An application of informational divergence to Huffman codes

A classification of all probability distributions over the finite alphabet of an information source is given, where the classes are the sets of distributions sharing the same binary Huffman code. Such a classification can be used in noiseless coding, when the distribution of the finite memoryless source varies in time or becomes gradually known. Instead of applying the Huffman algorithm to each new estimate of the probability distribution, if a simple test based on the above classification is passed, then the Huffman code used previously is optimal also for the new distribution.     

An overview of quality of service routing for next-generationhigh-speed networks: problems and solutions

The upcoming gigabit-per-second high-speed networks are expected to support a wide range of communication-intensive real-time multimedia applications. The requirement for timely delivery of digitized audio-visual information raises new challenges for next-generation integrated services broadband networks. One of the key issues is QoS routing. It selects network routes with sufficient resources for the requested QoS parameters. The goal of routing solutions is twofold: (1) satisfying the QoS requirements for every admitted connection, and (2) achieving global efficiency in resource utilization. Many unicast/multicast QoS routing algorithms have been published, and they work with a variety of QoS requirements and resource constraints. Overall, they can be partitioned into three broad classes: (1) source routing, (2) distributed routing, and (3) hierarchical routing algorithms. We give an overview of the QoS routing problem as well as the existing solutions. We present the strengths and weaknesses of different routing strategies, and outline the challenges. We also discuss the basic algorithms in each class, classify and compare them, and point out possible future directions in the QoS routing area     

一种改进的BGP路由策略冲突检测方案

本文针对路由仲裁者计划的不足，提出一种改进的BGP路由策略冲突检测方案，在改进方案中提出一种基于AS关系描述的路由策略冲突检测方法，研究表明所提出的检测方法可以克服RA计划的不足。对所提出方案的技术可行性进行论证，给出关键技术的实验结果和软件原型。     

An ANSA overview

With the appropriate architecture, telecommunications services can work with computer applications components to support networked information services. ANSA is an architecture that enables telecommunications services and computer application components to work together despite diversity of programming languages, operating systems, computer hardware, networks, communications protocols and management, and security policies. The architecture is relevant to telecommunications, manufacturing, sales, cooperative working, banking, health service, research, and other applications. It provides a framework for the design and implementation of distributed computer systems supporting networked information services. The framework ensures that different design choices, made for particular applications, present the maximum opportunity for interworking     

Reconfigurable terminals: an overview of architectural solutions

Key technical aspects concerning the realization of a reconfigurable user terminal based on software-defined radio technology are discussed. These include functionalities such as mode monitoring, mode switching, adaptive baseband processing, and software download. The implications of these functionalities and the need for related entities within the network are also discussed. The concepts presented here form part of the 5th Framework IST European Research project Transparent Reconfigurable Ubiquitous Terminal (TRUST). It is the intention of this article to present the technical achievements of the TRUST project together with an overview of the potential complexity in the realization of a reconfigurable user terminal     

IP组播在BGP/MPLS VPN环境中的实现与分析

首先对现有的传统组播协议进行了对比，然后从基本概念、工作流程和实现机制等方面详细介绍了基于协议无关组播(PIM)的组播虚拟专用网(MVPN)实现方案——组播城，并讨论了组播城的优化方案——聚合树，对现有的方案从扩展性、合理性方面做了分析和比较，列举了优缺点。此外，引入了一系列有创新思想的组播协议，最后展望了MVPN今后的发展方向。     

An overview of microprocessor applications

Microprocessors have become important tools for the electronic designer. Prime motivators for their success have been the advantages they offer in cost reduction and design flexibility. These and other microprocessor advantages are discussed in this paper. Typical microprocessor-based applications are described as well as the direction of future trends.     

An overview of Internet protocols

In a very short period of time, the Internet has risen from being viewed as a peculiarity of the defence and academic community of the late sixties to become a significant component of many of our working and home lives. The possible impact of this technology has the futurists talking of the collapse of national borders, the bypass of tax systems and traditional commerce and the emancipation of the individual from the clutches of government, corporations and the boundaries of culture, gender and physical constraints. Most users' experience of the Internet is through browser software and applications such as e-mail, World Wide Web, Newsgroups and media plug-ins. Beneath this glossy, graphical, multimedia world exists the architectural and protocol components which have enabled the Internet evolution to reach into so many parts of everday life in such a short time. The aim of this paper is to outline some of these components, their characteristics and limitations, and their ongoing development to address those limitations and add new capabilities. Even though an overview of Internet protocols is included in this paper, basic knowledge of Internet technology is assumed.     

