| Interworking heterogeneous wireless networks (HWN) enables users to enjoy seamless multimedia services when moving across heterogeneous networks. IP Multimedia Subsystem (IMS) provides foundation for implementation of network interworking, and IMS-based integration of heterogeneous wireless networks has the potential to become significantly concerned in mobile communication. However, owing to diversity and complexity of wireless network technologies, current interworking technologies of HWN are confronted with inherent defects which have not been thoroughly solved, such as unacceptable delay in session handoff, high packet loss rate, inflexible secure access solutions and so on.This thesis first details the trend of development of interworking technologies of IMS-based HWN, and elaborates various SIP-based mobility management schemes for interworking HWN.Second, with the aim to achieve fast and reliable handoff of IMS service sessions in HWN, a novel SIP-based vertical handoff scheme is proposed to reduce handoff delay and packet loss rate by adopting pre-register scenario and binding new and old addresses temporarily. A theoretical model is then developed to quantitatively estimate handoff delay and packet loss rate in the proposed scheme by using queueing network model and probability theory. After having been analyzed and compared with the typical existing handoff scheme by employing the derived model, it has been well verified that the new scheme prevails because of possessing lower handoff delay and packet loss rate, and it satisfies the demand of real-time multimedia services.In addition, with the purpose of providing secure access solutions for vertical handoff of mobile terminals, an integrated secure access platform for interworking HWN is designed, and further implemented. This platform allow legal users to flexibly and securely access interworking HWN, and security of data transmission via wireless links can be simultaneously guaranteed. |
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