Impact of Correlated Fading Channels on Cognitive Relay Networks With Generalized Relay Selection

In this paper, we investigate the secrecy performance of dual-hop decode-and-forward cognitive relay networks taking into account the channel correlation between the main and wiretapping channels. For the enhancement of the secrecy performance, a generalized relay selection scheme is utilized, where the kth strongest relay node is selected based on the main channel. In order to analyze the impact of key parameters on the secrecy performance, we first derive the exact closed-form expression for secrecy outage probability (SOP) of the considered networks. Moreover, to extract deep insights, the asymptotic approximation for SOP in high main-to-eavesdropper ratio (MER) regime is also provided. Our theoretical results as well as simulations demonstrate that: 1) the channel correlation does not affect the achievable secrecy diversity order, but has a positive impact on the secrecy coding gain in high MER regime; 2) the secrecy diversity order is decided by the generalized selection coefficient and the number of relays that can successfully decode the information transmitted from the secondary transmitter; and 3) the total amount of relays cannot influence the secrecy diversity order directly, but has a significant impact on the secrecy coding gain.