1、 International Telecommunication Union ITU-T L.19TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2010) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Multi-pair copper network cable supporting shared multiple services such as POTS, ISDN and xDSL
2、 Recommendation ITU-T L.19 Rec. ITU-T L.19 (05/2010) i Recommendation ITU-T L.19 Multi-pair copper network cable supporting shared multiple services such as POTS, ISDN and xDSL Summary Recommendation ITU-T L.19 describes some general considerations on services and systems, such as ISDN and xDSL, to
3、be supported by the access network. Some requirements for the digital local line characteristics are also given, as a factor contributing to the provision of good quality of service to the users. Furthermore, some issues for the use of multi-pair copper network cable supporting shared multiple servi
4、ces such as ISDN/xDSL are also described. This revision updates Recommendation ITU-T L.19 to include recent new or revised Recommendations for ADSL2 (ITU-T G.992.3, ITU-T G.992.4), ADSL2plus (ITU-T G.992.5) and VDSL (ITU-T G.993.1). History Edition Recommendation Approval Study Group 1.0 ITU-T L.19
5、1996-10-18 6 2.0 ITU-T L.19 2000-10-06 6 3.0 ITU-T L.19 2003-11-28 6 4.0 ITU-T L.19 2010-05-29 5 ii Rec. ITU-T L.19 (05/2010) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologi
6、es (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommuni
7、cation Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of
8、 information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operatin
9、g agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or
10、 some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice
11、 or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation developmen
12、t process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore s
13、trongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.19 (05/2010) iii CONTENTS Page 1 Scope 1 2 References. 1 3
14、 Definitions 2 4 Abbreviations 2 5 Conventions 2 6 General considerations 3 6.1 Objectives . 3 6.2 ISDN/xDSL technologies . 3 6.3 ISDN/xDSL: Technical problems 4 6.4 Transmission medium 4 7 Recommended DLL requirements for ISDN/xDSL . 5 7.1 Minimum digital local line requirements for ISDN/xDSL . 5 7
15、.2 Digital local line physical characteristics . 5 7.3 Principal electrical and transmission characteristics for ISDN/xDSL services and systems . 6 7.4 Use of a multi-pair copper network cable supporting shared multiple services such as POTS, ISDN and xDSL . 9 Appendix I Bridge taps: Effect of the l
16、oss due to the length of a bridge tap 10 I.1 Effect of BT loss in ISDN 10 I.2 Effect of BT loss in HDSL systems . 11 I.3 Effect of BT loss in ADSL and UADSL 11 Appendix II France Telecom experience 13 II.1 Mass deployment of ADSL: Loop qualification process . 13 II.2 Maximum reach of ADSL systems 13
17、 II.3 Field quality tests of the copper pair 13 Appendix III India experience 14 Appendix IV Brazil experience . 16 IV.1 Introduction 16 IV.2 Local loop requirements . 16 iv Rec. ITU-T L.19 (05/2010) Introduction The local subscriber network has been providing the means for subscriber connection to
18、the basic telephone service, without encountering any major transmission problems at voice frequencies (300 to 3400 Hz). With the evolution of transmission technologies, services and systems such as ISDN, HDSL, SHDSL, ADSL, ADSL2, ADSL2plus, VDSL and VDSL2 are being used into the existing copper lin
19、e. And there is now a trend also to support multiple services of one or more providers on common cables and in other parts of the network. This is called “unbundling the network“, i.e., more than one operator are sharing the network or are co-located in the same network. Providing the unbundling net
20、work makes crosstalk environment severer. Therefore, it is necessary to establish the quality of the subscriber loops for new services and systems such as ISDN, HDSL, SHDSL, ADSL, ADSL2, ADSL2plus, VDSL and VDSL2. Rec. ITU-T L.19 (05/2010) 1 Recommendation ITU-T L.19 Multi-pair copper network cable
