Secrecy outage probability of selective relaying wiretap channels with collaborative eavesdropping

We analyze the secrecy outage probability of selective relaying wiretap channels with K decode- and-forward (DF) relays and N collaborative eavesdroppers. In the main channel, we consider a two-hop relay network where the best relay is selected to transmit and the relay link is combined with the direct source-to-destination link at the destination. In the eavesdropper channel, we consider that the eavesdroppers can collaborate to exchange the information obtained from the source and relays. Different from previous works, we introduce an eavesdropping probability measure to model different intercepting capabilities of the malicious nodes. For this network, we derive new closed-form expressions for the secrecy outage probability in Rayleigh fading channels. The impact of the number of eavesdroppers and the eavesdropping probabilities are accurately reflected in the array gain of the asymptotic secrecy outage probability.