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Showing papers in "IEEE Communications Magazine in 1981"


Journal ArticleDOI
TL;DR: Data communications in Japan have begun a new era of rapid progress, and public-switched telephone and telex networks are available for data communications.
Abstract: T WO common carriers are operated under the administration of the Ministry of Posts and Telecommunications in Japan. One is NTT (Ni'ppon Telegraph & Telephone Public Corporation) for domestic services. The other is KDD (Kokusai Denshin Denwa Company, Ltd.) for overseas services. For the past year, NTT has had DDX (digital data exchange) circuitswitched data network and DDX packet-switched data network services, and KDD has commenced ICAS (international computer access service). Data communications in Japan have begun a new era of rapid progress. Their features are summarized as follows. 0 Both domestic and overseas telephone networks allow nonvoice communications as well as voice. Customers can connect their own terminals to the networks via Modems and NCU's. Public-switched telephone and telex networks are available for data communications. 0 Various speed class leased circuit service is provided.

98 citations



Journal ArticleDOI
J. Hayes1

30 citations



Journal ArticleDOI
TL;DR: A look at the major events in the development of antennas as well as some of the current technologies used in telecommunications.
Abstract: A look at the major events in the development of antennas.

22 citations



Journal ArticleDOI
TL;DR: This record testifies to the worth of the amateur approach in almost every phase of the radio communications art, from sparks and coherers to sophisticated solid-state transceivers.
Abstract: In this review, we look, however briefly, at some of the highlights in the nearly 70 years of amateur radio, from sparks and coherers to sophisticated solid-state transceivers. We believe that this record testifies to the worth of the amateur approach in almost every phase of the radio communications art. If we have coped with the rush of technology and kept our enthusiasm thus far hopefully, ham radio operators of the future will be able to carry on this tradition.

10 citations


Journal ArticleDOI
TL;DR: N integrated digital network which combines digital transmission and switches can provide efficient and economical paths to carry analog and digital information.
Abstract: N integrated digital network which combines digital transmission and switches can provide efficient and economical paths to carry analog ~ and digital information. Digital networks have been developed for data or voice services, and it is believed that they may be extended in the future to apply to the integrated services digital network (ISDN). Network synchronization is an essential technique in constructing an integrated digital network. In several countries, the domestic network synchronization systems have either been developed or are under development, These systems employ either the master-slave or mutual synchronization scheme. For the future international digital network, plesiochronous operation is recommended by the CCITT.

8 citations


Journal ArticleDOI
TL;DR: In this paper, a technical study by computer simulation has been performed to assess the potential of maximum likelihood sequence detection (MLSD) in a band-limited nonlinear satellite channel with two nonlinear elements [a high-power amplifier and a transponder traveling wave tube amplifier (TWTA)] operating in tandem.
Abstract: A technical study by computer simulation has been performed to assess the potential of maximum likelihood sequence detection (MLSD) in a band-limited nonlinear satellite channel with two nonlinear elements [a high-power amplifier (HPA) and a transponder traveling wave tube amplifier (TWTA)] operating in tandem. Starting with a brief background on digital modem development, this paper outlines the basic principle of MLSD and a conceptual structure suitable for satellite channel applications. The bit-error rate has been computed for a realistic nonlinear satellite channel using Forney's approach with the Viterbi algorithm. The upper bound of channel performance improvement in a typical satellite link has been identified.

7 citations




Journal Article
TL;DR: Analyzing a class of mixed-mode ARQ protocol models which incorporate a selectiverepeat mode with finite receiver buffer shows that it is desirable for best throughput performance in practical systems that at least the first retransmission of a block following an error should be in the selective-repeat mode to obtain superior performance over GoBack N schemes.
Abstract: In high bit rate data transmission systems with ARQ error control, the throughput efficiency is a function of bit error rate, block or packet size, and the effect of significant round trip delays such as may be experienced in satellite communication systems. The selective-repeat ARQ scheme is capable of providing superior throughput performance independent of round trip delay, but requires excessively large receiver buffers; as a result the inferior GoBack N procedure is commonly adopted. This paper analyzes a class of mixed-mode ARQ protocol models which incorporate a selectiverepeat mode with finite receiver buffer. The protocol models are shown to be amenable to exact throughput analysis, but do assume that the round trip delay is constant and known, blocks are of constant length, and the ACK/NAK signals are returned error free. These assumptions might create difficulties for practical implementation. However, the analytical model results highlight those aspects of ARQ protocols which affect throughput performance as round trip delays increase. The results show that it is desirable for best throughput performance in practical systems that at least the first retransmission of a block following an error should be in the selective-repeat mode to obtain superior performance over GoBack N schemes. Furthermore, alternative secondary retransmission modes are considered which ensure that reliable transmission can be achieved without receiver buffer overflow, even if the selective-repeat mode retransmissions fail. It is shown that the choice of secondary mode does not have a significant effect on the throughput efficiency but has a bearing on complexity.

