[Paper Review] Physical Layer Security of Terahertz and Infrared Wireless Links in Atmospheric Turbulence

Yu Mei, Xiao Zhang+3 more|arXiv (Cornell University)|Sep 2, 2020

Optical Wireless Communication Technologies23 references2 citations

TL;DR

This paper investigates physical layer security in terahertz (THz) and infrared (1550 nm) wireless links under atmospheric turbulence, modeling attenuation from turbulence, gaseous absorption, and beam divergence. It demonstrates that THz links achieve higher secrecy capacity and lower outage probability than IR links, indicating superior physical layer security in turbulent atmospheric conditions.

ABSTRACT

The future applications of terahertz (THz) wireless communication require investigations on link secrecy performance in all kinds of atmospheric conditions, including fog, snow, rain and atmospheric turbulence. Here, we present theoretical studies on physical layer security of point-to-point THz and infrared (IR) wireless links in atmospheric turbulence with a potential eavesdropper outside of the link path. Attenuations due to turbulence, gaseous absorption and beam divergence are included in the model to predict the propagation of both links. Secrecy capacity and outage probability of the THz links are calculated and compared with that of an IR (1550 nm) link. Dependences of link security on eavesdropper's position, atmospheric visibility, turbulence strength and intended data transmission rate are also presented and analyzed. We find that the THz link owns higher security at physical layer than the IR link.

Motivation & Objective

• To analyze the physical layer secrecy performance of terahertz (THz) and infrared (IR) wireless links under atmospheric turbulence.
• To evaluate the impact of atmospheric conditions—such as visibility, turbulence strength, and eavesdropper position—on link security.
• To compare secrecy capacity and outage probability between THz and IR (1550 nm) links in realistic propagation environments.
• To determine the conditions under which THz links outperform IR links in terms of physical layer security.

Proposed method

• Modeling signal propagation for both THz and IR links using a combined attenuation model including atmospheric turbulence, gaseous absorption, and beam divergence.
• Employing stochastic channel models to represent the statistical effects of atmospheric turbulence on signal fading.
• Calculating secrecy capacity based on the difference between the main link capacity and the eavesdropper's channel capacity.
• Deriving outage probability as the probability that secrecy capacity falls below a target rate, under varying turbulence and visibility conditions.
• Simulating and comparing performance metrics across different eavesdropper positions relative to the main link path.
• Using analytical expressions to quantify the dependence of security metrics on transmission rate, atmospheric visibility, and turbulence strength.

Experimental results

Research questions

• RQ1 How does atmospheric turbulence affect the secrecy capacity of THz and IR wireless links?
• RQ2 What is the impact of eavesdropper location on the physical layer security of THz and IR links?
• RQ3 How do variations in atmospheric visibility and turbulence strength influence the secrecy outage probability?
• RQ4 How does the intended data transmission rate affect the security performance of THz and IR links?
• RQ5 Under what conditions does the THz link provide superior physical layer security compared to the IR link?

Key findings

• THz links exhibit higher secrecy capacity than IR (1550 nm) links under the same atmospheric conditions, indicating better physical layer security.
• The secrecy outage probability is lower for THz links compared to IR links, especially in moderate to strong turbulence conditions.
• Eavesdropper position significantly affects security, with the highest secrecy performance observed when the eavesdropper is located far from the main link path.
• As atmospheric visibility decreases, the secrecy capacity of both links degrades, but the THz link maintains a performance advantage over the IR link.
• Higher data transmission rates increase the secrecy outage probability for both links, but the THz link remains more resilient under high-rate transmission.
• Turbulence strength has a stronger negative impact on IR links than on THz links, further enhancing the security advantage of THz in high-turbulence environments.