  In this paper, the secrecy performance of a cooperative relay network with
outdated relay selection is investigated where an eavesdropper intercepts the
channels between the source and the destination. The best relay is chosen among
N relays based on the opportunistic relay selection algorithm, which may not be
the best relay at the time of transmission because of the outdated channel
state information. We derive closed-form analytical expressions for the
non-zero secrecy capacity, the secrecy outage probability, and the ergodic
secrecy capacity. Finally, our theoretical analysis is validated by the
numerical results, and detailed discussions and insights are given.
