Additive white Gaussian noise

Covert

Philosophy

Power (physics)

Geometry

Constraint (computer-aided design)

Combinatorics

Physics

Transmitter power output

Channel (broadcasting)

Cloud computing security

Mathematics

Transmitter

Quantum mechanics

Operating system

Computer science

Cloud computing

Security information and event management

Algorithm

Linguistics

Block (permutation group theory)

Computer network

Covert channel

IEEE Transactions on Information Forensics and Security

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.

Delay-Intolerant Covert Communications With Either Fixed or Random Transmit Power