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In this paper, we consider the interference-mitigation based cognitive radio (CR) model where the CR and primary users can coexist at the same time and frequency bands, under the constraint that the primary rate remains the same with the single-user decoder. To meet such a coexistence constraint, the unidirectional cooperation from the CR user is performed by relaying the primary user's signal. We propose a new CR transmission scheme where both the CR transmitter and receiver help relaying the PR signals under the half-duplex constraints. Compared to the previous scheme with only CR transmitter cooperation, the additional cooperation from CR receiver not only provides diversity but a Â¿cleanÂ¿ relaying without interference from the CR. The numerical examples show that the proposed scheme provides significant rate gains over that with only CR transmitter cooperation.