Terahertz Channel Propagation Phenomena, Measurement Techniques and Modeling for 6G Wireless Communication Applications: A Survey, Open Challenges and Future Research Directions

Abstract

The Terahertz (THz) band (0.3-3.0 THz), spans a great portion of the Radio Frequency (RF) spectrum that is mostly unoccupied and unregulated. It is a potential candidate for application in Sixth-Generation (6G) wireless networks, as it has the capabilities of satisfying the high data rate and capacity requirements of future wireless communication systems. Profound knowledge of the propagation channel is crucial in communication systems design, which nonetheless is still at its infancy, as channel modeling at THz frequencies has been mostly limited to characterizing fixed Point-to-Point (PtP) scenarios up to 300 GHz. Provided the technology matures enough and models adapt to the distinctive characteristics of the THz wave, future wireless communication systems will enable a plethora of new use cases and applications to be realized, in addition to delivering higher spectral efficiencies that would ultimately enhance the Quality-of-Service (QoS) to the end user. In this paper, we provide an insight into THz channel propagation characteristics, measurement capabilities, and modeling techniques for 6G communication applications, along with guidelines and recommendations that will aid future characterization efforts in the THz band. We survey the most recent and important measurement campaigns and modeling efforts found in literature, based on the use cases and system requirements identified. Finally, we discuss the challenges and limitations of measurement and modeling at such high frequencies and contemplate the future research outlook toward realizing the 6G vision.

Reflective Metasurface With Steered OAM Beams for THz Communications

“…Frequencies at low spectrum blocks of the THz band (below 300 GHz) are not exposed to high levels of molecular absorption, allowing for short-range communications up to a few hundred meters [20]. Accordingly, it would be doable to operate THz IRSs to bypass the obstacles between the base stations (BSs) and users to achieve NLoS communications via short-distance links.…”

Ambit-Process based Spatial-Wideband MIMO Channel Model for Sub-THz Urban Microcellular Communication

“…With measurements currently ongoing, the 140 GHz band lacks a comprehensive geometrybased stochastic model that would provide a baseline to ongoing THz research in this direction [25]. Even with the advent of subsequent accurate models, stochastic channel models would still remain attractive for approximate scalable simulations.…”

Caching Through the Skies: The Case of LEO Satellites Connected Edges for 6G and Beyond

“…With data rates ranging from 100 to 200 Gbps depending on frequency and modulation technique, antenna directivity is critical for signal arrival. It is also noteworthy to mention that channel estimation relies heavily on link distance, Doppler sampling rate, and multipath resolution [7].…”