ATM-based TH-SSMA network for multimedia PCS

Personal communications services (PCS) promise to provide a variety of information exchanges among users with any type of mobility, at any time, in any place, through any available device. To achieve this ambitious goal, two of the major challenges in the system design are: (i) to provide a high-speed wireless subsystem with large capacity and acceptable quality-of-service (QoS) and (ii) to design a network architecture capable of supporting multimedia traffic and various kinds of user mobility. A time-hopping spread-spectrum wireless communication system called ultra-wide bandwidth (UWB) radio is used to provide communications that are low power, high data rate, fade resistant, and relatively shadow free in a dense multipath environment. Receiver-signal processing of UWB radio is described, and performance of such communications systems, in terms of multiple-access capability, is estimated under ideal multiple-access channel conditions. A UWB-signal propagation experiment is performed using the bandwidth in excess of 1 GHz in a typical modern office building in order to characterize the UWB-signal propagation channel. The experimental results demonstrate the feasibility of the UWB radio and its robustness in a dense multipath environment. A ATM network is used as the backbone network due to its high bandwidth, fast switching capability, flexibility, and well-developed infrastructure. To minimize the impact caused by user mobility on the system performance, a hierarchical network-control architecture is postulated. A wireless virtual circuit (WVC) concept is proposed to improve the transmission efficiency and simplify the network control in the wireless subsystem. The key advantage of this network architecture and WVC concept is that the handoff can be done locally most of the time, due to the localized behavior of PCS users     

Telecommunications network design with multiple technologies

In this paper we consider a telecommunications network design problem allowing for multiple technologies. The problem arises in wide-area network and metro-area network design for which a combination of technologies may be necessary due to high traffic volumes, long-distance transmission, and design restrictions. The network design problem builds the best network to channel traffic between a set of origins and destinations, which requires selecting links, equipping them with fiber, deciding on the type of technology, and locating switches. The goal is to minimize the total cost of the network, which accounts for the flow cost, the fiber and technology costs, and the switch-location cost. We model the problem using a multicommodity network design formulation with side constraints. We apply Benders decomposition to the problem and develop a two-phase solution method that uses a number of improvements over the basic Benders algorithm. We present promising results on randomly generated test problems.     

ATM-based switching for the integrated broadband network

Telecommunications networks based on synchronous 64 kbit/s channels are too restrictive for the future realisation of integrated broadband networks. New switching and transmission techniques, particularly those based on asynchronous transfer modes (ATM), are required. Roke Manor Research Ltd. and Plessey Research Caswell Ltd. are actively developing these new techniques at a system and technology level under the auspices of the European Commission's RACE programme. The authors introduce the issues pertinent to ATM, highlighting the system and technology aspects of the work being carried out within a RACE project entitled `Broadband Local Network Technology' (BLNT) and also describes previous ATM work relevant to the current research activities     

ATM-based signaling network topics on reliability and performance

The authors consider some reliability and performance aspects of ATM-based signaling networks. They present ideas on how ATM technology, suitable system concepts, as well as simplified and enhanced protocols could maintain or even improve the reliability level of the existing Common Channel Signaling System No. 7. They also discuss possible scenarios for the interworking of ATM-based signaling networks with existing signaling networks. They also examine the aspect of performance enhancement in terms of reduced delays and increased throughput due to the ATM signaling connections with higher bit rates and protocol simplifications     

互联网的设计理念与网络5.0技术

互联网发展了50年,其设计理念从未改变,业务网完全采用OTT方式,IP网至今还是“尽力而为”,制约了互联网的发展。要不断满足社会发展的需要,互联网设计理念需要变革,可行的方向是由“以应用为中心”变为“以网络为中心”。网络5.0是第5代数据网,与第4代数据网（IP网）相比,保留IP网的全部优点,填补了IP网在网络性能和能力上的不足,性能和能力上有质的进步。具体讨论了网络5.0在可扩展性、内生可信安全、确定性等多方面的关键技术。     

The design of a QoS-controlled ATM-based communications system inChorus

We describe the design of an application platform able to run distributed real-time and multimedia applications alongside conventional UNIX programs. The platform is embedded in a microkernel/PC environment and supported by an ATM-based, QoS-driven communications stack. In particular, we focus on resource-management aspects of the design and deal with CPU scheduling, network resource-management and memory-management issues. An architecture is presented that guarantees QoS levels of both communications and processing with varying degrees of commitment as specified by user-level QoS parameters. The architecture uses admission tests to determine whether or not new activities can be accepted and includes modules to translate user-level QoS parameters into representations usable by the scheduling, network, and memory-management subsystems     

视频监视系统监视中心实现的关键技术

视频图像是对客观事物形象、生动的描述，是直观而具体的信息表达形式，是人类最重要的信息载体。目前，视频监视系统已经广泛应用于生活中，已成为安全防范技术体系中重要组成部分。对实现过程中解压缩标准、传输层协议、以及显示方式等关键技术进行分析，提出了自己的观点。     

Analysis of unslotted direct-sequence spread spectrum multipleaccess network with packet combining

