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1.
目前MAN和城域接入网已成为网络从局域网到广域网跨越的瓶颈。弹性分组环(RPR)根据下一代MAN的要求提出的有发展前途的一种解决方案。本文首先介绍该技术的提出,然后重点分析其关键技术及与现有的技术比较。  相似文献   

2.
弹性分组数据环技术及进展   总被引:3,自引:0,他引:3  
目前MAN和城域接入网已经成功网络从局域网(LAN)到广域网(WAN)跨越的瓶颈。弹性分组环(RPR)是根据下一代MAN的要求提出的最有发展前途的一种解决方案。本首先介绍该技术的提出,然后重点分析其的关键技术及标准化和产业化发展。  相似文献   

3.
光纤以太网网是指在光纤上运行以太网局域网(LAN)数据包接入服务的网络,底层连接可以以任何标准的以太网速度运行,包括10Mbit/s、100Mbit/s、1Gbit/s或10Gbit/s。光纤以及网把以太网技术扩展到LAN之外,进入城域网(MAN)。光纤以太网也将以太网的优越性扩展到了MAN,大大降低了运营商的网络建设成本。  相似文献   

4.
这里所讲的城域网(MAN)是在一个城市范围内,具有统一协议的高速宽带网。 城域网并不是一个新的概念,它产生于20世纪90年代初期。早期的MAN是由TDM光纤环网组成的。90年代中期,ATM成为建设MAN的主导性技术。这是由于ATM被认为是可以融合数据、语音和图像的技术,而且ATM可以和SDH环网很好地适应。但是,自那以后发生了很多变化,SDH网络的建设和维护一直很昂贵,基于SDH的带宽速率等级并不适合  相似文献   

5.
介绍了一般的卫星ATM网络互连单元,重点讨论了互连LAN/MAN的ASIU的结构,并指出了设计LAN/MAN互连技术应该考虑的基本问题,最后指出用卫星ATM实现LAN/MAN互连所面临的挑战。  相似文献   

6.
陈金岭 《移动通信》1998,22(2):62-63
随着Internet应用的普及,电子邮件E-Mail越来越成为人们重要的通信方式。但目前人们还没有可随身轻松携带的网络接收终端,若要在第一时间知道收到E-Mail及其内容,那只有整天坐在电脑旁守候信息,这自然给人们的生活带来诸多不便。现在,一种寻呼新业务—“E-Mail寻呼”服务解决了这一难题:当E-Mail送到用户的电子信箱时,其用户机就会立即提醒机主,你收到E-Mail了,如果机主拥有寻呼机,便可直接在BP机上阅读E-Mail内容,从而实现了微机的“移动通信”。自美国TeleSKY寻呼公司推出E—Mail寻呼以来,全球各大寻呼公司纷…  相似文献   

7.
王耘 《今日电子》2003,(8):18-19
随着Internet技术的不断发展,通信系统的容量也正在日益增长, DSL、FTTH等宽带访问技术的普及,使大容量城域网(MAN)、局域网(LAN)市场得到了迅猛的发展。在MAN、LAN领域中的光通信容量增大的同时,也要求光通信元件向着小型化和低价位的方向发展。为此,小型封装(SFF: Small Form-factor)/小型封装可热插拔(SFP: SmallForm-factor Pluggable)收发器技术也日益流行起来。由于SFF/SFP收发器里采用了小型插入式激光二极管(LD),与以往支持LC连接器的收发器相比,更加节省空间、更加轻便。日本NEC公司开发出了11.6mm的小型可热插…  相似文献   

8.
3 面向连接的DQDB业务 由高速LAN和MAN所提供的CL业务,目前还不能提供必要的服务质量(QOS)以支持新的用户,除了传统的LAN数据业务外还需要扩充。比较起来CO技术的主要优点是在呼叫建立时有配置资源的能力。这样如果它不能保证可按受的性能,就应允许网络保持跟踪资源并不需连接。因此它堤供需要的性能预测性,这对敏感时间服务是很重要的。在宽带网络中高速  相似文献   

