高性能协同工作支撑环境设计与实现

允许多个协作同时运行是用户和应用对ＣＳＣＷ支撑环境的基本要求,但这一要求使支撑瓣管理和控制变得十分复杂,另外,多数ＣＳＣＷ支撑环境中未能较好地支持带实时多媒体组通信的同步交互功能,介绍了基于ＡＴＭ网络和工作站实验平台的ＣＳＣＷ支撑环境原型系统ＡＴＭ－ＣＳＣＷＥｎｖ的设计和实现,该支撑环境将管理与控制功能分开,并采用ＯＳＩ的Ｍａｎａｇｅｒ／Ａｇｅｎｔ模式管理支撑环境中协作和资源。环境中还引入多媒体多     

CSCW支撑平台的结构模型

传统分布式系统中面向系统的控制及分布透明性不能满足ＣＳＣＷ对面向用户的显式协作的要求。本文提出了一个ＣＳＣＷ系统的结构模型，该结构以一个ＣＳＣＷ支撑平台作为一般分布式系统与协作应用之间的适配层，来支持协作任务平台具有客户／服务器模式，它用面向对象方法处理各种异构性，将协作规则与协作机制分开，这样它就可以仅利用基本的分布功能，提供方便灵活的面向用户协作的服务。在此平台上可有各种多媒体协同应用，从而充     

RTP和TCP在实时传输中的比较

近年来,ＴＣＰ协议不适合传输实时的多媒体数据,新的为实时传输多媒体数据的ＲＴＰ协议也就应运而生。本文主要讨论了在传输实时多媒体数据方面ＴＣＰ和ＲＴＰ的不同点,并且提出了一个在局多内测试ＴＣＰ和ＲＴＰ传输多媒体数据的测试模拟模型。     

A CORBA Based QOS Support for Distributed Multimedia Applications

Advance object oriented computing platform such as the Common Object Request Broker Architecture (CORBA) provides a conducive and standardized framework for the development of distributed applications. Most of the off-the-shelf CORBA are implemented over legacy network transports and distributed processing platforms such as TCP/IP and RPC. They are not suitable for real-time applications due to their high processing overheads, and lack of features and mechanisms in supporting quality of service both at the network level and at the end-host level. To overcome this limitation we have designed and implemented a CORBA-based Real Time Stream Service (RTSS) that allows real-time streams to be managed through the CORBA channel but by-passing the heavy CORBA protocol stacks. RTSS aims to achieve an integrated QOS framework that incorporates both host scheduling and end-to-end network-level QOS to better support the processing of distributed multimedia applications over ATM networks. For host scheduling, a novel scheme of frequency-based scheduling mechanism has been proposed to cope with dynamic CPU load condition. The scheme has been implemented for a stand-alone host and will be extended to the networked environment. At the network-level QOS, RTSS provides object-oriented application programming interfaces (APIs) which guarantee end-to-end QOS when operating directly over ATM adaptation layers. The benefits of RTSS for the development of real-time multimedia distributed applications are demonstrated through a number of experiments.     

协同工作的人与人交互界面

计算机支持的协同工作ＣＳＣＷ一般涉及到多台机器、多个应用程序和多个人。这样不仅存在人机对话，而且要求计算机能支持人与人之间的协同效互，并对应用工具进行管理。本文提出了人与人交互界面的概念，并在ＳＵＮ ＳＰＡＲＣ上设计并实现了一个原型系统ＨＨＩ。ＨＨＩ以语言学中的言语－行为理论为基础，将多个应用程序和参与人员集中起来，进行统一管理并允许动态地变化。通过ＨＨＩ，不同地点的用户能同步或异步地交互。     

基于CSCW的远程教育中电子白板的实现

提出了计算机支持协同工作的概念和原理，讨论了Java语言的特点，并将Java语言的特点和电子白板的应用特征相结合，构造了一个用Java语言实现的网络电子白板框架，设计了同时使用TCP／IP协议和UDP协议进行网络通信，提高了网络电子白板的传输效率。     

