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Proceedings of the IEEE

Issue 11 • Date Nov. 1972

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Displaying Results 1 - 25 of 53
  • [Front cover and table of contents]

    Page(s): c1
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    Freely Available from IEEE
  • Scanning the issue

    Page(s): 1246 - 1248
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    Freely Available from IEEE
  • On the social role of computer communications

    Page(s): 1249 - 1253
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    Computer-communication systems appear essential to meeting many needs in our society resulting from greater interdependence and complexity of operation and from rising expectations. There are, in principle, different ways of utilizing them for the same purposes, with radically different social consequences. The choice, which amounts in effect to a social decision, is, in practice, severely restricted by the computer hardware and software and by the communication facilities that happen to be available at the time. The paper discusses some of the pressures that lead to more widespread use of computers in the operation of society and illustrates how specific characteristics of computer-communication systems may influence social trends and, in particular, individual freedom. View full abstract»

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  • Regulatory and economic issues in computer communications

    Page(s): 1254 - 1272
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    The rapid growth of computer communications in recent years has brought with it a number of difficult and controversial regulatory and economic problems. As the government agency responsible for the regulation of interstate common-carrier communications, the Federal Communications Commission (FCC) has been faced with many of these issues. This paper attempts to focus, in a tutorial fashion, upon four areas in the computer-communications field in which the influence of the FCC has been particularly significant. An overview of the regulatory process is given as background, after which we discuss the regulation of commercial computer-communications services, the interconnection of subscriber equipment to the telephone network, the creation of specialized communications carriers and of domestic satellite systems, and finally a number of data communications pricing problems which have arisen as a result of these developments. View full abstract»

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  • Terminals

    Page(s): 1273 - 1284
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    The rapid development of several different kinds of terminals and the greater ease that they offer for the use of real-time on-line systems are having a major impact on the computer industry and on computer applications. Trends that influence the increasing utilization of terminals are identified. The major subsets of the terminal market include keyboard/printer terminals, CRT terminals, "smart" terminals, remote-batch terminals, real-time data acquisition and control terminals, transaction and point-of-sale terminals, and several miscellaneous types of less frequently used terminals. Applications, characteristics, and some design considerations are discussed for each of these types of terminals. The important relationship between terminal capability and communications requirements is analyzed. To the extent that stored program capability in the terminal permits part of the task to be performed locally, communication of data between terminal and central communication can be reduced with a consequent reduction in communication costs and increase in overall system reliability. View full abstract»

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  • Modems

    Page(s): 1284 - 1292
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    The rapidly rising need for computer communications has been met for the most part by utilization of the ever expanding network of voice-bandwidth channels. Transmission of digital signals over these analog channels involves a modem for modulation and demodulation of a voice-frequency carrier. The usual forms of amplitude, frequency, and phase modulations are described together with their basic characteristics, such as efficiency of bandwidth utilization. The principles of signal shaping and filtering for optimum signal-to-noise performance and minimization of intersymbol interference are discussed. Also covered are methods of synchronization, carrier recovery, effects of channel impairments, and the application of automatic equalization. The choice among modem designs is shown to be influenced by bit speed requirement, permissible error rate, type of channel, receiver startup characteristic, and tradeoff between modem and line costs. The functions of the usual transmission and control leads between a data modem and a data terminal are described, and examples are given of leased private-line and switched telecommunications network applications. A current look at the physical aspects of voice-band modems is given and future trends are considered. View full abstract»

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  • Errors and error control

    Page(s): 1293 - 1301
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    In this paper the nature of errors on telephone data communications channels and the basic techniques for dealing with these errors are discussed. Results of measurements recently taken on dialed connections are reviewed, and it is observed that conventional random-error- or burst-error-correcting codes cannot assure reliable communication on these channels. More generally, it is shown qualitatively that automatic-repeat-request (ARQ) systems are inherently better suited to the task than forward-error-control (FEC) systems. The throughput, or effective data rate, of ARQ systems is discussed, and two basic types of ARQ systems, stop-and-wait and continuous, are compared. It is concluded that with the more common stop-and-wait system, the throughput is unsatisfactory in applications involving high transmission rates and/or long propagation delays. A brief summary of error-correcting codes suitable for use on telephone channels (when a return channel is not available for ARQ) is included. Finally, hybrid schemes where FEC systems are embedded within ARQ systems are briefly discussed. View full abstract»

