在IEEE 802.16 無線通訊標準中,802.16d是以提供固定式的無線城域連接服務。而在隨後所推出的IEEE 802.16e 是為支援可移動性的服務所產生的。為支援可移動性服務的狀況下,換手技術(handover)的應用是移動服務的重要關鍵。處於移動狀態下的使用者，其與基地台的訊號強度會因距離和環境的變化而有所改變。若彼此間的通訊訊號強度不足以維持目前通訊的要求，那麼使用者端就必須要向鄰近的基地台請求連線。由於此過程必須花費一些時間，使用者若是有及時性質的連線，就有可能會造成封包的遺失，嚴重時甚至會造成連線中斷。在”WiMAX End-to-End Network Systems Architecture”[7][8]裡，WiMAX Forum 提出了ASN Anchor Mobility 的方式。這種移動換手方式是將服務的區域範圍延伸擴大，主要是分成多個 ASN ，而透過 ASN 中 ASN-GW 來負責封包的轉送，包括與 CSN 和其他 ASN 間的連結溝通。本論文將以IEEE 802.16e換手技術(換手時機的決策)結合ASN Anchor Mobility 方式後模擬 MS 有跨越 ASN 之情況進行換手的探討。

In IEEE 802.16 wireless communication standard, 802.16d is the fixed connection of wireless. IEEE 802.16e can support the moving service. In order to support the moving serves, the application of handover technology is very important. In the moving status, the signal intensity will change because of changing distance and the environment. If the intensity of communication signal between each other is not enough to maintain the request of the communication at present, MS must contact neighbouring BS. Handover need spend some time, if the user has real-time services, the data maybe lose. In " WiMAX End-to-End Network Systems Architecture " [7 ] [8 ], WiMAX Forum has proposed the way of ASN Anchor Mobility. This kind of movement handover way will be the regional range of the service is extended and expanded. Divide a lot of ASN , and ASN-GW forward to the data between CSN and the other ASNs. This thesis base on IEEE 802.16e handover technology and ASN Anchor Mobility architecture, to discuss the performance of handover.

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