Short-Packet Covert Communication in Underlay Cognitive Radio Networks With Multiple Wardens

In this paper, we investigate short-packet covert communication in underlay cognitive radio networks (CRNs) with multiple randomly distributed wardens. Considering the limited energy of the secondary source (SS) node, SS harvests energy from the secondary destination (SD) node before sending covert messages to SD. The multiple randomly distributed wardens are modeled as a uniform Poisson point process, and a protective domain is set to avoid close-range detection by the wardens. The closed-form expression for the average covert age of information (CAoI) and average covert throughput under the non-combining and combining detection strategies of multiple wardens are derived and analyzed. The transmission power of SS and data packet length under the non-combining and combining detection strategies of multiple wardens are jointly optimized, achieving minimization of the average CAoI and maximization of the average covert throughput. The numerical results show that increasing the data packet length and protection domain is beneficial to improving the maximum average covert throughput of both strategies. The timeliness and covertness of the non-combining detection strategy of multiple wardens are superior to those of the combining detection strategy of multiple wardens.