臺灣博碩士論文加值系統

IEEE 802.11無線網路提供的行動性為網路使用者帶來更多的便利，如何讓無線行動裝置能夠平滑地在無線基地台(Access Point；AP)之間漫遊，達到無縫交遞，成為無線網路需要克服的問題之一。為降低無線區域網路的交遞延遲對於上層應用程式的影響，我們提出了一個建構於階層式無線網路架構下的快速交遞(Handoff)機制。由於每一個AP所能提供的無線網路服務範圍有限，通常在建構一個無線網路服務區時會使用多個AP共同提供無線網路服務，當無線行動裝置在無線網路服務區中漫遊時，無線行動裝置會依本身與AP之間的訊號品質交遞至適合連線的AP。
在交遞過程中，無線行動裝置使用者正在使用的網路服務會因為無線行動裝置搜尋可連線AP耗費的時間以及切換到新的AP上需要重新連線的影響而遭到中斷。在我們提出的方法中，我們利用IAPP (Inter Access-Point Protocol)來幫助AP完成交遞過程，並配合判斷RSSI (Received Signal Strength Index)來決定交遞時機。交遞過程完全由AP來負責完成，而無線行動裝置則不會發覺自己被AP交遞。此外我們也提出相關的負載平衡機制以平衡各個AP的負載，使網路資源得以平均分配至每個網路使用者。

Mobility of the IEEE 802.11 wireless network offers more convenient for the network users. How to offer wireless mobile device roam around all of the access point smoothly to reach the handoff of seamless is a challenging issue. we proposed a fast handoff scheme in the infrastructure network for reducing the delay of handoff for application. In general, many AP offer wireless network service area cooperatively while building a wireless network environment. Because the basic service area of AP is limited. The Wireless mobile device is base on signal strength index of APs to decide handoff while roam in wireless network.
In process of handoff, the network service that user using will be interrupt because mobile device spent more of time to search new AP and internet re-connected. We not only utilize IAPP (Inter Access-Point Protocol) to help handoff process of AP in our method, but also determine the opportunity of handoff by RSSI (Received Signal Strength Index). The handoff have no effects to the mobile device because all of the handoff process is operated by AP. For averaging the network resource, we also propose the balance of the load scheme to balance the load of APs, additionally.

摘要 I
ABSTRACT II
目錄 III
圖目錄 VI
表目錄 VIII
第一章 導論 1
1.1 緒論 1
1.2 研究動機與目的 2
1.3 論文架構 3
第二章 背景知識與相關研究 4
2.1 IEEE 802.11網路簡介 4
2.2 基本的IEEE 802.11網路 5
2.2.1 獨立型網路 5
2.2.2 中控型網路 5
2.2.3 傳輸系統(DS) 6
2.2.4 IEEE 802.11的服務項目 7
2.3 基本HANDOFF簡介 8
2.4 802.11F概要 10
2.4.1 IAPP定義的服務 12
2.4.1.1 IAPP-INITIATE 12
2.4.1.2 IAPP-TERMINATE 13
2.4.1.3 IAPP-ADD 13
2.4.1.4 IAPP-MOVE 13
2.4.1.5 IAPP-CATCH-NOTIFY 14
2.5 各種HANDOFF策略與IAPP的相關應用 14
第三章 系統架構與運作 16
3.1 基本原理 16
3.2 系統架構 16
3.3 以AP引導之交遞方法 20
3.3.1 初始化步驟 20
3.3.1.1 Registered STA list與Trace STA list列表的資料結構 22
3.3.1.2 Count值的計算 23
3.3.2 執行步驟 23
3.3.2.1 Registered STA list，Trace STA list結構的建構時機 24
3.3.2.2 AP接收STA資料封包時的動作 26
3.3.2.3 送出HANDOFF_REQ、HANDOFF_CONTEXT、REQ_MN_INFO封包的時機 26
3.3.2.4 收到HANDOFF_REQ、HANDOFF_CONTEXT、REQ_MN_INFO封包時AP的動作 28
3.3.2.5 負載平衡機制 33
3.4 以AP引導方式完成交遞的優點 33
第四章 AP引導交遞法在IAPP上所需的增援 34
4.1 IAPP的增援 34
4.2 IAPP-HANDOFFREQ服務 34
4.2.1 IAPP-HANDOFFREQ.request 35
4.2.2 IAPP-HANDOFFREQ.confirem 35
4.2.3 IAPP-HANDOFFREQ.indication 36
4.3 IAPP-HANDOFF-CONTEXT服務 37
4.3.1 IAPP-HANDOFF-CONTEXT.request 38
4.3.2 IAPP-HANDOFF-CONTEXT.confirem 39
4.3.3 IAPP-HANDOFF-CONTEXT.indication 39
4.4 IAPP-REQMNINFO 41
4.4.1 IAPP-REQMNINFO.request 41
4.4.2 IAPP-REQMNINFO.confirm 42
4.4.3 IAPP- REQMNINFO.indication 43
4.4.4 IAPP- REQMNINFO.response 44
第五章 模擬結果與結論 46
5.1 網路模擬軟體 46
5.2 模擬結果 46
5.2.1 AP與STA的訊號強度關係 46
5.2.2 AP 追縱的count值 47
5.2.3 Load值對於Key值的影響 49
5.2.4 交遞的延遲與封包遺失比較 49
5.3 結論 54
5.4 工作及未來展望 54
參考文獻 55

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