World Telecommunication Day 1999 |
Once upon a time, the capacity of voice-centric telecommunications networks grew in fairly steady and predictable increments. No longer. Today, with huge growth in Internet and multimedia traffic - to say nothing of mobile - some networks are beginning to burst at the seams.
Calculating what capacity will be needed in the future to accommodate the so-called ''data wave'' is fraught with difficulty. Adding to a network planner's dilemma is that while massive investments are needed to build new superhighways, the number of operators competing for business on these highways has rocketed in recent years.
Says Jost Spielvogel, member of the board of Siemens Information and Communication Networks Inc.: ''This means a risk, because it is not clear how much of the bandwidth explosion can be acquired and served by a certain operator or service provider.''
The growth in popularity of the Internet first started to highlight the bandwidth limitations of conventional networks in the mid-1990s. The initial response of operators was to accelerate deployment of asynchronous transfer mode (ATM) switching and increase their use of synchronous transmission equipment.
ATM is a very fast switching technology that can handle different traffic types in the same network. Synchronous transmission runs at speeds of billions of information bits per second, requires less equipment than earlier technology and provides operators with a means of managing unpredictable traffic growth.
More recently, operators have begun to install dense wavelength division multiplexers (D-WDMs) and are beginning to slot what are termed terabit router switches into their networks.
D-WDM systems carry traffic on different wavelengths of light in the same optical fiber and have truly astonishing capacity. Barry Flanigan, WDM analyst at the technology consultancy Ovum, notes, ''Vendors are bringing out products which take capacity to beyond 100 Gb/s,'' or 100 billion bits per second.
Terabit switch routers are also pretty agile. One from Avici Systems Inc., for example, has an in/out capacity of up to 5.6 trillion bits per second. Switch routers are also designed to handle more efficiently the swelling volumes of Internet Protocol (IP) traffic coming down the telecommunications turnpike.
According to some industry analysts, IP traffic will eventually dominate networks, and even a substantial part of voice traffic will be conveyed in IP form.
There is a general shift away from circuit technology, typified by the dial-up telephone network, to packet networks that are optimized for IP and data traffic. Circuit-switching technology maintains a path through the network for the duration of a call and does not make the most efficient use of available transmission capacity, or bandwidth.
''The basic limitation of circuit-switched systems,'' says David Gunning, vice president of marketing at the packet-based access platform vendor Integral Access Inc., ''is that they reserve bandwidth even if the telephone is on-hook or silence is present. This results in significant wasted bandwidth.''
By contrast, packet networks send messages in the form of data packets, each with an address header. Individual packets travel on the best available link at any moment in time and are reassembled at their destination into the appropriate sequence. Bandwidth is only used when and where there is traffic.
Attempts to beef up the core of telecommunications networks have necessitated a long hard look at new technologies for the local access infrastructure. Since the overwhelming majority of people are ultimately connected with pairs of copper wire, there has been considerable interest in a technology known as asymmetric digital subscriber line (ADSL).
ADSL use ramps up the capacity of copper pairs to as much as 8 million bits per second downstream to the end-user and several hundred thousand bits per second in the opposite direction.
''ADSL has some compelling advantages,'' says Martin de Prycker, president of Alcatel SA's Internet Access Division, ''not the least of which is the fact that it can be used on existing infrastructure, is now well standardized and can be rolled out by operators and service providers in close alignment with actual customer demand.''
Beefing up networks may be critical for operators' survival in the next century, but it is not the end of the story. They will then have to invest even more to deliver the services that people actually want. ''Those who don't reinvest will become gobbled up by the people that do,'' says Jackie Olivier, director of telco business at the software company CAP Gemini SA.
John Williamson