The VuNet desk area network: architecture, implementation, andexperience

The VuNet is a gigabit-per-second desk-area ATM network that interconnects general-purpose workstations, network-based multimedia devices, and bridges to other networks, workstations access the multimedia devices over the network and coordinate the movement of information streams among the different parts of the system. This architecture presents several advantages over the traditional workstation-centric models, including the ability to easily share network-based devices, to access nonlocal devices, and to relieve the workstation of a portion of the I/O work. This paper describes the philosophy, implementation choices, advantages, and limitations of the VuNet ATM network implementation, as well as performance and current status     

视听信息处理系统网络环境的设计与实现

本文讨论了超级智能视听信息系统（ＳＩＶＡＩＰＳ）所需的网络环境，给出了系统的网络结构，详细论述了基于Ｅｔｈｅｒｅｎｔ扩展的ＳＩＶＡＩＰＳ网络环境的设计思想与实现方法，并在包括语音，图形，图像，文本信息处理工作站及多媒质数据库管理工作站的互连系统中实现了ＳＩＶＡＩＰＳ网络环境。     

Elastic basket switching

This paper proposes a new integrated switching system, ‘elastic basket switching’, for broadband and multimedia communications, including voice and high-speed data. In elastic basket switching (EBS), it is possible flexibly and efficiently to handle multimedia information by adaptively assigning communication resources according to communication requests and bandwidth of switched information. For continuous information, such as voice, EBS functions just as a circuit switching system, and for burst data it achieves high-efficiency bandwidth usage equivalent to a packet switching system by demand-assign type time-slot assignment. The detail of EBS and its application to a departmental system-orientated PBX are described. The traffic handling capability and details of the hardware structure are presented. The experimental system, including use of LSIs in the main parts of EBS is also described.     

Media-intensive data communications in a "desk-area" network

The VuNet is a "desk-area" network where small switches are distributed throughout the work area, and multimedia devices usually found in the workstation are put on the network. This architecture has several advantages including distributed switching and the ability to share multimedia devices across a workgroup.<>     

A network management and control scenario for multimedia applications

Emergence of multimedia applications requires that appropriate management and control activities be provided and organized in a somewhat integrated framework. Such issues as coordination of operations on the shared information, provision of the user requirements in terms of quality of service and efficient handling of the available network resources result in more critical problems when they regard multimedia objects. Mainly this is due to the time-constrained requirements that arise from the need of synchronization among multiple streams of information which are different in their nature and granularity. This paper discusses the impact of the above issues on network management and control and proposes an architectural model for the management and control of broadband applications that require handling of multimedia information.     

An expandable time-division circuit switching LSI and networkarchitecture for broadband ISDN

A broadband network architecture is proposed that integrates multimedia services, such as data, video, and telephony information, using 52-Mb/s based STM-paths at the user network interface (UNI). The user can access any new service via the STM-based access network via either synchronous transfer mode (STM) switching or asynchronous transfer mode (ATM) switching. STM circuit switching supports long duration, constant bandwidth data transfer services such as video and high-definition television (HDTV) distribution and will also be used for the crossconnect system. Circuit switching can provide transparent transmission during long connection periods. This paper also proposes an expandable time-division switch architecture, an expandable time-division switching LSI, and an expandable switching module for small to large size system applications. The proposed time-division switching LSI, module, and system handle 52-Mb/s bearer signals and have throughputs of 2.4 Gb/s, 10 Gb/s, and 40 Gb/s, respectively. The time-division switch realizes video distribution with 1:n connections. Finally, a local switching node that features an expandable 52-Mb/s time-division circuit switching network is shown for multimedia access networking     

Multimedia Support for Wireless W-CDMA with Dynamic Spreading

The emerging multimedia communication needs more support in operating systems in order to be successful over a wireless environment. The system needs to support a seamless integration (i.e., transparent application switching) of voice, audio and conventional data (e.g., e-mails, and ftp). It should also support multiple users with a guaranteed quality. In this paper, we investigate effective protocol design with dynamic spreading factors such that various QoS based on different traffic types can be provided. Increasing spreading factors can benefit the system because it will increase the desired signal strength linearly. The measured bit error rate can be reduced 75 times with a long spreading factor. By taking advantage of this benefit, we propose some middle-ware solutions to monitor the network load and switch the spreading factors dynamically based on the current load with multimedia traffic. These middle-ware solutions are implemented in mobile and base stations and experiments are performed to measure the actual system performance. The preliminary results indicate that our proposed system can always maintain a desired quality for all the voice connections. We further extend our protocol to guarantee a balanced support among different traffic types. While the voice communication is still guaranteed to be non-interrupted, the data traffic is proved to be served with reasonable response time by our proposed system.     