9.
安全电子邮件解决方案   总被引:2,自引:0,他引:2  
吴韶波  于珏 《信息技术》2003,27(3):63-64,74
随着互联网的广泛应用,电子邮件作为一种快捷的联络手段越来越受到人们的喜爱,其安全性也越来越受到重视。针对E-mail用户,在介绍电子邮件不安全性的基础上,讨论了保护E-mail安全所要解决的问题,并给出安全电子邮件的全面解决方案。  相似文献   

10.
外观设计盈佳E—390音箱是一款三件式的音箱,包括左右声道的卫星音箱和一个低音炮音箱。颜色采用了蓝色与银灰色的搭配方式。功能特点盈佳E—390音箱前面板上一共提供了六个调节按钮,上面三个旋钮分别是音量、高音和中低音。E—390音箱具有几点比较特别的功能,这款  相似文献   

11.
Three alternative schemes for secure Virtual Private Network (VPN) deployment over the Universal Mobile Telecommunication System (UMTS) are proposed and analyzed. The proposed schemes enable a mobile node to voluntarily establish an IPsec-based secure channel to a private network. The alternative schemes differ in the location where the IPsec functionality is placed within the UMTS network architecture (mobile node, access network, and UMTS network border), depending on the employed security model, and whether data in transit are ever in clear-text, or available to be tapped by outsiders. The provided levels of privacy in the deployed VPN schemes, as well as the employed authentication models are examined. An analysis in terms of cost, complexity, and performance overhead that each method imposes to the underlying network architecture, as well as to the mobile devices is presented. The level of system reliability and scalability in granting security services is presented. The VPN management, usability, and trusted relations, as well as their behavior when a mobile user moves are analyzed. The use of special applications that require access to encapsulated data traffic is explored. Finally, an overall comparison of the proposed schemes from the security and operation point of view summarizes their relative performance. Christos Xenakis received his B.Sc. degree in computer science in 1993 and his M.Sc. degree in telecommunication and computer networks in 1996, both from the Department of Informatics and Telecommunications, University of Athens, Greece. In 2004 he received his Ph.D. from the University of Athens (Department of Informatics and Telecommunications). From 1998–2000 was with the Greek telecoms system development firm Teletel S.A., where was involved in the design and development of advanced telecommunications subsystems for ISDN, ATM, GSM, and GPRS. Since 1996 he has been a member of the Communication Networks Laboratory of the University of Athens. He has participated in numerous projects realized in the context of EU Programs (ACTS, ESPRIT, IST). His research interests are in the field of mobile/wireless networks, security and distributed network management. He is the author of over 15 papers in the above areas. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Greece, in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986, he was on the faculty of Electrical Engineering and Computer Science at the University of Connecticut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern University, Boston, MA. During the period 1993–1994 he served as Director of the Communications and Digital Processing Research Center at Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies & Services (ACTS) and Information Society Technologies (IST) programmes funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE). He is chairman of the board of the Greek Universities Network, the Greek Schools Network, and member of the board of the Greek Research Network. In 1994, he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.  相似文献   

12.
现代通信网络应能满足各种通信业务和通信容量日益发展的需求,实现话音、数据、视频、IP等业务的一体化综合交换和传输。在比较TDM、IP和ATM三种协议的基础上,提出"采用内置RPR和MPLS功能的MSTP平台"建设光纤综合通信网络平台的实现方法。MSTP采用SDH的数据帧结构,保持了SDH标准光接口、灵活分插低速信号、自愈环保护和功能强大的网管等优点,可对TDM、IP和ATM协议进行优化传输。  相似文献   

13.
微电子封装的新进展领域及对SMT的新挑战   总被引:2,自引:0,他引:2  
介绍了几种微电子新型封装材料,如LTCC、AIN、金刚石、AI-Sic和无铅焊接材料等,论述了正在发展中的新型先进封装技术,如WLP、3D和SIP等,并对封装新领域MEMS和MOEMS作了简介.最后,就这些新技术对SMT的新挑战作了些探讨.  相似文献   

