Once it seemed that network modernisation would more or less finish once the telecommunications operators had finished digitising their networks. But no. Along came a new architecture which promised to enable the operators use their networks more flexibly, manage them more easily and run them more cheaply. This architecture cum technology is Synchronous Digital Hierarchy and everyone is taking note. The European telecommunications operators are having to devise implementation strategies, not only the better to serve their customers, but also to prepare themselves against forthcoming competition. Widespread changes in switching technology are also affecting the manufacturers. On the one hand telecommunications operators buying more kit must be a Good Thing. On the other, the vendors are faced with crippling research and development costs, reduced product life cycles and the threat of new competitors challenging their traditionally protected home market.
Woodwork
Finally, of course, there is nothing like a new technology to bring the report writers out of the woodwork and Cambridge-based Analysys Ltd has taken up the challenge and just published ‘SDH strategies, Benefits and Technologies’. As the name implies, it begins by bringing the reader up to speed on the technology and standards before moving on to a tour d’horizon of the European public telephone operators’ implementation strategies and a section on how the manufacturers will cope. Synchronous Digital Hierarchy defines a hierarchical method by which the bandwidth demanded by end users can be aggregated into the high-speed pipes that the operators find more convenient. Today’s networks use the Pleiosochronous Digital Hierarchy which needs a cumbersome ‘mountain’ of multiplexors to aggregate the user bandwidth into the high speed links and then needs a similar mountain to demultiplex it all at the other end. This is expensive of course, but it also means that every time a user wants (say) a 64Kbps private circuit he or she has to wait while the operator installs all this complex machinery. On top of that there is precious little management control of the multiplexed sessions.
By Chris Rose
Synchronous Digital Hierarchy by contrast incorporates the tributary bit-streams into ‘virtual containers’ which are then loaded into frames. The frames contain management information and the way that the containers and frames are constructed means that various bit-rates can be incorporated into and pulled out of the aggregated high-speed circuits with a minimum of fuss and hardware. The result? Operators like Deutsche Bundespost Telekom are saying that assuming physical network connection is available, users will be able to have leased lines up and running within a few minutes or hours of ordering them. Likewise they will be able to have their lines for just a few hours a day if need be. Bundespost Telekom is also promising that the technology will enable users to manage the circuits themselves if required. However these direct benefits for the end user are relatively unusual. Unlike their counterparts in the US, Analysys finds, most of the European telecommunications companies see Synchronous Digital Hierarchy as a way of making their own lives easier, rather than a means of offering innovative services. Perhaps the single most important reason for telecommunications operators taking the new technology seriously is that it is specifically designed to work alongside existing pleiosochronous installations. They don’t have to junk their existing kit, and can instead pick and choose where Synchronous Digital Hierarchy facilities are needed and then arrange for cross-connects between the old and new networks. Each of the European telecommunications operators has a different idea of the most efficient way to deploy the new kit. Some are opting for a top-down approach where the trunk network is converted before the peripheral access network. Others are working from the bottom up with ‘islands’ of Synchronous Digital Hierarchy which will be connected at a later date.
Benefits
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ch has its benefits and the report takes the reader through a number of real implementation strategies as well as a number of computer simulations to show the theoretical benefits of different approaches. Don’t bother looking for British Telecommunications Plc’s plans though: in a competitive environment the company is holding its cards close to its chest. As for what Synchronous Digital Hierarchy means to the vendors, Analysys concludes that the new market represents a prize well worth competing for, however: There is a broad recognition in the European telecommunications equipment world that there is not room in the marketplace for the current number of players, either in switching or transmission. Largely, this is a result of the research and development costs, but also open procurement requirements dictated by the European Commission means that the North American and Japanese competition are knocking at the door. The result will be an increasing number of strategic alliances, the report suggests. The report is published by Analysys Ltd, Jesus Lane, Cambridge; the preview copy of does not include the price.