An overview of fiber-optic gyroscopes

The principles of operation of fiber-optic gyroscopes are reviewed. Performance-limiting phenomena are discussed along with methods to reduce their effect on the rotation-rate signal. Current technology and performance of state-of-the-art systems are presented. Finally, a direction of future research and possible applications are indicated.     

半导体产品用材料市场大观

电子器件是所有电子设备的核心,而半导体材料则是电子器件的基础。材料的进步又是牵引电子器件发展的重要动力。晶体管被通俗地叫做半导体,就因为它是使用半导体材料制成的。没有半导体材料,便没有今天的分立器件和集成电路。正是半导体材料Ge(锗)放大作用的发现,开辟了半导体材料新的一页,创造了固体器件的崭新时代,形象地称为新石器时代。Si(硅)是今天使用最多的半导体材料,随着晶体管结构、微细化技术和多层布线技术的应用,集成电路达到了高速度、低功耗、大容量、高集成等特性。Si圆片尺寸正向12英寸(300mm)过渡,目前还在开展铜布线、…     

An overview of X-ray lithography

Current achievements and future prospects of SR base x-ray lithography are explained through an account of research and development efforts made by NTT LSI Laboratories. The SR lithography system, including the compact SR light source Super-ALIS and beamlines with efficient mirrors, is now at the stage of practical use. The vertical x-ray steppers SS-1 and SS-2 have attained a repeatability of overlay accuracy as high as 25 nm (3σ). High-accuracy x-ray masks can be fabricated by applying the multiple-exposure method. Further improvement in pattern placement accuracy is expected with application of distortion compensation writing. Intense efforts made in development of x-ray mask inspection and repair technology resulted in the fabrication of defect-free x-ray masks. Test fabrication of CMOS/SIMOX LSIs has yielded fully functional devices, with an improved overlay accuracy of 0.1 to 0.15 μm (3σ), and a CD control of ±10% in 0.2 μm regions. Further application of SR lithography to the test fabrication of future LSIs will prompt the implementation of this technology into the practical process.     

An overview of sigma-delta converters

Using sigma-delta A/D methods, high resolution can be obtained for only low to medium signal bandwidths. This article describes conventional A/D conversion, as well as its performance modeling. We then look at the technique of oversampling, which can be used to improve the resolution of classical A/D methods. We discuss how sigma-delta converters use the technique of noise shaping in addition to oversampling to allow high resolution conversion of relatively low bandwidth signals. We examine the use of sigma-delta converters to convert narrowband bandpass signals with high resolution. Several parallel sigma-delta converters, which offer the potential of extending high resolution conversion to signals with higher bandwidths, are also described     

An overview of morphological filtering

This paper consists of a tutorial overview of morphological filtering, a theory introduced in 1988 in the context of mathematical morphology. Its first section is devoted to the presentation of the lattice framework. Emphasis is put on the lattices of numerical functions in digital and continuous spaces. The basic filters, namely the openings and the closings, are then described and their various versions are listed. In the third section morphological filters are defined as increasing idempotent operators, and their laws of composition are proved. The last sections are concerned with two special classes of filters and their derivations: first, the alternating sequential filters allow us to bring into play families of operators depending on a positive scale parameter. Finally, the center and the toggle mappings modify the function under study by comparing it, at each point, with a few reference transforms.     

视频分割技术概述

概述了基于内容的视频分割技术，主要介绍非压缩域和压缩域两个主要方面的镜头变换检测算法，展望了视频分割技术在自动化视频浏览和检索系统的应用前景。     

光纤陀螺研究综述

从光纤陀螺诞生以来，它就以其显著的优点、灵活的结构和诱人的前景引起了世界上诸多国家的大学和科研机构的普遍重视。为此综述了光纤陀螺的基本原理和它的特点以及分类，并着重介绍了光纤陀螺的国内外发展状况。     

Mobile radio: An overview

Following a brief prologue and historical overview, such technical issues as the repertoire of systems and services, management of the airwaves, the operating environment, service quality, network issues and cell size, channel coding and modulation, speech coding, diversity, multiplex, and multiple access (FDMA, TDMA, CDMA) are discussed. Also addressed are the potential economic and sociological impacts of mobile radio communications in the wake of the redistribution of airwaves at the World Administrative Radio Conference WARC '92. Performance dependence on multipath delay (related to the cell size and terrain configuration), Doppler frequency (related to the carrier frequency, data rate. and the speed of vehicles), and message length (may dictate the choice of multiple access) is briefly discussed     

数字电视概述

系统介绍数字电视的起源、原理、关键技术和发展状况,阐述了国际上数字电视方面最具影响力的两大标准;美国ＡＴＳＣ标准和欧洲ＤＶＢ标准,并对中国的数字电视的发展状况及前景予以介绍和展望。