| 摘要: | 感知無線電 (Cognitive Radio) 的出現，主要是因為頻譜使用率不佳，造成多餘的浪費。為了提升頻譜使用率，近年來多數人開始研究動態頻譜接取技術(Dynamic Spectrum Access, DSA)，而感知無線電 (Cognitive Radio, CR)是其中的一種，也是目前動態頻譜接取技術(DSA)的發展重點。在感知無線電 (Cognitive Radio, CR)的研究領域中，大家都提出許多的不同的研究方法，例如：改善碰撞機率、提高錯誤偵測率、增進效能等方式，藉此提升頻譜使用率。但大多數的討論議題中都存在一個統一管理的機制，例如：整合中心（Fusion Center）或 共用控制通道（Common Control Channel），此類機制相當於是存在一個類似基地台的裝置去控制感知無線電的使用者，對於感知無線電來說不算是一個很好的解決方案。因此本論文將基於無任何控制機制下，提出一個有系統的解決方法。本篇論文中，感知無線電使用者(Secondary Users, SU)將經由有規律的通道挑選方式，透過競爭的方式取得通道使用權，可以保證在有限時間內能有機會與欲傳送對象相遇，並分析續傳機制的效益，以及在續傳機制下遇到通道擁有者出現時的決策。由模擬結果發現，本論文所提出之方法，相對於隨機挑選方式有較佳的傳輸效能。The development of Cognitive Radio results from the poor utilization of spectrum in wireless network. In recent years, more and more people have been doing research on the technology of Dynamic Spectrum Access to upgrade the utilization of spectrum. And Cognitive Radio, which has been received much attention, is one of such technology.Researchers have been proposed several approaches to improve the spectrum utilization in the field of Cognitive Radio, like improving the performance of collision probability, false alarm rate, throughput, and so on. However, there is an additional device ( eg. fusion center or common control channel ) to manage CR users in most of these researches. The device, like a base station, can adjust CR network parameters by fusing the message which CR users are sensing. Moreover, this device enables CR users to access the channels in some researches. CR users, access of channels controlled by base station can make spectrum efficient, but the overhead, like PU’s interference, caused by this device, is seldom considered in such researches. In this thesis, we propose a systematic method for channel selection without any basic infrastructure. In this thesis, cognitive radio users will gain the right of channel use by the channel selection and competition, which promises the opportunity to find the receiver in limited time and analyzes the performance of the mechanism. The proposed spectrum hopping scheme can achieve degree n for the rendezvous of secondary users. Moreover, the proposed method would make decision for secondary users when meeting the primary users in the continuing transmission strategy. In addition, we propose continuing strategy for CR user who is channel owner. The simulation results show that the proposed method has better transmission performance compared to that of the random selection scheme. |
