Cooperative teleoperation of a multirobot system with force reflection via Internet

With the rapid development of information technology, the Internet has evolved from a simple data-sharing media to an amazing information world where people can enjoy various services. Recently, the use of the Internet has been expanded to the field of automation, i.e., using the Internet as a tool to control equipment located at remote sites. This work presents a system that enables multiple operators at different sites to cooperatively control multiple robots with real-time force reflecting via the Internet. To overcome instability and reliability problems caused by random time delay of the Internet communication, we adopt an event as the reference for the controller design. To improve real-time efficiency and reduce the complexity of the controller, a distributed approach is proposed for the control of remote robots, so that the time delay in one control loop does not affect performance of the others. A vision-based method is developed to monitor and render interactions between the robots. The usefulness and effectiveness of the developed method and system have been verified by teleoperation experiments on a two-robots cooperative system among Hong Kong, mainland China, and the U.S.     

Stochastic stabilization for bilateral teleoperation over networks with probabilistic delays

This paper studies the bilateral teleoperation over communication networks. Specifically, the network-induced random delays are modeled as being from a finite set, each delay in the set having a probability of occurrence. To fully utilize the stochastic information inherent with the delays, a novel design scheme combining the probability information and pole placement is proposed to achieve better tracking performance. The teleoperation problem is first formulated as the stabilization of an error dynamic system where the error is the difference between the states of the master and slave. Then, by constructing a Lyapunov function, a sufficient condition to guarantee the input-to-state stability is established in terms of linear matrix inequalities. The simulation results and comparison show a decrease in tracking error with the new design method.     

Enclaves: enabling secure collaboration over the Internet

The rapid expansion of the Internet means that users increasingly want to interact with each other. Due to the openness and unsecure nature of the Net, users often have to rely on firewalls to protect their connections. Firewalls, however, make real-time interaction and collaboration more difficult. Firewalls are also complicated to configure and expensive to install and maintain, and they are inaccessible to small home offices and mobile users. The Enclaves approach is to transform user machines into “enclaves”, which are protected from outside interference and attacks. Using Enclaves, a group of collaborators can dynamically form a secure virtual subnet within which to conduct their joint business. This paper describes the design and implementation of the Enclaves toolkit and some applications we have built using the toolkit     

Video multicast over the Internet

Multicast distribution of video is an important component of many existing and future networked services. The Internet lacks support for quality of service (QoS) assurance, which makes the transmission of real-time traffic challenging. In addition, the heterogeneity of the Internet's transmission resources and end-systems makes it extremely difficult, if not impossible, to agree on acceptable traffic characteristics among multiple receivers of the same video stream. We survey techniques that have been proposed for transmitting video in this environment. These generally involve adaptation of video traffic carried over the network to match receiver requirements and network conditions. In addition to their applicability to the near-term capabilities of the Internet, they also are of relevance to a future, QoS-aware Internet environment. We first consider source-based techniques in which the source adjusts the video stream traffic to match some consensus among the receivers about its desired characteristics. These techniques can result in an unfair treatment for receivers, especially those whose capability is significantly above or below the group consensus. We then consider techniques that aim to improve the fairness among the receivers by sending the video in multiple (layered or replicated) streams. We also discuss several error control mechanisms, using timely retransmission of missing data to further improve the quality of the received video. Finally, we discuss some of the issues in the development of Internet video multicast protocols     

Transporting real-time video over the Internet: challenges andapproaches

Delivering real-time video over the Internet is an important component of many Internet multimedia applications. Transmission of real-time video has bandwidth, delay, and loss requirements. However the current Internet does not offer any quality of service (QoS) guarantees to video transmission over the Internet. In addition, the heterogeneity of the networks and end systems makes it difficult to multicast Internet video in an efficient and flexible way. Thus, designing protocols and mechanisms for Internet video transmission poses many challenges. In this paper, we take a holistic approach to these challenges and present solutions from both transport and compression perspectives. With the holistic approach, we design a framework for transporting real-time Internet video, which includes two components, namely, congestion control and error control. Specifically congestion control consists of rate control, rate-adaptive encoding, and rate shaping; error control consists of forward error correction (FEC), retransmission error resilience, and error concealment. For the design of each component in the framework, we classify approaches and summarize representative research work. We point out there exists a design space which can be explored by video application designers and suggest that the synergy of both transport and compression could provide good solutions     

