A guide to data communications: interconnecting LANs

The use of T1 multiplexers, bridges, routers, and gateways to tie together LANs spread over areas from a single building to a metropolitan area is addressed. What each of these does is described. Also discussed are backbone networks for LANs. Network planning, transmission facilities, switched services, and network management are considered with reference to interconnected LANs     

A guide to data communications: high-speed local-area networks

Local area network (LAN) classifications based on speed are defined. The use of optical fiber, the fiber distributed data interface (FDDI) multitoken protocol, linear buses, and the dual queue distributed bus (DQDB) is examined. LAN limits are discussed. Supercomputer LANs and ultra-gigabit networks are considered. The so-called mass of glass, a wavelength-division-multiplexed architecture consisting of a passive optical broadcast medium, is discussed. Future issues and trends are indicated     

Impulse radio: how it works

Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum signaling, has properties that make it a viable candidate for short-range communications in dense multipath environments. This paper describes the characteristics of impulse radio using a modulation format that can be supported by currently available impulse signal technology and gives analytical estimates of its multiple-access capability under ideal multiple-access channel conditions     

A guide to engineering workstations: how ICs impact workstations

The process employed by a group of workstation designers in creating a prototype for a high-performance, low-cost workstation is described. The design team moved an existing architecture-the precision-architecture, reduced-instruction-set computer (PA-RISC) design-into the realm of a low-cost desktop computer. The goal was to make a PA-RISC implementation suitable for a high-performance single-user workstation that would provide exceptional application and graphics performance, yet would also provide continuity with existing systems. It is shown how performance goals and design capabilities influenced decisions about what types of ICs should be used     

Backpropagation through time: what it does and how to do it

Basic backpropagation, which is a simple method now being widely used in areas like pattern recognition and fault diagnosis, is reviewed. The basic equations for backpropagation through time, and applications to areas like pattern recognition involving dynamic systems, systems identification, and control are discussed. Further extensions of this method, to deal with systems other than neural networks, systems involving simultaneous equations, or true recurrent networks, and other practical issues arising with the method are described. Pseudocode is provided to clarify the algorithms. The chain rule for ordered derivatives-the theorem which underlies backpropagation-is briefly discussed. The focus is on designing a simpler version of backpropagation which can be translated into computer code and applied directly by neutral network users     

欧洲B－ISDN试验网：TRIBUNE

ＴＲＩＢＵＮＥ计划是欧洲先进通信技术研究计划（ＲＡＣＥ）的一部分。此计划的目的是在欧洲为先进的通信业务，特别是宽带综合业务数字网（Ｂ－ＩＳＤＮ），建立公共基础设施。本文将简要介绍该计划的概况。     

Connection architecture and protocols to support efficient handoffs over an ATM/B-ISDN personal communications network

The next generation personal communication network will likely internetwork wireless networks via the ATM/B-ISDN to enable ubiquitous broadband personal communication services. Support of user terminal mobility, particularly the capability for fast and seamless handoffs, over the ATM/B-ISDN is an expected requirement that is not currently met. We propose extensions to the ATM/B-ISDN user transport and signaling network architectures and signaling protocols to meet these requirements. The new architecture employs the Mobile Virtual Circuit (MVC), a dynamic connection tree in which routes are predetermined but not set up for potential handoff connections. During a handoff, associated signaling using source-routing with a new robust adaptation feature is employed for fast resource allocation to establish the handoff connection by distributed control. We also address the new problem of packet ordering synchronization to enable a seamless handoff. The connection tree reconfigures after each handoff to enable continuous support of successive handoffs. The proposed scheme optimizes handoff delay over the ATM/B-ISDN while minimizing unnecessary resource allocation, chances of handoff failure, and call processing load in the intelligent network, and the extensions are backward compatible to current ATM/B-ISDN standards and implementations.This paper was presented in part in PIMRC'95 in Toronto, and Globecom'95 in Singapore. This work was supported by the Canadian Institute of Telecommunications Research (CITR), funded under the Canadian Federal Government's Networks of Centres of Excellence Program.     

