IMS媒体传输采用完全依赖承载网络的单径传输模式，传输效率难以满足IMS业务发展需求，严重制约了IMS业务创新。本项目提出采用基于重叠网络的多径传输技术构建IMS媒体传输的新模式，在强调支持IMS“信令控制、QoS保证”的媒体传输原则下，可进一步支持多径传输模式，进而大大提升IMS媒体传输效率。项目主要研究：1）基于重叠网络的通用多径传输系统框架；2）面向多种业务需求的多径传输控制机制和协议；3）支持媒体多径传输的IMS信令控制机制；4）支持媒体多径传输的IMS QoS策略决策模型，并设计与实现相应的原型和仿真系统。项目主要创新体现在：基于重叠网络的通用多径传输系统框架、支持多种业务传输需求和多径传输模式的UDP中继服务等。研究目标是建立基于重叠网络的IMS媒体多径传输模式理论体系和技术框架。研究成果将有助于完善IMS体系结构，在促进IMS业务发展方面有重要应用前景。

Media transmission in IMS is entirely dependent on the underlying bearer network, which is in single-path transmission mode. The transmission efficiency of the underlying bearer network is unable to meet the development needs of fast-growing IMS services, and also has seriously hampered the IMS business innovation. This project proposes a new media transmission model in IMS using multipath transmission technology based on application-layer overlay network. In compliance with the principle of IMS architecture (i.e. signaling control while with QoS guarantees), the new transmission mode can further support multipath transmission, and thus greatly enhance the transmission efficiency of the IMS architecture. The research contents include 1) a general multipath transmission framework based on overlay network, 2) multipath transmission control methods and protocols supporting various end-to-end transport requirements, 3) media negotiation and signaling extension in IMS for multipath transport based on overlay network, and 4) IMS QoS policy and decision-making model supporting multipath transport. The related prototype and simulation systems will be designed and implemented. The main innovations include: the general framework of multipath transmission system based on application-layer overlay network, the simple and powerful UDP relay service supporting various end-to-end transport requirements and multipath transmission mode, and so on. The goal of this study is to establish the theoretical methods and technology framework of IMS media multipath transmission mode based on overlay network. The research results will contribute to the further improvement of IMS architecture, and will have important application prospect in the promotion of IMS applications and business development.