Detection Error Probability Maximization for Relay-Based Covert Communications
Mina Fadhil Hasan, Jihwan Moon · 한국통신학회논문지 · 2025
In this paper, we investigate the reliability of covert transmissions for a relay-based communications system. We specifically consider a scenario where a transmitter sends both public and covert messages to a receiver through a relay, while the detector embedded on the relay attempts to uncover covert messages. Considering the detection error probability (DEP) at the relay, we propose transmission strategies to confuse the detector as much as possible while maintaining a certain level of the reliability of covert transmissions. To this end, we first identify the worst-case DEP, i.e., the minimum possible DEP at the relay. We then solve optimization problems to obtain the optimal power ratio on between public and covert messages that simultaneously maximizes the worst-case DEP and guarantees a minimum covert rate threshold. Two well-known relay protocols, decode-and-forward (DF) and amplify-and-forward (AF), are studied by taking the processing delay difference into consideration. Hence, numerical results reveal not only how system parameters affect the DEP performance in general, but also instances in which DF or AF protocol outperforms each other.