具有优先级特征的多媒体流的资源管理

本文研究了具有优先级特征的分布式多媒体流的资源管理，提出了一种基于节优先级的资源管理的设计方法，包括资源管理机制，资源管理策略，服务质量（ＱｏＳ）协商调整算法和高优先级节枪占算法，它能够保证稳定的具估优先级特征的多媒体流，能够极大地调度并发的多媒体流，特别是在系统资源不足时，能够最大限度地调度高优先级的多媒体流，并能保证各多媒体流量了的ＱｏＳ。     

基于VBR多媒体流资源管理的研究

在分布式多媒体系统中,连续媒体流采用压缩方式传输,以减小最昂贵资源网络带宽的使用．但是压缩媒体流是变化位速度（ＶＢＲ）,在网络传输中产生突发情况,给网络资源管理带来了挑战．本文在基于未压缩本流节资源管理方案基础上,提出ＶＢＲ节概念,把变化尺寸的突发的媒体帧拆分成网络发送包,采用周期性调度,平滑突发帧的传输,给出了ＶＢＲ节在保证流ＱｏＳ基础上,ＣＰＵ周期、带宽和缓冲区资源的分配公式,显示出通过调整调     

基于事件驱动架构的分布式流处理弹性资源分配策略研究

针对具有多个数据源以及多个输出的流处理应用,使用单个分布式数据流引擎开发时,不论在架构还是可扩展性方面都存在着不足,而基于事件驱动架构的分布式流处理技术是解决该问题的主要方式.但是,事件驱动架构应用于流处理时,往往面临着数据注入速率与数据处理速率不一致的矛盾,当流数据源的数量发生变化、数据值的分布发生波动时,会导致处理延迟加大或资源利用不充分.针对数据注入与数据处理不一致的问题,现有的弹性资源分配策略难以有效处理生产者和消费者之间的依赖关系,且资源分配效果欠佳.论文提出了一种基于强化学习的弹性资源分配方法,解决了具有依赖关系的流处理应用程序之间的数据波动带来的延迟或者资源利用不充分的问题.通过建立状态矩阵和命令矩阵,使得资源管理器能够感知上下游应用的状态变化,从而及时调整流处理应用的资源需求,保证了流处理应用执行过程的延迟要求,提高了系统的资源利用率.经过测试,基于强化学习的弹性资源分配与Spark动态资源分配方法相比,延迟能减少15%,资源利用率能提高20%以上,其吞吐量能够提高10%左右.     

基于同步时间Petri网的细粒度多媒体同步模型研究

多媒体同步是分布式多媒体信息系统的关键问题。在分析和比较几种已有的典型的多媒体同步模型的基础上．本文提出了一种新的模型：同步时间Petri网(简记为STPN)。STPN不仅能完整、准确地对媒体流内和媒体流间的时间层次行为进行形式化描述，而且解决了时间流Petri网中存在的死托肯问题。特别地，通过引入抑止弧，STPN有效地克服了随机延迟、阻塞、丢包等因素的不良影响。尤其当丢失率较高时．STPN更能体现其优越性和鲁棒性。     

远程教学直播系统中媒体同步的研究与实现

对于远程教学直播系统这样包含不同媒体流的分布式多媒体应用而言，媒体同步是一项重要内容。利用RTP（实时传输协议）传输机制中的时间戳和序列号信息，提出同步控制算法，实现了流内同步和流间同步。考虑到分组网络带来的延时抖动，算法可以动态地适应网络延时变化，从而保证了分布式环境中媒体同步的服务质量。     

基于可修改区块链的互联网码号资源管理方案

为加强IP地址、自治域号等国际互联网码号资源的管理和控制,国际互联网工程任务组提出了互联网码号资源公钥基础设施,近年来有效解决路由劫持、路径篡改等问题,为保证域间路由稳定运行发挥了巨大作用.然而,它在互联网码号资源管理模式中存在的安全问题也逐渐突显,如单点故障、资源分配异常、证书撤销数据同步不及时造成验证失效等.本文针对上述安全问题,提出了一种基于可修改区块链的互联网码号资源管理方案,并通过实验验证了该方案的有效性和可行性.     

