tailieunhanh - Mạng và viễn thông P41

Building, Extending and Replacing Networks It is rare to come across a telecommunications network that is not in a state of continuous evolution. At its simplest, a network could be expanding simply to cope with increased demand. In addition the network may be expected at the same time to provide increasingly sophisticated telecommunications services. | Networks and Telecommunications Design and Operation Second Edition. Martin P. Clark Copyright 1991 1997 John Wiley Sons Ltd ISBNs 0-471-97346-7 Hardback 0-470-84158-3 Electronic PART 6 SETTING UP NETWORKS Networks and Telecommunications Design and Operation Second Edition. Martin P. Clark Copyright 1991 1997 John Wiley Sons Ltd ISBNs 0-471-97346-7 Hardback 0-470-84158-3 Electronic 41 Building Extending and Replacing Networks It is rare to come across a telecommunications network that is not in a state of continuous evolution. At its simplest a network could be expanding simply to cope with increased demand. In addition the network may be expected at the same time to provide increasingly sophisticated telecommunications services. For example since the mid-1980s many of the world s public telecommunications operators PTOs have responded to customer demand by the introduction of a freephone service offering the facility for call recipients to pay for the calls. As an introduction to the subject of network evolution which the operator must be able to cope with this chapter describes how networks may be built or extended to meet capacity and service needs. Particular attention is paid to the design factors inherent in the equipment ordering process these are crucial to the success of a network evolution plan. In addition and because it is not always possible to achieve the evolution without the entire replacement of the network and equipment the chapter describes various methods by which network modernization can be achieved without a major disturbance or interruption to the established service. MATCHING NETWORK CAPACITY TO FORECAST DEMAND No matter what type of telecommunications service is provided network costs are minimized by matching capacity to the demand. Both over-provision and underprovision increase costs. When equipment is provided before it is actually needed higher capital expenditure is incurred at an earlier date. In addition there are higher .