Journal ArticleDOI
TL;DR: An overview of the commercial communications systems in Canada that make use of geostationary satellites and a discussion of the forthcoming ANIK C and D are provided.
Abstract: The object of this paper is to provide an overview of the commercial communications systems in Canada that make use of geostationary satellites. The system includes active communications repeater satellites in geostationary orbits, tracking telemetry and command facilities, a satellite control center, a satellite network operations center, and over 100 earth stations of several different types. Transportable earth stations are also part of the system for short-term message service to remote areas and television services for special events. This includes an overview of commercial satellite communications systems and a discussion of the forthcoming ANIK C and D. The paper briefly reviews the characteristics of the present system, outlines the major features of the system under construction, and indicates future plans.

Journal ArticleDOI
TL;DR: TELIDON is a videotex development of the Canadian Department of Communications that differs radically in display presentation format from the earlier European developments.
Abstract: TELIDON is a videotex development of the Canadian Department of Communications that differs radically in display presentation format from the earlier European developments. The name videotex is used internationally to represent a class of home and business information services which disseminate information from information suppliers into the home or office. In general, a television receiver, suitably modified or augmented, can serve as the consumer's terminal equipment. The system essentially makes use of the set as a still-picture display medium where the consumer has control over what is displayed. By utilizing the common-carrier telephone line or other interactive network, or broadcast system, users of the service are able to retrieve information stored in computer controlled databases and have it displayed.

Journal ArticleDOI
TL;DR: A combination of new research techniques and optical system engineering has been selected to demonstrate the state of the art of optical signal processing, future research directions for this technology, and the quite major potential this discipline has to offer.
Abstract: ULK acousto-optic and other optical processors for spectrum analysis, correlation, ambiguity function computation, and other signal processing functions are described. Basic architectures and algorithms are reviewed and several case studies are described. These include spread spectrum, wide-band signal processors, radar ambiguity function processors, passive ambiguity function computation, and adaptive phased array radar processing. Advanced radar, sonar, and communication systems require increased processing capacity to keep abreast of the computation load produced by the larger bandwidth and longer time-bandwidth products of new sophisticated waveforms, as well as the denser target and signal environments to be handled. This paper contains a review of recent advances in optical signal processing for such applications. Major attention is given to bulk acousto-optic (AO) systems, since they have recently [ 11, [Z] emerged as a major component with the necessary high bandwidth and large time-bandwidth product for advanced signal processing needs. This has occurred because of parallel advances in devices, algorithms, and system architectures. The repertoire of basic A 0 processor architectures and algorithms are briefly reviewed in Section 1. Wide-band optical signal processing systems and techniques for folded-spectrum analysis are then described in Section 11.. Several spread spectrum OSP techniques for synchronization and decoding are treated in Section I l l . These involve new signal processors such as Spann correlators and hybrid time and space integrating and spacevariant A 0 systems. Simultaneous determination of the range and Doppler of multiple targets represents one of the most demanding radar processing functions. In Section IV, two optical processors that compute the ambiguity function are described, one for active radar applications and the second for passive signal processing use. Adaptive phased array radar signal processing applications are the subject of Section V. Major attention is given to an iterative optical vector-matrix processor that represents a new class of an optical system of quite general use for any problem that can be formulated as a vector-matrix equation or a set of simultaneous linear equations. Concluding and summary remarks are then advanced in Section VI. Throughout the various sections, new architectures and signal processing techniques as well as complete optical systems that have been fabricated and delivered to several agencies are noted. This combination of new research techniques and optical system engineering has been selected to demonstrate the state of the art of optical signal processing, future research directions for this technology, and the quite major potential this discipline has to offer.

Journal ArticleDOI
TL;DR: This paper highlights developments in communications antenna technology that are enabling these and other goals to be achieved.
Abstract: The radio spectrum suitable for communications is limited, and even with global allocation and management, the problem of spectrum congestion continues to increase. This has led to more and more being demanded from antennas so that they play their part in minimizing the problem. In the microwave bands used by satellites, the antenna characteristics must now be good enough for frequencies to be reused; at HF, broadband performance is required even from structures of a limited physical size, while in all bands, adaptive antennas are needed to minimize interference from unwanted transmissions. This paper highlights developments in communications antenna technology that are enabling these and other goals to be achieved.