多媒体流间同步参数计算

1 引言在分布式多媒体同步控制中,基于有界缓冲区(Boundary Buffer)的同步方式是其中一种主要的强制同步方式。为同步源设置有界缓冲区,将有助于减轻或消除因网络抖动或其他影响所带来的不连续现象,这是保证流内各个媒体单元的实时和连续的重要手段。对于流间同步,设置有界缓冲区的方式也是十分必要的,如快进或重播某些媒体单元等同步操作,都需要缓冲区的支持。     

基于移动Agent和混合蛙跳算法的网格计算资源管理

为了克服传统网格系统采用Globus集中式模型或P2P网络分布式模型具有的无法兼顾全局控制性和扩展性的问题,提出了一种基于移动Agent和混合蛙跳算法的网格资源管理模型;首先,引入移动Agent将资源管理模型划分为应用管理模块、资源管理模块和资源表示模块,然后通过在经典的混合蛙跳算法加入差分扰动设计了一种改进的混合蛙跳算法,最后,在资源管理模块中的资源分配Agent中运行改进的混合蛙跳算法实现用户任务到资源的调度;采用GridSim工具进行仿真,实验结果表明,文中的资源管理模型具有较强的全局控制能力和扩展性能,资源利用率高达95.65%,较其它方法具有较小的时间跨度和较高的资源利用率,是一种适用于网格环境的有效资源管理模型。     

一种基于知识的分布式网格资源管理模型

本文构建基于知识的分布式网格资源管理模型入手,提出了一种新的网格资源管理模型。该模型增强了网格资源管理系统的可扩展性。     

集成多媒体文件系统的建模与实现

视频、音频等连续媒体与文本有着不同的特性，对文件系统提出了不同的要求。该文提出了一个集成多种媒体数据类型的层次文件系统模型，在不同层次上根据媒体的实时性、周期性等特点进行优化资源分配，提供资源利用率和服务质量。通过建立原型系统对该模型进行了验证。     

基于自适应节的多媒体流QoS保证的研究

分布式多媒体计算机系统的一个关键问题是保证连续多媒体流的服务质量（QoS),大多数多媒体流要求的QoS是在一定范围内,即[QoSmin,QoSmax]。为了保证QoS,计算机系统和网络系统必须分配足够的CPU、I/O、内存和网络带宽资源。在多媒体流传输过程中,这些资源的可利用率是动态变化的,尤其是带宽资源,如Internet,文中提出了自适应节的概念,采用PID调节技术,在[QoSmin,QoSmax]内,动态调节QoS,自适应动态的可利用资源变化,既保证了多媒体流的QoS,又提高了资源的利用率。     

Multimedia Multicast in Mobile Computing: Handoff Management

With rapid technological advances being made in the area of wireless communications it is expected that, in the near future, mobile users will be able to access a wide variety of services such as multicast distribution of multimedia streams. These services are characterized by the integrated processing of different media types, such as audio and video. Different multimedia streams must be played out in a synchronized way. However, due to the asynchronous nature of the communication (packets or radio), some problems can disrupt the synchronization such as delay jitter. In this paper, we present a synchronization protocol for multicast of multimedia streams. It allows a mobile host to playback continuously a multimedia stream. When a mobile host moves from cell to cell, the scheme allows continuous playback. The mechanism used is based on the pre-buffering of media units. We present a computation of the handoff time and a mechanism for the restoration of the initial buffer size. Simulation results show that, when resources are already reserved, the handoff time is bounded and the buffer takes again its initial size.     

Multimedia streaming gateway with jitter detection

This paper investigates a novel active buffer management scheme, "Jitter Detection" (JD) for gateway-based congestion control to stream multimedia traffics in packet-switched networks. The quality of multimedia presentation can be greatly degraded due to network delay variation or jitter when transported over a packet-switched network. Jitter degrades the timing relationship among packets in a single media stream and between packets from different media streams and, hence, creates multimedia synchronization problems. Moreover, too much jitter will also degrade the performance of the streaming buffer in the client. Packets received by the client will be rendered useless if they have accumulated enough jitter. The proposed active buffer management scheme will improve the quality of service in multimedia networking by detecting and discarding packets that accumulated enough jitter, such as to maintain a high bandwidth for packets within the multimedia stream's jitter tolerance. Simulation results have shown that the proposed scheme can effectively lower the average received packet jitter and increase the goodput of the received packets when compared to random early detection (RED) and DropTail used in gateway-based congestion control. Furthermore, simulation results have also revealed that the proposed scheme can maintain the same TCP friendliness when compared to that of RED and DropTail used for multimedia streams.     

Increasing multimedia system throughput with consumption-based buffer management

In a multimedia server, multiple media streams are generally serviced in a cyclic fashion. Due to non-uniform playback rates and asynchronous arrivals of queries, there tends to be spare disk bandwidth in each service cycle. In this paper, we study the issue of dynamically using spare disk bandwidth and buffer to maximize the system throughput of a multimedia server. We introduce the concept of minimizing buffer consumption as the criterion to select an appropriate media stream to utilize the spare system resources. Buffer consumption measures not only the amount of buffer but also the amount of time such buffer space is occupied (i.e., the space-time product). Different alternatives to utilizing spare disk bandwidth are examined, including different rate-adjustable retrievals of an already activated stream and prefetching the next waiting stream. For rate-adjustable retrievals, we study buffer consumption-based and remaining-time-based criteria for selecting an active stream to increase retrievals. Simulations are conducted to evaluate and compare different cases. The results show that (1) minimizing buffer consumption is the right criterion for maximizing the system throughput with spare disk bandwidth; (2) in general, prefetching a waiting stream incurs more buffer consumption, and thus is less effective than rate-adjustable retrieval of active streams in maximizing the system throughput; and (3) the advantage of rate-adjustable retrieval over prefetching is especially significant when service cycle time is small.     

