Covert Wireless Communication with Artificial Noise Generation

TL;DR

This paper investigates covert wireless communication in environments with friendly nodes generating artificial noise, showing how to maximize covert data transmission rates while avoiding detection by adversaries, considering various node densities and adversary configurations.

Contribution

It introduces a strategy where the closest friendly node generates artificial noise to enhance covert communication, extending the limits of covert throughput in complex environments.

Findings

Artificial noise from the closest friendly node improves covert throughput.

Maximum covert bits depend on node density, path-loss exponent, and adversary count.

No higher covert throughput is possible beyond established bounds.

Abstract

Covert communication conceals the transmission of the message from an attentive adversary. Recent work on the limits of covert communication in additive white Gaussian noise (AWGN) channels has demonstrated that a covert transmitter (Alice) can reliably transmit a maximum of $\mathcal{O}\left(\sqrt{n}\right)$ bits to a covert receiver (Bob) without being detected by an adversary (Warden Willie) in $n$ channel uses. This paper focuses on the scenario where other friendly nodes distributed according to a two-dimensional Poisson point process with density $m$ are present in the environment. We propose a strategy where the friendly node closest to the adversary, without close coordination with Alice, produces artificial noise. We show that this method allows Alice to reliably and covertly send $\mathcal{O}(\min\{{n,m^{\gamma/2}\sqrt{n}}\})$ bits to Bob in $n$ channel uses, where $\gamma$ is the path-loss exponent. Moreover, we also consider a setting where there are $N_{\mathrm{w}}$ collaborating adversaries uniformly and randomly located in the environment and show that in $n$ channel uses, Alice can reliably and covertly send $\mathcal{O}\left(\min\left\{n,\frac{m^{\gamma/2} \sqrt{n}}{N_{\mathrm{w}}^{\gamma}}\right\}\right)$ bits to Bob when $\gamma >2$, and $\mathcal{O}\left(\min\left\{n,\frac{m \sqrt{n}}{N_{\mathrm{w}}^{2}\log^2 {N_{\mathrm{w}}}}\right\}\right)$ when $\gamma = 2$. Conversely, we demonstrate that no higher covert throughput is possible for $\gamma>2$.