On the security of cognitive radio networks: Cooperative jamming with relay selection

We consider the problem of secret communication through a relay assisted downlink cognitive interference channel in which secondary base station (SBS) is allowed to transmit simultaneously with the primary base station (PBS) over the same channel instead of waiting for an idle channel which is traditional for a cognitive radio. We propose a cooperative jamming (CJ) scheme to improve the secrecy rate where multiple relays transmit weighted jamming signals to create additional interferences in the direction of eavesdropper with the purpose of confusing it. The proposed CJ scheme is designed to cancel out interference at the secondary receiver (SR) while maintaining interference at the primary receiver (PR) under a certain threshold. Moreover, we develop an algorithm to select the effective relays which meet the target secrecy rate. Our results show that with the help of developed algorithm, a suitable CJ scheme can be designed to improve the secrecy rate at SR to meet the target secrecy rate.