In this work, we investigate a covert communication system in power Internet of Things (IoT) networks, wherein \( N \) users transmit confidential their messages to Bob while being monitored by a warden, Willie. To optimize this covert communication system, we introduce two user selection criteria: the first criterion aims to maximize the channel gain of the Alice-Bob link, thereby enhancing the transmission efficiency to Bob; the second criterion seeks to minimize the channel gain of the Alice-Willie link, effectively reducing the probability of detection by Willie. We rigorously evaluate the system performance under these criteria by deriving analytical expressions for the system secrecy outage probability (SOP). Finally, simulation results are provided to illustrate the influence of key system parameters, including the transmit signal-to-noise ratio and the average channel gains of both Alice-Bob and Alice-Willie links, on the system SOP. In particular, the system covert performance can be effectively enhanced by increasing the number of users. Such findings offer significant insights into the design and optimization of covert communication strategies in industrial IoT networks.
