Physical Layer Security for Amplify-and-Forward Relay Aided Cognitive Radio Networks
Abhilash Goswami, Shilpa Rao, Salil Kashyap · 2025
Wireless systems are susceptible to security attacks due to their broadcast nature. Physical layer security (PLS) technique, which exploits channel properties to secure wireless systems, is a promising alternative to traditional shared key based cryptographic methods. We deploy artificial noise (AN)-assisted PLS technique to secure messages from an eavesdropper (ES) in an instantaneous interference-constrained underlay relay-aided cognitive radio network (CRN). An amplify-and-forward (AF) relay, which is intercepted by an ES, forwards the message from the secondary source (SS) to secondary destination (SD). The transmit power of the SS and the relay are restricted by interference constraints of the primary network. We develop a PLS-integrated transmission protocol for the secondary network, wherein SD sends out AN simultaneously when SS transmits the message to the relay, to hinder interception. We determine secondary’s performance using the intercept probability (IP), which is the probability that the SS-relay-ES channel capacity exceeds the difference between transmission and secrecy rates, and the outage probability (OP), which is the probability that the SS-SD channel capacity is less than a specific transmission rate. We derive expressions for OP and IP under Rayleigh fading conditions and validate our theoretical results through Monte Carlo simulations. Our results also show IP and OP variations with changes in secondary’s transmit powers and primary’s interference thresholds. We observe that as the interference threshold reduces and RY-SD channel gain reduces, IP increases. We note that IP is lower when SD transmits AN when compared to the scenario when SD does not transmit AN.