Performance analysis of cognitive underlay DF relay protocol with Kth best partial relay selection

In this paper, we evaluate performances of cognitive underlay decode-and-forward relay protocol with Kth best partial relay selection. In the proposed protocol, the Kth best secondary relay which is chosen by using the secondary source-relay channel state information (CSI) helps the secondary source to transmit the signal to the secondary destination. We derive exact closed-form expressions of outage probability and average channel capacity over Rayleigh fading channel. The correctness of analytical results is verified by using Monte-Carlo simulations.