A packet combining scheme is investigated for an unslotted random access code division multiple access network over a frequency selective Rayleigh fading channel. It is shown that this simple diversity combining mechanism is highly advantageous for systems which can both tolerate a certain delay and operate over highly time-varying channels     

面向自组网的通感融合技术及软硬件设计

现有自组网通信和导航技术缺乏深度融合的框架和方法,在未来场景下难以保障未来“智慧城市”、“智能出行”等场景对通信感知的综合性需求,因此研究面向物联网、车联网等自组织网络的通感融合(ISAC)技术成为亟待解决的问题。本文针对自组网通感需求,提出了通信感知信号融合方法和技术方案,可在保障通信性能的同时提高测距感知估计精确度。针对自组网设备间、通感任务间资源需求冲突等问题,依据自组网集群业务需求,构建了保障通信需求的定位感知网络时频资源优化框架,设计了联合资源分配方案及相应迭代优化算法,实现有限资源情况下的高可靠、强稳定自组网协同感知能力。针对当前自组网通信模组存在时延高、网络覆盖范围小、感知能力缺失等问题,设计并搭建了通感一体化模块原型样机I型,可在卫导数据缺失下提供全网高精确度时钟同步,保障集群协同感知能力,并在长距离下提供自组网通信协同传输支撑,从硬件设备上为通感融合提供支撑。最终形成了一套包含通感信号融合设计、时频资源联合优化方案的自组网通信感知系统框架,并研制搭建了一套通感融合软硬件平台(含通感一体化原型样机4台)。在外场测试中,2 km内通信速率≥320 kbps,丢包率≤0.0...     

Cable measurements supporting xDSL technologies

The ongoing developments in the field of high-speed data transmission over twisted-pair cables (DSL-Digital Subscriber Line) leads to methods that can exploit the transmission media with increased efficiency. MIMO (Multiple-Input Multiple-Output) transmission, i.e., the coordinated use of many pairs within a bundle, is such an emering DSL technology. A further goal is to maintain a certain transmission quality in the presence of non-DSL noise. For example, cancellation techniques to combat narrowband radio interference, which is generated by radio amateur transmitters and may be picked up by the wire close to the subscriber or by the in-hourse wiring, become important. The efficiency of these techniques strongly depends on cable properties that have not been the focus of cable measurements so far. This paper gives an overview of special cable measurements and shows their importance for future DSL technologies.     

H.263的差错恢复视频编码及其在IP网络传输中的应用

以H.263 为主要依据，详细介绍了H.263标准中的差错恢复技术，着重探讨了差错恢复视频编码技术在基于分组的网络（IP网）视频传输中的应用。     

An interconnect-centric design flow for nanometer technologies

As the integrated circuits (ICs) are scaled into nanometer dimensions and operate in gigahertz frequencies, interconnects have become critical in determining system performance and reliability. This paper presents the ongoing research effort at UCLA in developing an interconnect-centric design flow, including interconnect planning, interconnect synthesis, and interconnect layout, which allows interconnect design and optimization to be properly considered at every level of the design process. Efficient interconnecter performance estimation models and tools at various levels are also developed to support such an interconnect-centric design flow     

Performance measurements on an ATM-based metropolitan area network: OASICE case study

The city of Colmar is developing a Metropolitan Area Network (MAN) called OASICE. Our MAN uses ATM technology to provide a range of business, academic and community tele-services such as tele-teaching, tele-information, tele-documentation, tele-management and tele-surveillance of property, high definition tele-conference, VOD (Video On Demand), etc. This revised version was published online in August 2006 with corrections to the Cover Date.     

视频编码的技术基础及发展方向

现有视频编码采用基于块的混合编码架构,利用预测、变换、量化和熵编码技术实现对视频信号的高效压缩.在现有架构基础上进一步优化,提供针对视频图像信号局部特性的更加灵活的处理和编码.基于机器学习的视频编码技术有望部分或全面地改变现有的混合编码框架,给视频编码带来新的研究思路.未来视频除了现有的二维平面视频,还需要编码面向AR/VR应用的球面视频数据和体视频数据,这些新的视频源数据格式也给视频编码技术研究带来新的机会和挑战.     

应急通信网络设计中的关键技术探究

应急通信网络通过监控和连接的形式,主要在发生紧急及突发等状况使用,以确保应急通信信息的高效传递效果。所以,应急通信网络的设计必须依靠高科技的技术支持,以便能最大限度的提高预警的准确度。就现今情况而言,因技术含量在应急通信网络中确实起着至关重要的作用,也大大提高了应急通信的使用效率,所以,本文通过把应急通信网络作为基石,着重分析应急通信网络中设计的关键因素。     

针对网络视频应用的视频转码技术综述

对视频转码的技术基础,尤其是3种典型的体系结构进行了简述和比较,然后讨论了利用从输入视频流中易于得到的信息,减少计算复杂度和改善视觉质量的方法。同时,对近年来出现的一些热点技术,如信息(包括水印和具有差错抑制特征的数据)嵌入的视频转码、H.264码流转码等进行了重点讨论。对视频转码技术的未来发展也进行了展望。