Synchronization of multimedia data for a multimedia news-on-demandapplication

We present a complete software control architecture for synchronizing multiple data streams generated from distributed media-storing database servers without the use of a global clock. Independent network connections are set up to remote workstations for multimedia presentations. Based on the document scenario and traffic predictions, stream delivery scheduling is performed in a centralized manner. Certain compensation mechanisms at the receiver are also necessary due to the presence of random network delays. A stream synchronization protocol (SSP) allows for synchronization recovery, ensuring a high quality multimedia display at the receiver. SSP uses synchronization quality of service parameters to guarantee the simultaneous delivery of the different types of data streams. In the proposed architecture, a priority-based synchronization control mechanism for MPEG-2 coded data streams is also provided. A performance modeling of the SSP is presented using the DSPN models. Relevant results such as the effect of the SSP, the number of synchronization errors, etc., are obtained     

Simulation analysis of a communication link with statisticallymultiplexed bursty noise sources

Variable bit rate (VBR) coding techniques have received great research interest as very promising tools for transmitting bursty multimedia traffic with low bandwidth requirements over a communication link. Statistically multiplexing the multimedia bursty traffic is a very efficient method of maximizing the utilization of the link capacity. The application of computer simulation techniques in analyzing a rate-based access control scheme for multimedia traffic such as voice traffic is discussed. The control scheme regulates the packetized bursty traffic at the user network interface of the link. Using a suitable congestion measure, namely, the multiplexer buffer length, the scheme dynamically controls the arrival rate by switching the coder to a different compression ratio (i.e., changing the coding rate). VBR coding methods can be adaptively adjusted to transmit at a lower rate with very little degradation in the voice quality. Reported results prove that the scheme greatly improves the link performance, in terms of reducing the probability of call blocking and enhancing the statistical multiplexing gain     

Path selection in user-controlled circuit-switched optical networks

User-controlled circuit-switched optical networks are gaining popularity in an effort to fulfill the insatiable data transport needs of the online community. In this paper we consider the resource allocation challenges that arise in such networks, in particular problems related to construction of end-to-end lightpaths for carrying large multimedia streams. Specifically, we discuss variations of the least cost and widest path problems that address two unique aspects of the user-controlled environment. First, since network resources are exposed for user-control using a service-oriented software control plane, each lightpath is subject to an expiry time. Second, because Wavelength Division Multiplexing (WDM) and resource partitioning introduces multiple redundant paths, classic least cost path computations tend to yield multiple optimal solutions, and so it is useful to break ties among these in a judicious manner. We present polynomial-time path selection techniques that address these issues using efficient data structures. We also show the benefit of breaking ties in shortest path computations in a manner that reduces harmful fragmentation of capacity.     

NGN及其关键技术探讨

NGN是一种综合、开放的网络架构,提供语言、数据和多媒体等业务。NGN通过优化网络结构,不但实现了网络的融合,更重要的是实现了业务的融合,使得分组交换网络能够继承原有电路交换网中丰富的业务功能,同时可以在全网范围内快速提供原有网络难以提供的新型业务。主要介绍了NGN的概念与体系架构,叙述了NGN涉及的主要技术及优势,并对NGN进行了展望。     

A network interface unit to support continuous media

The combination of high-speed multiservice networks and multimedia workstations offers considerable potential for the development of distributed multimedia applications. A key problem is how to integrate continuous-media types such as audio and video into a distributed workstation environment. An experimental system architecture based on a specialized multimedia network interface that attempts to provide this integration is described. The design and implementation of this system are discussed in depth in terms of workstation enhancement and distributed system support. A new approach to the problem of media synchronization is introduced, and the importance of quality of service in the architecture is highlighted. Experiences encountered during this work are described, comparison with other approaches is made, and likely future developments in multimedia network interfacing are discussed     

Medium Access Control for ATM-to-CDMA Interface

An integrated medium access control framework for a direct sequence code-division multiple access (CDMA) radio access to an asynchronous transfer mode (ATM) network is considered. The system accommodates multimedia services such as voice and data. The inherently high error rate associated with the multipath fading channel is partly overcome by the introduction of a data link control layer employing one- and two-dimensional CRC codes for error detection/correction in voice and data packets, respectively. Analysis and simulations show promising average delay and error probability performance, as well as low coding redundancy. Two-dimensional CRC, particularly in conjunction with automatic repeat request (ARQ), outperforms convolutional coding with much less overhead and processing requirement at the ATM-CDMA interface.     

