針對WLAN與UMTS的新穎異質切換控制演算法

Abstract

隨者各式無線通訊系統蓬勃的發展，如何運用一個有效率且流暢的切換來整合各式各樣的通訊系統是一個被期望能達到高速傳輸、高流通性以及高服務品質的方法。本論文主要針對無線區域網路(WLAN)以及廣域移動通訊系統(UMTS)這兩系統提出一個新穎的異質切換演算法，在這個演算法中，包含了(1)以傳輸速率為基準的對應函數來解決沒有共同指標來提供切換判斷的窘境，(2)以服務品質(QoS)為依據的動態調整切換邊界來滿足各式服務的需求，(3)以效能為主的觸發計時機制來避免乒乓效應的發生。為了驗證這套控制方法，一個可提供分析的數學模組也在此論文提出並用來分析切換控制下的各種系統表現，最後，數值分析的結果證明了這個新穎的異質切換控制法確實能夠利用不同的系統特性去做切換的動作來達到不同的服務需求，使得整合系統表現更佳。

How to design an effective and smooth vertical handover algorithm is a trend for the integrated system to achieve the high-speed transmission, high mobility, and satisfied QoS. In this thesis, a novel vertical handover control algorithm, consisting of a throughput-based mapping function, QoS-based dynamic handover thresholds, and performance-based trigger timers, are proposed to resolve uncommon pilot problems, QoS requirements, and ping-pong effects, respectively. An analytic model based on a finite state machine is developed to evaluate the proposed algorithm in terms of the handover frequency and achievable throughput. A numerical analysis is also provided to further quantify the performance impacts. The analytic results show that the proposed algorithm could improve the transmission throughput for non-real-time services and can substantially reduce the packet loss rate for the real-time services by reducing the vertical handover frequency.