communication had originally been limited due to several reasons, including (i) no immediate need for such high data rates available via terahertz bands and (ii) challenges in designing sufficiently high power terahertz systems at reasonable cost and efficiency, leading to what was often referred to as "the terahertz gap". This roadmap paper first reviews the evolution of the hardware design approaches for terahertz systems, including electronic, photonic, and plasmonic approaches, and the understanding of the terahertz channel itself, in diverse scenarios, ranging from common indoors and outdoors scenarios to intra-body and outer-space environments. The article then summarizes the lessons learned during this multi-decade process and the cutting-edge state-of-the-art findings, including novel methods to quantify power efficiency, which will become more important in making design choices. Finally, the manuscript presents the authors' perspective and insights on how the evolution of terahertz systems design will continue toward enabling efficient terahertz communications and sensing solutions as an integral part of next-generation wireless systems.

Figures (13)

• Figure 1: Classification of major use cases for terahertz communications and sensing.
• Figure 2: Power amplifier survey. Saturated output power vs frequency for different electronic front-end technologies wang2023power.
• Figure 3: Energy efficiency of and .
• Figure 4: Chip element area for different circuits/system types.
• Figure 5: Schottky-diode-based frequency multipliers survey. Output power vs frequency for achieved by different groups, including the NASA JPL, Virginia Diodes Inc (VDI), ACST. LERMA at the Observatoire de Paris/C2N, and Chalmers University.