| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 99 === In the recent years, lots of studies indicated that the ineffective usage of licensed bands due to the static spectrum allocation. In order to solve this problem, cognitive radio is therefore proposed to dynamically exploit the primary frequency spectrums when the frequency spectrum is not occupied by a user. In this paper, we will focus on three problems, the first one is the delay time when secondary users searching an unoccupied channel, the second one is the probability of secondary user colliding with primary users, and the third one is the energy efficiency of secondary users. There are four chapters in this paper. In the first chapter, we will introduce the cognitive radio networks. In the second chapter, a dynamic channel selection using partially observation Markov decision process (POMDP) is proposed to find an unoccupied channel in minimum delay time. In the third chapter, we will analysis the situations of secondary users colliding with primary users. Then, we will propose an algorithm that constrains the collision probability. In the fourth chapter, we will propose an energy efficiency dynamic channel selection that minimizes the power secondary users wasting.
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