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標題: 基礎架構式無線區域網路與行動網際網路的快速漫遊
Fast Handoff for Infrastructure-Mode Wireless LANs and Mobile IP
作者: 謝育琦
Hsieh, U-Chi
關鍵字: Mobile IP;行動網際網路;Wireless LAN;Fast Handoff;synchronize Scan;Multiple Connection;無線區域網路;快速漫遊;同步化掃描;多重聯結
出版社: 電機工程學系
IEEE 802.11以絕佳的便利性、功能性和持續下降的價格在全球已經造成一股風潮。隨著802.11的普及化,人們開始對它有更多的期待,從一個定點式的無線上網到類似行動通訊的高行動性,再加上殺手級的網路語音服務(VoIP),讓無線網路似乎有取代行動通訊的可能而成為明日之星,因此我們可以預見一個具有高度行動能力且大規模部署的無線網路環境正在成型。如何能夠快速漫遊交遞是使這個網路具有高度行動能力的核心問題,IEEE 802.11f標準已經定義STA如何在AP之間漫遊,但是這似乎不能滿足網路即時影音服務的需求,過慢的交遞過程會導致影音斷斷續續而使人詬病;另外對於IP層來說,因為原始設計的關係使得IP先天上具有地理上的限制,也就是IP會隨著移動到不同網域而更動,因此我們還需要Mobile IP的幫忙,但是Mobile IP的漫遊過程一樣太過緩慢,所以我們將針對這兩個層次來研究如何加速交遞漫遊。
我們使用Network Simulator (NS2)來模擬Mobile IP的交遞過程,並且利用一種以MAC層為觸發條件的演算法來偵測是否移動到不同網域,以利提早進行交遞的步驟。我們還提出同步化掃描與區域性多重聯結的方法,事先將耗時的漫遊步驟完成,加快802.11的交遞時間。

IEEE 802.11 wireless LAN has become popular because of its convenience, functionality and low price. With the popularity of 802.11, people can connect to the Internet at anytime and anywhere using laptops or PDAs. Especially, we can use Voice-over-IP (VoIP), for audio communication to replace mobile phone communication.
Mobile Internet Protocol (Mobile IP) takes wireless LAN one step further by giving mobile nodes the ability to roam across IP subnets without loss of network-layer connectivity. With mobile IP, mobile nodes do not need to reconfigure their IP address while moving from their home subnets to foreign subnets. But the handoff latency for both 802.11 and mobile IP is still too high to be usable for interactive multimedia application.
We present a fast handoff scheme for both 802.11 and mobile IP in the thesis. The algorithm is based on a triggering mechanism in MAC layer to speed up handoff in different subnets. We simulate the algorithm using Network simulator 2(ns-2). A new fast handoff algorithm called “SyncScan” is also studied.
Appears in Collections:電機工程學系所

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