Un élément du réseau local tout optique: Le concentrateur-distributeur

The authors describe the operation principle and the technology of a distributorconcentrator which can be used for implementing a broad-band local network designed for simultaneous one-way and two-way transmission of signals at high and low rates, in analogical and digital modulation. By multiplexing three wavelengths on a multimode optical fibre, several videocommunication services can be offered to the subscribers.     

The Development of Cable Data Communications Standards

Commercially successful application of data communications technology to coaxial cable distribution networks requires the creation of systems useful to large numbers of subscribers sharing common communications procedures. Furthermore, it is desirable, particularly in entertainment CATV networks, that subscriber ownership of some or all terminal equipment and peripheral attachments be possible since such ownership enables the sharing of capital costs between the network operator and the subscriber. Systems designers are led inescapably to the need for standard interfaces and protocols. The paper describes some of the major types of cable data systems currently under development for both institutional and entertainment network applications. Common to both is the concept of a local interface unit to act as a link between the subscriber's terminal equipment and the cable drop. The design of the drop-side interface of this unit raises some major standardization issues. Another important issue is that of compatibility between data and video channels where both types of services are offered on the same cable television plant. The major thrust of present standardization activity has been founded upon the open systems interconnection (OSI) reference model and has taken place within a joint CVCC/EIA committee on teletext and within the IEEE Project 802.6 subcommittee on metropolitan area networks. The paper reviews this activity and explains the principal issues to be resolved.     

Progress Towards Digital Subscriber Line Services and Signaling

With digital connectivity, future subscribers will be able to exercise local and network services involving the routine delivery, management, and processing of information. Accelerated by rapidly advancing technology, the evolutionary process towards digital connectivity and integrated voice and data services in the network is underway. This paper describes the methods of integrating voice and information capability into the telecommunications network. The attributes of this network will include the availability of digital connectivity directly to the subscriber, the availability of a robust signaling means between the subscriber and his local switching office, and common channel signaling to implement all interexchange signaling. Issues of interest include an overview of digital subscriber connectivity, signaling and information structures for these kinds of lines, communications protocols, and general network considerations for the provision of information services. Partitioning of intelligence between intelligent subscriber terminals and controllers and their switching system is investigated. The use of message and virtual channel switching facilities to handle limited information rate services is discussed. Finally, an exploratory digital subscriber line under investigation at Bell Laboratories is described.     

深化双向网改造实现单向机顶盒的互动功能

数字电视双向平移已成为广电网络走向＂三网融合＂和业务向纵深发展的必经之路。广电网络公司前期在数字电视整体平移过程中,基本上是以单向机顶盒为主进行整体平移,约占总数的80%左右。怎样使这80%的单向数字电视用户实现双向互动功能,这对广电今后的发展具有战略性的意义。根据丽水市城区和所属8县（市）的具体情况,因地制宜,对各种双向网络改造进行技术比较、成本测算、综合应用,对丽水市有线电视双向网络进行深化改造,使单向机顶盒实现双向互动功能,加快全网数字电视双向平移。     

Architecture of Broad-Band Communications Systems

At present there are worldwide efforts directed towards a services-integrated broad-band network. The first section of this paper describes different solutions of broad-band network components such as subscriber premises networks, local loops, subscriber exchanges, and trunk networks. The design of these components was taken from various proposals and broad-band communication field trials carried out in several countries up to 1984. In the second section, we consider the possibilities and implications of integrated optical components and of optical coherent communication techniques for broad-band networks in the far future.     

A Transmission Scheme for Integrated Services on Broad-Band Internal Private Business Networks

Internal business networks are expected to present an economic area of application for broad-band communications. A star network with switches optimized for various services is envisaged. An asynchronous switch for video in square wave frequency modulation (SWFM) format can provide a practical solution for full bandwidth switched video services. A transmission scheme is described which combines a SWFM video service together with synchronous PCM data and voice services, asynchronous data up to 9.6 kbauds and network clocks at both 2 MHz and 160 kHz for ISDN, so that all services destined for one terminal site may be transmitted in binary format on cable or fiber. An experimental link is described which provides up to 10 Mbit/s data capacity together with the video service. The hardware is constructed with 74HC family CMOS. An analysis of the effects of data modulation on video quality is given. Measurements of video S/N and distortion are reported. Measured bit-error rate in a 64 kbit/s data channel is reported. The measurements relate to a coaxial cable link with link lengths from 200 to 400 meters.     

