| With the rapid development of the mobile communication technology and wide applications of laptops, Personal Digital Assistants, mobile phones and other mobile devices, it is hoped that Internet access and continuous communications are maintained in the process of moving.Compared with IPv4, there are more addresses for IPv6, which is more benefit for the development of mobile technology. Now IPv6 has become current research trend.Because of IPv6 being the core protocol of the next-generation Internet, the present IPv4 networks and Internet applications will be a gradual transition to the IPv6 network. At the same time, with the mobile communication and the Internet technology trending towards fusing, Internet services urgently need the support for mobility, but the mobile communication also needs to strengthen data and multimedia services, there will be many new challenges and opportunities in the implementations and applications with the integration of the two. The handover technology of the mobile IPv6 is one of the research trends of this field, whose aim is to improve the Quality of Service in the real-time transport of the mobile network. It means that to reduce handover delay and data packet loss rate so as to achieve seamless handover, however, current network protocols and handover process can not satisfy these needs. As a result, the handover technology, especially under the mobile IPv6, is the key issue facing in the real-time applications of the next-generation network environment, which is worthy of research, and also the core contents of this paper. This paper describes the basic mechanism of IPv6 protocol and MIPv6 handover problems in details. The handover delay of the standard MIPv6 protocol is a little longer, which is easy to cause the communication interruption and data packet loss. So it can not meet the needs of real-time application and sensitive data loss applications such as VoIP.The Paper expatiates on the expansion technologies of MIPv6 handover protocol, such as fast handover technology for MIPv6, smooth handover technology for MIPv6, Hierarchical MIPv6, analyzing and comparing performances of series of handover expansion technology. Although F-MIPv6 and HMIPv6 improve handover performance of MIPv6 network to some extent, they still have some drawbacks in some cases. For example, HMIPv6 handover performance is not better than basic MIPv6 when mobile terminal devices handover in different subnets, because of the addition of interactive signal in networks. Therefore, to design a better MIPv6 handover program to meet practical applications is another important goal of this paper.In the process of the HMIPv6 protocol handover, this protocol configures LCoA and RCoA for MN by stateless autoconfiguration, and there is need to perform DAD procedure for ensuring uniqueness of address, which results in significant handover delay. Hence Improving HMIPv6 handover performance by eliminating effect caused by DAD procedure is feasible.This paper modifies CoA configuration methods for HMIPv6 handover protocol by establishing address pools for every AR and MAP that store IP addresses used in the subnets. The MN applys to current AR for CoA when it finds itself will move to a new subnet. Therefore, DAD procedure is not necessary any longer. At the same time, communication mechanisms and message format of handover process have been made.The Improved program proposed in the paper can sharply reduce handover delay and significantly improve handover performance in IP layer by comparing HMIPv6 with improved HMIPv6.Finally, we carry out simulation experiments of two handover protocols listed above by using NS-2 network simulation tools. The results show that the proposed program can effectively avoid the DAD procedure for CoA in HMIPv6, reduce handover delay as well as data packet loss, improve QoS of real-time communication in mobile networks and implement seamless handover. |
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