Covert Underlay Communication in IoT Networks With Colluding Wardens

We investigate the performance of covert communication in a crowded Internet of Things (IoT) scenario. In this context, we consider overt devices communicating with a gateway, attempting to access the medium randomly in a grant-free manner, while a pair of covert devices leverage the crowded environment to conduct underlay transmissions. Our analysis focuses on the impact of this setup on covert information exchange, accounting for the presence of multiple colluding wardens who share their channel observations with a central processing unit to detect covert transmissions. Numerical results demonstrate that the crowded environment significantly enhances the concealment of covert communication, with the optimization of network parameters, such as the overt transmission probability, covert device transmit power, and target data rates playing crucial roles.