| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 100 === In the very first version of the IEEE 802.11 standards, only the Physical Layer and Data link layer are defined but no mechanism about the handoff process. In most implementations, the handoff mechanism is triggered when mobile nodes are out of range of the access points. As a result, problems, such as network disconnection, large amount of packet loss, and long-term packet delay are frequently incurred. To improve these problems, we propose a new Layer-2 handoff mechanism called Fast Pre-scanning Scheme for Layer-2 Handoff or FPSLH is short. The proposed mechanism adopts pre-scan process and packet buffer; the two designs can reduce the packet loss rate. Moreover, active scanning is substituted by passive scanning to reduce the packet delay caused by the long wait time of the active scanning mode. The proposed Layer-2 handoff mechanism is verified by simulations using NS-2. Not only did it efficiently decrease the End to End Delay time in the Layer-2 handoff mechanism, but it also has no packet loss during the whole stimulation process.
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