Multirate video multicast over the Internet: an overview

Multirate multicast is an effective method for video distribution to a set of heterogeneous receivers. We present a comprehensive survey on multirate video multicast over the best effort Internet. We first review the key techniques in video encoding and network transport, and describe the representative approaches. We then study various trade-offs based on some important design issues and performance criteria, such as bandwidth economy, adaptation granularity, and coding complexity. Finally, we present some ongoing work and discuss possible avenues for future research.     

Adaptive video multicast over the Internet

The authors survey existing solutions to adaptive video multicast, providing a taxonomy of solutions according to several distinct features. They also review the principal techniques from both video coding and network transport perspectives. Finally, they discuss the evaluation methodologies and metrics for adaptive video multicast systems.     

Internet电视会议系统

计算机网络近年来获得了飞速发展。现在,随着计算机及通讯技术的迅猛发展和成熟,生活水平的提高和实际的需要,计算机通信已成为我们社会结构的一个基本组成部分,计算机网络已遍布各个领域。     

基于Internet互联的多媒体通信

本分析了Internet对多媒体通信的发展所起的推进作用，介绍了基于Internet的会议，会话，检索，分配，消费和收集等多媒体业务以及网络层次，业务层次，综合多媒体多端的互联技术。     

基于SIP的Internet电话

文章先给出了基于ＳＩＰ（会话初始化协议）的Ｉｎｔｅｒｎｅｔ电话的协议结构,随后对其中传输数据的ＲＴＰ（实时传输协议）和ＲＴＣＰ（实时传输控制协议）进行了介绍和分析,并对会话初始化协议的组成实体、命名、寻址、操作进行了详细的论述。     

Picture-perfect streaming over the Internet: is there hope?

Quality of service in streaming of continuous media over the Internet is poor, which is partly due to variations in delays, bandwidth limitations, and packet losses. Although continuous media applications can tolerate some missing data, non-recoverable information loss degrades these applications' QoS. Consequently, a number of application areas (e.g., those related to the entertainment industry) have backed away from streaming of their content over the Internet. Inability to control the resulting visual and auditory quality of the resulting streamed presentation is an important reason for such a trend. We believe that this trend can be reversed. To this end, our work focuses on providing high-quality streaming through the exploitation of multiple paths existing in the network. By high quality, we mean with significant bandwidth requirements, of relatively long duration, and without information loss or hiccups in data delivery. In this article we present evidence that multi-path streaming is a promising approach.     

Wireless Internet over LMDS: architecture and experimentalimplementation

LMDS is currently a promising emerging technology in broadband fixed wireless communications. The cellular structure, high data rates, and flexibility make it perfect for multimedia, digital television, and interactive services. These high-bandwidth multimedia services received most of the research attention until lately. There has been a clear gap when considering UDP/TCP/IP and other data services over LMDS. We examine the ramifications of using standard TCP/IP data communication over a two-layer LMDS system. We argue that the former emphasis only on multimedia and ATM-based communication over LMDS was a mistake. The most exciting prospect for LMDS should be in the role of enabling Internet and data services together with multimedia. We introduce a basic architecture for two-layer IP-LMDS based on a trial network built between 1996 and 2000     

Multimedia broadcasting over the Internet. I

Although the industry is still in the early stages of webcasting, we can already foresee what the Internet will offer a few years down the line: clear, crisp audio and full-screen, high-quality, on-demand video. We have developed a technology that provides all these required features for Internet webcasting. This technology consists of: IP Simulcast, a new Internet broadcast protocol, which provides inexpensive, efficient, and reliable audio and video broadcasting; and new audio and video compression algorithms, which allow real-time audio and video transmission of data at low bit rates and with high quality. In this article, we describe a new Internet broadcast technology     

