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To improve the utilization of the precious radio spectrum, we propose a channel-hopping based cognitive radio medium access control (MAC) protocol for synchronized wireless networks that can enable the secondary (unlicensed) users to opportunistically utilize the unused licensed-spectrum without interfering with the primary (licensed) users. In our proposed scheme, the secondary users switch across the licensed channels with their distinct channel-hopping sequences. In particular, when a secondary user sender wants to send packets to its intended secondary user receiver, the secondary user sender changes its hopping schedule and follows the hopping sequence of the intended receiver to conduct the negotiation and then transmit data packets if the channel is not currently used by primary users. The main advantages of our proposed scheme include the followings: (1) no extra control channel is needed; (2) it overcomes the single control channel bottleneck; and (3) one transceiver is sufficient. We develop an Markov chain based analytical model to analyze the performance of our proposed scheme in terms of throughputs. We also identify the tradeoff between the channel utilization and the packet transmission delay.