網路應用從文字轉變成以影音多媒體為主，而隨著無線寬頻網路時代的來。在異質無線網路環境下，頻寬不如有線網路高，無線的連線品質易受到天氣、距離及遮蔽物的影響而容易不穩定，更是重要，使用者的移動性又會造成路徑變更甚至無線網路系統改變，在這樣的環境下使得提供QoS相對困難。而且一條網路連線並不會只經過一個無線接取網路，可能經過多家業者的的網路，因此若要維持端點到端點的QoS，所經過的傳輸線路都必須提供一定程度的QoS才能達成。 因此，本論文將針對異質無線網路之特性，提出一以動態SLA為基礎的端點至端點QoS保證機制。在量測方面，本系統將依據網路環境的變動情形，調整無線網路的量測頻率，並使用Network Coding技術來降低分享無線網路狀態資料所需要的頻寬。在QoS方面，當量測到使用者在異質無線網路的環境中移動或者網路環境改變時，動態修改與骨幹網路服務提供者所簽訂的 SLA ，使SLA契約可隨網路狀態或時段而改變，藉以達到端點至端點QoS保證。 When network applications from context turned into multimedia and the coming of Wireless WAN, providing QoS in heterogeneous wireless networks are urgent. The bandwidth of wireless network is less than wired network. Network connection quality is sensitive to weather, distance and shelter interference. The mobility of users could change the connection path or even alter wireless network system. Furthermore, a network connection would not only across one wireless access network, but also it could across many networks which belong to different ISPs. To support end-to-end QoS, the domains which in this path must guarantee a level of service quality. For these reasons, this paper proposes a dynamic SLA-based end-to-end QoS provisioning mechanism according to heterogeneous wireless networks characteristics. In the part of measurement, this system will adjust measurement frequency by the changing of network environment. Use network coding technology to reduce the packets of sharing network status information. In the part of QoS provisioning, when roaming in heterogeneous wireless network and network environment conditions changed, the SLA contract signed with backbone network provider could be dynamically modified according to current network states and time for end-to-end QoS guarantee.
