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 'd-{a,w}=\omega (n^{1/(2\alpha)})' , Alice can reliably and covertly transmit '\mathcal {O}(\log -{2} {n})' bits to Bob in 'n' 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.