On physical-layer security in underlay cognitive radio networks with full-duplex wireless-powered secondary system

We consider an underlay cognitive radio system, in which a source in a secondary system transmits information to a full-duplex (FD) wireless-powered destination node in the presence of an eavesdropper. In particular, the destination node is equipped with a single receiving antenna and a single transmitting antenna to enable FD operation. The receiving antenna can simultaneously receive information and energy from the source through power-splitter architecture. The received energy is then used in the transmitting antenna to send jamming signals to degrade the eavesdropper's decoding capacity. Upper and lower bounds of probability of strictly positive secrecy capacity (SPSC) have been derived. Numerical results show that under the condition that the interference from the source and destination at primary user's receiver is smaller than the interference temperature limit, upper and lower bounds merge together to become the exact SPSC.