In cognitive radio, reliable detection of the primary system is crucial for the secondary system. However, there is an uncertainty in the received power level due to shadowing. The cooperative sensing where the stations in the secondary system share their sensing information can improve the detection accuracy of the primary system. In this paper, a new secondary system for reducing interference to the primary system is proposed. In the proposed system, a secondary transmitter receives sensing information by using multi-hop transmission from all secondary stations which detect the primary system, and makes decision of its transmission based on the received sensing information. Moreover, it controls the transmit power by the received CINR information from the secondary sensing stations. Simulation results assuming spatially independent shadowing and ideal multi-hop transmission in the secondary system reveal that the proposed system is helpful to protect the primary receivers which have no transmission ability.