الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Wireless communications gain lot of interests in the last twenty years. Cognitive radio technology is one of the promising wireless technologies that will change the way how the available spectrum is used today. It aims to gives more intelligence and flexibility to wireless devices when utilizing the spectrum. Furthermore, it aims to overcome the spectrum scarcity problem. To reach this goal, efficient spectrum management scheme is a must. This scheme should use the available spectrum resources efficiently. In addition, the performance of the cognitive user or secondary user (SU) should be evaluated in a proper way to measure the impact of the developed spectrum management scheme. Before mentioning the thesis for our contribution, we introduce a comprehensive survey of analytical models for spectrum management and mobility techniques in Cognitive Radio Networks (CRNs). Then, the thesis provides the most powerful contribution. We propose a new spectrum management concept called Buffering and Switching (BuSw) scheme for admission control in CRNs. The BuSw scheme utilize two finite size buffers to hold the newly arriving SUs and the interrupted SUs in case of Primary User (PU) appearance. In addition, the SUs can perform a channel switching technique in a mixed spectrum environment on licensed and unlicensed bands. In addition, we evaluate the performance of the proposed scheme using extensive analytical model using Markov Chain. Different performance metrics is measured such as blocking probability, dropping probability and SU completion rate. The obtained results show that the performance of the SUs is enhanced greatly by using the BuSw scheme compared to the ones utilizing either buffering or switching.