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  • Line control procedures

    Page(s): 1301 - 1312
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    An exposition of the basic principles underlying data communication line control procedures is presented. Two specific line controls are then described, with special attention given to their embodiments of these principles. View full abstract»

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  • Multiplexing and concentration

    Page(s): 1313 - 1321
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    Obtaining a cost-effective teleprocessing network is postulated on efficient utilization of the communication links and processing equipment. A variety of line-sharing devices and procedures are commonly used for this purpose. The functional, economic, and application aspects of frequency-division multiplexing (FDM), synchronous time-division multiplexing (STDM), asynchronous time-division multiplexing (ATDM), message switching concentration (MSC), and line (or circuit) switching techniques are discussed. The motivations for line sharing stem from economies of scale in the cost of bandwidth and from the traffic smoothing effect which such devices produce when serving a large terminal population characterized by unscheduled requests for service. The discussion of these techniques includes a detailed contrast between multiplexing and concentration, two terms which are often (and unfortunately) used synonymously. It is shown that FDM and STDM are examples of conventional multiplexing, whereas message switching and line switching usually illustrate concentration. ATDM is shown to be a hybrid line-sharing scheme embodying certain features of both concepts. Thus it is often referred to as statistical multiplexing. The first part of the paper is devoted to a functional explanation of the various concepts referenced above. The balance of the paper is concerned with applications and systems-design considerations involving multiplexing and concentration techniques. The application section focuses on important economic factors pertaining to the selection and use of the various methods. The role of line-sharing devices in contemporary common-carrier and end-user networks is also considered. The economic and technical aspects of these contrasting application environments are emphasized and illustrate the multiplicity of uses for line-sharing devices. The concluding portion of the paper includes a discussion of system-design considerations. This section illustrates precisely how the decision to use multiplexers or concentrators in a typical computer-communication network is implemented. Various techniques for geographically positioning multiplexers and concentrators to minimize total costs are presented. The use of one of these procedures is demonstrated using a typical de- sign problem as a case study. View full abstract»

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  • Communication processors

    Page(s): 1321 - 1332
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    A review is given of the use of small digital computers for the processing of data received over communication lines. A detailed discussion is presented of the hardware and software requirements of front-end processors, network processors, remote data concentrators, and message switching systems. Finally, the desirable features common to all communications processors are analyzed. Examples of actual applications are given, so that a realistic basis can be established for the determination of the features which should be included in the design of new communication processors. View full abstract»

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  • Communication software

    Page(s): 1333 - 1341
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    A tutorial introduction to the function and construction of communications software in modern teleprocessing systems is presented, Communication functions include network control, message preprocessing and queuing, and error recovery. These functions are provided by the communication subsystem, which includes components of the supervisory system, special-purpose software, and cooperating peripheral processors. The construction of communication subsystems is described, including aspects of both software and hardware, in the context of a multiprogramming and multiprocessing environment. The application of distributed-function processing, virtual memory, and segmentation techniques to the design of these subsystems is discussed. View full abstract»

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  • AT&T facilities and services

    Page(s): 1342 - 1349
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    This paper describes the U. S. telecommunications network with particular emphasis on aspects that are of importance to data- and computer-oriented services. The major portion of this network is owned and operated by the AT&T Company and the associated operating units of the Bell System as well as the independent branch of the industry. The services which the telephone network offers for data today depend in large part on transmission and switching systems which have evolved over the past decades primarily for voice transmission. An understanding of the history of the growth of the network and its facilities is useful background for the description of the current data services given later in this paper. After the current data services have been outlined, plans for AT&T's new Digital Data System, which utilizes a network of digital carriers for data transmission, will be described. View full abstract»

