- 學位論文
具換手程序考量之移動式WiMAX網路系統的服務品質機制設計
The Design of QoS Mechanisms in Mobile WiMAX Network Systems with Handover Procedures
摘要
在現今多媒體的服務越來越多，使用者對網路品質的要求也越來越高，而固有的WiFi無線網路已無法滿足這高度的需求，因此為提高無線網路傳輸效能及涵蓋範圍，無線都市區域網路(WMAN)已逐漸發展起來。WiMAX(Worldwide Interoperability for Microwave Access)，系統具有支援服務品質保證機制(QoS)和頻寬管理的能力，能確保即時服務擁有一定程度的服務品質，並且在IEEE802.16e-2005標準規格中支援移動性的需求，讓服務的範圍更加廣泛，使WiMAX可能成為WMAN中重要的技術。 本研究主要是探討移動式WiMAX網路系統的服務品質機制設計。透過允入控制、連線及封包分類、頻寬分配以及封包的排程等機制的設計來完成WiMAX的服務品質模擬平台的建置。本研究提供了一個公平且合理的頻寬分配機制，直接涵蓋了頻寬分配以及封包的排程這兩項功能。此外，本研究設計出了參照IEEE802.16e-2005規格制定的一般換手(General Handover)演算法來達到移動式網路系統所需具備的換手的目的。最後針對無換手機制和有換手機制的WiMAX環境來進行模擬與效能評估。由於移動式WiMAX環境下，傳輸品質容易受到變動的調變率影響而導致系統的傳輸效能下降。本研究由模擬結果，證實了所製作的頻寬分配機制與換手機制能有效地減少連線阻隔率以及封包丟棄率，來提高系統的傳輸效能。
並列摘要
With the ever growing of the multimedia applications, it has become more and more difficult to satisfy the individual Quality of Service (QoS) requirement demanded by each type of multimedia service. To provide the mobility capacity and enlarge the coverage area which the WiFi networks are poor of, Wireless Metropolitan Network (WMAN) technology has been proposed and gained wide attention over the past few years. Among WMAN, Worldwide Interoperability for Microwave Access (WiMAX) system, which is able to support the guaranteed QoS requirement of real-time data and provide mobility support, is poised to become a major player in the WMAN technology. This research works aim to design the QoS mechanisms for mobile WiMAX systems. We combine admission control, packet classifier, bandwidth allocation and packet scheduling to design the QoS simulation platform for such a WiMAX system. We propose a fair and dynamic bandwidth allocation mechanism, which contains two functions of bandwidth allocation and packet scheduling simultaneously. We also design the handover mechanism according to the general handover procedure specified by the IEEE802.16e-2005 standard. Finally, performance evaluations via simulations are conducted to assess the system performance for the network with or without handover procedures employed. It is found that the transmission quality is subject to the modulation rate change significantly in the mobile environments. The proposed bandwidth allocation and handover mechanisms are shown to reduce connection blocking rate and packet dropping rate effectively to enhance WiMAX system efficiency.