想要在無線環境中提供頻寬需求較大的多媒體服務，使用無線非同步傳輸模式網路(wireless ATM network)是一個很好的解決方案。無線非同步傳輸模式網路提供了行動支援(mobility support)，使得行動台(mobile terminal；MT)能夠在不同的基地台(base station；BS)之間移動。在支援使用者移動的同時，有一個最主要的議題，就是在基地台之間的移交(handoff)問題。由於無線ATM網路的細胞(cell)相對較小，細胞之間重疊的距離也較小，所以移交程序(handoff procedure)必須能夠很快地完成，也就是必須具有相當小的移交延遲(handoff delay)。除此之外，由於ATM的服務方式屬於連接導向(connection oriented)，當移交發生時，在建立新的連線前必須要先尋找出新的路徑，此過程即稱為再繞徑(rerouting)。
在本論文中，我們提出一個以道路拓樸為基礎的再繞徑機制(Road-Topology-Based Rerouting Scheme)；這是一種移交預測的技術，使用行動台即時的位置資訊以及資料庫當中的道路拓樸資訊以準確地預測行動台將來可能移交過去的目的移交細胞(target handoff cell)，藉此先預建好路徑到目的移交細胞中，除了可以達成快速再繞徑，使得移交程序能夠很快、很順利地完成之外，還可以避免網路資源的浪費。

In order to provide broadband multimedia services in wireless environments, wireless ATM (WATM) network is a good solution. WATM network provides mobility support, allows mobile terminal (MT) to move among different base stations (BSs). While giving mobility support for users, a major issue is the handoff between BSs. Since the cells in WATM network are smaller, the overlapping distance between two neighboring cells is also smaller. Therefore, the handoff procedure must be finished in a short time, that is, to have very small handoff delay. Besides that, since the service in ATM is connection-oriented, when handoff occurs, the system has to set up a new connection to the new BS, and this procedure is called "rerouting".
In this thesis, we propose a road-topology-based (RTB) rerouting scheme. It is a kind of handoff prediction scheme, which utilizes real-time positioning information of MT and road topology information in the prediction database to precisely predict the possible (target) handoff cell of that MT. We can therefore set up a connection to the target handoff cell and reserve bandwidth for that MT in advance of a handoff actually happens. This not only achieves fast rerouting, so that handoff procedure can be finished very soon, but also avoids wasting of network resources.

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