Secure and Covert Communications for Cooperative Cognitive Radio Networks

This paper addresses the dual challenges of physical layer security and covert communication in cooperative cognitive radio networks (CCRN). Current research typically isolates these issues, either focusing on enhancing security or improving covertness. We guarantee secure and covert communication for the primary user (PU) by enabling the secondary user transmitter (SU-Tx) to play as a cooperative jammer. Our innovative approach jointly studies these aspects using cooperative jamming technology under both perfect and statistical channel state information (CSI) conditions. For perfect CSI, we analyze network security through the secrecy rate and covertness via the detection error probability (DEP), proposing an optimization problem to maximize the secrecy rate under a covert constraint. We employ semidefinite relaxation (SDR) and slack variable relaxation techniques to solve this problem. For statistical CSI, we introduce the covert secrecy throughput (CST) metric to jointly assess security and covertness, using the secrecy outage probability (SOP) and DEP. Simulation experiments validate our methodologies, demonstrating significant improvements in both security and covertness. This study provides a comprehensive framework for enhancing CCRN robustness, bridging a critical gap in current research and paving the way for future developments in secure and covert CRNs.