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
$k$
th 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.