On Physical Layer Security of Correlated Multiantenna Cognitive Radio Receivers

In limited space scenarios, the antennas in the multiantenna cognitive radio (CR) system are closely spaced and often experience correlation among them. In this work, the secrecy performance of correlated multiantenna CR receiver over Nakagami-m fading channels with imperfect channel state information is studied and analyzed. We consider the underlay CR paradigm wherein Alice in the secondary network communicates with Bob while Eve tries to overhear the communication. We also consider that the antennas at Bob and Eve are closely spaced and thus uniformly correlated. To this extent, we derive the analytical expressions for the first and second order secrecy measures like secrecy outage probability, average secrecy outage rate & average secrecy outage duration, respectively for the CR receiver. Moreover, in order to gain insights at high SNR, asymptotic analysis of secrecy outage probability is derived, thus obtaining the secrecy diversity gain of order LD (i.e., the number of antennas at Bob). Monte Carlo simulations are carried out to validate the proposed analytical framework.