Multi-Antenna Covert Communications with Delay Constraint

In this work, we investigate a delay-constrained covert communication system wherein a multi-antenna transmitter is considered for the first time. Under the assumption of Rayleigh fading and a warden existed, beamforming method is adopted to assist in delivering private message covertly. We derive the closed-form expression of the tight average covert probability, which emerges as the covertness metric. Furthermore, an optimization framework for maximal covert throughput incorporating blocklength and transmit power designs is established. In particular, we prove that adopting the maximum blocklength is optimal under the above framework. Our numerical results show the significant superiority of overall rate performance improvement through multi-antenna technology.