基于资源调度的远程在线实验室设计

远程在线教育实验室和基于Web的远程学习课程一样迅速地部署在世界各地传统的校园里.本文介绍了远程在线实验室资源调度系统,以用来为地理上分散的多用户协调共享实验室资源,避免用户在时间上的资源冲突,并为不同用户请求提供三种不同优先级处理的功能.     

Efficient Architecture and Handoff Strategy used for VoIP Sessions in SIP Based Wireless Networks

In the near future, the Internet is likely to become an All-IP network that provides various multimedia services over wireless networks. Although the earliest VoIP applications did not consider the end-node mobility, researchers have attempted to support mobility in current VoIP protocols, such as Session Initial Protocol (SIP)-based mobility. The SIP-based mobility is considered because it can readily support mobility. However, calling disruptions may occur in traditional SIP mid-call terminal mobility because handoff procedure may be required, depending on the implementation and the real network deployment considerations. In any case, issues in the combined SIP/RSVP for guaranteeing QoS of VoIP service under mobile environment are also considered to be crucial. Therefore, this study describes the solutions by devising novel hierarchy network architecture. Also, the mechanisms including help with neighboring users in adjacent cells and the third party call control to overcome those issues are included. The simulation results indicate that the proposed technique is practical and better executive than conventional schemes.     

TD-SCDMA系统中多媒体广播业务的实现

多媒体业务是目前被业界看好的一个非常有潜力的应用。多媒体广播的一种主要技术种类是基于移动通信系统蜂窝网的多媒体广播和组播技术（MBMS）标准。主要介绍了在TD-SCDMA移动通信系统中如何实现多媒体广播业务,并介绍了相关技术的标准进展、网络架构以及具体的技术方案。     

IP网络分组传送性能讲座 第1讲:IP网络性能参考模型

随着IP技术的发展,其应用领域不断扩大.现有的IP网络能够较好地支持非实时数据业务,为r使它也能够支持各种实时业务与多媒体业务,就必须研究和规范IP网络传送信息的性能.本讲座在研究和分析ITU-T关于IP网络性能的标准和实际解决工程技术问题的基础上,讨论和介绍了IP网络性能方面的有关内容.其中包括:IP业务性能描述的参考模型、IP业务性能测试的环境与条件、IP业务的性能参数、IP业务的可用性等.     

宽带网络流媒体技术的应用与发展

流媒体技术是在数据网络上以流的方式传输多媒体信息的技术。近年来,随着宽带网络的发展和用户需求的驱动,流媒体技术和相关的应用得到越来越多的关注,被认为是未来高速宽带网络的主流应用之一。文中介绍了流媒体的概念与特点,深入分析了流媒体系统及其关键技术,研究了流媒体技术在宽带网络中的应用及在国内外的发展情况,对流媒体技术在发展中遇到的问题做了说明。还针对国内目前的宽带网络现状提出了流媒体技术的应用和发展建议。     

A Context-Aware Network Equipment for Dynamic Adaptation of Multimedia Services in Wireless Networks

B3G (Beyond 3rd Generation) networks is the next step in the wireless world. It will enable the delivery of services to end-users, on different underlying wireless access networks and customised to users’ context. Furthermore, seamless mobility between networks and switch of devices will be handled in a transparent way. In this paper, a Context-Aware Network Equipment (CANE) is introduced, that is able to dynamically adapt multimedia services according to the users’ context. The term context includes the users’ device, the users’ preferences, the network conditions as well as the service provider adaptation policies. As a proof of concept, an implementation of a CANE is given for a 802.11 network use-case. An evaluation of the prototype as well as simulations of the proposed solution, both for an audio streaming service and a video streaming service, are presented. The results show that adapting multimedia services in case of network overload can enable to maintain an acceptable quality of service delivered to end-users and even to allow more users to enjoy the services, which will not be possible without the CANE.     

