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题名	基于IMS的移动多媒体广播时移系统关键技术研究
作者	肖琳
学位类别	博士
答辩日期	2009-05-25
授予单位	中国科学院声学研究所
授予地点	声学研究所
关键词	移动多媒体广播 IP多媒体子系统 时移 会话初始协议 移动性管理 资源调度策略 缓存替换算法
其他题名	Studies on Key Technologies of IMS-based Time-shifting System for Mobile Multimedia Broadcasting
学位专业	信号与信息处理
中文摘要	移动多媒体广播实现移动环境下的数字多媒体接收，用户可以通过多种移动终端在不同地点移动地享受数字多媒体服务。在其上进一步开展时移业务可以使用户不再受电视节目表的时间限制，实现真正的随时随地接入网络享受服务，必将为移动多媒体广播带来新的业务增长点。面向移动终端的时移业务需要双向性网络的支持，现今成熟的基于IP核心网络的移动通信网络为移动终端上的时移业务开展提供了有利的条件。在移动通信网络上发展起来的IP多媒体子系统（IMS），实现了固定和移动的融合，成为下一代网络的核心网络架构，为网络融合奠定了基础。基于IMS网络架构构建移动多媒体广播上的时移系统，既是技术的选择，又符合网络融合的发展趋势。 本文对基于IMS的移动多媒体广播时移系统关键技术进行深入研究，主要研究内容包括：基于IMS的移动多媒体广播上的时移系统架构、支撑时移业务的统一SIP控制信令、移动环境下对时移业务的移动性管理以及提供时移业务的时移服务器关键技术等。本文通过对以上关键技术的研究，分析技术难点，并提出相应的解决方案和关键算法。本文的主要贡献和创新点如下： 1、提出一种混合网络的组网方式来提供移动多媒体广播上的时移业务，并对其进行性能分析。以广播网络为基础，辅以移动通信网络来提供时移业务的混合组网方式，弥补了广播网络单向性的不足，可以充分利用现有资源，减少部署，快速应用于移动多媒体广播环境中。 2、提出一种基于IMS的移动多媒体广播时移系统架构。定义了系统中与时移功能相关的功能实体，并通过理论分析验证了系统的可行性。实验数据表明，时移服务器的服务强度影响时移业务的信令延迟，可以通过控制时移服务器的服务强度，来保障时移业务的实时性。 3、提出采用SIP协议作为支撑时移业务的统一控制信令方案，包括会话控制和媒体控制。一方面避免接入IMS网络的信令转换，另一方面使得业务提供平台和用户终端的协议栈简单化、轻量化，仅需采用SIP作为控制协议即可，易于业务提供商进行时移业务的开发。 4、提出一种改进的应用层移动性管理方案，主要包括水平切换和垂直切换，可以对移动多媒体广播时移业务中的终端移动性和模式移动性进行支持。通过对切换延迟和用户体验延迟进行分析和仿真，改进后的切换算法，虽然需要增加一定的切换延迟，但是在用户体验延迟方面比改进前有了较大的改善，可以保证无缝的时移业务体验。 5、提出一种基于可预测用户行为的TS-PMS资源调度策略，并采用最大概率预测法和最大期望预测价值预测法对用户行为进行预测。该策略充分考虑时移业务的特点，通过减少用户时移操作时的等待延迟，改善了用户体验。仿真结果表明，TS-PMS采用可预测用户行为的资源调度策略后，减少了用户的平均等待延迟，其中最大期望预测价值预测法优于最大概率预测法。 6、提出一种基于期望预测价值（EPV）的TS-PMS缓存替换算法。该算法提供了多用户情况下时移服务器的缓存替换策略。仿真实验表明，基于EPV的缓存替换算法与传统的基于FIFO的缓存替换算法相比，提高了预测缓存的命中率，减少了用户平均等待延迟，从而提高了多用户情况下时移系统的服务性能。
英文摘要	Mobile multimedia broadcasting supports digital multimedia service in mobile environment, by which users can enjoy digital multimedia service everywhere with various terminals. Time-shifting service based on mobile multimedia broadcasting enable users to enjoy the service anywhere and anytime, without the limitation of the traditional TV schedule, thus it can bring new business. Time-shifting service on mobile terminals requires bi-directional communication network, while modern mobile communication network is IP-based, that means the bi-directional communication feature of the core network makes it easy to support time-shifting service. Furthermore, the IMS(IP Multimedia Subsystem) developed on mobile communication network supports the convergence of fixed and mobile communications, and it is the kernel infrastructure of NGN(Next Generation Network). Taking both technical issues and industry trends into consideration, it is a good choice to implement time-shifting system for mobile multimedia broadcasting based on IMS. This dissertation presents in-depth researches on key technologies of IMS-based time-shifting system for mobile multimedia broadcasting. The researches focus on: the architecture of IMS-based time-shifting system for mobile multimedia broadcasting, universal SIP signaling mechanism for time-shifting feature, mobility management for time-shifting service under mobile circumstance and key technologies of time-shifting server. Through the research and analysis for the above contents, solutions and key algorithms are proposed to solve the difficulties and problems. The main contributions and innovative work of this dissertation are described as follows: 1.A hybrid network architecture to support time-shifting service on mobile multimedia broadcasting is proposed and the performance is proved by theoretical analyses. The hybrid network architecture for time-shifting service is based on broadcast network with mobile communication network assisted, which makes up for the deficiency of unidirectionality of broadcast network. By fully utilizing existing resources to reduce the infrastructure deployments, it can be quickly implemented into the mobile multimedia broadcasting. 2.An IMS-based time-shifting system architecture for mobile multimedia broadcasting is proposed. Related functional entities are defined and a theoretical analysis is derived to prove the feasibility of this system. The simulation result shows the signaling delay is related with the traffic intensity of the time-shifting server. Therefore, by controlling the traffic intensity of the time-shifting server the real-time ability of time-shifting service can be guaranteed. 3.SIP protocol is used as the uniform signaling mechanism for time-shifting service, including session management and media control. By using SIP only, not only signaling converting can be avoided, but also the protocol stacks of service server and client application can be simplified and lightweight, which makes it easy to develop the time-shifting service for providers. 4.An improved mobility management scheme is proposed, including horizontal handoff and vertical handoff, which can support both terminal mobility and mode mobility of time-shifting service for mobile multimedia broadcasting. By conducting analysis and simulation on handoff delay and user experienced delay, a conclusion is got that user experienced delay can be reduced by our proposed scheme, even though the handoff delay is increased. The result shows that the improved scheme can guarantee seamless experience for time-shifting service. 5.A strategy of resource scheduling for TS-PMS based on predictable user behaviors is proposed. Furthermore two prediction algorithms, the algorithm based on maximum transition probability and the algorithm based on maximum expectation prediction value, are proposed for prediction of user behaviors. This strategy takes the characteristics of time-shifting service into consideration, which improves the user experience by reducing average waiting delay caused by time-shifting operations. The simulation results show that the average waiting delay is reduced by the proposed strategy with two prediction algorithms, and the algorithm based on maximum expectation prediction value is superior. 6.A cache replacement algorithm for TS-PMS based on EPV(Expected Prediction Value) is proposed. This algorithm is applied to the cache replacement in multiple-users environment. The simulation results show that the algorithm based on EPV achieves higher hit rate of the prediction cache and lower average waiting delay than the algorithm based on FIFO, which helps improve the performance of the time-shifting system.
语种	中文
公开日期	2011-05-07
页码	155
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/336]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	肖琳. 基于IMS的移动多媒体广播时移系统关键技术研究[D]. 声学研究所. 中国科学院声学研究所. 2009.

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