21、supporting shared multiple services such as POTS, ISDN and xDSL 1 Scope This Recommendation deals with the general considerations and the requirements of the digital local line characteristics, which are used between the line termination and the network termination, to provide ISDN and xDSL services
22、. The field of home network is not addressed in this Recommendation. Moreover, this Recommendation describes the guidance for the use of multi-pair copper cable supporting shared multiple services such as ISDN/xDSL. The values used in this Recommendation are based on a number of DSL technologies as
23、they are known at the moment of publication of this Recommendation. However, the general principles are applicable to any type of DSL technology, generally referred to as xDSL. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this t
24、ext, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition
25、 of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.961 Recommendation ITU-T
26、G.961 (1993), Digital transmission system on metallic local lines for ISDN basic rate access. ITU-T G.991.1 Recommendation ITU-T G.991.1 (1998), High bit rate digital subscriber line (HDSL) transceivers. ITU-T G.991.2 Recommendation ITU-T G.991.2 (2003), Single-pair high-speed digital subscriber lin
27、e (SHDSL) transceivers. ITU-T G.992.1 Recommendation ITU-T G.992.1 (1999), Asymmetric digital subscriber line (ADSL) transceivers. ITU-T G.992.2 Recommendation ITU-T G.992.2 (1999), Splitterless asymmetric digital subscriber line (ADSL) transceivers. ITU-T G.992.3 Recommendation ITU-T G.992.3 (2009)
28、, Asymmetric digital subscriber line transceivers 2 (ADSL2). ITU-T G.992.4 Recommendation ITU-T G.992.4 (2002), Splitterless asymmetric digital subscriber line transceivers 2 (splitterless ADSL2). ITU-T G.992.5 Recommendation ITU-T G.992.5 (2009), Asymmetric digital subscriber line (ADSL) transceive
29、rs Extended bandwidth ADSL2 (ADSL2plus). ITU-T G.993.1 Recommendation ITU-T G.993.1 (2004), Very high speed digital subscriber line transceivers (VDSL). ITU-T G.993.2 Recommendation ITU-T G.993.2 (2006), Very high speed digital subscriber line transceivers 2 (VDSL2). ITU-T G.995.1 Recommendation ITU
30、-T G.995.1 (2001), Overview of digital subscriber line (DSL) Recommendations. 2 Rec. ITU-T L.19 (05/2010) ITU-T G.996.1 Recommendation ITU-T G.996.1 (2001), Test procedures for digital subscriber line (DSL) transceivers. ITU-T G.996.2 Recommendation ITU-T G.996.2 (2009), Single-ended line testing fo
31、r digital subscriber lines (DSL). ITU-T O.9 Recommendation ITU-T O.9 (1999), Measuring arrangements to assess the degree of unbalance about earth. IEC 62255-x IEC 62255-x (in force), Multicore and symmetrical pair/quad cables for broadband digital communications (High bit rate digital access telecom
32、munication networks) Outside plant cables. 3 Definitions For the purpose of this Recommendation, the definitions given in ITU-T G.961, G.991.x-series, G.992.x-series, ITU-T G.995.1 and in IEC 62255-x apply. 4 Abbreviations This Recommendation uses the following abbreviations: ADSL Asymmetric Digital
33、 Subscriber Line BT Bridged Tap DLL Digital Local Line DSL Digital Subscriber Line ELFEXT Equivalent Level Far-End crosstalk FEXT Far-End crosstalk HDSL High-speed Digital Subscriber Line ISDN Integrated Services Digital Network LCL Longitudinal Conversion Loss LT Line Termination NEXT Near-End cros
34、stalk NT Network Termination PSL Power Sum Loss SHDSL Single-pair High-speed Digital Subscriber Line UADSL Universal Asymmetric Digital Subscriber Line VDSL Very high-speed Digital Subscriber Line xDSL Any of the various types of Digital Subscriber Line systems 5 Conventions None. Rec. ITU-T L.19 (0
35、5/2010) 3 6 General considerations 6.1 Objectives Considering that the digital access section between the local exchange and the customer is a key element of the successful ISDN/xDSL services and systems, the following requirements for the network should be taken into account: the ability to operate
36、 on the existing two-wire unloaded lines, with open wires being excluded; the objective of achieving 100% cable fill for ISDN/xDSL services and systems without pair selection, cable rearrangements or the removal of bridged taps (BTs); the objective of being able to extend the new ISDN/xDSL services
