Covert Wireless Communication in IoT Network: From AWGN Channel to THz Band

Covert communication can prevent an adversary from knowing that a transmission has occurred between two users. In this article, we consider covert wireless communications in an Internet-of-Things (IoT) network with dense deployment, where an IoT device experiences not only the background noise but also the aggregates interference from other Tx devices. Our results show that in a dense IoT network with lower frequency AWGN channels, when the distance between Alice and the adversary Willie <inline-formula> <tex-math notation="LaTeX">$d_{a,w}=\omega (n^{1/(2\alpha)})$ </tex-math></inline-formula>, Alice can reliably and covertly transmit <inline-formula> <tex-math notation="LaTeX">$\mathcal {O}(\log _{2}\sqrt {n})$ </tex-math></inline-formula> bits to Bob in <inline-formula> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> channel uses. In an IoT network with terahertz (THz) band, covert communication is more difficult because Willie can simply place a receiver in the narrow beam between Alice and Bob in order to detect or block their line-of-sight communications. We demonstrated that covert communication is still possible in this occasion by utilizing the reflection or diffuse scattering from a rough surface. From the physical-layer security perspective, covert communication can enhance the security of IoT network from the bottom layer.