Covert Communications with Constrained Age of Information

TL;DR

This paper explores the balance between information freshness and covertness in covert communications, proposing an optimization of transmit probability under AoI constraints using artificial noise from a full-duplex receiver.

Contribution

It introduces a novel formulation linking AoI constraints with covert communication strategies, revealing that optimal transmit probability varies and is not always 0.5.

Findings

Optimal transmit probability is not always 0.5.

Average AoI constraints influence transmit power and covertness.

A positive lower bound on transmit power exists for non-zero covertness.

Abstract

In this letter, we consider the requirement of information freshness in covert communications for the first time. With artificial noise (AN) generated from a full-duplex (FD) receiver, we formulate a covertness maximization problem under the average age of information (AoI) constraint to optimize the transmit probability of information signal. In particular, the transmit probability not only represents the generation rate of information signal but also represents the prior probability of the alternative hypothesis in covert communications, which builds up a bridge between information freshness and communication covertness. Our analysis shows that the best transmit probability is not always 0.5, which differs from the equal prior probabilities assumption in most related works on covert communications. Furthermore, the limitation of average AoI enlarges the transmit probability at the cost of the covertness reduction and leads to a positive lower bound on the information transmit power for non-zero covertness.