Cognitive radio networks(CRNs)is new paradigm that provides the capability to share or use the spectrum is an opportunistic manner. It ability to sense the unused spectrum at a specific time and location (spectrum hole).Cognitive Radio (CR) technology is a promising solution to enhance the spectrum utilization by enabling unlicensed users to exploit the licensed spectrum in an opportunistic manner. In this paper, sequential channel sensing problems for single and multiple secondary users (SUs) networks are powerfully modeled through finite state Markovian processes. The objective of this paper is to maximize the throughput for secondary user and reduced the number of handovers. A model for single user case is introduced and its performance is validated through analytical analysis. A modified p-persistent access (MPPA) protocol is proposed for multiple user. Since the method utilized experiences a high level of collision among the SUs, to mitigate the problem appropriately, p-persistent random access (PPRA) protocol is considered, which offers higher average throughput for SUs. The structure of the proposed scheme is discussed in detail, and its efficiencies are verified through a set of illustrative numerical result.
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