Multiantenna Joint Covert Communication System With Finite Blocklength

Abstract

Multiantenna technique can provide a substantial rate gain for wireless communication; however, when applied in covert wireless communication, the potential detecting risk of pilot transmission is always neglected. In this article, for the first time, we consider the effect of pilot leakage on the performance of covert communication over a finite transmission blocklength. First, we construct a general analysis model of multiantenna joint covert communication (JTCC), where the uplink covert pilot, the imperfect channel estimation issues, and the downlink covert communication is taken into account. Second, we evaluate the covertness performance of the proposed system in which an independent detection scheme (IDS) and two joint detection schemes (JDSs) are adopted at an unintended warden, respectively. In particular, the closed-form expressions of tight average covert probability are derived under the different detection schemes. Third, we establish an optimization framework for the covert throughput maximization subject to the constraints of covertness, reliability, and blocklength. Moreover, a simple and robust solution is provided by jointly designing the pilot length and the transmit power. Numerical results highlight the advantages of the JTCC system in resisting pilot detection and indicate the tradeoff of pilot design between the achievable covertness, the required reliability, and the overall rate performance.