Strategies in Covert Communication with Imperfect Channel State Information

This paper considers the problem of covert communication over a multiple-input single-output channel (MISO) in the case of the imperfect channel state information. The transmitter wants to communication with the receiver while the eavesdropper detects the existence of the transmission. We first study the scenario that the accurate channel state information (CSI) is known and show that the condition achieving the positive rate by the beamforming vector. However, because of the non-cooperation between the transmitter and the eavesdropper, we consider the CSI is imperfect. There are estimation errors for the transmitter. When the positive rate can not be achieved, the objective is to maximize the communication rate. We discuss the deterministic bounded CSI errors for the covert communication. Robust beamforming and the transmitter power is investigated, which can be transformed as a second order cone programming (SCOP) problem. We consider the line-of-sight (LoS) channel and the linear array antenna model. Comparing with the perfect CSI, the results show that the strategy of the transmitter is more conservative under the imperfect CSI. The capacity declines by the estimation errors.