发展中的MPEG-21标准及其应用

介绍了多媒体框架国际标准MPEG—21的体系结构、主要内容和核心技术，讨论了使用MPEG—21在异构网络环境中进行综合多媒体访问的技术。     

多媒体框架标准MPEG-21

1999年提出的作为多媒体框架标准的MPEG—21目前也取得了重大进展，正引起人们的广泛关注。文中即对MPEC一21的目标、基本概念、关键要素、工作规划及应用领域等给予概括阐述。     

基于MPEG-21数字项改编的UMA系统

介绍了UMA系统的基本功能以及不同的视频格式和网络状况给UMA系统带来的失配问题.阐述了在UMA系统中引入MPEG-21的第7部分--数字项改编,来实现资源改编引擎以支持转换编码工具和资源改变引擎QoS的实现,从而解决失配问题.     

Improved rate control for MPEG-4 video transport over wireless channel

Video streaming over wireless channel is challenging due to a number of factors such as limited bandwidth and loss sensitivity. In this paper, we develop a novel rate control algorithm for MPEG-4 video coding. Unlike traditional rate control schemes, we jointly consider the encoding complexity variation and buffer variation as well as human visual properties to optimize the rate control efficiency. We also analyze the sensitivity of a macroblock (MB) as a result of bit errors and calculate its error sensitivity metric. This metric is used in unequal error protection of the MB. Simulation results show that proposed approach can improve the decoded picture quality in wireless video coding and transmission.     

基于漏桶的内容适配系统接纳控制

综合终端特征、内容对象语义特征和通信特征,根据系统负载情况估计用户感受到的服务质量,作为接纳控制的依据,并引入漏桶模型和PID控制法进行反馈控制,从而解决了在网页内容适配系统对内容进行动态适配时,由于异构用户服务请求的系统资源需求特征差异很大,导致适配资源耗费过大,难以有效进行的问题。理论说明和仿真测试结果表明该方法从一定程度上提高了用户的主观服务质量,为内容适配的接纳控制研究做出了有益的探索。     

Integrated scheduling and link adaptation for heterogeneous networks: design and performance analysis

ABSTRACT

This paper presents novel integrated scheduling and link adaptation (ISLA) schemes for links which have a common spectrum and possibly different rates and reliability constraints. We consider the problem of weighted sum average rate maximisation of wireless links. In an orthogonal transmission system, a link is selected using instantaneous signal-to-noise (SNR) of all the links, and its rate and power are set in a jointly optimised manner. To demonstrate the effectiveness of the proposed approach, we analyse ISLA schemes with continuous rate adaptation using constant or adaptive transmission powers. ISLA schemes are designed in similar settings for practical discrete rate-adaptive systems using adaptive modulation and coding. To this end, a design framework is presented, which relies on a partitioning of space of links’ SNRs into regions, similar to structured vector quantisation. Within this framework, a particular ISLA design with high performance and polynomial complexity is suggested. The proposed schemes are designed before the start of the transmission, based on closed-form solutions, and can easily be applied to multiple access or broadcast networks. We also analyse several schemes for comparison, which employ modified Round-Robin, opportunistic scheduling or online generalised scheduling. Numerical results demonstrate how the proposed ISLA schemes outperform the benchmark schemes and effectively meet various user requirements.¹     

TIRAMISU: A novel approach to content representation and key management for seamless super-distribution of protected media

Media delivery over heterogeneous networks requires both flexible representation and robust protection of content. This paper provides details on the framework for audiovisual content creation, delivery, consumption and protection as conceived within the IST project The Innovative Rights and Access Management Interplatform SolUtion. The proposed framework is based on the emerging MPEG-21 standard for multimedia content delivery and consumption and at the same time it complements it in several aspects, most notably by fully specifying a digital rights management (DRM) scheme. Central to the described framework is a novel key management system, relying on smartcards, which addresses many issues that previously blocked wider adoption of DRM: obtrusiveness of the DRM technology perceived by the end-user, flexibility in licence formulation and adequate level of trust as requested by content owners.     

一种MIMO-WLAN的跨层速率控制方案

针对下一代无线局域网高速率演进的要求,该文提出一种跨层的多输入多输出(MIMO)系统速率控制算法。首先分析了保证业务误码率的物理层吞吐率最大的速率控制算法存在的不足;然后结合自适应调制编码技术,实现了基于预测的MAC(Media Access Control)层吞吐率最大的跨层速率控制算法。仿真和分析表明算法可以取得近似优化的速率选择结果,能够保证业务的误码率性能,提高业务的吞吐率。该文的算法计算简单、预测准确、运行高效,不仅可以实现闭环速率控制,还可用于帧重传和多业务调度等应用的速率控制。