在無線網路系統的未來發展中,相信必定會致力於無線網路系統中的無線接取技術之效能,以及即時的多媒體應用。當使用者在不同系統的無線網路服務中進行移動行為時,由IP 與MAC層所提供的異質網路間的無縫隙換手服務對於多重網路系統的使用者來說,是非常的重要。 IEEE 802.21 就是基於這種目的,而被設計研發成一個可提供異質網路間的無縫隙換手的基本平臺。它可針對每一種無線網路系統提供一個專屬的服務接取裝置,並且藉由三種服務:MIH Event Service、MIH Command Service、MIH Information Service來為使用者提供一個多重無線網路系統的溝通平台。 在本論文裡提出了一個具有可動態調整的暫存器裝置,以及暫存器裝置大小的預測演算法的IEEE802.21輔助裝置。這個輔助裝置有一個服務決策層裝置,此服務決策能裝置能提供網路選擇的功能,以及暫存器裝置的大小預測和動態調整的能力,並且藉由這個能力進而儲存換手時需要的資料。 在本論文中將會分析並描述IEEE802.21 MIH層、服務決策層以及暫存器裝置三者之間的服務及通訊流程。藉由這些執行流程的分析以及相關實驗模擬,可以發現暫存器大小的預測以及事先的動態調整,可以確實減少因異質網路間的換手而造成的服務中斷。 Future generations of wireless networks will place great demands on the performance of radio access technology and the real-time multimedia applications provided by these new wireless environments. During the mobility between heterogeneous wireless networks, the quality of multimedia services for users depends heavily on seamless handover which should be provided by the middleware of IP to MAC protocol stack. IEEE 802.21 is designed for this reason which provided the basic platform for seamless handover between heterogeneous wireless networks. Due to each kinds of Wireless network service system, it can provide an individual service access point. The IEEE80.21 also offers three kinds of service: MIH Event Service、MIH Command Service、MIH Information Service. With these two abilities, it can provided an communication platform for users. In this paper, a dynamically adjusted buffer component with algorithm for prediction of the buffer size is proposed to enhance the functionality of IEEE 802.21. The mechanism of proposed scheme included Service Specific Layer which decides the opportunity of handover, and adjusted Buffer which stores the temporal streaming data for applications between handover. The services and communication flows among service specific layer, buffer and IEEE 802.21 Media Independent Handover function are described and analyzed. According to analysis of the connection process and simulation, buffer prediction and pre-allocation could indeed reduce the influence of handover between heterogeneous wireless networks.