ITU-T HDBK HTP-1993 Handbook on Transmission Planning《传输计划手册》.pdf

1、INTERNATIONAL TELECOMMUNICATION UNION ITU-TS TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU HANDBOOK ON TRANSMISSION PLANNING Geneva, 1993 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services - STDnITU-T HDBK HTP-ENGL 1993 YB62591 0682073

2、55T INTERNATIONAL TELECOMMUNICATION UNION ITU-TS TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU i L HANDBOOK ON TRANSMISSION PLANNING 1 Geneva, 1993 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTDmITU-T HDBK HTP-ENGL 1773 m 48b2591

3、 b82074 4qb O U 1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. COPYRIGHT International Telecommunications Union/ITU Telecommun

4、icationsLicensed by Information Handling Services1 . 1.1 1.2 1.3 1.4 I 2 . 2.1 2.2 2.3 2.4 2.5 3 . 3.1 3.2 3.3 3.4 3.5 3.6 3.7 I I 3.8 . . STD-ITU-T HDBK HTP-ENGL 1993 48b2591 0682075 322 II TABLE OF CONTENTS Introduction Purpose of the booklet . Network structure . Planning . Management Coordinatio

5、n of planning between transmission and other fundamental technical plans . Traffic forecasting: technical development . Physical routing and route capacity . Re-planning of traffic routes . Dig i tali zat i on Planning for transmission maintenance . Transmission performance and planning . Loudness a

6、nd loss allocation . Stability. singing. hollowness and open loop loss Impedance and sidetone . Noise and interference Fidelity and distortion . The effect of talker echo Subjective effects of direct crosstalk thresholds of audibility and intelligibility Requirements of non-telephone services Pacle

7、3 3 3 4 4 9 9 17 29 32 36 41 45 52 CCITlHANDBCOMXIITRPLVJE 1 .DOC COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services4 . 4.1 4.2 4.3 4.4 5 . 5.1 5.2 5.3 6 . 6.1 6.2 6.3 6.4 6.5 7 . 8 . STD-ITU-T HDBK HTP-ENGL L993 m 4862591 Ob8207b 269 m -

8、2- Review of equipment . Subscriber sets Transmission systems . Switching systems . Other systems Dedicated networks . Mobile telephone networks Private networks Conference networks . Economic aspects and subscriber reaction . Aspects of the implementation and operation; planning for optimization .

9、Utilization and operation Economic aspects and subscriber reaction . Charge . Network planning responsibilities . Outlook References Annex . Transmission plan of Canadian network Paae 52 52 53 55 55 55 56 57 58 60 60 61 63 64 64 65 65 66 CCITnHANDBCOMXlITRPLV2El . DOC COPYRIGHT International Telecom

10、munications Union/ITU TelecommunicationsLicensed by Information Handling Servicesi STD-ITU-T HDBK HTP-ENGL 1993 W 4862593 Ob82077 ZT5 W -3- 1. Introduction 1.1 Purpose of the booklet The main purpose of the booklet is to assist in the preparation of a transmission plan in accordance with the CCITT R

11、ecommendations. It explains the links between the transmission plan and the other fundamental plans and sets out to identify and consolidate the material needed to establish a transmission plan in accordance with the new CCITT Recommendations on transmission impairments and their acceptable limits,

12、having regard to technical, economic and development constraints on the telecommunications network. Generally speaking, increasingly high levels of performance are now being expected of telecommunications networks because all the administrations are facing the urgent requirements of the “information

13、 society“ and are compelled to introduce as many new services as possible, economically. The most important supports to these activities are those new and partly or completely amended and redrafted earlier Recommendations which are on the one hand dealing with the new references (e.g. national and i

14、nternational circuit and digital path models for planning purposes) and on the other hand with the objectively defined quality measures of the communications (e.g. Loudness Rating). In the present evolving phase, at the planning, operating and managing the mixed connections (analogue and digital sec

15、tions as chains in the network), one has to be very careful with problems such as the stability, impedance strategy, distribution of loss and LR and the summing up of the effects of the disturbances of various nature. which proved to be the essence of the future telecommunications and ISDN - all dep

16、end on the putting into practice of aspects, guidances and rules discussed in the following paragraphs of this booklet. Nevertheless, this booklet is not meant to rule by exact and minute formulations, however, it is intended to support the planners showing them the course of planing and guide them

17、in the judgement and evaluation of the results of various quality influencing effects. general idea of the network planning. Therefore, planning and developing the steps towards general and full digitalization - The Reader may find below a short introductory survey and some remarks concerning the 1.

