Dynamic spectrum access is a key technique in cognitive radio. Whenever primary users appear, secondary users must evacuate the primary channel rapidly, and switch the appropriate channel to primary users. There are two types of channel access methods, namely reactive and proactive channel access. In reactive method, cognitive radio does not need to switch channel until primary users appear, while in proactive method, secondary users predict future channel traffic by using channel history and

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... itch channel before primary users appear. Most of the previous researches assume that all primary users possess the same channel bandwidth. In this paper, we take various channel bandwidths into consideration to make spectrum handoff decision with the method proposed before under real cognitive radio environment, and use this method to analyze the performance. Channel utilization rate in both methods is enhanced while considering various bandwidths.