Technology 1991: data communications

Significant developments during 1990 are examined, and future trends are delineated. Two major events were the rapid acceptance by end users of the 10BASE-T standard for Ethernet interconnections using unshielded twisted-pair wiring and the widespread acceptance of the fiber distributed data interface (FDDI) by corporate planners and MIS (management information system) people, as well as government planners, as the way to wire the corporate backbone. 1990 also saw commercialization begin of the FDDI interface by which data is transmitted on an optical-fiber network at 100 Mb/s rates. The development of twisted-pair wiring for Ethernet and FDDI will lead to integration of Ethernet. Token Ring, and FDDI local networks in one concentrator in one wiring closet, while the pace of growth of the LAN market continues to accelerate. The seven layers of the Open Systems Interconnection (OSI) protocol received a big boost last year from the US government, and it is likely to become the routine way of organizing data networks worldwide     

Error detection and correction options for data services in B-ISDN

The authors investigate error detection and correction options for data services in the broadband integrated services digital network (B-ISDN). They discuss and analyze different options for error detection and correction by considering the various alternatives ranging from no error protection to only error detection. Based on the analysis and results presented, a per-cell cyclic redundancy check (CRC) has been adopted in the adaptation layer for all data services. The authors focus on the ATM (asynchronous transfer mode) adaptation layer (AAL) error protection alternatives available within the framework of a per-cell CRC. The ATM cell header and AAL fields are described. A 4 bit cell sequence number for detecting cell misordering is analyzed. Based on the analysis, it is concluded that the 4 bit sequence number provides a powerful capability for detection of cell misordering     

Dislocation filtering: why it works,when it doesn’t

Dislocation filtering, or the removal of threading dislocations using a superlattice structure, has much potential for fabrication of high-quality semiconductor heterostructures for which buffer layers or low-quality substrate material must be used. An accurate and predictive model for the filtering phenomenon, however, has not yet been identified, leading to erratic results when attempts to design dislocation filters are made. Filtering has traditionally been treated in terms of various quasi-equilibrium models, which are often found to be lacking when applied to real systems. These mechanisms are examined with a view toward understanding their limitations in the real world. A fundamentally new mechanism for dislocation filtering, based on metastable freezing of non-equilibrium configurations encountered during crystal growth, is proposed. This non-equilibrium mechanism overcomes many of the limitations presented by the conventional filtering models.     

Technology '89: data communications

Advances in data communications during 1988 are highlighted. Among the notable developments are an increased use of facsimile machines, an epidemic of computer viruses, growing support for open-system network standards, and higher-performance, more cost-effective local area networks     

Technology '90: data communications

The growing use of local area networks during 1989 is examined. The fiber distributed data interface (FDDI), a 100 Mb/s dual-ring, optical fiber LAN that is nearing approval by the American National Standards Institute, is discussed. Other developments reviewed are the increasing support for the Internet Transmission Control Protocol/Internet Protocol, setbacks in promoting the OSI (open systems interconnection) approach due mainly to the scarcity of products and weak sales, work on ways to bridge the two sets of protocols, and the emergence of high-speed networking as a viable technology     

ATM: customer needs in the transition to B-ISDN

The development of the broadband integrated-services digital network (B-ISDN) is part of the continuing evolution of the telecommunications network. The author considers the expected rate of increase in information-carrying capacity to the general public and its needs for interfacing and service. He proposes a technique of shaping/policing the channel capacity which will be easily understood by both user and network provider. Finally the uncertainties that remain in the way that applications may exploit the ATM network and the consequent different needs for signalling and control have been highlighted     

现代光通信中的CMOS时钟数据恢复

针对现代光通信和其他高速串行通信,设计了一个用于高速串行收发器中的CMOS数字bang-bang时钟数据恢复系统.采用的数字bang-bang时钟数据恢复的结构,具有简单、功耗低、性能稳定的优点.时钟数据恢复采用改进编码方式的相位插值器,输出具有恒定幅度和良好的线性相位特性.测试表明,功耗为35 mW. 输入信号眼图闭合0.5UI,信号差分峰-峰值150 mV条件下误码率小于10-12.     

移动IP的安全威胁及对策

移动IP是目前唯一可以在Internet上为移动计算机提供无缝漫游的协议,它突破了计算机机房、电话插座和地域等的限制,使人们能够随时、随地、更加灵活地访问互联网、企业局域网(LAN)等,以便及时获得所需信息和进行商务活动.     

地下通信工程面临的威胁及如何防护

随着世界各个国家之间在信息技术方面的关系起来越密切,国家的安全问题也越来越重要,同时由于科学技术的不断发展,社会进行了信息化时代,地下通信工程所表现出来的作用也越来越明显,本文通过地下通信工程所面临的威胁方面分析并提出了地下通信工程防护工作的重要性,然后详细分析了地下通信工程防护伪装工作的有效开展,希望在提高我国地下通信工程建设水平方面可以提供有效地理论指导和借鉴作用.     

Integrated voice and data communications overview

The author reviews architectures and traffic characteristics for voice and data communications, and addresses important issues in integrated voice and data communications. He discusses some possible methods of integrating voice and data and presents an example of implementing integrated voice and data communications. He considers ISDN (integrated services digital network) as a vehicle for supporting integrated services including voice and data as well as image and video. Although the concern is mainly with switched networks, some of the concepts discussed are applicable to both switched and special-services networks