隨著無線網路科技的快速發展,無線網路使用者將能夠利用各種不同的傳輸媒介取得網路服務,然而在此異質性網路環境下,如何針對不同使用情境,並且滿足使用者的需求,將是很重要的問題。由於不同使用情境以及使用者的需求,會造成影響的參數也相當的多樣(如Packet Loss、Delay、Jitter、Signal Strength等),且各種參數之間亦會互相影響,如此一來將造成決策上的困難,目前大部分的使用者或行動終端設備在換手部分都是依據無線網路訊號的強度做為換手的依據,但由於各種不同因素對於不同的使用情境,所產生影響的程度也不同,例如封包的延遲對於(Voice over Internet Protocol, VoIP)所產生的影響較大,但對於(File Transfer Protocol , FTP)傳輸並不會造成使用者相當大的困擾,因此在本篇論文中,我們將探討利用多屬性決策(Multi Attribute Decision Making, MADM)方法來做目標網路換手的選擇,而各種不同的參數將透過IEEE 802.21的機制整合,並且針對使用者不同的情境(如VoIP、視訊會議、FTP傳輸)採取相對應的影響參數,提出換手機制,使得使用者在異質性網路環境下漫遊時,能夠依據使用情境,達到符合使用者的需求。
With the rapid development of Internet and wireless communication and the technology in current years, the wireless network user are capable of utilizing multiple radio access technologies to link to the Internet. However, in heterogeneous wireless networks environment, how to meet the needs of users in different situation are very important. Due to different use scenarios, user needs and parameters are also quite diverse(such as Packet Loss、Delay、Jitter、Signal Strength),it will cause difficulties in handover decision-making. At present, most of the users or mobile terminals handover are based on signal strength. However, the parameters will cause different affect in different situation. Therefore, in this paper, we will utilize the IEEE 802.21 standard to integrate with heterogeneous wireless access technologies, and use Multi Attribute Decision Making (MADM) to making handover decision to achieve meet the needs of users when the mobile station roaming(MS) across the heterogeneous wireless networks.