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ISDN: a solution in search of a problem?
Comment
ISDN: a solution in search of a problem? Tony Newstead This article discusses the measures being taken by telecommunications companies and policy makers to provide ISDN services. The movement towards ISDN has seemed a logical extension of the integrated digital switching and transmission network, providing improved flexibility and performance. However, the author argues that these expectations have yet to be verified in practice. He calls for further technical and economic studies before any premature dedication to ISDN is made. Tony Newstead, formerly head of the engineering function of Hong Kong Telephone Company Ltd, is principal of his own
consultancy firm, Telecommunications Management Support, 91 Stanhope Street, Malvern, Victoria 3144, Australia.
‘Data Communications, May 1985, p 48. ‘Data Communications, September 1982, p 39. %ommunications News, April 1985, p 122.
2
Despite the plethora of plans. articles, advertisements. public statements and rhetoric, there are many behind the scenes who are challenging the conventional wisdom of the telecommunications world’s apparent headlong rush to embrace ISDN. In at least one of the largest manufacturers of digital equipment, staff are saying that it stands for ‘Innovations Subscribers Don’t Need’! Joseph Weber. AT&T’s Director, Strategic Planning. calls ISDN ‘a technologist’s dream. It was invented and is being implemented by technologists in the absence of any compelling, specific applications.” Ted de Haas, the US Department of Commerce Liaison Officer to the CCITT on ISDN, pointed out in 1982 that ‘it does not pay to build a network to the highest requirement which for 80’X-90% of the time will be used for the lowest requirement’.’ In the past 25 years there have been some salutary, misplaced direction signposts for telecommunications, erected by talented but misguided technocrats who ignored the basic motivations and requirements of potential users - need. perceived value, simplicity and cost. Bell System’s ‘Picturephone’ of the 1960s provided ‘eyeball-to-eyeball’ communications - an uneasy. expensive and unwanted complement to the telephone. Some hundreds of millions of dollars later, the service was discontinued. In the 1970s video conferencing was seen as a major substitute for business and the cost calculations travel, proved it. What was overlooked were the side and personal benefits of busi-
ness trips, and the marked limitations of the medium for certain types of communication. Videotex was to provide universal information access for residential and business customers, with home shopping and education thrown in. A couple of years ago the majority of British Telecom’s Prestel computers were put into mothballs and the system has been reoriented, largely towards specialized business user groups. Today’s PABXs advertise a lengthy menu of exotic features as major selling points. Studies have shown that few users ever activate more than three; most do not even understand how to. This is not to say that there is no potential for all these services, but there was gross misjudgement about their need, their complexity to users, or their cost effectiveness at the time. The issue with ISDN is not a conceptual one; there would be general agreement with the long-term ISDN goal, articulated by AT&T as ‘graceful evolution of today’s telecommunication network towards a powerful, unified, network’fabric featuring universal ports, dynamic allocation of bandwidth and other resources and adaptive, logically provided services’. AT&T’s Universal Information Service (UIS) would allow ‘people everywhere to have access to any kind of voice, data or image service, in any place, at any time, with maximum convenience and economy’.’ The only questions are ‘how’ and ‘when’? On this point Edward Goldstein, an AT&T Corporate Vice President, says: ‘I can’t and I don’t think
TELECOMMUNICATIONS
POLICY
March 1986
Commenr
anybody could. define the exact steps and the timing of these steps to get from where we are today to the digital dreamworld of tomorrow’.’ It is against this canvas that we need to evaluate the very specific measures being taken by many administrations, including former Bell operating comto provide ISDN services panies, based on the current CCI’M recommendations of series ‘I’.
Historical
background
These recommendations represent the culmination of over a decade of CCITI studies towards ISDN objectives which, at the time, were a logical extension of the concept of Integrated Digital (ID) switching and transmission, ie the ID Network. The benefits of IDN are well established and beyond dispute. In summary:
0 Greatly
reduced switching and transmission costs. transmission perform0 Improved ance. voice and non0 All information, voice, in common digital format with network transparency.
‘The acid test is whether ISDN is more economic or offers improved performance’
Extension of the IDN to subscribers’ premises and the integration of services to create an ISDN was predicated on the grounds of economy. flexibility and improved performance. This means economy to users since a single cable pair could carry a variety of services, and to the network operator since a single, multi-purpose network should be less costlv, than several, special-purpose networks. Likewise, increased flexibility would be available in the subscriber’s use of facilities and in the network’s ability to deliver them. Improved performance follows the digitalization of the local distribution network, converting it from a two-wire to a four-wire path with enhanced stability, echo improvement and added gain where required.