18、2 Network structure planning methods call for the overall problem to be broken down into a number of more easily soluble sub-problems. The network must be structured so as to permit decentralized planning and so that routine A network may be organized around technical, geographical and administrativ

19、e structures. CCITTHANDBCOMXIITRPLVBEl .DOC COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTDmITU-T HDBK HTP-ENGL 1993 W 48b2591 Ob82078 O31 W -4- 1.2.1 Technical organization While a distinction is usually drawn between switchina. tr

20、ansmission and the subsc riber network, it is sometimes useful to distinguish diaital and analoaue metal cables, radio-relay systems, satellites, fibre optics, depending on the extent to which they are used in the network. 1.2.2 Geographical organization A distinction is drawn between: - urban netwo

21、rks, characterized by high density, heavy traffic and short subscriber lines; - - rural networks, characterized by low density, light traffic and longer subscriber lines; trunk and international networks linking the other two types of network and consisting essentially of transit exchanges and trans

22、mission routes. 1.2.3 Administrative organization requirements and charging problems. This is based largely on geographical distribution but also takes account of administrative 1.3 Planning requirements and promote the development of the telephone network into a genuine telecommunication network. T

23、he most important plans include: A telecommunication network is organized around basic plans which must reflect service - - the numbering plan which identifies subscribers; the routing plan which, for services other than point-to-point service, determines the optimum logical traffic route; the trans

24、mission plan which guarantees adequate transmission quality for the service carried by the network (speech, data, etc.) to all users (universal service); - the charging plan which defines the network utilization cost of each service offered. A transmission plan can be introduced and followed most di

25、rectly for a hierarchical structure which considerably simplifies management and traffic routing calculations. However, some organizations have found it advantageous to evolve a non-hierarchical architecture that uses dynamic routing. As implemented, routing constraints are improved and high transmi

26、ssion quality is achieved. - 1.4 Management network itself must be properly managed to ensure that it is operational regardless of such contingencies as: - - The aim is to ensure satisfactory quality of service at all times and under all network Network planning must be based on forecasts which are

27、as accurate as possible and the temporary overload, both foreseeable and unforeseeable; temporarily reduced capacity owing to failures or removal of equipment from service for maintenance purposes. operating conditions. CCImHANDBCOMXIITRPLEl.DOC COPYRIGHT International Telecommunications Union/ITU T

28、elecommunicationsLicensed by Information Handling ServicesSTD.ITU-T HDBK HTP-ENGL 1993 rn VLZI 082079 78 m -5- 2. Coordination of planning between transmission and other fundamental technical plans Even if the people responsible for the transmission plan can, to a large extent, do their activities a

29、utonomously, they must nevertheless function as part of the telecommunication administration as a whole. This means that for some input data they must rely on the other results, while some of their planning output can have an impact on other planning elsewhere. taken into account, e.g. by periodic d

30、iscussions between the different bodies or by other appropriate exchange of information. What has to be sought is a final plan which represents an overall economic optimum and not merely a collection of sub-optimizations. This underlines the need to give particular attention in general planning to t

31、he coordination of all interdependent planning functions. The organization of the administration must ensure that these repercussions are properly 2.1 Traffic forecasting: technical development long-term forecasts of all different kinds of (switched) traffic between various localities are primarily

32、the responsibility of the operating services; these services also plan routing and switching, .e. how this traffic is to be established by means of switched connections, for this purpose determining the location of switching centres and the number of circuits between each pair of centres as a functi

33、on of time. Nevertheless, over the short term, the factors affecting demand may not vary greatly, and a fairly good model of traffic development may be possible. Under ideal circumstances it may then be possible to calculate from the forecasting model the optimum stages of extension to route capacit