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  • Western union digital services

    Page(s): 1350 - 1357
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    Developments in the plans for providing a comprehensive set of dedicated and switched digital services are reviewed. Descriptions are given of the considerations which influence the decisions on the technical solutions to be used to modernize the transmission plant. The description covers long-distance transmission, local distribution, multipoint systems, store-and-forward switching, access from unequipped customers, and circuit switching. View full abstract»

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  • The Datran system

    Page(s): 1357 - 1368
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    The Datran system is designed to serve the specific needs of the data communications user. Data communications terminals almost universally employ a digital format; therefore, an early consideration was the use of digital transmission in lieu of the analog transmission employed by most conventional common-carrier systems. The location of the potential users was examined, this having an important bearing on the transmission media selected. Growth expectancy for future years establishes the base upon which to plan the initial system capacity, the hierarchy of system subassemblies for economical modular growth, and phased construction. The employment of digital channel derivation equipment provides a high channel capacity for a given channel bandwidth as compared to analog transmission and permits the use of highly reliable integrated components at a significant reduction in channel end costs. Time-division multiplexing (TDM) switching with a stored program controller provides reliability and flexibility to meet the changing needs of the data communications user and affords significant savings in space, power, and implementation costs of conventional space-division switches. View full abstract»

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  • New data networks in Europe

    Page(s): 1369
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    This short paper, which serves as an introduction to the four papers that follow it, comments on the plans for international data communications in Europe. It points out that plans for public data networks, while understandably varying from country, to country, have a promising degree of compatibility and commonality. View full abstract»

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  • Plans and principles for public data switched networks in France

    Page(s): 1370 - 1374
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    The principles of new switched data networks planned in France are explained together with a short survey of the present state of the art. Basic techniques, offered services, compatibility with telephone, envelope concept, synchronization, and international compatibility are covered. The general ideas underlying the outline of its implementation are given but many technical details are still under study both in the French Post, Telegraph, and Telephone (PTT) Administration and in international bodies such as the International Telegraph and Telephone Consultative Committee (CCITT). Such studies, made by various administrations in Europe, should lead to new possibilities by sharing many features which are presently afforded within private networks, but interchange of information between potential users and administrations should throw light on the extent with which many services should be offered. View full abstract»

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  • Plans for data communications in Germany

    Page(s): 1374 - 1377
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    The Electronic Data Switching system (EDS) and its introduction into the network of the Federal German Post Office are presented. The great demands of future data transmission will be unable to be met by conventional techniques. Therefore, special networks for data traffic are being discussed in several countries. This paper deals with the plans of the Deutsche Bundespost (Federal German Post Office) to establish a data network by making use of the newly developed EDS system. Furthermore, it describes the individual components of the network, such as the connection of the subscriber and the techniques for transmission, concentrating, and switching. The new network will offer a great number of operational and technical facilities which cannot be provided using conventional techniques. Starting from the present international agreements, the most important operational facilities of the data network are described, and an outlook is given on future synchronous modes of operation with the EDS system. View full abstract»

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  • Plans for a public data network in Sweden

    Page(s): 1378 - 1381
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    At the Central Administration of Swedish Telecommunications, a study of a national public data network has been completed. The network is aimed at accommodating subscriber data-transmission speeds up to 9600 bits/s. The study shows that the network shall be of the synchronous type utilizing circuit-switching techniques with a connection time on the order of 100-200 ms. It shall provide means for accommodating both synchronous and asynchronous subscriber terminal equipment. In the former case, the information flow to and from the subscriber shall be transmitted within a fixed format synchronized by the network. In the latter case the asynchronous data flow shall be converted to a synchronous data flow at a concentrator. Concentrators shall be connected to exchanges via 64-kbit/s time-division multiplexing (TDM) data channels, whereas exchange interconnections shall be via TDM data channels with speeds up to 2.048 Mbits/s. A public data network gives possibilities for: introducing new services; standardizing operational and maintenance network routines; standardizing subscriber procedures; traffic with other public data networks; simplifying customer network buildup; integration with other types of telecommunications. A trial network will be built up in order to test principles and hardware for the public data network. View full abstract»

