In this paper, two novel Automatic-Repeat-REQuests (ARQ) based protocols are proposed, which exploit cooperation opportunity inherent in secondary retransmission to create access opportunities. If the signal was not decoded correctly by destination, another user can be acted as a relay to reduce retransmission rounds by relaying the signal. For comparison, the authors also propose a Direct ARQ Protocol. Specifically, they derive the exact closed-form outage probability of three protocols, which provides an effective means to evaluate the effects of several parameters. Moreover, they propose a new metric to evaluate the performance improvement for cognitive networks.