ABSTRACT
We present secrecy performance of a two-way communication (TWC) with a number of amplify and forward (AF) relays in a cognitive radio network (CRN) as well as TWC with the help of DF relays. A TWC with multiple untrusted half-duplex AF relays is set up in an underlay CRN where two sources are not directly connected due to shadowing and path loss. In this cognitive network, two sources share their information to each other over two phases via an intermediate relay selected among multiple AF relays. A power-splitting scheme based energy harvesting from radio frequency signal is considered at the relay. Further, the AF relays are untrusted and eavesdrops the message also. Due to the CRN, the transmit power of the transmitting nodes are controlled under the cognitive constraints such as outage probability threshold of the primary network. Further, the TWC is analyzed with DF relays where an external eavesdropper eavesdrops the message from both the sources but not simultaneously. We have evaluated the physical layer security (PLS) through a metric known as secrecy outage probability (SOP). We have derived SOP in closed-form expression and presented in for both the scenarios of investigations. The analytical results, based on the closed-form expression, are justified by the MATLAB-based simulation results. We observe that PLS increases with an increase in the number of relays, primary network transmit power, and transmit power of the cognitive device. In TWC with DF relays, an optimal value of transmit power of a source and fraction of supply power to the relay are obtained at which secrecy performance is maximized.
