【作者】 于波；

【导师】 于东；

【作者基本信息】 中国科学院研究生院（沈阳计算技术研究所） ， 计算机应用技术， 2012， 博士

【摘要】 IMS即IP多媒体子系统作为下一代网络的核心架构，逐步被各国际标准化组织认可。凭借其接入无关的特点和统一的业务模型，能够支持多种接入网络在统一的平台提供丰富的多媒体业务。所以IMS成为移动网、固定网融合以及电信网、广播电视网、因特网融合的最佳解决方案，为最终实现核心网和接入网向全IP化方向演进奠定了坚实的基础。然而，IP网络是一种“尽力而为”的服务网络，如何在IP网络上提供服务质量保证的电信级服务将是IMS顺利发展的关键。为了解决IMS网络的服务质量问题，国际标准化组织纷纷制定了基于策略的IMS QoS框架。采用策略决策和策略执行方式，通过IMS信令控制平面和传输平面协作，完成接入网的资源分配与准入机制。但是这种基于策略的QoS框架，并不能解决接入网络链路质量损失所带来的服务质量下降问题。此外IMS的集中控制思想没有充分考虑网络资源利用情况，容易引起集中式网络存在的典型问题。本文旨在通过在IMS网络中引入符合QoS框架的重叠网络，并在该网络上利用多路径传输技术实现应用层传输优化，从而解决IMS集中式网络的服务质量问题。本文主要的创新性研究工作如下：1．提出了一种符合IMS QoS要求的重叠网络构建方法。通过重叠网络服务功能实体，实现在传统IMS网络上构建业务相关的DHT重叠网络。本文提出的重叠网络服务功能还具备网络测距能力，通过网络测距算法根据BGP属性信息推测候选服务节点网络相对距离，实现拓扑感知的重叠网络为多路径传输奠定了基础。2．提出了一种基于马尔科夫决策过程的多路径冗余传输调度算法。通过对多路径并行传输SCTP协议的改进，实现了根据路径质量动态调整数据传输调度策略的方法。对于实时业务中的关键数据进行冗余传输，能够避免单一路径失效导致的实时业务服务质量严重下降问题。3．提出了一种IMS架构下支持多路径传输的混合式内容分发机制。通过利用拓扑感知的重叠网络和传统内容分发网络，实现流媒体业务的流量边缘化，降低中心媒体服务器负载，提高网络资源利用率和系统服务容量。通过对直播和点播业务的服务流程设计，证明了方法的可行性。该机制为IMS流媒体服务提供了新的思路和方法。4．提出了一种IMS异构无线网络中，利用多路径并行传输技术，实现无缝垂直切换的方法。通过借鉴IEEE802.21提供的媒介无关的切换方法，结合多路径并行传输技术，提出了一种IMS异构无线网络垂直切换算法。算法能够在切换发生前通过多路径方式冗余传输数据，避免切换导致的数据丢失及延迟问题。论文对上述创新工作给出了具体实现方式、信令流程和相关的算法描述，并通过仿真工具对各关键技术进行了仿真验证。仿真实验表明，本文提出的基于IMS重叠网络的多路径传输关键技术与传统IMS网络相比，能够实现应用层传输优化，有效提高网络资源利用率，改善服务网络的QoS体验。更多还原

【Abstract】 As the next generation network architecture, IP Multimedia Subsystem (IMS) isgradually accepted by international SDOs (Standards Development Organizations).With its access independent feature and unified business model IMS can supportmultiple access network in a unified platform to provide rich multimedia services. IMSis the best solution for FMC (Fixed Mobile Convergence) and Triple Play. The goal ofIMS development is evolution to ALL IP method for the core network and accessnetwork.However, the IP network is a best-effort service network. How to providecarrier-grade QoS on IP network will be the key problem for IMS development. Inorder to solve the problem of quality of service for the IMS network, the internationalSDOs have developed policy-based IMS QoS framework. Access network resourceallocation and admission mechanisms are realized by collaboration of policy decisionand policy execution in the IMS signaling control plane and transport plane. However,the policy-based QoS framework can not solve the problem of link quality loss inaccess network, which makes the QoS decline. In addition, the opinion of centralizedcontrol in IMS network does not give full consideration to the use of network resources,and easily lead to the typical problems a centralized network always has. This paperaims to resolve the QoS problems in IMS by the way of introduction of an overlaynetwork which is compatible with the IMS network QoS framework for applicationlayer transmission optimization in IMS network whith the multipath transmissiontechnology.In this paper, innovative research works are as follows:1. The overlay network construction method is proposed which is compatible withIMS QoS framework. The service related DHT overlay network is built by the overlayservice function. The proposed overlay service function also has the ability ofmeasuring network distance by which the algorithm can speculate the relative networkdistance for candidate service node by BGP attributes. So the topology-aware overlaynetwork for multipath transmission is realized.2. This paper also presents a MDP-based multipath redundant transmissionscheduling algorithm. Concurrent multipath transmission SCTP protocol is improvedto achieve a method of dynamically adjusting the data transmission scheduling policyaccording to the path quality. Redundant transmission of critical data in real-timeservice can avoid single path failure which leads to real-time service quality serious decline.3. A hybrid content distribution mechanism supporting multipath transmission inIMS architecture is proposed. Streaming media service traffic is decentralized by theuse of topology-aware overlay network and traditional CDN to reduce the centralmedia server load and improve network resource utilization and system servicecapacity. Live and on-demand service signaling follow are designed which prove thefeasibility of the method. The mechanism can provide new ideas and methods for IMSstreaming media services.4. A seamless vertical handover method is proposed for IMS heterogeneouswireless networks by multipath concurrent transmission technolog. By drawing on theIEEE802.21media independent handover method combined with multipathconcurrent transmission technology, an IMS vertical handover algorithm forheterogeneous wireless networks is proposed. The algorithm is able to achieve theredundant transmission of data by the way of the multipath transmission technologybefore handover to avoid the issues of data loss and latency in the process of thehandover.Finally, the paper gives signaling processes, algorithm description andimpementation for the above innovation. Several key technologies of multipathtransmission are simulated by simulation tools. The results show that compared totraditional IMS network, the presented multipath transmission based on IMS overlaynetwork in this paper can realize the application layer transmission optimization,effectively improve the utilization of network resources and promote the QoSexperience for service network.更多还原