在IEEE 802.11的無線網路架構下，每個Mobile Node以競爭的方式（CSMA/CA）來取得無線網路資源。在此競爭模式的運作下，每個Mobile Node所分配到的頻寬並非固定不變。因此Mobile Node在進行Handoff時，不能只單單考量所測量的RSS（或RSSI）值。

　　本篇論文所提出如何在IEEE 802.11的網路環境下快速在Access Point（AP）間作Handoff，以達到行動性的要求。我們提出一個Mobile Node在作Handoff時應該考慮的兩個因子：AP所能提供的頻寬與該AP的訊號品質狀況，因此在本篇論文中將會說明如何計算一個AP所能提供給Mobile Node的Throughput與該AP環境下的Bit Error Rate（BER）。我們實作了一個系統實際觀察各個Mobile Node的Handoff情況，並以simulation的方式驗證出我們的方法確實效能較佳。

　　The IEEE 802.11 extended service set (ESS) allows mobile users to move from one basic service set (BSS) to another by handoff between access points. Unlike GSM or GPRS cellular system, the contention-based CSMA/CA mechanism is adopted in the IEEE 802.11 MAC layer protocol. Thus, the BSS can not provide guaranteed bandwidth for each associated mobile station. In this paper, we consider the worst case available bandwidth and the received signal strength as the handoff factors. We modify the traditional handoff algorithm by referring the Integrated Handoff Factor (IHF) rather than the Received Signal Strength (RSS) as usual. We also develop fast handoff architecture to reduce the time spending in micro-handoff and macro-handoff. Extensive simulation and experiment results show that our IHF-based handoff mechanism can provide better network quality for mobile stations. The time spent in micro-handoff and macro-handoff is less than the handoff time spent in traditional handoff architecture.

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