34、y. Even though the size of such jumps in traffic demand will be known less precisely, resources should be available to cope with them, if necessary by having to bring forward the next stage envisaged for provision. Encroaching on other capacity resources, e.g. emergency stand-by, should be avoided,

35、as this will result in a service degradation. Service degradation (which can also result from such causes as deferred circuit provisioning due to budget cuts) can easily lead to loss of revenue, increased costs for handlina comdainIs, etc., which can to a large extent offset the “savings“ on investm

36、ent. Since provision of either switching or transmission facilities requires time, it is essential that mutual information on changes liable to have far-reaching traffic effects should be exchanged as early as possible, to ensure coordination. The fact that forecasts are always uncertain makes it im

37、portant to consider the possible effects of the uncertainty. A not uncommon way of doing this is to make separate calculations of return on a proposed investment with a “pessimistic“ and an “over-optimistic“ forecast scenario, and check that neither gives wholly unacceptable results. Forecasting is

38、the subject of CCITT Recommendation E.506. As a rule, the short- and CCITnHANDBCOMXIITRPLEl .DOC COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTD-ITU-T HDBK HTP-ENGL 1793 48b257L Ob82080 79“ -6- 0.1 0.2 0.3 0.4 0.5 0.6 0.8 1 2 345681

39、0 20 30 40 50 60 80 100 a bc ta=- T1205030-92 FIGURE 1/2.1 Diagram for calculation of economic period of provision The foregoing example and the use of Figure 1/2.1 must be considered as an ideal application of the principle of an economic period of provision. In actual practice, however, it will be

40、 found that the period may be influenced by one or more of the following factors: a) the non-linear growth of subscribers; b) a possible saturation in the area concerned; c) the maintenance costs (including rearrangements in the existing network); d) premature replacement of cables in ducts, etc.; e

41、) efficient use of limited duct space, etc. In assessing the effects of the factors listed above, the following notes could be helpful: Any errors, which may have occurred due to the assumption of a linear increase of the number of subscribers with time, are corrected when the extension is planned.

42、At that time, in fact, all the technical/economic parameters included in the variable c should be reviewed and updated in the light of all the information available to the planner. This means that the actual curve of the annual demand for circuits for successive installations is only very approximat

43、ely a straight line. It is, however important for the planner to allow sufficient margin in his planning, in the form of reserve circuits, to overcome the inherent uncertainties of the forecasts and to prevent the next extension being needed significantly earlier than planned. Maintenance costs are

44、an essential component in economic comparisons and every effort should therefore by made to estimate them as accurately as possible. If they are omitted or estimated with appreciable inaccuracy, the results of economic studies may well be significantly affected. In planning a duct installation, acco

45、unt must be taken of any external restraints (such as the prohibition of any future excavations), which could override the normal economic considerations. In such cases, all future requirements along the route (such CCITTHANDWCOMXIITRPLV2El. DOC COPYRIGHT International Telecommunications Union/ITU T

46、elecommunicationsLicensed by Information Handling Servicesas the long-term requirements of the local and long distance networks, and any requirement for ducts rented by other companies, etc.), must be taken into account. The forecasts should be suitably rounded upwards, because the increased costs f

47、or the slightly larger duct installation are partially offset by the lower cost per ductway per unit length of the number of ductways increased. 2.2 Physical routing and route capacity From the operating point of view, a call to a particular destination can be offered to different traffic routes, vi

48、z. a first-choice high-usage route or to one or more alternative routes. From the transmission point of view, all of these traffic routes might be combined in a single physical route, .e. in the same transmission system. On the other hand a single large traffic group could be physically routed on a

49、number of separate systems (choosing preferably those following different physical routes). Again from the operating point of view, the marshalling of circuits into groups is purely a matter of an economic optimum for traffic handling. The classical calculations regarding the economic justification or not of an alternative route, and if so the economic dimensioning of a high- usage route, .e. the optimum proportion of traffic to be carried by a high-usage route rather than by an overflow route. traffic routes. Transmission groups on the other hand are of fixe