Performance Analysis for Dual-Hop Covert Communication System with Outdated CSI

Covert communication aims to hide the very existence of wireless transmissions which provides a strong security guarantee for wireless networks. This article considers a dual-hop covert communication system with outdated channel state information (CSI). The source transmits the message to the destination via a relay, while the relay wants to transmit its message to the destination and hide the communication process. Under this consideration, we conduct the covert performance analysis of the concerned system under the rate-control scheme. Specially, we derive the closed-forms of the minimum detection error probability (DEP) at the source and the effective covert rate (ECR) at the relay. Further, we study the ECR maximization problem under the DEP constraint. Finally, we provide extensive numerical results to illustrate the achievable covert performance with the outdated CSI. The results indicate that the larger the CSI feedback delay is, the more beneficial it is to the detective, but it is not conducive for the relay to conduct the covert communication.