In order to apply the mobile multimedia communication to the road information system, a seamless handover scheme is needed. Therefore, we present a novel micro-mobility scheme based on explicit multicast (Xcast) in this article. In our proposal, the mobile traffic of its forward direction is sent to the potential access routers of a mobile node (MN) by including IP addresses of the access routers explicitly in the IP headers. As for 802.11 wireless LAN, because it is difficult to know the potential ARs of a mobile node, a new trigger, called as the Candidate AR Trigger (CAT), is introduced to get this information from the link layer. The handover mechanism of our proposed scheme is depicted in detail and the merits of this scheme are also discussed. Finally, by using a combination of performance evaluation and simulation, we argue that our architecture is capable of providing seamless handover while introducing limited network overhead.

Due to the cost of multicast state management, multicast address allocation, inter-domain multicast routing of traditional IP multicast scheme, ASM leads to a search for other multicast schemes. This paper presents a new solution to the problems mentioned above based on IPv6. The proposed scheme provides an enhanced scheme supporting the strengths of SSM in basic Xcast. This is achieved by adding MLDv2 operations at recipient's side and a new control plane into existing Xcast. The proposed scheme does not only provide the transparency of traditional multicast schemes to sources and recipients, but it also enhances the routing efficiency in networks. Intermediate routers do not have to maintain multicast state, so that it results in a more efficient and scalable mechanism to deliver native multicast datagrams. Also, the seamless integration in Mobile IPv6 can support multicast efficiently for mobile nodes in IPv6 networks by avoiding tunnel avalanches and tunnel convergence. We've attempted to prove this alternative architecture by both simulation and implementation, respectively. Our approach cannot fundamentally perform for many large groups distributed widely as effectively as traditional multicast schemes. However, we believe that the resulting scheme is simple, efficient, robust, transparent, and to the extent possible, scalable in case that recipients are clustered in subnets.

In video conference systems over the Internet, audio and video data are often lost due to UDP packet losses, resulting in degradation of assurance. In this paper we describe a high-assurance video conference system applying the following two techniques: (1) packet loss recovery using convolutional codes, which improves the assurance of communication; and (2) Xcast, a multicast scheme that is designed for relatively small groups, reducing the bandwidth required for a multi-point conference. We added these functions to a GateKeeper (GK), a device used in conventional conference systems. Encoding/decoding and Xcast routing were then implemented as the upper layer for the UDP. We examined the functions of the system over the Internet in a multi-point conference between three sites around Tokyo, as well as a conference between Tokyo and Korea. We also investigated the effectiveness of the proposed system in experiments using an Internet simulator. Experimental results showed that the quality of received picture was improved in comparison with the case where no encoding schemes were applied.