14.
In this paper, a 1-V bulk-driven analog winner-takes-all circuit with programmable k-winners capability is proposed. By presetting a set of binary bits, the desired k-winners-take-all or k-losers-take-all function is programmable. The proposed upward-and-downward searching greatly improves the response time. The chip has been fabricated with a 0.25-μm CMOS technology. Simulated results show that the response time of the winner-takes-all circuit is 50 μs under 5-mV identified resolution. The input range is approximately to be rail-to-rail. This work was in part supported by the Chip Implementation Center and the MOE Program of Promoting Academic Excellence of Universities under the Grant EX-93-E-FA09-5-4. Yu-Cherng Hung was born in Changhua, Taiwan, R.O.C., in 1964. He received the M. S. degree in electronics engineering from the National Chiao Tung University, Hsinchu, Taiwan, R.O.C., in 1992, and the Ph.D. degree in electrical engineering from National Cheng Kung University, Tainan, Taiwan, R.O.C., in 2004. From Dec. 1986 to Jan. 2005, he was with the Division of Computer/Information, Chinese Petroleum Corp., Taiwan. He is currently an Assistant Professor with the Department of Electronic Engineering, National Chin-Yi Institute of Technology, Taiwan, R.O.C. His main research interests include analog circuit design, low-voltage VLSI design, and neural network applications. Dr. Hung is a Member of Phi Tau Phi Honorary Scholastic Society, IEEE, and the Institute of Electronics, Information, and Communications Engineers (IEICE). Bin-Da Liu received the Ph.D. degrees in electrical engineering from the National Cheng Kung University, Tainan, Taiwan, R.O.C., in 1983. Since 1977, he has been on the faculty of the National Cheng Kung University, where he is currently a Distinguished Professor in the Department of Electrical Engineering and the Director of the SoC Research Center. During 1983–1984, he was a Visiting Assistant Professor in the Department of Computer Science, University of Illinois at Urbana-Champaign. During 1988–1992, he was the Director of Electrical Laboratories, National Cheng Kung University. He was the Associate Chair of the Electrical Engineering Department during 1996–1999 and the Chair during 1999–2002. Since 1995, he has been a Consultant of the Chip Implementation Center, National Applied Research Laboratories, Hsinchu, Taiwan. He has published more than 200 technical papers. He also contributed chapters in the book Neural Networks and Systolic Array Design (D. Zhang Ed. Singapore: World Scientific, 2002) and the book Accuracy Improvements in Linguistic Fuzzy Modeling (J. Casillas, O. Cordón, F. Herrera, and L. Magdalena Eds. Heidelberg, Germany: Springer-Verlag, 2003). His current research interests include low power circuit, neural network circuit, CMAC neural network, analog neural network architecture, design of programmable cellular neural networks, and very large-scale integration implementation of fuzzy/neural circuits and audio/video signal processors. Dr. Liu is a Fellow of IEEE and the Vice President of Region 10, IEEE Circuits and Systems Society. He served as a CAS Associate Editor of IEEE Circuits and Devices Magazine and an Associate Editor of IEEE Transactions on Circuits and Systems I: Regular Papers. He is serving as an Associate Editor of IEEE Transactions on Very Large Scale Integration (VLSI) Systems. Chung-Yang Tsai was born in Mian-Li, Taiwan, R.O.C. He received the B.S. and M.S. degrees both in electrical engineering from the National Cheng Kung University, Tainan, Taiwan, R.O.C., in 2001 and 2003, respectively. His research interests include very large-scale integration design and signal processing.  相似文献   

