  In this work, we consider a system of covert communication with the aid of a
full-duplex (FD) receiver to enhance the performance in a more realistic
scenario, i.e., only the channel distribution information (CDI) rather than
channel state information (CSI) is known to a warden. Our work shows that
transmitting random AN can improve the covert communication with the infinite
blocklength. Specifically, we jointly design the optimal transmit power and AN
power by minimizing the outage probability at Bob, and we find that the outage
probability decreases and then increases as the maximum allowable AN power
increases. Intuitively, once AN exceeds an optimal value, the performance will
become worse because of the self-interference. The simulation results also show
that the performance behaviors of CDI and CSI are different. When Willie only
knows CDI, there is an optimal AN power that minimizes Bob's outage
probability. However, when Willie knows CSI, the outage probability
monotonically decreases with AN power.
