  In this work, we propose a covert communication scheme where the transmitter
attempts to hide its transmission to a full-duplex receiver, from a warden that
is to detect this covert transmission using a radiometer. Specifically, we
first derive the detection error rate at the warden, based on which the optimal
detection threshold for its radiometer is analytically determined and its
expected detection error rate over wireless fading channels is achieved in a
closed-form expression. Our analysis indicates that the artificial noise
deliberately produced by the receiver with a random transmit power, although
causes self-interference, offers the capability of achieving a positive
effective covert rate for any transmit power (can be infinity) subject to any
given covertness requirement on the expected detection error rate. This work is
the first study on the use of the full-duplex receiver with controlled
artificial noise for achieving covert communications and invites further
investigation in this regard.
