Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P7

The telecommunications access network is the section of the network that connects the local exchange to the customers. At present most of the access network is composed of low bandwidth copper cable. Electronic communications are becoming an essential feature of life both at home and at work. The increasing use of applications that require larger bandwidths (such as the internet and video on demand) are making the copper infrastructure inadequate. These demands could be met using optical fibre technologies....
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P7 Telecommunications Optimization: Heuristic and Adaptive Techniques. Edited by David W. Corne, Martin J. Oates, George D. Smith Copyright © 2000 John Wiley & Sons Ltd ISBNs: 0-471-98855-3 (Hardback); 0-470-84163X (Electronic)7Optimizing the Access NetworkDavid Brittain and Jon Sims Williams7.1 IntroductionThe telecommunications access network is the section of the network that connects thelocal exchange to the customers. At present most of the access network is composed of lowbandwidth copper cable. Electronic communications are becoming an essential feature oflife both at home and at work. The increasing use of applications that require largerbandwidths (such as the internet and video on demand) are making the copperinfrastructure inadequate. These demands could be met using optical fibre technologies. At present, optical fibre is principally used in the trunk network to provide connectionsbetween exchanges, and to service customers with high bandwidth requirements. Point-to-point links are used. In the access network, customers generally have lower bandwidthrequirements and also require a cost-effective service. For them, point-to-point links are notviable as both the link and the dedicated exchange-based equipment are expensive. Anetwork based on point-to-multi-point links provides a high capacity service, together withshared equipment costs. Point-to-multi-point networks can be created using optical fibreand passive splitting devices. They are known as Passive Optical Networks (PONs). With this new architecture and a commercial environment that is increasinglycompetitive, there is a need for improved methods of network planning to provide cost-effective and reliable networks. Currently, much of the access network planning that takesplace is performed by hand which may mean networks are not as cost-effective as theycould be. There have been many attempts to produce systems that optimise the topology ofcopper networks, although they often make use of much simplified network models. Thetask of designing optical networks is significantly different to that for copper networks andlittle work has been published in this area. Most access networks are installed gradually,over time, and so a dynamic approach to planning is also required.Telecommunications Optimization: Heuristic and Adaptive Techniques, edited by D.W. Corne, M.J. Oates and G.D. Smith© 2000 John Wiley & Sons, Ltd116 Telecommunications Optimization: Heuristic and Adaptive Techniques This chapter describes a methodology for optimising the installation cost of opticalaccess networks. The plans produced specify where plant should be installed, thecomponent sizes and when the plant should be installed. In fact, the system is not limited tooptical networks and could easily be extended to plan most types of access network. Twooptimisation methods are presented: genetic algorithms and simulated annealing; the first ofthese is found to have the best performance on the problems considered. The chapter starts with a presentation of the problem of network planning by describingthe network technologies involved and the decision variables. This is followed by a briefreview of Genetic Algorithms (GA) and simulated annealing (SA), and a description ofhow they can be applied to designing a network; some results and comparisons are thenpresented. Finally, the issue of demand uncertainty in the planning process is discussed. Local Exchange Customer Premises FEEDER RING (OR SPINE) Customer Premises = Node (and splitting point) = Primary = SecondaryFigure 7.1 A schematic of a generic optical access network. If the nodes contain splicing units then itis a point-to-point network and if they contain splitting units it is a Passive Optical Network (PON).7.1.1 Access Network ArchitecturesThe simplest possible optical fibre architecture for the access network is a point-to-point(PTP) network in which each customer has a dedicated fibre pair from the exchange. Thesenetworks still have the same topology as traditional tree-and-branch topologies (see Figure7.1). There are cost advantages in aggregating a number of fibres in ...