Secrecy Performance of SIMO Underlay Cognitive Radio Networks Over α – μ Fading Channels

This paper investigates the secrecy performance of a single-input multiple-output (SIMO) based underlay cognitive radio networks. In particular, a single-antenna secondary transmitter transmits its secret message to a multi-antenna equipped secondary node in the presence of a multi-antenna equipped passive eavesdropper under a peak interference constraint at the single-antenna primary receiver. We proficiently derive the expressions for secrecy outage probability (SOP), intercept probability, and ergodic secrecy capacity (ESC) for the considered system over α-μ fading channels. Further, we carry out the asymptotic analysis of SOP and intercept probability under two cases of interest; 1) when the average signal-to-noise ratio (SNR) of the main link, i.e., between the secondary source and secondary destination, goes to infinity with a fixed average SNR of wiretap link between the secondary source and secondary eavesdropper, and 2) when the SNRs of both the main and wiretap links tend to infinity. We can infer that a secrecy diversity order of α
_D
N
_D
μ
_D
/2 can be achieved under case 1, where α
_D
and μ
_D
are the main link fading parameters, and N
_D
denotes the number of antennas at the destination. Whereas, under case 2, the system's secrecy diversity order becomes zero. Moreover, we also present some interesting findings for the ESC when the interference constrained secondary transmitter power is considerably high. Further, we validate our analytical framework through extensive simulation and numerical results, and demonstrate the effects of system/channel parameters on the secrecy performance of the considered system. Our results reveal that the higher number of eavesdropper antennas can have a more deleterious impact on the system's secrecy performance.