不同的無線網路技術環境交織重疊在我們的生活周遭，而無線技術的蓬勃發展也使得透過無線存取網際網路資源的需求量大增，其中觀賞多媒體影音串流（Multimedia Streaming）服務更是熱門的服務之一。然而，不同的無線網路技術和網路存取點使得使用者漫遊於異質性網路（Heterogeneous Networks）架構時必須重新提出使用網路頻寬的要求，這會造成原有的網路服務因而中斷。本論文提出以Mobile IP為基礎在異質性網路中的垂直性換手（Vertical Handoff）機制，針對在WiMAX及WLAN的訊號重疊區域中，Mobile Node會根據平均訊號強度、網卡傳送封包的暫存佇列長度（Queue Length）和網路的剩餘頻寬量作為是否執行垂直性換手的依據，其目的在於當Mobile Node在異質性網路移動而產生垂直性換手及網路發生壅塞導致頻寬不足時，可以降低觀賞RTP影音串流時所受到的影響。
我們在Linux平台上以Dynamics Mobile IP為基礎新增或修改加入垂直性換手判斷機制以支援WiMAX及WLAN之間的垂直性換手，最後整合我們撰寫的Linux模組擷取系統的各項資訊，並以實驗結果證明我們的機制可以避免RTP影音串流在Mobile Node進行垂直性換手時，有效改進Packet Loss Ratio及System Processing Ratio對RTP影音串流品質的影響，進而避免畫面上發生馬賽克或影格慢速重疊的現象。

Many different wireless technologies have increased the demand of accessing Internet resources through wireless networks. One of the most popular applications is watching multimedia streaming over wireless. However, when a user is roaming in a heterogeneous network, he needs to acquire adequate bandwidth from different wireless access points. In this Thesis, we propose a Mobile-IP based vertical handoff scheme in a heterogeneous WiMAX and WLAN. When a mobile node is in the overlapped area of WiMAX and WLAN, it may have to execute the vertical handoff based on the received average signal strength, the transmitting queue length of network interface, and the available network bandwidth. Our goal is to reduce the influences of RTP-based video streaming when the network is congested and when a mobile node executes the vertical handoff in the heterogeneous network.
We implement the Dynamic Mobile-IP based vertical handoff on Linux platform by modifying handoff decisions between WiMAX and WLAN. The above-mentioned performance parameters are implemented as modules on Linux platform. At last, we prove that our scheme can effectively improve packet loss ratio and system processing ratio. As a result, the frame mosaic phenomenon and frame slow-playing phenomenon in RTP-based video streaming can be significantly improved.

第一章 導論
1.1 研究動機
1.2 研究方向與實作
1.3 章節介紹
第二章 異質性網路中垂直性換手的相關研究
2.1 以SCTP為基礎
2.1.1 簡介
2.1.2 相關研究
2.2 以Mobile IP為基礎
2.2.1 簡介
2.2.2 相關研究
2.3 其他換手方式
2.4 比較不同的換手機制
2.5 本論文的垂直性換手機制
第三章 以Mobile IP為基礎的垂直性換手機制
3.1 垂直性換手的問題
3.2 機制流程及演算法
3.2.1 由WiMAX換手至WLAN 的演算法
3.2.2 由WLAN換手至WiMAX的演算法
3.3 在Linux平台上的實作
3.3.1 Mobile Node新增部分
3.3.2 Home Agent及Foreign Agent新增部分
3.3.3 RTP封包擷取
3.4 實作上遭遇的困難與解決方法
第四章 效能量測與結果分析
4.1 實驗拓樸與設備
4.2 實驗環境設定
4.2.1 實驗一
4.2.2 實驗二
4.3 實驗結果與分析
4.3.1 實驗一的結果分析與討論
4.3.2 實驗二的結果分析與討論
第五章 結論與未來工作的方向
5.1 結論
5.2 未來工作
REFERENCES
索引 (Index)
附錄A

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