Prognosemetoder – en oversikt - Telenor

Abstract
1 Introduction
Scenarios for introduction of broadband services
in telecommunication networks
BY ROLF B HAUGEN AND BENTE MANNSÅKER
There are large activities world-wide to specify and experiment with broadband networks and services. At the moment most people
believe that the broadband network of the future will be based on ATM technology, and switching manufacturers and research institutions
are making detailed plans for how ATM technically is to be incorporated into next generation’s systems and networks. But
the crucial question for the PNOs is how to economically introduce a B-ISDN concept; it is a fact that, except for CATV, there is
really no broadband service that at the moment is attractive enough to pay for the enormous investments necessary. We discuss in
this paper two types of broadband services: video related services and data network services, the former type being the traditionally
discussed end user services, whereas the latter is the aggregation of services from several users connected to various types of local
networks. We argue that the data network services will be the driving force towards a broadband network and discuss some scenarios
from broadband islands towards a B-ISDN.
Broadband services have been very much discussed, and even
experimented with, during the last couple of decades. Some services,
like cable TV, have found their implementations in dedicated
networks. Others, like picture phone and video conferences,
have been introduced in the public telephone networks by
digital coding (compression) of the video signals to smaller
bandwidths. But, except for this recent breakthrough in compression
techniques, there is still no real broadband service
offered in public networks that can be said to run on sound economical
terms.
In Europe, there has been a tremendous effort the last five years
to specify a public broadband network as well as to initiate the
development of components and subsystems that would make
such networks cost effective. Several long term EC projects have
been established to this end; RACE being the most influential
within the telecommunications area.
By now, the evolving broadband network, B-ISDN, based on
ATM technique seems to be rather well defined and agreed
upon among telecom operators. But one thing is specification of
a network, another is cost effective implementation; i.e. at prices
that subscribers can afford. Needless to say, the subscriber loop
is the overwhelming bottleneck.
Optical fibres in the subscriber loop are considered to be a prerequisite
for broadband services. For business users fibre connections
are today, economically spoken, within reach; in fact,
medium and large companies might already be connected to the
public network via fibre cables. This is by no means the case for
residential subscribers and small firms. For these categories the
cost of installing optical fibres are still an order of magnitude
larger than with ordinary copper cables. And for residential
users, most PNOs (Public Network Operators) are for
political/regulatory reasons excluded from offering the most
popular broadband service of today, namely cable TV. An integration
of TV and tele services on the same cable might have
rendered a fibre optical solution into residential homes cost
effective in the near future. The RACE project TITAN is developing
computerized tools for calculating (life cycle) costs of
optical access networks. With this tool the network planners can
extract detailed estimates of total and partial fibering of the
local loop as a function of the years up to and beyond year
2000. In the computer program there are forecasting models for
service demands and prices of the various network components.
Services that will be driving forces for the PNOs to start implementing
broadband networks can be divided into two classes
- video related services
- data network services.
The first class contains services of the type: video telephony,
video conferences, TV distribution, multimedia communications,
etc. These services typically direct themselves to one, or
at least a limited number of end users. To offer videophone or
TV distribution services there must be a broadband connection
all the way to the end user. That is what makes these types of
services hard to offer in the public networks.
The other class of services is of the type: LAN-LAN interconnect,
high capacity main frame communication (Cray), etc.
These types of services direct themselves towards clusters of
users that are hooked on to local networks, hence the “users” are
often LANs. And it is the aggregation of traffic that creates a
need for broadband solutions rather than the demand from single
users.
To begin with, attention was directed towards the first class of
users; in fact, the very notion of B-ISDN somehow leads our
minds towards an end user concept. Hence, most broadband services
that were experimented with throughout the eighties were
of this type, and there was, and perhaps still is, an increasing
frustration for not being able to bring these services to the customers
at prices they would be willing to pay.
But it is the second class of services that presently “takes off”
and requires solutions. Up to now, inter-networking solutions
have mostly been provided by bridges and routers that are interconnected
by leased lines. More recently, solutions like Frame
Relay, MAN (Metropolitan Area Network), ISDN and even
ATM are being discussed.
From a PNO’s point of view, the latter type of solutions are by
far the more interesting. Could intra-LAN traffic be transported
in the switched (public) network? And which type of the above
mentioned network solutions have the potential to evolve into
the broadband network of the future?
These are the questions many PNOs are discussing today. They
all know that there are tremendous revenue potentials in the
multimedia revolution that will eventually come, a revolution
that is just waiting for cheap network solutions. On the other
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