Covert backscatter communication with directional MIMO

TL;DR

This paper introduces a covert backscatter communication protocol using directional MIMO antennas, enabling reliable and covert data transmission that surpasses traditional limits, with practical implications for IoT security.

Contribution

It demonstrates that covert communication can be scaled linearly with channel uses using directional MIMO, breaking the square-root law barrier.

Findings

Achieves $ heta(n)$ covert bits over $n$ channel uses.

Utilizes directional MIMO to hide the presence of the tag.

Provides the first practical evidence for covert backscatter communication.

Abstract

We study a backscatter communication protocol over a AWGN channel, where a transmitter illuminates a tag with a directional multi-antenna. The tag performs load modulation on the signal while hiding its physical presence from a warden. We show that, if the transmitter-to-tag channel is inaccessible to the warden, then $\Theta(n)$ reliable and covert bits can be transmitted over $n$ channel usages. This overcomes the square-root law for covert communication. This paper provides the first evidence for practical implementation of covert backscatter communication, with potential applications in IoT security.