37、and systems to the majority of customers without the use of regenerators. In the remaining few cases special arrangements may be required; the coexistence, in the same cable unit, with most of the existing services such as telephony and voiceband data transmission; various national regulations conce
38、rning electro-magnetic compatibility (EMC); the provision of power feeding via the network under normal or restricted modes; the provision of the capability to support maintenance functions. 6.2 ISDN/xDSL technologies The most important technologies, shown in Table 1, are: ISDN ITU-T G.961 basic acc
39、ess, which offers 160 kbit/s (2B + D) full duplex. HDSL ITU-T G.991.1, which offers 2 Mbit/s in each direction, but requires up to three copper pairs. SHDSL ITU-T G.991.2, which offers 2 Mbit/s in each direction over a single copper pair. ADSL ITU-T G.992.1, which offers up to 8 Mbit/s (in case of I
40、TU-T G.992.2 ADSL, 1.5 Mbit/s) bandwidth in downstream for fast Internet access but not video applications. ADSL2 ITU-T G.992.3, which offers up to 8 Mbit/s (in case of ITU-T G.992.4 ADSL, 1.536 Mbit/s) bandwidth in downstream for fast Internet access but not video applications. ADSL2plus ITU-T G.99
41、2.5, which offers up to a minimum of 16 Mbit/s bandwidth in downstream for fast Internet access but not video applications. VDSL ITU-T G.993.1, which offers up to tens of Mbit/s bandwidth in downstream for fast Internet access but not video applications. VDSL2 ITU-T G.993.2, which offers up to 200 M
42、bit/s at a bidirectional net data rate (the sum of upstream and downstream rates). The technologies considered in this clause were the most popular ones at the time of approval of this Recommendation. The list should be revised according to the development of new processes. 4 Rec. ITU-T L.19 (05/201
43、0) Table 1 xDSL rates xDSL “family“ Data rate (downstream) References ISDN 160 kbit/s ITU-T G.961 ADSL (ADSL2) up to 8 Mbit/s (or above) ITU-T G.992.1, ITU-T G.992.2, ITU-T G.992.3, ITU-T G.992.4 ADSL2plus Min. 16 Mbit/s ITU-T G.992.5 HDSL 2 Mbit/s ITU-T G.991.1 SHDSL up to 2 Mbit/s ITU-T G.991.2 VD
44、SL tens of Mbit/s ITU-T G.993.1 VDSL2 200 Mbit/s (downstream + upstream) ITU-T G.993.2 6.3 ISDN/xDSL: Technical problems Technical problems can occur with ISDN/xDSL-based services when more than one operator share pairs in the same cable. The degree of interference between different applications, in
45、 the same cable, depends on the technology used and the physical characteristics of the cabling (separation between pairs, insulation used, etc.). High-powered technology such as ADSL creates the greatest interference problems. There are five main technical challenges to use ISDN/xDSL services: the
46、need to preserve the integrity of existing services: The interference created by xDSL loops can cause existing services (e.g., ISDN, HDSL on leased lines) to fail or to operate with significantly inferior performance; the need to modify line testing procedures: The presence of the ADSL modem in the
47、local loop complicates line testing; a requirement to minimize interference between ISDN/xDSL transmission technologies; a need to maximize the use of local loops for broadband xDSL services; how best to select lines for xDSL use: Not all lines are suitable for ADSL. The most important factor preven
48、ting the use of ADSL is signal loss. This is dependent on distance, but the exact distance over which ADSL will operate also depends on the characteristics of the loop and the intended data rate. Other factors also affect performance (e.g., noise, crosstalk or radio-frequency interference, etc.). 6.
49、4 Transmission medium The transmission medium over which the digital transmission system is expected to operate is the access copper network which connects customers to the local exchange, or street cabinets, via local lines. This network employs cables of copper pairs to provide services to customers. A copper local line is expected to be able to simultaneously carry bidirectional digital transmission providing ISDN/xDSL rates between the line termination (LT) and th
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