快速Internet小波图像传输

图像通常利用无损协议（如ＴＣＰ／ＩＰ）在因特网上进行传输。无损协议需要重发丢失的数据包,而这必然引起传输时间的增加。本文介绍了压缩图像的一种快速有损因特网图像传输方案（ＦＬＩＩＴ）。它通过添加冗余比特保护图像的重要部分来消除重发时延。文中论述了一种高效地分配量化比特和冗余比特来控制量误差和预测数据包传输丢失的信源和信道联合编码算法。并讨论了这种算法的实现过程,以及将它在Ｉｎｔｅｒｎｅｔ上传输的性能     

Internet over direct broadcast satellites

High-powered direct broadcast television satellites can be used to broadcast high volumes of data directly to home terminals. Using the telephone network or a similar low-speed network, an asymmetrical system can be implemented which offers interactive Internet services. Two such interactive data broadcast systems are described which have been implemented as demonstration platforms for interactive multimedia services; one is based on digital subcarrier techniques for analog television channels, the other on the MPEG-2 and DVB standards. The architecture of the hardware and software is presented, particularly the solutions available for carrying Internet datagrams over MPEG-2 transport systems. A multicast transport protocol with selectable reliability is described which is the basis of a generic distribution application. It exploits the potential benefits of direct broadcast satellites for delivering data to large groups of local caches     

IP over DWDM—新一代的因特网

未来网络的数据平台趋于IP化，传输平台趋于DWDM化，故IP over DWDM必将成为新一代因特网的支柱。简要论述IP over DWDM技术及其特点，并指出了该技术面临的主要挑战：一是网络必须稳定可靠；二是要解决服务质量保障及链路管理问题等。概要介绍了光因特网的组成及优点；最后指出IP over DWDM适用于未来的城域网、高容量普遍IP业务和未来大型IP骨干网的核心汇接，是支撑未来光因特网的核心技术。     

The PingER project: active Internet performance monitoring for theHENP community

The extraordinary network challenges presented by high energy nuclear and particle physics experiments has created a need for network monitoring both to understand present performance and to allocate resources to optimize performance between laboratories, and the universities and institutes collaborating on present and future experiments. The resulting Internet end-to-end performance monitoring project is called PingER. The monitoring infrastructure reflects the wide geographical spread of the collaborations, and involves a large number of research and commercial networks. The architecture of the data acquisition and methodology of the analysis have evolved over several years, and are described here in their present state. The strengths and weaknesses of the project are reviewed, and the derived metrics are discussed in terms of their diagnostic functions. The observed short-term effects and long-term trends are reviewed, and plans for future developments are described     

基于Internet的实时视频信号传输研究进展

随着Internet带宽和计算机处理能力的迅速提高,实时Internet视频传输在科研和工业领域引起了极大的研究兴趣。本文介绍了实时Internet视频传输的基本方法,针对Internet分组的丢失特性,讨论了具有差错复原能力的视频压缩与编码技术,详细介绍了Internet视频传输的信源／信道联方编码技术,并对今后的研究方向进行了概括的描述。     

Proxy caching for media streaming over the Internet

Streaming media has contributed to a significant amount of today's Internet traffic. Like conventional Web objects (e.g., HTML pages and images), media objects can benefit from proxy caching; but their unique features such as huge size and high bandwidth demand imply that conventional proxy caching strategies have to be substantially revised. This article discusses the critical issues and challenges of cache management for proxy-assisted media streaming. We survey, classify, and compare the state-of-the-art solutions. We also investigate advanced issues of combining multicast with caching, cooperating among proxies, and leveraging proxy caching in overlay networks.     

因特网广播电视实时传输系统

分析了传统电视信号传输所存在的问题与不足，提出并设计了基于WindowgMedia的因特网广播电视实时传输系统的网络框架，重点阐述了本系统采用的传输方案。