在未來無線通訊的發展裡，異質無線網路整合現有環境的技術是一個趨勢，它可以使用最新的無線技術，使網路達到更好更快的效能，也提供向前相容的能力，使現有無線網路能繼續使用。在這樣的環境裡我們遇到一個重大的挑戰，如何讓每一個網路存取點(NAP, Network Access Point)都有很好的系統負載並且提供每一個行動終端(MN, Mobile Node)良好的通話，因為異質環境下每一個NAP的負載能力、對MN速度容忍性和訊號強度(RSS, Receive Signal Strength)不一定相同，因此我們將模糊系統應用在異質無線網路的換手決策，並且提出一個模糊正規化的概念將各種無線網路技術的環境參數正規化使得各個網路的系統負載能在最平衡的狀態。這樣的概念保留了傳統的模糊系統應用在無線網路換手決策的優點，也讓異質無線網路整合環境中，不同無線技術的環境參數可以經由模糊正規化的程序來達到參數可以直接比較。達成了不同無線技術環境整合的NAP可以直接比較並決定出最合適的換手目標。經由實驗結果可以得知在模糊正規化的決策方法下，只要設定合適的模糊歸屬函數和模糊推論系數，便可以得到網路系統負載在最佳的狀態且優於傳統模糊系統在垂直換手決策上之應用。

This concept retains the traditional fuzzy system applied to the advantages of wireless network handover decision also makes integration of heterogeneous wireless network environment, the environmental parameters of different wireless technologies can be normalized by fuzzy procedures to achieve the parameters can be directly compared. Reached a different wireless technology environment can be directly compared NAP integration and determine the most appropriate handover target. The experimental results were obtained in the handover decision of fuzzy normalization approach, as long as the appropriate set of fuzzy membership functions and fuzzy inference coefficient, it can get good performance system load better than the traditional fuzzy system in the vertical handoff decision on the application.

目錄
1	緒論	1
2	相關背景知識	4
2.1	異質無線網路換手管理(Heterogeneous Wireless Network Handover Management)	4
2.1.1	換手的分類	4
2.1.2	換手程序	5
2.1.3	垂直換手決策	5
2.2	模糊系統應用於換手決策	6
3	FUN-HODS演算法	11
3.1	模糊正規化	12
3.1.1	模糊化	13
3.1.2	模糊規則庫與推論引擎	16
3.2	換手決策	16
4	實驗模擬與結果	18
4.1	模擬環境	18
4.2	模擬結果	19
5	結論及未來研究	25
參考文獻	26
附錄—英文論文	29

圖目錄
圖1. 垂直換手決策考量參數分類	5
圖2.模糊系統	7
圖3. Adaptive Fuzzy Logic Based Handover Algorithm for Hybrid Networks	8
圖4. Block diagram of the access network selection base on MCDM fuzzy	9
圖5. FUN-HODS架構	12
圖6.模糊正規化的模糊系統	13
圖7.模糊正規化的模糊化	13
圖8. 3G、WiMAX、IEEE 802.11的RSS歸屬函數	14
圖9. 3G、WiMAX、IEEE 802.11的Velocity歸屬函數	14
圖10. 3G、WiMAX、IEEE 802.11的Loading歸屬函數	15
圖11. 換手決策流程	17
圖12. 模擬環境	18
圖13. 系統負載(T0)	20
圖14. 系統負載(T20)	20
圖15. 系統負載(T40)	21
圖16. 系統負載(T60)	21
圖17. 系統負載(T80)	22
圖18. 系統負載(T100)	22

表目錄
表1. 符號意義	16
表2. 規糊正規化與傳統糊化系統的系統負載率	19
表3. 規糊正規化與傳統糊化系統因速度過快導致的換手失敗率(速度隨機)	23
表4. 規糊正規化與傳統糊化系統因速度過快導致的換手失敗率(速度固定)	23

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