15.
As the convergence in digital industry takes shape, the digital networks, both wireline and wireless, are also converging to offer seamless services and enhanced experience to the user. With the arrival of the mobile Internet the mobility is also moving into new areas, e.g., imaging, games, video, multimedia, and across different types of networks. In this paper we explore why, what, and how of the network convergence, and identify how the industry viewpoints align and differ. We also identify the key barriers to achieving true network convergence. We then discuss the role of the Internet Protocol (IP) as the common thread that enables network convergence, and the key industry and standards initiatives to actually provide solutions and the equipment to implement a cost-efficient and high performance converged network. Sudhir Dixit joined Nokia Research Center in 1996, where he is currently a Research Fellow and works on next generation wireless networks. From 1996 to 2003 he was a Senior Research Manager, focusing on IP/ATM, wireless, content networks, and optical networks. Prior to that he worked at NYNEX Science & Technology (now Verizon), GTE (now Verizon), Codex Motorola, Wang, Harris, and STL (now Nortel Europe Labs). He has published or presented over 150 papers, published three books, and holds 14 patents. He is on the Editorial Board of the IEEE Communications Magazine, Springer's Wireless Personal Communications Journal, and KIC's Journal of Communications and Networks. He received a B.E. degree from MANIT, Bhopal, India, an M.E. degree from BITS, Pilani, India, a Ph.D. degree from the University of Strathclyde, Glasgow, Scotland, and an M.B.A. degree from Florida Institute of Technology, Melbourne. He is a Fellow of IEE (UK) and IETE (India). He represents Nokia on the Steering Board of the Wireless World Research Forum, and is also Chair of the SIG on Self-Organization of Wireless World Systems.  相似文献   

16.
孙忠贵  高新波  张冬梅  李洁  王颖 《电子学报》2018,46(8):1969-1975
近年,形态学非局部拓展工作在图像处理领域受到众多关注.而附益性算子是经典形态学的最基本形式,也是形态学分析方法最重要的变换工具.为此,一些研究者就形态学非局部拓展中如何保持算子的附益性开展工作.本文从理论及实例两个方面说明,相关拓展工作为保持算子的附益性而丢失了保序性的不足;进一步,通过设计非局部权值的获取过程,并结合现有工作,本文提出了一个新的形态学非局部拓展,并定理证明了所得算子同时具备附益性及保序性两个重要性质;人工合成图像及自然图像上的仿真实验也表明了本文所提算法的有效性.  相似文献   

17.
组呼通信在指挥调度中有着重要作用,而在一些地面没有基站的地方,就无法正常使用。卫星通信具有无视地形,通信范围广,不易受陆地灾害影响,易于建设等优点。把卫星通信和组呼通信结合在一起的卫星组呼通信技术兼顾两者的优点,能更好的发挥指挥调度这一作用。当前卫星组呼通信采用固定频率方式,组呼成员在一个频率下进行通信,这种方式实用性不好。本文研究的是移动卫星组呼,在GMR-1系统的基础上研究了卫星组呼通信中MAC层的功能,提出了MAC-Ready-Gcc、MAC-Dedicated-Gcc这两个为了支持组呼的状态,并针对在MAC层发生的PTT竞争提出了一种回退策略。  相似文献   

18.
One of the most important and challenging issues in the design of personal communication service (PCS) systems is the management of location information. In this paper, we propose a new fault-tolerant location management scheme, which is based on the cellular quorum system. Due to quorum's salient set property, our scheme can tolerate the failures of one or more location server(s) without adding or changing the hardware of the systems in the two-tier networks. Meanwhile, with a region-based approach, our scheme stores/retrieves the MH location information in the location servers of a quorum set of the local region as much as possible to avoid long delays caused by the possible long-distance of VLR and HLR. Thus, it yields better connection establishment and update delay. Ming-Jeng Yang received the M.S. degree in computer science from the Syracuse University, New York, in 1991, and the Ph.D. degree in computer science from National Taiwan Normal University, Taiwan, in 2004. He is an associate professor in the Department of Information Technology, Takming College, Taiwan. His research interests include wireless networks, mobile computing, fault-tolerant computing, and distributed computing. He is a member of the IEEE Computer Society and the ACM. Yao-Ming Yeh received the B.S. degree in computer engineering from National Chiao-Tung University, Taiwan, in 1981, and the M.S. degree in computer science and information engineering from National Taiwan University, Taiwan, in 1983. In August 1991, he received the Ph.D. degree in the Department of Electrical and Computer Engineering, The Pennsylvania State University, Pa., U.S.A. He is a professor in the Department of Information and Computer Education, National Taiwan Normal University, Taiwan. His research interests include fault-tolerant computing, web and XML computing, and distributed computing.  相似文献   

