Study on covert rate in the D2D networks with multiple non-colluding wardens

This paper investigates the covert communication of cellular link in the device -to -device (D2D)-enabled underlaying cellular network, including a base station, a cellular user, a D2D pair, and multiple non-colluding wardens. To conduct covert communication between the base station and the cellular user without being detected by the wardens, the underlaid D2D pair transmits with a random power to add uncertainty to wardens. We first model the detection of multiple non-colluding wardens, and the average minimum detection error probability of the worst case is derived. To measure the covert performance of the cellular link, the average covert rate of the cellular link and the outage probability of the D2D link are explored. Then, we formulate an optimization problem of maximizing the average covert rate under the constraint of the average minimum detection error probability, and an optimization algorithm is designed to solve the optimization problem to identify the optimal transmit power of the D2D pair. Last, the extensive numerical results are presented to show the impacts of network parameters on the covert performance, which indicates that although D2D communication causes interference to the cellular link, it can also help achieve covert communication by carefully designing its maximum transmit power.