Metropolitan-area networks

Metropolitan-area networks (MAN), which fill the gap between local area networks (LANs) and wide-area networks (WANs), are discussed. MANs were originally oriented toward data, but now often carry voice and video traffic as well. Supplying more bandwidth than LANs, they support two-way communication over a shared medium such as an optical-fiber cable, and may offer point-to-point high-speed circuits or packet-switched communication. The two most favored topologies, double-star and double-ring, are described and emerging MAN protocols are examined     

One-stage one-sided rearrangeable switching networks

Switching networks consisting of subscriber lines and crosswires connected by switches are considered. A connection between two subscribers is made along one crosswire via two switches. The minimum number of switches necessary for such a switching network to be rearrangeably nonblocking is determined and a switching arrangement which achieves this minimum for any (even) number of subscriber lines is constructed. Two procedures for assignment of crosswires to subscriber line pairs are described. One makes the correct choice of connection route without backtracking provided all connections are known beforehand; the other determines a rearrangement of existing assignments when a new connection is required. The switching networks which have the minimum number of switches for networks with up to eight subscriber lines and give nonisomorphic solutions for larger networks are characterized     

The wireless art and the wired force of subscriber access

Different technologies for subscriber access are put side by side. Starting from the various transmission media characteristics of all systems, the well-known twisted pair lines with their corresponding digital subscriber line services are evaluated against wireless local loops, communications over ubiquitous power lines, high-bandwidth cable modems, and mobile radio. Each technology has its advantages and disadvantages. The different technologies will find their fields of applications. Most networks will have to provide a mixture of solutions for individual subscribers and customer segments to meet their boundary conditions. As a result, the future of subscriber access is a hybrid solution     

Integrated Circuits for Broad-Band Communications Systems

Integrated circuits for broad-band communication systems which enable broad-band communication between subscribers require LSI's with a performance concerning speed, complexity, and power dissipation which cannot be fully met by present semiconductor technologies. The requirements for coders and decoders, line transmission circuits, and broad-band switching network elements depend upon the system concept chosen. For one chosen system concept, these requirements are derived. By using a representative model for the development of the demand, characteristic curves for the demand of subscriber-line circuits and for central unit elements are resulting. From these curves the optimum semiconductor technologies, complexities, and design strategies are derived. It can be assumed that the results are rather independent of variations of system concept and introduction models.     

Optical Fiber Facilities for Subscriber Loops

This paper gives an overview of the introduction and subsequent development of optical fiber cable and its application to subscriber networks enabling economical broad-band services, such as video and high-speed digital data transmissions. This paper also outlines NTT's developments on subscriber optical fiber cable technology-in particular, the five-fiber ribbon cable structure, mass-fusion splicing machine, and multifiber connector-in its ongoing endeavors to establish economical and flexible subscriber optical fiber networks which provide optical fibers to each subscriber.     

DISA comes through [C4I architecture]

The development of a command, control, communications, computers, and intelligence (C4I) architecture for the central command (CENTCOM) theater of operations during Operations Desert Shield and Desert Storm is described. CENTCOM C4I merged commercial and military communications systems into a fully integrated network. It employed tactical ground mobile forces (GMF) satellite systems, line-of-sight (LOS) radio systems, unit-level circuit switches (ULCS), and the primary interfaces to strategic systems, the TRI-TAC switching centers, automatic circuit (TTC-39A) and automatic message (TYC-39) switchboards. By the end of the ground war, the CENTCOM strategic network considered of over 100 defense satellite communication system (DSCS) satellite links, nine T-1 systems, over 300, DSN trunks, 26 AUTODIN circuits, and numerous dedicated-user, point-to-point, and data circuits     

Fiber Optic Transport Systems for Present and Future Local Networks

This paper describes fiber optic transport systems for present and future local networks. The present most important fiber optic system in a local network emerges as a broad-band video distribution system, because large-scale system introduction might be attained only for distributed video services. The system architecture and system parameters are presented. As for future integrated services, a highspeed digital transmission system and local network architecture are very important. The network architecture should be constructed to meet the demands for increased flexibility, capacity, reliability, and economy. Considering expected future demands and technologies, a new fiber optic local network architecture is proposed. The architecture's main features are the use of transmission processing nodes and a multilane-ring structure in subscriber transfer networks in combination with star-shaped subscriber access lines.     