19.
LTE和LTE-Advanced关键技术综述   总被引:2,自引:0,他引:2  
为满足移动宽带业务的需要,LTE正日渐成熟,它采用扁平化网络架构,关键技术包括OFDM、更高阶调制、HARQ、先进的多天线技术、快速同步技术、灵活的控制信道设计、自适应资源分配、干扰抑制技术等。有关LTE-Advanced的讨论也以展开,考虑的技术包括聚合多载波、高阶MIMO、智能中继、异构网络、协调多点发送和先进的干扰管理。  相似文献   

20.
This paper describes a 10 bit 30 Msample/s (MSPS) CMOS analog-to-digital converter (ADC) for high-speed signal processing, especially for subsampling applications, for example digital video broadcasting over cable (DVB-C), terrestrial (DVB-T) and handheld (DVB-H) systems. The proposed pipelined ADC shows a good figure-of-merit (FoM). It adopts a power efficient amplifier sharing technique, a symmetrical gate-bootstrapping technique with modified timing for the bottom-sampling switch of a wideband sample-and-hold (S/H) circuit, a proposed stable high-swing bias circuit for a wide-swing gain-boosting telescopic amplifier. The measured differential and integral nonlinearities of the prototype in a 0.25-μm CMOS technology show less than 0.4 least significant bit (LSB) and 0.85 LSB respectively at full sampling rate. The ADC exhibits higher than 9 effective number of bits (ENOB) for input frequencies up to about 60 MHz, which is the fourfold Nyquist rate (fs/2), at 30 MSPS. The ADC consumes 60 mW from a 3-V supply and occupies about 1.36 mm2. Jian Li received the Bachelor of Engineering (B.E.) degree in electronic engineering from Xi’an Jiaotong University, Xi’an, China, in 2003. He is currently working toward the Ph.D. degree at Microelectronics department, Fudan University, Shanghai, China. His current research interest is high-speed high resolution A/D converter design. Xiaoyang Zeng was born in Hunan Province, P.R. China on April 17, 1972. He received the B.S. degree from Xiangtan University, China in 1992, and the Ph.D. degree from Changchun Institute of Optics and Fine Mechanics, Chinese Academy of Sciences in 2001. From 2001 to 2003, he worked as a post-doctor researcher at the State-Key Lab of ASIC & System, Fudan University, P.R. China. Then he joined the faculty of Department of Micro-electronics at Fudan University as an associate professor. His research interests include information security chip design, VLSI signal processing, and communication systems. Prof. Zeng is the Chair of Design-Contest of ASP-DAC 2004 and 2005, also the TPC member of several international conferences such as ASCON 2005 and A-SSCC 2006, etc. Jianyun Zhang received the B.S., M.S. and Ph.D degree in electrical engineering from Fudan University, Shanghai, China in 1997, 2000 and 2006 respectively. From 2000 to 2002, he was with Alcatel microelectronics, Belgium, where he was involved in circuit design for GSM and GPRS. In 2002, he joined Trident microsystem, where he concentrated on the design of Video AFE including data converters and mixed signal circuits. In 2005, he joined Shihong microelectronics Corp., where he is now a director of mixed signal IC for video high speed interface. His research interests include data conversion, HDMI SerDes, and analog circuit design. Lei Xie received the Bachelor of Science (B.S.) degree in microelectronics from Nankai University, Tianjin, China, in 2005. He is currently working toward the M.S. degree at Fudan University, Shanghai, China. His current research interest is high-speed high resolution A/D converter. Huan Deng received the B.S. degree in microelectronics from Fudan University, Shanghai, P.R. China, in 2003. He is currently working toward the M.S. degree in microelectronics at the State Key Lab of ASIC & System, Fudan University. He is currently involved in the design of low-power, high-speed PLL’s. Yawei Guo received the B.S. and M.S. degree in electrical engineering from Fudan University in 1999 and 2002 respectively. From 2002 to August 2003, he was with Philips Semiconductors in Shanghai. Since August 2003, he has been with Shanghai MicroScience Integrated Circuits Co., Ltd., based in Shanghai, P. R. China. He has been leading a group and developing analog and mixed signal circuits. His research interests include high-speed data communication, data converters, and phase locked loops.  相似文献   

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