異質網路整合與漫遊之跨階層中介軟體設計與實作

Abstract

隨著許多無線接取技術和服務的成熟，我們已經可以隨時隨地透過無線網路存網際網路。同時，在行動裝置上配備多種異質無線網路介面以成為趨勢。例如市面上許多智慧型行動電話和個人數位助理已經裝置了無線區域網路介面和GPRS介面。但是這些行動裝置卻往往缺乏一個有效的行動管理機制，來同時充分利用這些異質網路介面。為了解決這個問題，我們在以Windows CE為基礎的手持裝置上，利用Mobile IP網路協定，設計和實作了一套能夠有效整合異質網路，能在異質網路間漫遊和做無接縫的換手的中介軟體。 另一方面，在設計行動管理機制時通常會遇到一個嚴重的問題，就是行動管理程式缺乏底層網路的資訊，而不能做有效的行動管理，例如造成在異質網路間換手時會產生嚴重延遲，以至於不能提供良好的服務品質。而為了增加行動管理的效率，減少換手時的延遲，我們的中介軟體導入了跨階層網路設計的概念。我們的中介軟體能提供在應用層的行動管理程式底層網路的資訊，並透過我們設計的事件觸發機制，讓在應用層的行動管理程式能夠快速的被告知底層網路的改變，並做出適當的反應，而能提供良好的服務品質。

Because of recent advances in wireless access technologies and services, we can access Internet anytime and anywhere. Furthermore, it is now a trend to equip a mobile device with multiple network interfaces of different wireless accessing technologies. For instance, there are many off the shelve Smartphones and PDAs (personal Digital Assistant) equipped with WLAN (Wireless LAN) and GPRS interfaces. However, in these mobile devices, there is absence of an effective mobility management mechanism to utilize multiple wireless network interfaces simultaneously. In the thesis, we proposed and implemented a middleware to integrate the multiple heterogeneous network interfaces for the handheld device based on Windows CE operating system, so that handheld device can roam and handover between heterogeneous networks seamlessly. On the other hand, there is often a seriously problem in mobility management. Mobility management is not efficient enough due to lack of underlying network interface status. For example, handover between heterogeneous networks produces long handover delay, so that quality of service can not be guaranteed well. Therefore, we proposed the concept of cross-layer network design in our middleware. Our middleware can provide underlying network information to mobility management program in application layer. In advance, by means of event trigger mechanism we proposed, mobility management program can be notified underlying network status change rapidly and react to the change promptly, so that quality of service can be guaranteed.