在IEEE 802.11無線網路提供服務品質保證之研究

Abstract

IEEE 802.11 DCF無線網路因其簡單、容易建制及維護，已成為存取Internet最廣泛的無線媒介。但在DCF的設計原理下，每個無線點(如筆記型電腦、PDA、無線手機等)都公平的享用無線網路頻寬，因此不能針對特定應用程式，例如網路電話及網路影音，提供服務品質保證。IEEE 802.11e雖然制定了一套以優先順序為基礎的架構，但其參數設定以提供特定程度之服務品質，仍需許多研究，故本論文主要在IEEE 802.11無線網路下，以提供服務品質保證之研究。提供服務品質保證之範圍相當廣泛，我們的研究重點在提供設計嚴格分級(strict priority)、差別性公平(proportional fairness)機制及公平的無線網路資源分享(fair resource allocation)。 首先，我們在無線區域網路(Wireless LAN)環境下，針對多媒體資料在DCF媒體存取層(MAC)隨意競爭行為下，設計以訊框(frame)間隔時間(inter-frame space)為基礎的排程方法，以提供不同無線點差別性公平機制(proportional fairness)，並經由模擬證明我們的機制相較於文獻的方法，更能提供有效能且有效率的差別性服務；此外，我們也在EDCA 媒體存取層隨意競爭行為下所衍生的問題，設計嚴格分級(strict priority)及差別性公平機制；並提出一適用於無線區域網路競爭行為的階層性資源分享架構，以同時提供不同服務品質於上傳及下傳資料。最後，我們並延伸至多重跳躍網路上(multi-hop wireless backhaul network)，成功利用賽局理論解決因multi-hop及網路中存在selfish mesh node所衍生不公平資源共享問題

IEEE 802.11 WLANs with DCF is the dominant wireless medium due to its simple, robust and fast installation with minimum management and maintenance costs. However, it is still challenge to provide desired quality of services for different requirements of applications since DCF provides best effort service only. This calls for solutions to providing differentiated service and fairness resource allocation in resource sharing among mobile stations for IEEE 802.11 based wireless networks. In this dissertation, we provide different quality of services to meet different service requirements for integrated applications, and fair resource allocation in IEEE 802.11 wireless networks. We first propose an IFS-based MAC-layer scheduling discipline to provide weighted fair service among stations in IEEE 802.11 DCF WLANs. Next, we propose a differentiated service model, which can provide both strict priority and weighted fair service among different ACs to meet the different QoS requirements in integrated networks, and a MAC-layer service discipline DS-EDCA to support the service model in IEEE 802.11e EDCA WLANs. Additionally, we propose a hierarchical link sharing model for WLANs to control the resource usages of downlink and uplink traffic. Last, we use the game theoretic approach to design a fairness mechanism for wireless multi-hop backhaul networks with selfish transit Access Point