25 research outputs found
Covert Communication in Fading Channels under Channel Uncertainty
A covert communication system under block fading channels is considered where
users experience uncertainty about their channel knowledge. The transmitter
seeks to hide the covert communication to a private user by exploiting a
legitimate public communication link while the warden tries to detect this
covert communication by using a radiometer. We derive the exact expression for
the radiometers optimal threshold which determines the performance limit of the
wardens detector. Furthermore for given transmission outage constraints the
achievable rates for legitimate and covert users are analyzed while maintaining
a specific level of covertness. Our numerical results illustrate how the
achievable performance is affected by the channel uncertainty and required
level of covertness.Comment: to appear in IEEE VTC2017-Sprin
Covert Communications with a Full-Duplex Receiver over Wireless Fading Channels
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.ARC Discovery Projects Grant DP15010390
Achieving Covert Wireless Communications Using a Full-Duplex Receiver
Covert communications hide the transmission of a message from a watchful
adversary while ensuring a certain decoding performance at the receiver. In
this work, a wireless communication system under fading channels is considered
where covertness is achieved by using a full-duplex (FD) receiver. More
precisely, the receiver of covert information generates artificial noise with a
varying power causing uncertainty at the adversary, Willie, regarding the
statistics of the received signals. Given that Willie's optimal detector is a
threshold test on the received power, we derive a closed-form expression for
the optimal detection performance of Willie averaged over the fading channel
realizations. Furthermore, we provide guidelines for the optimal choice of
artificial noise power range, and the optimal transmission probability of
covert information to maximize the detection errors at Willie. Our analysis
shows that the transmission of artificial noise, although causes
self-interference, provides the opportunity of achieving covertness but its
transmit power levels need to be managed carefully. We also demonstrate that
the prior transmission probability of 0.5 is not always the best choice for
achieving the maximum possible covertness, when the covert transmission
probability and artificial noise power can be jointly optimized.Comment: 13 pages, 11 figures, Accepted for publication in IEEE Transactions
on Wireless Communication