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Overview of Communication Network Evolution

Toshiki Tanaka, D.E. ABSTRACT: The shifts in social paradigm can trigger diversified Minoru Inayoshi communication services. Therefore, technical “seeds” must be fostered Noboru Mizuhara to meet these needs. This entails building an infrastructure for communication networks and technologies for user systems. We can observe significant developments in (a) transmission systems, in which the characteristics of technological “seeds” in optical transmission and transmission meet these requirements, (b) switching systems, which are moving towards ATM (asynchronous transfer mode) technology, and (c) storage systems, which handle multimedia above transmission and switching systems. Furthermore, it is expected that the communication network infrastructure will evolve towards greater reliability and contain more intelligent functions by modification of the management system.

INTRODUCTION DIVERSIFIED COMMUNICATION SERVICES TODAY, the environment of communication network The paradigm shifts observed in modern society is changing dramatically. The explosive growth of represent major changes in the social framework, such new communication services such as the , the as shifts from “centralized to distributed,” from “local rapid and widespread proliferation of mobile to global,” from “shared-use to personal-use,” and communications, and the global alliance of from “monopoly to competition.” These changes are communication carriers, following communication very important for social progress, while solving many deregulation in many countries, suggest that we are current challenges, such as the aging of society, entering an advanced of true substance. environmental problems, and globalization. The impetus for such big changes comes from The concept of paradigm shifts is also applicable to society’s needs. Whether these changes are actually corporate strategies in this information-intensive age. accomplished depends on the provisioning of technical The re-engineering of these changes is currently being “seeds” to meet these demands. The implementation discussed.(1) One major topic in this discussion is the of infrastructure technologies which support the basis strategic and effective use of computers and of communication networks, such as transmission and in a new social environment. switching, has been promoted to match the changes in Today, communication services are being social needs at good cost-performance, based on the diversified at a rate which has not been experienced evolution of devices, computers and before. They are also undergoing drastic changes, software technology. ongoing against the backdrop of certain social paradigm On the basis of a comparison between the progress shifts. of communication networks and its relation to society’s A typical example of this is the rapid proliferation evolution, this article describes the direction in which of mobile . The rate of this massive ongoing change is heading, and gives an increase in subscriptions for pagers, mobile phones overview of the future. and PHS (personal handyphone system) achieved

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45 PHS 250 40 Japan Worldwide WLL 35 CDMA 200 18% 30 CAS 25 150 CDMA 20 82% 100 15 TDMA TDMA Number of subscribers (million) 10 50 5 Analog Analog 0 0 1995 1996 1997 1998 1999 2000 1995 1996 1997 1998 1999 2000 PHS: personal handyphone system; CDMA: Code Division Multiplex Access; TDMA: Time Division Multiplex Access; WLL: Wireless Local Loop; CAS: Cordless Access System Fig. 1—Spread of Mobile Services. It is expected that the number of subscribers to mobile telephone services in Japan will come close to the total number of current wire-based (62 million) by the year 2000. WLL will continue to expand in the global market.

average figures of 45% annually during the period also acts as a driving force for accelerating the between 1994 and 1997. The number of pager development of technical “seeds.” subscribers reached 8.3 million, while the number of The keywords associated with social needs are mobile and PHS subscribers reached 35.7 million by “personal,” “multimedia,” “global,” and “low-cost.” December 1997. It is expected that the number of It is expected that services which fulfill these needs subscribers to mobile telephone services will come will appear in a variety of forms. close to the total number of current wire-based telephones (62 million) by the year 2000 (Fig. 1).(2),(3),(4) EVOLUTION OF COMMUNICATION It is regarded that this situation has arisen from the NETWORKS paradigm shift from “shared-use” to “personal-use.” Technological changes in infrastructure for The astonishing explosion in the number of users communication networks and communication connecting to the Internet is not an exception. While terminals for human-to-machine interfacing are the number of hosts connected to the Internet in July indispensable for diversified communication services. 1995 reached 6.6 million, by January 1998 this figure This section gives an overview of the progress of the had increased to a staggering 29.7 million, a rate of infrastructure technology which constitutes the increase unprecedented in history.(5) It is assumed that network. this phenomenon is a result of the combination of Management of the network functions and the three many factors, and is closely related to the two paradigm technological aspects, housed within it, transmission, shifts, from “local to global” and “centralized to switching and storage, are all requested from the distributed.” infrastructure. So far, there has been a huge The formation of mega-carriers at the global level, technological change at each alternation of generation. typified by the alliance among communication carriers Even at present, a technological change is afoot for mainly in Europe and America, and the movement to needs becoming manifest by the social paradigm shifts. provide low-priced communication services, can be seen from the same perspective. While deregulation Transmission Systems brings about an active, competitive environment and (1) Transmission is classified into backbone works as a trigger for making latent needs manifest, it transmission, to interconnect switches, and subscriber

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10 Gbit/s 10

Fig. 2—Capacity of Backbone 1.7 Gbit/s 2.4 Gbit/s Transmission System.

