針對無線區域網路探討快速換手的機制

Abstract

爾來台灣廠商致力推動無線區域網路(WLAN)，使得無線區域網路的建置更加地普及，例如在機場、校園或是大型的購物中心等，均已建構無線區域網路。再者由於手持裝置的盛行，例如：個人數位助理、筆記型電腦以及平板電腦，使得使用者可以在移動中存取網路，而不再是局限在固定位置。並且隨著即時性的多媒體應用程式的快步增加，若要維持移動過程中連線的高品質，在無線存取點之間的換手機制必需要快速地進行。在本篇論文中，我們提出了一個以預測方式(forecasting scheme)為核心概念的方法，將其運用在無線區域網路上來達到快速換手的目的，這個方法主要的概念是根據使用者過去的行徑記錄。同時我們利用數學模式來描述使用者的移動行為。最後，由模擬結果更佐證了我們所提出的方法，在不同的移動模式下能夠減少換手程序的延遲時間進而達到快速換手的目標。

Over the last several years, wireless local area network (WLAN) has evolved rapidly in hot spot regions such as hotels, airports, campus, and shopping malls. With the popularity of portable devices, user mobility is tendency in the future. However, real-time multimedia applications need fast handoff mechanism especially when user is moving in order to maintain the quality of service. If the latency of handoff is long, the users of real-time multimedia applications will have excessive jitter. In this thesis, we propose a fast handoff method by using forecasting scheme. The concept of forecasting scheme is predicting the mobile station’s next location based on mobile station’s movement history. We also formulate a mobility model to describe the mobile station’s moving behavior. The simulation results show that our approach can minimize the reassociation delay to accomplish fast handoff and achieve the requirement of real-time multimedia applications.