Covert Communications under Multiple-Antenna Eavesdropping without Channel State Information

In this paper, we investigate covert communications under multiple-antenna eavesdropping, and explore the impact of the channel state information (CSI) at the adversary on the covertness of the system with noise uncertainty. We first analyze the detection performance of the adversary without the CSI of the eavesdropping channel. Specially, the generalized likelihood ratio (GLR) detection is adopted to handle this scenario. Then, a more practical scenario with the uncertain noise power at the adversary is considered, and the covertness of the system is analyzed. In addition, the optimal transmit power at the legitimate transmitter is derived theoretically to maximize the covert throughput. Finally, we present numerical results to compare the covert throughputs when the adversary knows or doesn't know the CSI. The results demonstrate the significance of unknown CSI at the adversary when considering the covert throughput of the system.