# Throughput Scaling of Covert Communication over Wireless Adhoc Networks

## TL;DR

This paper analyzes how covert communication throughput scales in wireless ad hoc networks with legitimate nodes and wardens, proposing strategies to maximize throughput while maintaining covertness under power constraints.

## Contribution

It introduces novel transmission schemes and bounds for covert communication in large-scale wireless networks with multiple wardens, considering power limitations and preservation regions.

## Key findings

- Throughput scales as a function of network size and warden density.
- Modified multi-hop and hybrid schemes improve covert throughput.
- Matching upper bounds establish fundamental limits under power constraints.

## Abstract

We consider the problem of covert communication over wireless adhoc networks in which (roughly) $n$ legitimate nodes (LNs) and $n^{\kappa}$ for $0<\kappa<1$ non-communicating warden nodes (WNs) are randomly distributed in a square of unit area. Each legitimate source wants to communicate with its intended destination node while ensuring that every WN is unable to detect the presence of the communication. In this scenario, we study the throughput scaling law. Due the covert communication constraint, the transmit powers are necessarily limited. Under this condition, we introduce a preservation region around each WN. This region serves to prevent transmission from the LNs and to increase the transmit power of the LNs outside the preservation regions. For the achievability results, multi-hop (MH), hierarchical cooperation (HC), and hybrid HC-MH schemes are utilized with some appropriate modifications. In the proposed MH and hybrid schemes, because the preservation regions may impede communication along direct data paths, the data paths are suitably modified by taking a detour around each preservation region. To avoid the concentration of detours resulting extra relaying burdens, we distribute the detours evenly over a wide region. In the proposed HC scheme, we control the symbol power and the scheduling of distributed multiple-input multiple-output transmission. We also present matching upper bounds on the throughput scaling under the assumption that every active LN consumes the same average transmit power over the time period in which the WNs observe the channel outputs.