With the employment of cognitive radio technology, dynamic spectrum management has the potential to solve the underused spectrum problem. In this paper, we introduce and compare two periodic sensing and transmission schemes for secondary users (SUs) in cognitive radio networks, namely, periodic single sensing scheme and periodic continuous sensing scheme. In an attempt to maximize the exploitation of spectrum opportunities in these two schemes, we analyze three metrics of SUs, namely, channel utility, collision rate and sensing overhead. Optimizations of SU's slot period are analyzed under single-SU single-channel scenario. The proposed schemes are applicable to any i.i.d. ON-OFF channel distribution.