| Summary: | 碩士 === 國立臺北科技大學 === 電機工程系所 === 93 === In recent years, since the network technologies are getting mature gradually, how to integrate various network architectures has become an important research issue. In order to get rid of the inconvenient wire constraint, Internet Engineering Task Force (IETF) proposed the mobile IP protocol in 1996. This protocol enables the mobility of those devices using wireless network.
In general, all packets in wireless network are forwarded by home network no matter where the user’s mobile node locates. Because the wireless network has limited coverage, packets might be forwarded by foreign network for keeping uninterrupted connection when user moves around. The handoff procedure occurs while two networks are switching over. Right now, IEEE 802.11 protocol does not allow to access two networks simultaneously and even makes no compensation to lost packets. These bottlenecks obstruct the wireless network for further development and spoil the linking quality. Solutions for these problems were proposed, most of them need to totally remodel the current network architecture and it’s difficult to apply. In this paper, we propose a seamless handoff mechanism which combines pre-tunneling scheme with delayed registration and needs minor revise on both protocols for agent and mobile node. This mechanism can shorten the disconnection interval needed for switch over, reduce the packet loss rate, and improve the service quality of wireless network. We adopted NS2 for simulation and analysis, and proved that the mechanism really works.
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