| Summary: | 碩士 === 義守大學 === 資訊工程學系碩士班 === 98 === Recently, many of popular multimedia communication services are composed of heterogeneous information networks in the Internet, which including a large number of wireless and mobile communication networks, including WiFi, WiMAX, 3G, etc. Especially, WiMAX has become one of the candidates of next-generation of wireless access networks. In Taiwan, there are a lot of telecom companies ready to provid WiMAX services for users. On the other hand, the multicast multimedia services (such as IPTV) have become one of the most concerned technologies in Internet applications. Because of the user’s mobility, the mobile node (user) must re-send a join message to the multicast group and rebuild the new multicast tree at each time of handover. It may result in the uncontinuous service caused by the breakdown of the communication connection and packet lost. The quality of service will not be tolerable for the real-time services.
Although many researches have proposed handover mechanisms to speed up the process of handover, but we found that there are still some problems of the delay time. For example, in the handover process, it usually needs to take time for registering and updating. For multicast services, because of the disconnection with the server before sending the re-join message to the multicast group and rebuild the new multicast tree, leading the situation of long delay time. For solving these problems, we proposed a cross-layer handover mechanism for multicast services in IEEE 802.16e networks, including these points: (1)Adding hierarchical[5] for modifying the structure of transmission path of the handover procedure and sequences of messages transmission to eliminate the delay time cause by re-registration; (2)While processing handover, send the re-join message to the multicast group in the meatime; Through these modifies to improve tthe situation that takes long delay time caused by re-registration or executing the re-join message.
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