在感知無線電環境中，動態頻譜存取是重要的一環。感知無線電是使用授權頻段間的閒置時間進行暫存性動態存取，提高頻譜的使用率以及未授權的頻段來提供服務；因此當授權頻段的主要使用者出現，次要使用者就必須離開原來的頻段切換到另一個可用的頻段。這樣的的過程稱為頻譜換手。頻譜換手時可能會造成傳輸中斷，讓傳輸品質己感知無線電網路系統效能下降。
頻譜換手分為兩種，一種是主動式換手和反應式換手，主動式頻譜換手，感知無線電會利用過去通道使用的歷史訊息以及預測未來頻譜動向，好讓主要使用者出現前就會先進行頻譜換手動作。而反應式頻譜換手中只要使用者出現時才會進行頻譜換手動作，但常造成主要使用者干擾。
本論文提出在多種傳輸長度環境下進行高頻寬換手，在未考量高頻寬時，次要使用者會壅擠在同一個時槽內，無法有效利用閒置通道，考量時間網路環境後，挑取較高的頻寬進行換手，讓次要使用者有效的利用閒置通道，提升傳輸品質，再以多種傳輸長度進行主動式頻譜下的換手方式性能分析。

Dynamic spectrum access is an important part of cognitive radio (CR) network. Spectrum utilization efficiency can be improved by use of the idle spectrum with dynamic spectrum access. The secondary users must yield back the channels once the primary users intend to use the spectrum again, and this process is called handoff. Handoff may result in the transmission interruption and hence degrade the performance of CR network.

　　There are two kinds of handoff processes, namely the proactive and the reactive handoff processes. In proactive handoff, CR network uses the past history to predict the emergence of the primary users so that the secondary users can yield back the channels before the primary users actually show up. In reactive handoff, only when the primary users emerge do the secondary users yield bak the channels. It usually interferes with the primary users by so doing.

　　In this thesis, a broad bandwidth spectrum hole handoff process with various transmission time and distances is proposed. Without this handoff, all secondary users are congested in the same time slot and it is hard for them to use the idle channels efficiently. By taking time-domain network environment with random bandwidths into consideration, the secondary users can select broad bandwidth for handoff so as to better use the idle channels and enhance the transmission quality. The performance analysis is done by the proactive handoff with various transmission distances.

致謝I
摘要II
ABSTRACTIII
目錄IV
圖目錄VI
表目錄X
第一章 緒論1
1-1前言1
1-2研究動機與目的2
1-3論文架構3
第二章 研究背景5
2-1感知無線電技術概述5
2-1-1感知無線電5
2-1-2感知無線電網路架構8
2-2頻譜管理10
2-2-1頻譜感知10
2-2-2頻譜決策15
2-2-3頻譜分享17
2-2-4頻譜移動性19
2-3感知無線電換手種類19
2-3-1 主動式頻譜換手20
2-3-2反應式頻譜換手22
第三章 系統模擬25
3-1通道模擬25
3-2 主動式換手機制27
3-2-1 主動式頻譜存取架構27
3-2-2 通道預測28
3-2-3換手決定28
3-2-4 通道頻寬考量機制30
第四章 模擬流程與數據分析31
4-1系統參屬設定31
4-2主動式頻譜換手流程32
4-3數據分析33
第五章 結論71
參考文獻73

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