Application layer QoS optimization for multimedia transmission over cognitive radio networks

In cognitive radio (CR) networks, the perceived reduction of application layer quality of service (QoS), such as multimedia distortion, by secondary users may impede the success of CR technologies. Most previous work in CR networks ignores application layer QoS. In this paper we take an integrated design approach to jointly optimize multimedia intra refreshing rate, an application layer parameter, together with access strategy, and spectrum sensing for multimedia transmission in a CR system with time varying wireless channels. Primary network usage and channel gain are modeled as a finite state Markov process. With channel sensing and channel state information errors, the system state cannot be directly observed. We formulate the QoS optimization problem as a partially observable Markov decision process (POMDP). A low complexity dynamic programming framework is presented to obtain the optimal policy. Simulation results show the effectiveness of the proposed scheme.     

Mobility Testbed for 3GPP2-Based Multimedia Domain Networks

Wireless service providers strive to preserve the quality of service and user experience for mobile users. Several standards bodies are defining architectures that can be used as a platform to provide secure and seamless services to these mobile users. These architectures aim to provide several required functions such as signaling, configuration, security association, encryption, and billing. However, the placement of several functional components and their interaction at several layers contributes to the operational complexity and thus affects the optimal results. Testbed realization of any standardized architecture can help investigate the underlying networking issues. In this article, we describe a mobility test bed implementation based on one of the architecture alternatives of 3GPP2, where the outbound signaling servers are distributed around the edges of the network. We experiment with three different hand-off techniques and analyze the associated experimental results. Analysis of these experimental results and experiences obtained from the testbed implementation can be helpful to any service provider that plans to deploy a version of the MMD (multimedia domain) architecture with distributed signaling servers.     

信息设备资源共享协同服务标准的体系结构

信息设备资源共享协同服务标准（IGRS）是为了实现信息设备智能互联、资源共享、协同服务而制订的。IGRS采用了开放性的体系结构。遵从IGRS标准的设备能够与采用其他标准（如通用即插即用标准）的设备进行互操作。IGRS支持多种应用框架和特色应用。开发者可以通过IGRS媒体类应用框架结合多种媒体格式标准，如AVS、MPEG-2等，进行多媒体应用的开发。IGRS标准适用于在计算机、家用电器和通信等设备之间，在一定范围网络域内，通过有线或无线方式实现资源共享与协同服务。     

Subscriber terminal units for video dial tone systems

The subscriber terminal unit (STU) receives and decodes video signals and provides interactive support for server-based multimedia applications delivered over a video dial tone network. The STU can be a maddening bottleneck or a gateway to the world. Done properly, it is the vital link that exploits the sophisticated capabilities of the broadband network. We describe the service model upon which applications are based and our current understanding of the application requirements. Different STU types, their capabilities, and expected availability are presented. A model of the functionality of a generic STU is presented, as well as several different development scenarios, including our approach to an actual implementation     

ATM to the desktop: Impacting modern business communications with broadband technology

Asynchronous transfer mode (ATM) technology is being touted as a “silver bullet” solution that will enable a host of new and advanced multimedia services seamlessly across both local and wide area networks. While it appears likely that ATM will have a genuine impact on the future of business communications, a major hurdle that needs to be overcome before this happens lies with the semantic gap that exists between the ATM technology development and marketing community and the prospective customer base which stands to benefit from the technology. The work described in this paper represents our attempt to help close this gap through an examination of the kinds of multimedia business applications we believe ATM technology will provide its end users. We describe sample demonstration applications developed at GTE Laboratories that help to explain how ATM can impact business communications from the desktop. A further theme of the work described concerns our efforts to take best advantage of key features of ATM to assist ongoing investigation of multimedia application concepts and their implementation.     