Underlying
4Data Communications,
May 1985, p 45.
TELECOMMUNICATIONS
POLICY
assumptions
These are laudable objectives, but the expectations of economy and flexibility have yet to be verified in practice. In addition, they rest on a number of
March 1986
implicit assumptions which need to be confirmed in today’s technological and service environment. These assumptions include the following. First, subscribers will want the equivalent of more than one exchange line. This is certainly true of business users. For residential services, only a small percentage in the more affluent countries has this need today. although clearly the need will grow. Present solutions are to rent additional exchange lines. Second, alternative use of lines for voice and data is required. Today’s solutions are to use switchable modems (analogue or baseband) on PSTN lines - eg for data transmission. videotext, FAX. etc, or, where traffic levels justify it. to rent additional lines dedicated to specific uses, including access to specialized networks - notably public packet-switched networks. Third, subscribers need higher data speeds than normal PSTN facilities provide. But PSTN data speed limitations are imposed by analogue media. Digital networks (without implying ISDN facilities) can extend offerings to the same channel speeds as ISDN provides. It is significant that none of the ISDN trials, in train or currently proposed, using the 2B+D CCITI’ standard. basic access, offers any services or facilities which are unavailable to subscribers today. They just perform the same function differently, but the user would be unaware of the difference. The acid test is therefore whether it is done more economically and/or with improved performance.
Economies
of ISDN
The costs of ISDN include: A completely new signalling system between subscribers and local exchanges. New line terminationg equipment at both the subscriber’s and the exchange ends of each ISDN line. New, digital telephones for all subscribers. Selective upgrading of local loops to accommodate 144 Kbps transmission. Until the distant
and debatable
era of
3
Comment
‘Premature dedication to ISDN implementation could be disastrous’
4
packetizing all voice transmission, there is no evidence to support the thesis that one general-purpose network (capable of handling both voice and packet data, for example) could be less costly than separate networks designed and dimensioned to their particular traffic needs. This now seems to be accepted and the focus is on common access rather than on one multi-purpose network. In this case. we must look for the economies in the area of local distribution. For ‘2B+D’ ISDN to be economically viable here, the additional costs of an ISDN provision must be less than the sum of the costs of the additional cable pairs which subscribers would otherwise require. For high penetration of ISDN usage, say over 50% of subscribers, this might conceivably be feasible through economies of scale. As a guide. the marginal cost of an additional local cable pair in a metropolitan location would not exceed around $150. Breakeven at 50% penetration would require that the additional cost for ISDN be less than $75 per exchange line. (Switching costs are considered to be common, since use of an ISDN line. or use of a second cable pair, would both require another exchange switching path.) If, however, penetration were only, say. 10% of subscribers, the ISDN cost would have to fall below $15 per line. The alternative would be to equip only a proportion of the exchange for ISDN, using separate line modules, as in present trials. But then the economies of scale could hardly apply. The above analysis is, of course, highly simplistic but it illustrates the type of economic studies which need to be made and which have hardly been tackled, let along published. So far ISDN has been largely regarded as research expenditure by both administrations and manufacturers; this position cannot be sustained indefinitely. Finally, a further issue of serious concern is the viability of the technical
standards so painstakingly developed over the past ten years. Central to this is 64 Kbps encoding. This requirement dates back to transmission plans developed for analogue networks where up to around 16 modulation/ demodulation points could theoretically occur in an international connection. Because of quantizing noise in digital encoding, a 128 level (7+l) bit scheme was adopted to ensure satisfactory transmission performance under the worst conditions. With digital networks, however, there is an economic reduction in the number of levels of network switching hierarchies and the earlier hypothetical maximum number of links in tandem is no longer appropriate. Hence 32 Kbps encoding is sufficient to give comparable noise performance and can double the number of available channels on a digital bearer, with immense transmission economies. Already 32 Kbps encoding is used on expensive international circuits and their use is expanding rapidly. This is acknowledged by the CCITT which has the study of 32 Kbps standards on the list of questions for the current Plenary period (1985-88). With these and other developments, premature dedication to ISDN implementation based on current standards could be disastrous. In the long run, wideband optical fibre distribution will be extended down to subscriber networks, giving a much expanded concept of ISDN, encompassing video interactive and entertainment services as well as telephony, data and other non-voice services. This is the AT&T concept of UIS. Meanwhile the special purpose data and other networks are proliferating and are proving economic and effective. ISDN. over the next decade at least, must therefore be a halfway house between the initial 2B+D standards of today - with internetwork access rather than integration - and the wideband ISDN of the future. SO tread carefully and beware the Emperor’s new clothes!
