Research On The Key Techniques Of Relay-based Media Multipath Transport And Service Access Control In IP Multimedia Subsystem

IMS (IP Multimedia Subsystem) has lots of technical advantages including end-to-end integrated all-IP networks, modular system architecture, separation of services and access technologies. It is generally believed as the underlying trend and the main direction of the next generation telecommunications technology. The most important principles and advantages of IMS are having service signaling control system and quality of service assurance mechanism.However, IMS applications and services are still in its infancy and progress slow currently. This is because there are many problems in the technical aspects of IMS.1) The single-path media transmission mode builded by the traditional routing technology in IMS lags behind, which is difficult to adapt to and support the rapid growth of broadband communication application demands.2) The value-added services in IMS are scarce, which is difficult to meet the communication needs of users. For these problems, this dissertation aims to put forward the corresponding solutions at the bearer network level and the service network level in IMS system, providing a novel IMS technical architecture for the next generation network. The main contents and innovations are as follows:(1) Multipath transport has been shown to be an effective way to improve the efficiency of data delivery. In order to achieve multipath transport, one of the key issues is how to build multiple paths between source and destination. This dissertation presented a general framework of multipath transport system based on application-level relay (MPTS-AR). A relay service system composed of control server and a large amount of application-level relay servers is deployed to provide multipath conditions between source and destination, getting rid of the dependence on the network environments in the existing multipath transmission technologies. As overlay nodes, relay servers don’t care about the end-to-end transmission requirements and only provide UDP-based forwarding service. So relay server’s behavior is greatly simplified and it is helpful to the standardization of the relay service. In order to facilate the specialized relay transmission service, a relay service control protocol named OpenPath was defined in the control plane of MPTS-AR. A session negotiation control mechanism supporting media multipath transport was presented in order to apply MPTS-AR framework to IMS system. A new multipath transport service was defined to enable IMS network side to manage media transmission process and provide multipath transport function. MPTS-AR is general and can be applied to various application programs, and has no requirements and modifications to the network setting of endpoints and network infrastructure. And the centralized control of MPTS-AR is beneficial to allocate transmission bandwidth and other network resources from macro perspectives.(2) For the topological organization problem of relay overlay network, this dissertation presented a two-level topology model of relay overlay network based on application-level traffic optimization and application awareness. Using underlying network information provided by network operators, relay servers were organized effectively according to the underlying network topology information. And through the performance detection process among relay servers, a number of transmission performance metrics of overlay network were obtained. This topology model has the characteristics of physical network awareness, application awareness, and the high scalability. For high-quality relay path assignment problem, this dissertation presented a relay path assignment scheme based on the application layer traffic optimization and application awareness, on the basis of the presented overlay network topology model. This scheme includes a relay path cost evaluation method, which combines multiple factors such as routing overhead, transmission performance and relay server processing power, and an optimal relay path generation algorithm. This scheme not only has a better performance in choosing high-quality relay path, but also provides the flexibility to balance loads among provider-defined domains and among relay servers.(3) For load distribution problem in multipath transmission, this dissertation presented a kind of load distribution mechanism supporting a variety of application types. A new partition granularity, flow block, was introduced. The partition method and size of flow blocks are related to the application type, which is used to meet the transport needs of a variety of application types. For reliable and non-real-time application type, an earliest free path preference reliable multipath transport load distribution algorithm was presented to maximize the data throughput of end users. For real-time application type, a packet reordering-controlled realtime multipath transport load distribution algorithm was presented for the purpose of minimizing the packet reordering risk. In the data plane of the multipath transmission general framework, this dissertation designed a multipath transmission protocol suite supporting a variety of transmission demands and being easily extensible. Each concrete multipath transport protocol is aimed to meet the transmission requirements of a specific category of upper applications.(4) In view of the lack of value-added services in IMS and the shortage of control and quality assurance mechanism in the cloud computing, this dissertation presented a cloud computing service model supporting IMS signaling access control, which is named IMSCloud. Cloud computing services are effectively controlled by the signaling system, QoS policy decision and charging strategy in IMS. For telecom operators, IMSCloud is able to quickly deploy content-rich and commercially valuable cloud computing services without changing the existing IMS architecture. And IMSCloud is able to provde users with quality-quaranteed cloud computing services using policy and charging control framework. IMSCloud will be able to promote the popularity and growth of IMS. For cloud computing service providers, IMSCloud can make full use of the existing perfect authentication and policy and charging control framework in IMS to implement the commercial operations of cloud computing services and the standardization of cloud computing service management interfaces.