远程遥控驾驶场景下基于网络信息开放的QoS预测

5G系统的飞速发展支持许多车联网用例对服务质量（quality of service,Qo S）的苛刻要求。但网络和应用的适配仍然存在很多问题。网络信息开放是一种潜在的解决方案,旨在实现网络向应用程序实时提供蜂窝无线网络信息,从而帮助服务提供方实现更好的策略控制并改善用户体验。提出一种基于网络信息开放的服务质量预测（predictive QoS,PQo S）方法,通过提前预测即将发生的网络变化来支持应用做出提前响应,提高用户的体验质量（qualityofexperience,Qo E）。介绍了网络信息开放及PQo S的背景,并介绍了PQo S的国内外研究、标准及落地现状;提出一种远程遥控驾驶（tele-operateddriving,To D）场景下基于网络信息开放的Qo S预测方法;对实际测试的数据进行分析,评估验证了PQo S的可行性。结果表明,基于网络信息开放的Qo S预测技术能够良好地支持包括5G ToD在内的车联网应用,为5G系统在智慧交通行业的落地提供了参考。     

A QoS Monitoring System in a Heterogeneous Multi-Domain DVB-H Platform

The MobileTV, IPTV, and DVB standards (DVB-H/T) have been defined to offer mobile users interactive multimedia services with quality of service (QoS) consistency analogous to TV services. However, the market has yet to provide effective and economical solutions for the real-time delivery of such services to the corresponding transmitters over multi-domain IP networks. The monitoring system proposed in this paper enables the QoS in the IP networks involved in the delivery of real-time multimedia content to the transmitters to be ascertained. The system utilizes the QoS parameters defined in MPEG-2 Transport Streams to detect problems occurring in the heterogeneous multi-domain IP networks. The ability to detect problems having an adverse effect on QoS allows appropriate control actions to be determined to recover the QoS across the composite IP network. The design and implementation of the proposed QoS-Monitoring system (QoS-MS) is presented, followed by analysis of experimental results that demonstrate the feasibility of the system.      

An MPEG‐4 Compliant Interactive Multimedia Streaming Platform Using Overlay Networks

This paper presents a multimedia streaming platform for efficiently transmitting MPEG‐4 content over IP networks. The platform includes an MPEG‐4 compliant streaming server and client, supporting object‐based representation of multimedia scenes, interactivity, and advanced encoding profiles defined by the ISO standard. For scalability purposes, we employ an application‐layer multicast scheme for media transmission using overlay networks. The overlay network, governed by the central entity of the network distribution manager, is dynamically deployed according to a set of pre‐defined criteria. The overlay network supports both broadcast delivery and video‐on‐demand content. The multimedia streaming platform is standards‐compliant and utilizes widespread multimedia protocols such as MPEG‐4, real‐time transport protocol, real‐time transport control protocol, and real‐time streaming protocol. The design of the overlay network was architected with the goal of transparency to both the streaming server and the client. As a result, many commercial implementations that use industry‐standard protocols can be plugged into the architecture relatively painlessly and can enjoy the benefits of the platform.     

Next-generation satellite networks: architectures andimplementations

A new generation of satellite networks is being developed to handle highly bursty Internet and multimedia traffic. In these networks, satellite links are used for interconnecting remote network segments as well as for providing direct network access to homes and businesses. In this environment, the satellite network must support not only circuit switched traffic, but also packet services with highly bursty traffic patterns. The traditional circuit switched approach based on the user or network signaling is inadequate to carry dynamically varying packet traffic efficiently, necessitating faster bandwidth allocation solutions. Standard interworking solutions and air interfaces are very important for interoperability leading to proliferation of satellite networks to potentially millions of home and business users. In this article we provide an overview of the standardization effort that has started at the TIA in the area of satellite ATM networks. Subsequently, a bandwidth-on-demand multiservice satellite network architecture implementation is described     

Real-Time Streaming Relay Mechanism for P2P Conferences on Hierarchical Overlay Networks

A peer-to-peer (P2P) multimedia conferencing service is operating that users share their resources to each other on the Internet. It can solve the problem in the centralized conferencing architecture, such as the centralized loading, single point error, and expensive infrastructure. However, P2P networks have the problem that a peer has a difference between the physical location and logical location in the overlay network. In the viewpoint of P2P networks, the nearest conference resource may be far away geographically. The P2P-session initiation protocol (P2P-SIP) multimedia conference is to construct an application-based logical multicast network efficiently according to physical network information. Thus, this paper proposes a real-time streaming relay mechanism for P2P conferences on hierarchical overlay networks. The real-time streaming relay mechanism can improve the transportation efficiency of conferencing stream exchange well based on the application-layer multicast (ALM) structure and the hierarchical overlay networks.     

