| Summary: | 碩士 === 國立中正大學 === 資訊工程所 === 97 === In this article, we investigate the network mobility support in the IMS-based next generation networks and propose two interworking architectures: loosely coupled and tightly coupled. The loosely coupled approach is to integrate SIP-NEMO into IMS; the tightly coupled approach is to extend IMS with network mobility support. The loosely coupled architecture maintains the original characteristics of SIP-NEMO and IMS, and session control signals are passed through the interrogating network in the IMS. In order to achieve the consistency of encryption algorithm, authorization, authentication and charging in the loosely coupled architecture, we make some modifications on the interworking components in the SIP-NEMO network. In tightly coupled architecture, we define a Super User Agent (SUA) for each mobile network. The SUA has its IMS home network and acts as a mobile gateway to manage the mobility issue on behalf of all the users attached in the mobile network. The tightly coupled architecture can be considered as hierarchical IMS networks, and session control signals either originating or terminating at the UA are passed through the IMS home networks of both the SUA and the UA. A tunnel mechanism between the SUA and the S-CSCF of the SUA is proposed for the security consideration so that all the users on the vehicle could communicate with their respective IMS home networks through the SUA. We respectively present four basic scenarios: registration, session establishment, node handoff and network handoff in the two interworking architectures to verify their feasibility, and show these architectures achieve the fourth level of interworking. In addition, we derive a network-based SIP (Net-SIP) handoff mechanism by collaborating with the modified context transfer to diminish the number of messages exchanged for network mobility and the handoff latency. Analytical results show that the handoff delay in the loosely coupled architecture can be shortened significantly, compared with the SIP-based macro-mobility in the standard IMS. We also demonstrate that the tightly coupled architecture makes the value-added services provided in the vehicle more intelligent by integrating them with the IMS session control.
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