Covert communications for dual-hop FSO-RF systems with NOMA.

Area of Science:

• Wireless Communication
• Optical Communication
• Information Security

Background:

• Hybrid optical-radio frequency systems offer combined advantages.
• Non-orthogonal multiple access (NOMA) enhances spectral efficiency.
• Covert communication is crucial for secure data transmission.

Purpose of the Study:

• To propose and analyze a covert hybrid free-space optical-radio frequency system using NOMA.
• To evaluate system performance under a warden's detection.
• To maximize the effective covert rate while ensuring security and reliability.

Main Methods:

• Developing analytical expressions for warden detection error probability and user outage probability.
• Considering two warden location scenarios (inside/outside beam divergence).
• Obtaining the optimal detection threshold for the warden.
• Utilizing Monte Carlo simulations for validation.

Main Results:

• Derived analytical expressions for key performance metrics.
• Identified optimal detection threshold for the warden.
• Presented the maximum effective covert rate under constraints.
• Validated theoretical analysis through simulations.

Conclusions:

• The proposed system effectively balances covertness and performance.
• Analytical models accurately predict system behavior.
• The study provides a framework for designing secure hybrid communication systems.