Attenuation and Loss of Spatial Coherence Modeling for Atmospheric Turbulence in Terahertz UAV MIMO Channels

TL;DR

This paper models the effects of atmospheric turbulence on THz UAV MIMO channels, revealing significant attenuation and loss of spatial coherence that impact high-frequency, long-distance communications.

Contribution

It introduces a novel model for turbulence-induced attenuation and spatial coherence loss in THz UAV MIMO channels, considering frequency and altitude dependencies of atmospheric turbulence.

Findings

Turbulence causes up to 10 dB attenuation below 1 THz over 10 km.

Loss of spatial coherence can add 10 dB additional loss in ultra-massive MIMO systems.

The turbulence attenuation depends on altitude and frequency, affecting system design.

Abstract

Terahertz (THz) wireless communications have the potential to realize ultra-high-speed and secure data transfer with miniaturized devices for unmanned aerial vehicle (UAV) communications. The atmospheric turbulence due to random airflow leads to spatial inhomogeneity of the communication medium, which is yet missing in most existing studies, leading to additional propagation loss and even loss of spatial coherence (LoSC) in MIMO systems. In this paper, the attenuation and loss of spatial coherence for atmospheric turbulence are modeled in THz UAV MIMO channels. Specifically, the frequency- and altitude-dependency of the refractive index structure constant (RISC), as a critical statistical parameter characterizing the intensity of turbulence, is first investigated. Then, the LoSC, fading, and attenuation caused by atmospheric turbulence are modeled, where the turbulence-induced fading is modeled by a Gamma-Gamma distribution, and the turbulence attenuation as a function of altitude and frequency is derived. Numerical results show that the turbulence leads to at most 10 dB attenuation with frequency less than 1 THz and distance less than 10 km. Furthermore, when the distance is 10 km and the RISC is 10^-9m^(-2/3), the loss of spatial coherence effect leads to 10 dB additional loss for a 1024*1024 ultra-massive MIMO system.