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  • Plans and ideas on the future of data communications in Switzerland

    Page(s): 1382 - 1384
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    Due to the long lifetime of telecommunication equipment, the introduction of new services such as data transmission requires careful long-range planning. Some of the considerations influencing this planning, as seen from a research laboratory in a small country, are presented in this paper. The conclusion is that data communication would best be integrated with a future digital telephone network. Apart from economic advantages, this would open the possibility to design a general-purpose audio-visual terminal for man-to-man and man-machine communication, as a modern replacement for the telephone set. View full abstract»

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  • Topological optimization of computer networks

    Page(s): 1385 - 1397
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    Modeling, analysis, and design problems and methodologies for centralized and distributed computer-communication networks are discussed. The basic problem is to specify the location and capacity of each communication link within the network. The design objective is to provide a low-cost network which satisfies constraints on response time, throughput, reliability, and other parameters. Fundamental network models for queuing and reliability analysis are described, as are basic properties of various network structures. A number of approaches to the topological design problem are presented; areas where further research is needed are indicated; possible approaches to several unsolved problems are suggested. View full abstract»

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  • Resource-sharing computer communications networks

    Page(s): 1397 - 1407
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    The development of resource-sharing networks can facilitate the provision of a wide range of economic and reliable computer services. Computer-communication networks allow the sharing of specialized computer resources such as data bases, programs, and hardware. Such a network consists of both the computer resources and a communications system interconnecting them and allowing their full utilization to be achieved. In addition, a resource-sharing network provides the means whereby increased cooperation and interaction can be achieved between individuals. An introduction to computer-to-computer networks and resource sharing is provided and some aspects of distributed computation are discussed. View full abstract»

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  • Terminal-oriented computer-communication networks

    Page(s): 1408 - 1423
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    Four examples of currently operating computer-communication networks are described in this tutorial paper. They include the TYMNET network, the GE Information Services network, the NASDAQ over-the-counter stock-quotation system, and the Computer Sciences Infonet. These networks all use programmable concentrators for combining a multiplicity of terminals. Included in the discussion for each network is a description of the overall network structure, the handling and transmission of messages, communication requirements, routing and reliability consideration where applicable, operating data and design specifications where available, and unique design features in the area of computer communications. View full abstract»

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  • A case study: Airlines reservations systems

    Page(s): 1423 - 1431
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    The historical development of airlines reservations systems is traced. Characteristics are defined which are those of any real-time, conversational, highly interactive system. The structure of the system is described--agent terminal area, communications facilities, and central site. Lessons learned in the design, development, testing, implementation, and tuning of two generations of systems are discussed. These discussions include initial system design, simulations and systems measurement tools, systems stability and reliability, serial processing, parallel- or multiprocessors, split front-end back-end processing, storage hierarchy, standard and special communications disciplines, and flexibility versus performance. Unlike batch processing the real-time system cannot simply take more run time for a job that has been underestimated. It may well not be able to perform the job at all. Design of these systems is as much an art based on experience as a science and is an iterative process. Systems now being installed have capacities of 180 messages/s, accommodate 10 000 terminals which have access to a 10 billion-byte data base, and provide response times of less than 3 s. View full abstract»

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  • A method toward improved convergence of moment-method solutions

    Page(s): 1436 - 1437
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    A technique for improving the convergence of moment-method solutions through the use of a priori knowledge is presented. The idea is that known good approximations such as physical-optics current may be subtracted from the unknown total current with the result that the residual difference current, which is now the quantity to be determined, will converge more rapidly. Use of this method as applied to plane-wave scattering from conducting strips is given as an example. View full abstract»

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  • Boundedness of a class of second-order time-delay systems with large retardations

    Page(s): 1437 - 1438
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    The boundedness of the solutions of some second-order systems with large retardation is investigated on the basis of a comparison of solutions of nonlinear time-delay systems with a time-delay system whose solutions ca be obtained. View full abstract»

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North Carolina State University