Performance Comparison of Relay-Based Covert Communications: DF, CF and AF

Area of Science:

• Wireless communication systems
• Information theory
• Signal processing

Background:

• Covert communication is crucial for secure data transmission.
• Relay systems enhance communication range and reliability.
• Optimizing covertness while maintaining communication rates is a key challenge.

Purpose of the Study:

• To analyze and compare the performance of decode-and-forward (DF), compress-and-forward (CF), and amplify-and-forward (AF) relay systems for covert communications.
• To optimize power allocation between public and covert messages to maximize covert rates, considering the relay's detection error probability (DEP).
• To conduct a delay-aware comparison of DF, CF, and AF systems and examine their asymptotic behaviors.

Main Methods:

• Investigated covert communication performance across DF, CF, and AF relay architectures.
• Optimized power distribution to maximize covert rate while minimizing DEP at the relay.
• Derived closed-form covert rates and performed delay-aware comparisons.
• Analyzed system performance under various channel models and asymptotic conditions.

Main Results:

• Compress-and-forward (CF) or amplify-and-forward (AF) relays generally outperform decode-and-forward (DF) relays at high source transmit power or low relay transmit power.
• The performance hierarchy among DF, CF, and AF relays is sensitive to system parameters like processing delay, quality of service for public messages, and DEP threshold, especially at high relay transmit power.
• Numerical results validated the performance comparisons across different channel models.

Conclusions:

• The choice between DF, CF, and AF relay systems for covert communications depends significantly on power constraints and system parameters.
• Optimal power allocation strategies are essential for maximizing covert rates in relay-assisted covert communication systems.
• Further research can explore more complex relaying protocols and realistic channel conditions for enhanced covert communication security.