Journal ArticleDOI
TL;DR: The era of experi~ mental and trial installations appears to be near an end, and customers are ready for standard commercial offerings, but there remain certain pro,blems to be solved in such systems as ubscriber loops and long-haul and undersea transmission systems.
Abstract: n a recent Special Issue on Optical Fiber Communications (PROCEEDINGS OF THE IEEE, October 1980), S.E. Miller, the Guest Editor, said “ . . . The era of experi~ mental and trial installations appears to be near an end, and customers are ready for standard commercial offerings.” This is indeed the case for most of the optical fiber systems: short-haul and intraoffice systems, on-premises applications, data links, etc. However, there remain certain pro,blems to be solved in such systems as ubscriber loops and long-haul and undersea transmission systems. The long-haul system involves technical difficulties because it necessarily demands the use of single mode fibers. The optical undersea system ~~~ ~~ ~ ~~ ~~ ~~


Journal ArticleDOI
TL;DR: The paper presents some significant technical considerations for the economical provision of both telephone and television services to geographically large rural areas by satellite launch vehicles, operating radio frequency band, spacecraft communications implementation and earth station engineering.
Abstract: GEOSYNCHRONOUS satellite systems designed specially for providing domestic communications to geographically large rural areas are currently under investigation by several countries. The paper presents some significant technical considerations for the economical provision of both telephone and television services to such areas. Satellite launch vehicles, operating radio frequency band(s), spacecraft communications implementation and earth station engineering are discussed.


Journal ArticleDOI
A. Rudrapatna1
TL;DR: An exploratory evaluation of potential future switching technologies for integrated voice/data applications for private line point-to-point applications based on future switching techniques that use activity compression and presently tariffed transmission facilities.
Abstract: I HIS paper is an exploratory evaluation of potential future switching technologies for integrated voice/data applications. The evaluation was for private line point-to-point ' applications based on future switching techniques that use activity compression' and presently tariffed transmission facilities including terrestrial and satellite-based private lines. Packet switching (PS), Hybrid switching (HS), and Digital Speech Interpolation systems (DSI), which use activity compression, are compared with the traditional Circuit switching system (CS), which does not use activity compression. Systems that use activity compression typically need a lower transmission bandwidth than those that do not (Le., CS) and, hence, they can be expected to save in transmission costs. However, because of increased processing at the switkh, switching costs for these systems are higher. The tradeoff between the transmission and switching costs are used to identify various potential regimes of usefulness for each switching technology. The regimes of usefulness are given in terms of the total traffic, the ratio of voice to data traffic, the internodal switch distances, and other parameters. The purpose of this paper is to illustrate the regimes and to highlight some of the important sensitivities. More detailed investigations need to be performed before any firm conclusions on switching technology comparisons can be made. The general setup for comparing the different systems is.a

Journal ArticleDOI
TL;DR: To meet Japan's diverse data communication needs, Nippon Telegraph & Telephone Public Corporation (NTT) has been researching and developing the digital switching network, DDX.
Abstract: To meet Japan's diverse data communication needs, Nippon Telegraph & Telephone Public Corporation (NTT) has been researching and developing the digital switching network, DDX. The circuit-switching network was put into commercial service in Tokyo, Osaka, Nagoya, and Yokohoma on 25 December 1979.



Journal ArticleDOI
TL;DR: It is argued that to report accurately on trends in engineering education, one must first explain that higher education, in general, is in a state of crisis.
Abstract: It is argued that to report accurately on trends in engineering education, one must first explain that higher education, in general, is in a state of crisis. Problems in individual departments must be viewed in the context of being a small part of the beleagured university as a whole.


Journal ArticleDOI
TL;DR: The author discusses applying fiber optic technology in two remote towns with the aim of reducing the present economic barriers to new rural services integrated on a common carrier system.
Abstract: The author discusses applying fiber optic technology in two remote towns. Current efforts by Canadian telephone companies are aimed at ther eduction of multiparty line loads to a maximum of four customers per rural line. The telephone companies providing service to rural areas of Canada share a common problem, that of economics. Recognizing this fact, studies have been undertaken to come up with solutions. The outcome of these studies indicatetsh at the increasedv alue of new rural services integrated on a common carrier system would greatly reduce the present economic barriers. These studies also led to the Department of Communications (DOC) and the Canadian Telecommunication Carriers Association (CTCA) jointly sponsoring the Elie-St. Eustache Fiber Optic Technology Trial.



Journal ArticleDOI
TL;DR: From 21 May to 3 June 1981, a delegation from the IEEE Communications Society visited the People's Republic of China, invited by the Chinese Institute of Electronics (CIE) which oversaw the entire trip.
Abstract: From 21 May to 3 June 1981, a delegation from the IEEE Communications Society visited the People's Republic of China. The group was invited by the Chinese Institute of Electronics (CIE) which oversaw the entire trip. Some of their staff personnel accompanied the mission throughout its stay. The group's technical visits included universities, research institutes, an earth station, an integrated circuits factory, and the Beijing International Telephone Service. A separate program of visits was prepared for the spouses. On several occasions the entire group visited monuments of outstanding cultural interest (a full itinerary is included at the end of article). The delegation Leader, Donald Schilling, requested that each delegate prepare a report daily to summarize the day's events. These were collected at the end of the trip and the commentaries synthesized and used to prepare this report.