Transmission capacity (Gbit/s) 1 Since optical transmission was introduced into communication networks, an excellent cost-performance 560 Mbit/s has been recognized. This is one example where the social needs for a 0 larger capacity in backbone 1985 1990 1995 2000 transmission match the technical Year “seeds.”

access, to connect users to a switch. The most and greater diversification (Fig. 3). significant technological innovation in backbone The Internet is regarded as the driving force for transmission is optical transmission. The prime factor higher speeds. The use of ISDN (integrated services attributed to the shift from conventional wireless digital network) to access the Internet more quickly is communications, such as transmission, to gaining precedence over analog , because optical transmission is the excellent cost-performance ISDN can support a greater amount of data (up to 128 associated with optical systems. This is a good example kbit/s) using existing telephone lines. However, new of the case in which the technical “seeds” match the access technology will be necessary to implement social needs for a larger capacity of backbone higher access speeds to meet the future requirements transmission systems. expected for multimedia applications. The capacity of backbone transmission systems To address this challenge, two technologies are shows a trend of increase of one order higher being developed: FTTH (Fiber to the Home) which approximately every eight years. Today, 10-Gbit/s provides fiber-optic cables to each home, and FTTC systems are available for practical use (Fig. 2). (Fiber to the Curb) which provides fiber-optic cables Previously, only the need for the information transfer to a local hub and then uses existing that would utilize such a huge capacity was discussed. telephone lines to distribute the information to each However, these trends indicate that any increase in home. The “seeds” which allow high-speed information capacity will always be consumed by new and delivery in optical transmissions are evolving towards improved services. In other words, latent needs for the implementation of broadband ISDN, even in the communication services will always exist in a variety field of subscriber access. of ways, and will become manifest in correlation with Another change in the field of subscriber access is other technologies and the paradigm shift of social the diversification of access measures, in particular, structure. access, which will play an important role in the (2) On the other hand, the area of subscriber access is future progress of communication networks. In the closely related to the switching system, so both must history of communications, radio has been used as the be coordinated to meet these needs. The current goals standard technology for backbone transmission. Upon of this subscriber access are to achieve a higher speed entering the era of large-capacity transmission, radio

Overview of Communication Network Evolution 47 Communication Access system Network terminals

Wireline (analog) Local switch Telephone ISDN (digital) Tandem switch XDSL (digital) Backbone transmission Notebook computer equipment FTTC

FTTH

Personal computer Backbone transmission equipment PHS Mobile phone Tandem switch Broadband CDMA Local switch Wireline PDA

FTTC: Fiber To The Curb; FTTH: Fiber To The Home; PDA: personal digital assistant; ISDN: integrated services digital network; XDSL: X Fig. 3—Diversified Access Systems. The proliferation of ISDN, mobile phone and PHS in society is remarkable. It is expected that multimedia access systems will further evolve by using optical access systems and broadband CDMA.

conceded its position to optical transmission development of such technologies is actively technology. However, the seeds of radio technology, underway.(7) which have been closely linked with the paradigm shift of “personal,” have recently found favor in the Switching System field of mobile communication, in a way different (1) One of the major technological innovations from backbone transmission. previously developed in switching was digital Communication through personal computers (PCs) electronic exchange, the basic concepts of which are via mobile telephone terminals is already in widespread reflected even in today’s exchanges. use, as are PHS-based services, What is noteworthy in this evolution of digital which began operating in Japan in April 1997. It is technology is the provisioning of the ISDN service. expected that the establishment of e-mail as a regular ISDN was introduced in various countries around 1988 means of communication, together with the use of as the international-standard infrastructure technology hand-held PCs, will boost the demand for a reliable to support the entirety of communication services, high-speed data service in mobile communication including voice, data and video. There was already a systems. Mobile communication is expected to concept of multimedia communications at that time, progress from the conventional telephone-oriented and ISDN was expected to be a service which would system to a system which supports multimedia spread into every home. However, the initial users communications. New technologies, such as broadband were mainly corporations. This means that although CDMA, which have already received much attention, there were latent needs for multimedia communication will address the challenge of high-speed multimedia at home, the environment was insufficient to make communication via radio technology. Research and them manifest.