Subscriber Stations in Service Integrated Optical Broad Band Communications Systems

Subscriber stations in service integrated communications systems can be implemented in many different ways. Within the HHI Broad-Band Communications System two extremely different solutions have been realized: on the one hand, subscriber stations in a conventional star type network with central exchange and analog transmission, and on the other hand, subscriber stations in a digital, loop-structured network employing distributed control. In both cases, the same services (telephone, data, videophone, TV, and stereo broadcasting) are carried to the subscriber via one single optical fiber. This paper describes these different realizations of service integrated subscriber stations in detail. The size of terminal equipment, power consumption, extendability to further subscribers, and services and reliability are the main parameters of an appropriate comparison. An analysis of both realizations, giving emphasis to the switching and multiplexing, and the feasibility of analog optical transmission will be made. Alternative realizations and an estimation concerning subscriber stations for future service integrated broad band communications systems will be presented.     

Configuration and Characteristics of a Fiber-Optic Video Distribution System

A multiservice fiber-optic subscriber system using wavelength division multiplexing technology has been developed by Nippon Telegraph and Telephone Corporation to provide both 64 kbits/s and broad-band communication services on a single multimode fiber. The subscriber network is formed in a star topology to facilitate bidirectional connection. The system was put in service in March, 1985, as part of the information network system (INS) model system. This paper describes the configuration and characteristics of the video distribution system of this fiber-optic subscriber system. The distribution system uses analog baseband video transmission at a 0.89μm wavelength. The video channel selection is made by an FDM video tuner installed in a central office. The overall performance successfully met design objectives.     

Broad-Band Systems Standards

The broad-band communications industry is small and fractionated (about 3100 cable television systems serving 8.5 million subscribers in the U.S.), but has a high potential for growth by offering a wide variety of communications services. If this large number of systems is to collectively provide nationwide services, performance and interconnection standards will be essential. In this paper we note relevant existing standards and examine highlights of ongoing standards-making activities.     

Bring home the Internet

In the good old days, the only two-way communications link with a residence was provided by the local telephone company (telco). But the growth of the Internet and the passing, in the United States, of the Telecommunications Act of 1996 have changed that tradition. Today, a competitive local exchange carrier can compete in the turf of the local telco, now called an incumbent local-exchange carrier. In addition, cable TV operators are allowed to offer telephony and Internet access services to their subscribers along with TV programs. The question of who will supply the `last mile' pipe to the home could lead to some of the toughest fights the communications marketplace has ever seen. Winners will gain the revenues from supplying a cornucopia of phone, TV and Internet services. The paper discusses these issues as well as asymmetric digital subscriber line, cable modems, service billing, wireless connections, and power grid use for optical cable laying for communications     

Wide-Band Interactive Services Experiment (WISE): A First Test of Future Video Services

An experiment of wide-band switched interactive services (video services) is presented. The experiment, named WISE (Wide-Band Interactive Services Experiment) is limited to a small number of subscribers but is representative of a future domestic environment. After a brief presentation of the scope of the activity, the video services that have been implemented, both unidirectional and bidirectional, are described. The system organization, based on a wide-band switching matrix and on the transmission of video signals on a single optical fiber by wavelength-division multiplexing, is then discussed, and the solutions adopted for the transmission equipment are examined. The structure of the service center is afterwards described, together with the subscriber procedures required to access the different services. Finally, some improvements and future possible developments of wide-band interactire systems are briefly highlighted.     

Present Trends in High-Speed and Broad-Band Communications Services in Japan

This paper describes present trends in high-speed and broad-band communications services in Japan. It gives an overview of video, high-speed digital leased circuit and satellite digital communications services, and gives examples of their applications. Recent trends in telecommunication services and technology are described, including video conferencing services presently available in more than ten cities throughout Japan, as well as a video response system which is about to be put into service. It also describes the present status of Japan's cable television (CATV) system and discusses its future development. Finally, NTT's plans for high-speed and broad-band communications service in the future are previewed.     

WiMAX点对点宽带无线接入容量分析

随着通信技术的迅猛发展,移动宽带化和宽带移动化是通信网发展的必然趋势。WiMAX城域网无线宽带接入技术,可提供大范围及高速率无线接入,同时支持视距传输和非视距传输,能提供面向互联网的高速无线连接。WiMAX可作为线缆和用户数字线的无线扩展技术,实现无线宽带接入。首先简要介绍WiMAX的应用模式,然后重点分析其点对点应用中上行链路和下行链路的通信容量,提供相关工程技术人员进行方案设计的参考。