TCP友好拥塞／速率控制算法及其在多媒体数据传输中的应用

基于Intenret的以UDP为传输协议的实时多媒体数据传输,需要在保证 实时性和可靠性基础上,能够与Internet其它服务所使用的TCP协议共享有限的带宽,基于这种需要,该文在研究了多种拥塞控制算法的基础上,提出了一种简单实用的TCP友好拥塞／速率控制算法,并将该算法应用在一个实用的Internet IP电话软FreePhone中,通过试验证明,该方法实用有效,并取得了预期的效果。     

TCP/IP网络环境下的视频图像传输

为了在ＴＣＰ／ＩＰ网络环境下有效地传输连续视频图像,文章提出了一种对ＵＤＰ扩展的视频图像传输协议,保证传输的正确性和有序性。同时在一个可变带宽的远程多媒体通信模拟平台上实现了视频图像的实时网络传输。     

支持CSCW的系统集成框架的设计与实现

结合CSCW系统的开发，对集中式CSCW系统结构的特点进行综合和提炼，设计并实现了一个基于构件及构件代理的应用集成框架。这个集成框架不仅对个体工作提供支持，同时对协同工作也提供支持。首先论述该框架的基本组成及各组成模块的主要功能，然后对该框架所提供的诸如工作流管理、电子会议等通用工具的功能进行了介绍。     

基于分布式环境的多媒体同步应用框架的设计

多媒体信息的同步是分布式多媒体信息系统的关键技术，在Meyer,Effelsberg等人的4层媒体同步参考模型的基础上，提出了一个实际应用的分布式多媒体同步应用框架，并对其中的一些关键内容及模块进行了讨论。     

地图协同标绘感知系统的设计与实现

传统标绘系统都是单用户标绘，它不能满足多用户同时进行标绘的要求。文中设计构建了一个CSCW标绘系统，以解决远程多用户同时进行协同标绘行为的难题，并提出主席一用户模式体系结构，以协同标绘层和协同管理层为核心的系统框架以及分布式加锁策略等技术来解决协同管理、实时交互和协同感知，以此实现异地协同标绘系统。     

Distributed computing architecture for effective management of multimedia streams on DPE

We study a networking architecture model that is built on a distributed processing environment (DPE) for multimedia services suitable for high speed transport networks such as ATM networks. In this architecture, the applications are deployed as units of software building blocks. Each building block provides a layered view for the effective management and control of the multimedia network resources and services according to the concept of telecommunications management network (TMN) and telecommunications information networking architecture (TINA). For the purpose of flexible service provision to users and effective service introduction by service providers, this architecture proposes the adoption of ad hoc service building blocks such as a video on demand building block and a CSCW building block that have interactions with a general purpose building block. This paper also proposes a naming structure for the management of user profiles and session profiles using a directory service system, and an effective control model for multimedia logical device objects using a stream process approach. The proposed model is implemented on a DPE platform that provides various transparencies, ANSAware.     

分布式多媒体网络协作平台的研究

计算机支持的协同工作(CSCW)体现并符合信息时代人们工作的分布性、交互性和协同性的特征,涉及分布式系统、计算机通信、人机交互、人工智能和社会科学等诸多方面,因而日益受到人们的重视。文章结合CSCW技术提出了一个通用分布式多媒体网络协作平台的体系结构,分析了多媒体通信,用户协作信息管理,协同应用的并发控制机制等问题,最终实现了分布式、网络传输、多媒体技术在平台中的集成,并介绍了几个应用实例。     

基于Web Services架构的CSCW应用研究

WebServices技术给CSCW提供了一个新的实现平台。论文分析了当前几项CSCW应用主流实现技术的局限性,指出了基于WebServices实现CSCW应用的理由,研究了WebServices在CSCW系统中的应用模式,并着重讨论了消息同步问题的解决方法,提出了系统的体系结构,最后给出了一个基于WebServices的协同图形编辑器的实例。     