下一代网络多媒体流自适应QoS研究

下一代网络是一个支持话音、数据和视频的多媒体网络。随着网络的发展,如何保障下一代网络多媒体流QoS是一个重要的研究课题。为保证多媒体流QoS,系统必须分配足够的CPU、I/O、网络带宽资源,在多媒体传输过程中,这些资源是动态变化的。论文提出一种带优先级的自适应节调节方法,采用AIMD调节技术调节数据帧长度,自适应调节QoS,实验表明,该方法保证了NGN多媒体流的QoS,也使得网络资源得到充分利用。     

Efficient support for interactive service in multi-resolution VOD systems

Advances in high-speed networks and multimedia technologies have made it feasible to provide video-on-demand (VOD) services to users. However, it is still a challenging task to design a cost-effective VOD system that can support a large number of clients (who may have different quality of service (QoS) requirements) and, at the same time, provide different types of VCR functionalities. Although it has been recognized that VCR operations are important functionalities in providing VOD service, techniques proposed in the past for providing VCR operations may require additional system resources, such as extra disk I/O, additional buffer space, as well as network bandwidth. In this paper, we consider the design of a VOD storage server that has the following features: (1) provision of different levels of display resolutions to users who have different QoS requirements, (2) provision of different types of VCR functionalities, such as fast forward and rewind, without imposing additional demand on the system buffer space, I/O bandwidth, and network bandwidth, and (3) guarantees of the load-balancing property across all disks during normal and VCR display periods. The above-mentioned features are especially important because they simplify the design of the buffer space, I/O, and network resource allocation policies of the VOD storage system. The load-balancing property also ensures that no single disk will be the bottleneck of the system. In this paper, we propose data block placement, admission control, and I/O-scheduling algorithms, as well as determine the corresponding buffer space requirements of the proposed VOD storage system. We show that the proposed VOD system can provide VCR and multi-resolution services to the viewing clients and at the same time maintain the load-balancing property. Received June 9, 1998 / Accepted April 26, 1999     

Quality-based I/O resource managementfor multimedia document database servers

Slow access to disk-based multimedia data is a major limiting factor in the performance of modern multimedia Web servers connected over broadband networks. The I/O bottleneck becomes even more pronounced for currently evolving systems handling multimedia data, such as audio and video. Retrieval of complex multimedia documents needs to be handled at two levels: I/O bandwidth management for multiple multimedia streams, and interstream and intrastream synchronization for multimedia objects constituting these documents. In this paper, based on the diverse characteristics of multimedia data, we propose efficient techniques for synchronous retrieval and delivery of such data from the storage system to the main memory of the server. We propose methods to quantify user perceived quality via quality-of-presentation (QoP) parameters. We combine QoP and Object Composition Petri Net (OCPN) multimedia data modeling to develop techniques for efficient synchronous retrieval of multimedia data. Since I/O bandwidth is a precious resource, the proposed techniques have low overhead, which is , where m is the number of logical I/O channels and n is the total number of frames of multimedia data in a scheduling period. We simulate the relative performance of these techniques under diverse I/O conditions and determine the tradeoffs between the system resources, such as memory, bandwidth, and the improvement in QoP for multimedia applications.Published online: 9 February 2005 Correspondence to: M. Farrukh Khan     

Performance evaluation for VBR Continuous Media File Server admission control

A file server for continuous media must provide resource guarantees and only admit requests that do not violate the resource availability. This paper addresses the admission performance of a server that explicitly considers the variable bit rate nature of the continuous media streams. A prototype version of the server has been implemented and evaluated in several heterogeneous environments. The two system resources for which admission control is evaluated are the disk bandwidth and the network bandwidth. Performance results from both measurement and simulation are shown with respect to different admission methods and varying scenarios of stream delivery patterns. We show that the vbrSim algorithm developed specifically for the server outperforms the other options for disk admission especially with request patterns that have staggered arrivals, while the network admission control algorithm is able to utilize a large percentage of the network bandwidth available. We also show the interactions between the limits of these two resources and how a system can be configured without wasted capacity on either one of the resources. Copyright © 2004 John Wiley & Sons, Ltd.