TELECOMMUNICATIONS
POLICY
March 1986
ISDN: a solution in search of a problem? Tony Newstead This article discusses the measures being taken by telecommunications companies and policy makers to provide ISDN services. The movement towards ISDN has seemed a logical extension of the integrated digital switching and transmission network, providing improved flexibility and performance. However, the author argues that these expectations have yet to be verified in practice. He calls for further technical and economic studies before any premature dedication to ISDN is made. Tony Newstead, formerly head of the engineering function of Hong Kong Telephone Company Ltd, is principal of his own
consultancy firm, Telecommunications Management Support, 91 Stanhope Street, Malvern, Victoria 3144, Australia.
‘Data Communications, May 1985, p 48. ‘Data Communications, September 1982, p 39. %ommunications News, April 1985, p 122.
2
Despite the plethora of plans. articles, advertisements. public statements and rhetoric, there are many behind the scenes who are challenging the conventional wisdom of the telecommunications world’s apparent headlong rush to embrace ISDN. In at least one of the largest manufacturers of digital equipment, staff are saying that it stands for ‘Innovations Subscribers Don’t Need’! Joseph Weber. AT&T’s Director, Strategic Planning. calls ISDN ‘a technologist’s dream. It was invented and is being implemented by technologists in the absence of any compelling, specific applications.” Ted de Haas, the US Department of Commerce Liaison Officer to the CCITT on ISDN, pointed out in 1982 that ‘it does not pay to build a network to the highest requirement which for 80’X-90% of the time will be used for the lowest requirement’.’ In the past 25 years there have been some salutary, misplaced direction signposts for telecommunications, erected by talented but misguided technocrats who ignored the basic motivations and requirements of potential users - need. perceived value, simplicity and cost. Bell System’s ‘Picturephone’ of the 1960s provided ‘eyeball-to-eyeball’ communications - an uneasy. expensive and unwanted complement to the telephone. Some hundreds of millions of dollars later, the service was discontinued. In the 1970s video conferencing was seen as a major substitute for business and the cost calculations travel, proved it. What was overlooked were the side and personal benefits of busi-
ness trips, and the marked limitations of the medium for certain types of communication. Videotex was to provide universal information access for residential and business customers, with home shopping and education thrown in. A couple of years ago the majority of British Telecom’s Prestel computers were put into mothballs and the system has been reoriented, largely towards specialized business user groups. Today’s PABXs advertise a lengthy menu of exotic features as major selling points. Studies have shown that few users ever activate more than three; most do not even understand how to. This is not to say that there is no potential for all these services, but there was gross misjudgement about their need, their complexity to users, or their cost effectiveness at the time. The issue with ISDN is not a conceptual one; there would be general agreement with the long-term ISDN goal, articulated by AT&T as ‘graceful evolution of today’s telecommunication network towards a powerful, unified, network’fabric featuring universal ports, dynamic allocation of bandwidth and other resources and adaptive, logically provided services’. AT&T’s Universal Information Service (UIS) would allow ‘people everywhere to have access to any kind of voice, data or image service, in any place, at any time, with maximum convenience and economy’.’ The only questions are ‘how’ and ‘when’? On this point Edward Goldstein, an AT&T Corporate Vice President, says: ‘I can’t and I don’t think
TELECOMMUNICATIONS
POLICY
March 1986
Commenr
anybody could. define the exact steps and the timing of these steps to get from where we are today to the digital dreamworld of tomorrow’.’ It is against this canvas that we need to evaluate the very specific measures being taken by many administrations, including former Bell operating comto provide ISDN services panies, based on the current CCI’M recommendations of series ‘I’.
Historical
background
These recommendations represent the culmination of over a decade of CCITI studies towards ISDN objectives which, at the time, were a logical extension of the concept of Integrated Digital (ID) switching and transmission, ie the ID Network. The benefits of IDN are well established and beyond dispute. In summary:
0 Greatly
reduced switching and transmission costs. transmission perform0 Improved ance. voice and non0 All information, voice, in common digital format with network transparency.
‘The acid test is whether ISDN is more economic or offers improved performance’
Extension of the IDN to subscribers’ premises and the integration of services to create an ISDN was predicated on the grounds of economy. flexibility and improved performance. This means economy to users since a single cable pair could carry a variety of services, and to the network operator since a single, multi-purpose network should be less costlv, than several, special-purpose networks. Likewise, increased flexibility would be available in the subscriber’s use of facilities and in the network’s ability to deliver them. Improved performance follows the digitalization of the local distribution network, converting it from a two-wire to a four-wire path with enhanced stability, echo improvement and added gain where required.
Underlying
4Data Communications,
May 1985, p 45.