48 Hitachi Review Vol. 47 (1998), No. 2 Today, however, the widespread increase in the demanded to handle increasing traffic. It is expected number of users accessing the Internet, and the that ATM technology will be able to cope with this increasing demand for high-speed data communication, increase. owing to the dramatic decrease in the price of personal In the future, ATM technology will be used to computers, are two of the factors which are accelerating support the demands of multimedia communication, the proliferation of ISDN into the home. which will surely evolve in the network infrastructure (2) Around the time when the international standard toward the ultimate goal anticipated in the beginning for ISDN was being established, the research and of its development. development of broadband ISDN was actively being promoted for use as the infrastructure for a fully- Storage Systems fledged, multimedia communication era. During this While the demands of the communication service time, many other technologies emerged. One of the are becoming more diversified, so the information technical “seeds” which has the potential to drastically storage systems are evolving too. The voice message change the communication infrastructure is ATM service, best represented by the answering machine, is (asynchronous transfer mode). This method of perhaps the most familiar communication service transferring and processing all information in short which uses information storage. packets or “cells” was a revolutionary idea for the Voice mail services are becoming an essential item coming multimedia era. for users of cellular and PHS telephones. In addition, Today, ATM technology is being introduced into voice mail is also being introduced as a new service the infrastructure of communication networks in a for telephones and pager systems. variety of ways. It will be especially effective as the High-efficiency voice encoding and large-capacity backbone technology for high-speed data transfer, such file technologies are two basic technological “seeds” as in frame-relay networks. These networks extensively which are deemed necessary to implement such a use an architecture which realizes a good cost- service. Voice encoding evolved into the technology performance by adopting ATM technology for the which can be seen today, triggered by (a) the need to internal processing of the switch, while using frame- use digital leased lines economically in corporate relay networks in the user interface. With regards to networks, and (b) the need to accommodate more the Internet, a significant improvement in the subscribers within a limited band frequency. processing capacity of IP (Internet protocol) is being The evolution of the high-efficiency voice encoding

Management TMN integrated network management information and operation system

Management Switching network Management Transmission network Management Storage network information management information management information management

Management Management Transmission equipment Management Storage equipment information Switch management information management information management

Switch Transmission equipment Storage equipment

Fig. 4—Network Management System using TMN (Telecommunications Management Network). A huge amount of management information is integrated by the hierarchical structure, from the equipment management at the lower level to the integrated network management and operation system at the top.

Overview of Communication Network Evolution 49 technology was supported by the advanced voice network infrastructure from the viewpoint of social analysis and encoding algorithm, and paradigm shifts. processing (DSP) technology. It is expected that the Hitachi will contribute to the realization of a highly further development of both of these technologies will information-oriented affluent society in the result in the embodiment and widespread use of new by providing a variety of devices to quickly meet the services, such as voice recognition and media diversified communication service needs. Hitachi will conversion. also contribute to the realization of a seamless network The development of large-capacity, low-cost through the use of software and the provision of a total magnetic and optical disks will become increasingly solution which responds to the needs of each user. more important in the future to meet the demands of new services, which are required for the realization of REFERENCES a fully-fledged multimedia environment in (1) D. Tapscott et al., translated by Nomura Research Institute, telecommunications. Paradigm Shift—The New Promise of Information Technology Web servers are also advancing rapidly to encompass (1994). multimedia applications such as sound and video. The (2) Society of Telecommunications Carriers, Society News (19 server, which has evolved as the data storage or I/O March 1997). device in computer systems, is expected to serve as a (3) Telecommunications Technology Council, Report from the Committee on the Efficient Frequency Use in Mobile Phones, key storage subsystem in communication networks in etc. (February 1997). the future, primarily in new Internet services. (4) Ric Telecom, , No. 152 (March 1997). (5) Ministry of Posts and Telecommunications, Communications Management System White Paper ’96 (June 1996). The communication network is an important (6) Network Wizard, http://www.nw.com infrastructure which supports social activities. The (7) Special Issue on Broadband Coherent DS-CDMA Radio Access, news about the national-level discussion ongoing to NTT DoCoMo Technical Journal 4, No. 3 (October 1996). improve the reliability of the communication network (8) Ministry of Posts and Telecommunications, Report from the Study Group on Security and Reliability of Telecommunication during disaster after the Hanshin-Awaji earthquake in Networks (November 1995). Japan in 1995 is still fresh in our memory.(8) Each of the transmission, switching and storage ABOUT THE AUTHORS subsystems which constitute the communication network requires a management function to monitor Toshiki Tanaka, D.E. the operating state and take actions if failures occur. Joined Hitachi, Ltd. in 1972 and is now the General The integrated management of the entire network is Manager of the CDMA Systems Business Operation performed by the upper management system, or TMN of the Telecommunications Division. He is a doctor of (Telecommunications Management Network). The engineering and a member of IEEE, IEICE, and IPSJ. E-mail: [email protected] TMN handles a vast amount of the management information obtained from these subsystems (Fig. 4). The evolution of the digital, computer and software Minoru Inayoshi technologies in the communication network Joined Hitachi, Ltd. in 1974 and is now the continuously enhances the functions of the network Department Manager of the Business Strategy Center of the Telecommunications Division. He is currently management system. It is expected that new services, engaged in planning the strategies for closely associated with economic activities, such as telecommunication business. electronic commerce and electronic money, will be E-mail: [email protected] introduced and expanded globally throughout the communication network in the future. In this respect, Noboru Mizuhara network security and reliability are becoming a critical Joined Hitachi, Ltd. in 1974 and is now the Chief issue. Expert of the Public Telecommunications Operation of the Telecommunications Division. He is currently CONCLUSIONS engaged in research and development of high We have discussed the current situation, as well as performance Internet systems. He is a member of IEICE and IPSJ. the direction of future evolution, of the communication E-mail: [email protected]

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