隨著無線網路的蓬勃發展，未來的無線網路會是將現有的數種不同技術的無線網路整合起來，讓使用者能享受到隨時隨地都能上網的好處。而現有的無線網路有很多種，本文將重點放在同是IEEE所提的Wi-Fi & WiMAX並存的網路架構下，探討使用者在其間的換手問題，並提出了一種能考量到維持使用者原先的訊務品質的前提下之一種換手機制，其主要是當使用者要換手時，可能的目標網路不只一種時，不僅以傳統的訊號強度做為考量，還考量到是否換手過去的網路能否盡量維持使用者原先的服務品質甚至更好；考量的這部分則用了MIH的service加上多屬性決策的方式來選出一個較佳的網路；透過模擬的數據顯示出來，本文所提出來的方法較傳統的以訊號強度為考量的換手方式，不管是在換手次數、call被drop 的機率，或是基地台使用率的變化，都有較佳的結果。 With the rapid growth of wireless networks, the next generation wireless networks tend to be the integration of the existing wireless networks, which allow users to enjoy the benefits of the Internet anywhere and anytime. There are many kinds of wireless networks. This thesis will focus on the Wi-Fi & WiMAX co-existing environment and discuss the handover problem. We propose a handover mechanism to maintain the user’s quality of service(QoS) after handover. The main idea is to consider not only the received strength of the signal but also the user’s QoS when a user has to handover. We use the MIH services and the MADM method to choose a best network if there is more than one network nearby. The results of our simulation show that the proposed mechanism is better both in handover times and dropping rate.