Techniques for Packet Voice Synchronization

Packet switching has been proposed as an effective technology for integrating voice and data in a single network. An important aspect of packet-switched voice is the reconstruction of a continuous stream of speech from the set of packets that arrive at the destination terminal, each of which may encounter a different amount of buffering delay in the packet network. The magnitude of the variation in delay may range from a few milliseconds in a local area network to hundreds of milliseconds in a long-haul packet voice and data network. This paper discusses several aspects of the packet voice synchronization problem, and techniques that can be used to address it. These techniques estimate in some way the delay encountered by each packet and use the delay estimate to determine how speech is reconstructed. The delay estimates produced by these techniques can be used in managing the flow of information in the packet network to improve overall performance. Interactions of packet voice synchronization techniques with other network design issues are also discussed.     

Designing an on-demand multimedia service

A quantitative study of techniques for designing a high-performance multiuser multimedia on-demand information service is presented. The problem of maintaining continuity of playback of each media stream in the presence of multiple subscriber requests is formulated, and admission control algorithms that permit a multimedia server to satisfy the maximum number of subscribers simultaneously are presented. A feedback technique in which a multimedia service uses lightweight messages called feedback units that are transmitted back to it by subscribers' mediaphones to detect asynchrony among them and steer them back to synchrony thereafter is presented. The feedback technique guarantees synchronous playback of media streams transmitted by the multimedia server to subscribers over metropolitan-area networks     

SIP终端语音聊天的设计与实现

SIP协议是多媒体通信网的控制协议，在分组交换网中，它提供基本的呼叫控制，负责建立、修改和终止多媒体（话音、数据、视频等）会话等应用。概述了SIP终端软件的设计思想，并详细介绍了SIP终端软件中语音聊天功能的关键技术，从宏观和微观2个角度阐述了语音聊天功能的实现过程，构造了系统测试环境。SIP终端软件实现了语音聊天功能，具有良好的性能。     

Software architecture for integration of video services in theEtherphone system

Software mechanisms that make use of analog transmission and storage of video for computer-controlled video communication and file storage are described. The authors extended the Etherphone voice management system to support video conferencing and file storage. The software mechanisms for conference management consist of a central connection manager, and video and user interface agents running on client workstations. A conferencing architecture that supports multiplicity in the number of conferences and media is presented. The video file server stores and retrieves full-motion video information within conferences. It uses optical disks to store video frames and builds a high-level file and directory interface. The user interface to the directory interface is a multimedia document editor that permits video annotations to be freely interspersed with text. The performance of the system, which spans multiple media networks, has been highly satisfactory     

End to end QoS provisioning multimedia wireless/mobile networksusing an adaptive framework

This article presents a framework for multimedia networking in a wireless and mobile environment. We consider both multimedia application needs as well as networking requirements, and try to bridge these paradigms using an adaptive framework. Central to this framework is the concept of representing a multimedia connection in terms of multiple substreams each with their own specified QoS requirement and making network elements (switching and access points), services, and protocols (signaling, control, routing) aware of the QoS requirements of such substreams. As resource availability in the wireless and mobile network fluctuates, the network selects and schedules substreams in order to present the information content with an acceptable quality at a receiver (or each receiver in case of multicast connections). This is done while achieving a reasonable utilization efficiency of network resources and sharing them in a fair manner     

一种基于FPGA的媒体网关设计与实现

基于IP的软交换网络实现话音业务并能与PSTN交换网实现互联互通,关键要解决网络之间的信令互通和话音互通。现给出了一种与PSTN交换网络能够实现互通的一种媒体网关的硬件、软件和FPGA设计的实现方案介绍,该设计方案采用模块化设计,单板接口数量多,可通过控制软件灵活配置,还兼具有可扩展性。对媒体网关中FPGA的整体设计方案,以及上行数据处理和下行数据处理部分中各个模块的设计和功能进行了比较详尽的介绍,其中下行数据处理模块设计中还兼具有保证Qos的一种方法。