IEEE 802.16 被視作下一代無線寬頻接取技術，針對移動的環境也提出了IEEE 802.16e。WiMAX Forum針對此技術的商用營運提出了WiMAX Network Architecture Stage 2 與 WiMAX Network Architecture Stage 3。其中針對換手定義了ASN anchored mobility與CSN anchored mobility。CSN anchored mobility 模式中，MS會執行IP更新的動作。此份文件中也建議執行ASN anchored mobility後再進行 CSN anchored mobility以進行無縫換手。 針對IP層的換手，IETF也制定了 Mobile IPv4與 Mobile IPv6以支援移動節點維持與網路的連線。但是Mobile IPv6協定仍然有一些缺陷像是耗費太多時間產生Home Address與Care of Address的連結，以及三角路由的問題等。其中Hierarchical IPv6藉由選擇有效的錨點降低換手的延遲。 本篇論文中我們將Hierarchical IPv6應用在WiMAX Network Architecture，分析不同錨點位置的選擇對網路端負擔與換手延遲造成的影響。並且提出一較佳的實際應用模式具有降低ASN-GW負擔以及較少的換手延遲。 IEEE 802.16e is viewed as a promising next-generation broadband wireless technique. It provides better transmission distance and wider bandwidth. In the documents released by WiMAX Forum, it proposes two scopes of mobility. One is ASN anchored mobility. And the other is CSN anchored mobility, which is known as R3-Reanchoring. When CSN anchored mobility is executed, it is involved in CoA update. Applying ASN Anchored Mobility prior to the CSN anchored mobility minimizes the handoff delay and packet loss. Mobile IP is a layer 3 protocol which assists mobile station with retaining IP layer connectivity in a mobile environment. There are two versions of mobile IP. Mobile IPv6 is one of them. IETF released Hierarchical Mobile IPv6 (HMIPv6) in 2005. This RFC is an extension of mobile IPv6. It defines a conceptual anchor point router to reduce the times processing route optimization. It also defines extension header to apply HMIPv6 over IP backbone network. In this thesis, we apply Hierarchical Mobile IPv6 to the WiMAX network architecture. The main emphasis is placed on the problem of handoff overhead. We analyze the message flow with and without R3-Reanchoring method, and consider the effects caused by the MAP location. The concept of service area is implemented to achieve reducing the load of ASN-GW and minimizing handoff delay.