TCP友好的多媒体通信流控制机制

该文给出了一个端到端的适应性多媒体流控制策略,称为基于丢失延时的算法LDA(loss-delaybasedalgo-rithm),它调整多媒体流的发送行为,以符合网络的当前拥塞状况。LDA算法利用实时传输协议RTP(real-timetransportprotocol)来收集分组丢失和延时统计信息,并用来调整发送端的发送行为,使它和TCP的拥塞控制有类似的统计特性,是TCP友好的。仿真的结果显示LDA算法对于网络资源的利用、拥塞避免和TCP流的公平性都是比较好的。     

APAIMD算法及基于此算法的APTCP协议

本文提出了一种可调参数AIMD算法和一种在接收端实现该算法的适合在Internet上传输多媒体流的可调参数传输控制协议。UDP不适合传输多媒体数据，因为它没有拥塞控制机制。TCP遇到单个数据包丢失传输速率就减半，会造成速率剧烈抖动，也不适合传输多媒体数据。在APTCP控制下传输的多媒体流具有良好的速率平滑性，并能够与竞争的TCP流公平的分享带宽。APTCP便于升级到组播多媒体业务，可用于非对称网络。     

实时语音传输中的语音缓冲区设计

该文以多媒体网络实时监控平台为例,介绍了基于TCP/IP进行实时语音传输的基本模型,详细探讨了在该模型上影响语音缓冲区设计的几个关键问题以及循环缓冲队列管理机制,并结合实例提出了计算语音缓冲区大小的方法。     

SCTP: a proposed standard for robust Internet data transport

The stream control transmission protocol (SCTP) is an evolving general purpose Internet transport protocol designed to bridge the gap between TCP and UDP. SCTP evolved from a telephony signaling protocol for IP networks and is now a proposed standard with the Internet Engineering Task Force. Like TCP, SCTP provides a reliable, full-duplex connection and mechanisms to control network congestion. However, SCTP expands transport layer possibilities beyond TCP and UDP, offering new delivery options that are particularly desirable for telephony signaling and multimedia applications.     

Groupware Environments as Action Constitutive Resources: A Social Action Framework for Analyzing Groupware Technologies

Computer Supported Cooperative Work (CSCW) is a relatively new and dynamic field dealing with the development and use of groupware technologies in organizations. Several frameworks and models have been proposed for studying CSCW, each conveying a different perspective and theoretical basis. Although these frameworks have contributed much to our understanding of the field, they can be criticized for a lack of holistic understanding of the complex social activity that is constitutive of groupwork. This often leads to the failure of otherwise well designed CSCW applications. In this paper we take up this challenge and propose a social action framework for analyzing groupware technologies. The framework is based on Habermas's theory of social action and four action categories, and the idea that groupware applications serve as sets of rules and resources which mediate group interactions. We demonstrate the value of the framework by analyzing a wide range of existing groupware technologies for their appropriateness to specific groupwork situations in terms of their espoused or implicit assumptions of groupwork, and the action constitutive resources they provide. Our analysis points out that a host of current groupware applications can be fairly easily classified and examined by the way they are configured to support different types of social action. It also suggests that, when implementing groupware applications, developers should critically evaluate: (a) the need for supporting a rich variety of action types, (b) the possible role of computer support in the specific groupwork situations, and (c) the underlying assumptions of groupwork embedded in the groupware platform. Finally, we will discuss how the framework can inform future research and development in the field.     

多媒体合著系统中群体感知技术的研究与实现

多媒体合著是ＣＳＣＷ的一个重要应用领域，它融合了多媒体技术和网络通讯技术，是高效创作多媒体应用软件原有效手段。本文介绍了多媒体合著系统的特点、要求以及设计思想，着重讨论了在复制式结构下实现群体感知的技术和方法。