TELECOMMUNICATIONS
POLICY
assumptions
These are laudable objectives, but the expectations of economy and flexibility have yet to be verified in practice. In addition, they rest on a number of
March 1986
implicit assumptions which need to be confirmed in today’s technological and service environment. These assumptions include the following. First, subscribers will want the equivalent of more than one exchange line. This is certainly true of business users. For residential services, only a small percentage in the more affluent countries has this need today. although clearly the need will grow. Present solutions are to rent additional exchange lines. Second, alternative use of lines for voice and data is required. Today’s solutions are to use switchable modems (analogue or baseband) on PSTN lines - eg for data transmission. videotext, FAX. etc, or, where traffic levels justify it. to rent additional lines dedicated to specific uses, including access to specialized networks - notably public packet-switched networks. Third, subscribers need higher data speeds than normal PSTN facilities provide. But PSTN data speed limitations are imposed by analogue media. Digital networks (without implying ISDN facilities) can extend offerings to the same channel speeds as ISDN provides. It is significant that none of the ISDN trials, in train or currently proposed, using the 2B+D CCITI’ standard. basic access, offers any services or facilities which are unavailable to subscribers today. They just perform the same function differently, but the user would be unaware of the difference. The acid test is therefore whether it is done more economically and/or with improved performance.
Economies
of ISDN
The costs of ISDN include: A completely new signalling system between subscribers and local exchanges. New line terminationg equipment at both the subscriber’s and the exchange ends of each ISDN line. New, digital telephones for all subscribers. Selective upgrading of local loops to accommodate 144 Kbps transmission. Until the distant
and debatable
era of
3
Comment
‘Premature dedication to ISDN implementation could be disastrous’
4
packetizing all voice transmission, there is no evidence to support the thesis that one general-purpose network (capable of handling both voice and packet data, for example) could be less costly than separate networks designed and dimensioned to their particular traffic needs. This now seems to be accepted and the focus is on common access rather than on one multi-purpose network. In this case. we must look for the economies in the area of local distribution. For ‘2B+D’ ISDN to be economically viable here, the additional costs of an ISDN provision must be less than the sum of the costs of the additional cable pairs which subscribers would otherwise require. For high penetration of ISDN usage, say over 50% of subscribers, this might conceivably be feasible through economies of scale. As a guide. the marginal cost of an additional local cable pair in a metropolitan location would not exceed around $150. Breakeven at 50% penetration would require that the additional cost for ISDN be less than $75 per exchange line. (Switching costs are considered to be common, since use of an ISDN line. or use of a second cable pair, would both require another exchange switching path.) If, however, penetration were only, say. 10% of subscribers, the ISDN cost would have to fall below $15 per line. The alternative would be to equip only a proportion of the exchange for ISDN, using separate line modules, as in present trials. But then the economies of scale could hardly apply. The above analysis is, of course, highly simplistic but it illustrates the type of economic studies which need to be made and which have hardly been tackled, let along published. So far ISDN has been largely regarded as research expenditure by both administrations and manufacturers; this position cannot be sustained indefinitely. Finally, a further issue of serious concern is the viability of the technical
standards so painstakingly developed over the past ten years. Central to this is 64 Kbps encoding. This requirement dates back to transmission plans developed for analogue networks where up to around 16 modulation/ demodulation points could theoretically occur in an international connection. Because of quantizing noise in digital encoding, a 128 level (7+l) bit scheme was adopted to ensure satisfactory transmission performance under the worst conditions. With digital networks, however, there is an economic reduction in the number of levels of network switching hierarchies and the earlier hypothetical maximum number of links in tandem is no longer appropriate. Hence 32 Kbps encoding is sufficient to give comparable noise performance and can double the number of available channels on a digital bearer, with immense transmission economies. Already 32 Kbps encoding is used on expensive international circuits and their use is expanding rapidly. This is acknowledged by the CCITT which has the study of 32 Kbps standards on the list of questions for the current Plenary period (1985-88). With these and other developments, premature dedication to ISDN implementation based on current standards could be disastrous. In the long run, wideband optical fibre distribution will be extended down to subscriber networks, giving a much expanded concept of ISDN, encompassing video interactive and entertainment services as well as telephony, data and other non-voice services. This is the AT&T concept of UIS. Meanwhile the special purpose data and other networks are proliferating and are proving economic and effective. ISDN. over the next decade at least, must therefore be a halfway house between the initial 2B+D standards of today - with internetwork access rather than integration - and the wideband ISDN of the future. SO tread carefully and beware the Emperor’s new clothes!
TELECOMMUNICATIONS
POLICY
March 1986