Covert Communications in a Hybrid DF/AF Relay System.

Area of Science:

• Wireless communication systems
• Information security
• Signal processing

Background:

• Covert communication is essential for transmitting sensitive information undetected.
• Hybrid relay systems offer flexibility but require optimal mode selection.
• Existing methods may lack efficiency in balancing covert rate and complexity.

Purpose of the Study:

• To develop optimal and low-complexity criteria for mode selection in hybrid DF/AF relay systems.
• To maximize the covert communication rate while minimizing detection probability.
• To analyze the trade-offs between delay, covert rate, and computational complexity.

Main Methods:

• Analysis of delay-aware achievable covert rates for individual DF and AF modes.
• Derivation of an optimal DF/AF mode selection criterion.
• Proposal of a simplified, low-complexity selection criterion for practical applications.
• Numerical simulations to evaluate performance.

Main Results:

• The optimal criterion maximizes covert rate by considering delay-aware achievable rates.
• The low-complexity criterion significantly reduces computational time.
• Achieved covert rate gains up to 50% and running time gains up to 20% for specific system parameters.
• Demonstrated effectiveness of proposed criteria in enhancing covert communication performance.

Conclusions:

• The proposed DF/AF mode selection criteria effectively enhance covert communication rates.
• The low-complexity criterion offers practical advantages for real-world implementations.
• This research contributes to more secure and efficient wireless communication systems.