QoE in video streaming over wireless networks: perspectives and research challenges

The deployment of 3G/LTE networks and advancements in smart mobile devices had led to high demand for multimedia streaming over wireless network. The rapid increasing demand for multimedia content poses challenges for all parties in a multimedia streaming system, namely, content providers, wireless network service providers, and smart device makers. Content providers and mobile network service providers are both striving to improve their streaming services while utilizing advancing technologies. Smart device makers endeavor to improve processing power and displays for better viewing experience. Ultimately, the common goal shared by content providers, network service providers, and smart device manufactures is to improve the QoE for users. QoE is both an objective and a subjective metric measuring the streaming quality experience by end users. It may be measured by streaming bitrate, playback smoothness, video quality metrics like Peak to Signal Noise Ratio, and other user satisfaction factors. There have been efforts made to improve the streaming experiences in all these aspects. In this paper, we conducted a survey on existing literatures on QoE of video streaming to gain a deeper and more complete understanding of QoE quality metrics. The goal is to inspire new research directions in defining better QoE and improving QoE in existing and new streaming services such as adaptive streaming and 3D video streaming.     

A flexible overlay architecture for mobile IPv6 multicast

The Internet has evolved from a wired infrastructure to a hybrid of wired and wireless domains. As network access is now provided with much of the last mile being a wireless mobile environment, delivering rich multimedia to users is now a necessity. However, despite the advent of new technology and standards such as Mobile Internet protocol version 6 (MIPv6), there is still an important dilemma over the choice of systems that either achieve high levels of performance or offer easier deployment. The very deployment of IPv6 is delayed for this reason; network providers continue to use legacy systems. The goal of this paper then is to offer insight into this issue by examining the case of data streaming to MIPv6 users through the use of multicast. By specifically considering the debate over network and application layer multicast, we examine a spectrum of possible alternatives and evaluate the potential of enhancing the functionality of access routers. The result is an overlay architecture that can bring the desired balance between deployment complexity and performance.     

End-to-end quality-of-service coordination for mobile multimedia applications

Transmitting real-time multimedia streams over heterogeneous mobile networks is a challenging task. Variation in network and system conditions can dramatically affect application performance. When providing end-to-end quality-of-service (QoS) multiple system facets should be coordinated: orchestration of local and peer resources, reservation of network resources, adaptation of multimedia streams, etc. This paper presents an end-to-end negotiation protocol (E2ENP) for negotiating and coordinating QoS on an end-to-end basis both at application and network layer. Based on a flexible extensible markup language (XML) model and extending SDPng concepts, the protocol enables the negotiation of system capabilities and allows provider-services to effectively influence the negotiation process. The aim of the E2ENP design is to optimize the efficiency of multimedia call setup and reduce the time for QoS renegotiations, whenever vertical handovers or spontaneous network reconfigurations occur. The basic protocol is presented, together with implementation and measurement results, stemming from several studies on current and future third-generation/fourth-generation scenarios.     

Performance analysis of cellular mobile communication networks supporting multimedia services

This paper illustrates the development of an analytical model for a communication network providing integrated services to a population of mobile users, and presents performance results to both validate the analytical approach, and assess the quality of the services offered to the end users. The analytical model is based on continuoustime multidimensional birth–death processes, and is focused on just one of the cells in the network. The cellular system is assumed to provide three classes of service: the basic voice service, a data service with bit rate higher than the voice service, and a multimedia service with one voice and one data component. In order to improve the overall network performance, some channels can be reserved to handovers, and multimedia calls that cannot complete a handover are decoupled, by transferring to the target cell only the voice component and suspending the data connection until a sufficient number of channels become free. Numerical results demonstrate the accuracy of the approximate model, as well as the effectiveness of the newly proposed multimedia call decoupling approach.