17 research outputs found
Covert communication with finite blocklength in AWGN channels
Covert communication is to achieve a reliable transmission
from a transmitter to a receiver while guaranteeing an
arbitrarily small probability of this transmission being detected
by a warden. In this work, we study the covert communication
in AWGN channels with finite blocklength, in which the number
of channel uses is finite. Specifically, we analytically prove that
the entire block (all available channel uses) should be utilized to
maximize the effective throughput of the transmission subject
to a predetermined covert requirement. This is a nontrivial
result because more channel uses results in more observations
at the warden for detecting the transmission. We also determine
the maximum allowable transmit power per channel use, which
is shown to decrease as the blocklength increases. Despite the
decrease in the maximum allowable transmit power per channel
use, the maximum allowable total power over the entire block is
proved to increase with the blocklength, which leads to the fact
that the effective throughput increases with the blocklength.ARC Discovery Projects Grant DP15010390
Delay-Intolerant Covert Communications with Either Fixed or Random Transmit Power
In this paper, we study delay-intolerant covert communications in additive white Gaussian noise (AWGN) channels with a finite block length, i.e., a finite number of channel uses. Considering the maximum allowable number of channel uses to be N, it is not immediately clear whether the actual number of channel uses, denoted by n, should be as large as N or smaller for covert communications. This is because a smaller n reduces a warden’s chance to detect the communications due to fewer observations, but also reduces the chance to transmit information. We show that n=N is indeed optimal to maximize the amount of information bits that can be transmitted, subject to any covert communication constraint in terms of the warden’s detection error probability. To better make use of the warden’s uncertainty due to the finite block length, we also propose to use uniformly distributed random transmit power to enhance covert communications. Our examination shows that the amount of information that can be covertly transmitted logarithmically increases with the number of random power levels, which indicates that most of the benefit of using random transmit power is achieved with just a few different power levels.This work was supported by the Australian Research Council’s Discovery Projects under Grant DP180104062