Analysis of Terahertz Orbital Angular Momentum Communications for 6G: Propagation Constraints, Atmospheric Windows, and Deployment Feasibility
Hsing-Cheng Liu
Signals and Telecommunication Journal, Vol. 15, No. 1, 2025.
DOI: https://doi.org/10.6025/stj/2026/15/1/15-28
Link: https://www.dline.info/stj/fulltext/v15n1/stjv15n1_2.pdf
Abstract:
This research document comprehensively examines terahertz (THz) communications leveraging orbital
angular momentum (OAM) for next generation 6G wireless systems. It establishes that OAM provides an
additional spatial multiplexing dimension, thereby enhancing spectral efficiency beyond conventional
techniques. However, the analysis reveals fundamental physical constraints limiting practical deployment.
Key findings demonstrate that THz propagation is governed by a dual loss mechanism: free space path loss
and severe frequency selective molecular absorption particularly from water vapor resonances at 183, 325,
and 380 GHz. These absorption peaks create distinct atmospheric transmission windows while rendering
other bands unusable beyond short distances. Environmental factors critically impact performance: humidity
variations introduce 6+ dB of path loss uncertainty at 500 m, and beam divergence combined with stringent
alignment requirements further constrain reliability.
The study presents a physics based simulation dataset comprising 270,000 samples across four deployment
scenarios (laboratory, indoor, urban, and high mobility environments), characterized by 33 parameters
spanning atmospheric conditions, channel physics, hardware impairments, and performance metrics. Results
confirm THz OAM systems are inherently range limited (<100-500 m), environment sensitive, and require
operation within specific atmospheric windows. Successful implementation demands adaptive strategies:
dynamic frequency selection, high gain directional antennas (ï‚³ 25 dBi), and AI-assisted beam steering. The
technology is best suited for specialized short range applications indoor 6G networks, wireless backhaul,
and device to device communications where environmental conditions can be controlled or dynamically
adapted.