1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.995.1 (02/2001) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system - Access networks Overview of digital subscriber line (DSL) Recommendations IT
2、U-T Recommendation G.995.1 (Formerly CCITT Recommendation) INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.995.1 (02/200 1 ) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system - Access networks
3、 Overview of digital subscriber line (DSL) Recommendations ITU-T Recommendation G.995.1 (Formerly CCITT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS TRANSMISSION SYSTEMS GENERAL CHARACTERI
4、STICS COMMON TO ALL ANALOGUE CARRIER- INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TESTING EQUIPMENTS TRANSMISSION MEDIA CHARACTERIST
5、ICS DIGITAL TERMINAL EQUIPMENTS DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH Gen er a 1 Parameters for optical fibre cable systems Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s Digital lin
6、e transmission systems on cable at non-hierarchical bit rates Digital line systems provided by FDM transmission bearers Digital line systems Digital section and digital transmission systems for customer access to ISDN Optical fibre submarine cable systems Optical line systems for local and access ne
7、tworks Access networks G.1004.199 G.200-G.299 G.300-G.399 G.400-G.449 G.4504.499 G.500-G.599 G.600-G.699 G.700-G.799 G.800-G.899 G.900-G.999 G.900-G.909 G.9 1 O-G.9 1 9 G.920-G.929 G.930-G.939 G.940-G.949 G.950-G.959 G.9604.969 G.970-G.979 G.980-G.989 G.99-G.999 For further details, please refer to
8、the list of ITU-T Recommendations ITU-T Recommendation 6.995.1 Overview of digital subscriber line (DSL) Recommendations Summary This Recommendation provides the necessary guidance and an overview of the DSL family of Recommendations and is therefore informative. It also describes how the various Re
9、commendations in this family are related. It also contains a definition of a generic system reference configuration and how it relates to the system reference models of the DSL Recommendations. Additionally, the definition of a generic protocol reference architecture for DSL Recommendations and deri
10、vations of the appropriate user or management plane protocol reference architectures for the DSL Recommendations is included. Illustrations of the data service presentation options using the DSL Recommendations are also provided. A glossary of the terms used in the DSL Recommendations is also includ
11、ed. Source ITU-T Recommendation G.995.1 was revised by ITU-T Study Group 15 (2001-2004) and approved under the WTSA Resolution 1 procedure on 9 February 2001. ITU-T G.995.1 (02/2001) 1 .FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of
12、telecommunications. 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 Te
13、lecommunication 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
14、 areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized
15、 operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice 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 Intellec
16、tual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. Howeve
17、r, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2002 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, inclu
18、ding photocopying and microfilm, without permission in writing from ITU. 11 ITU-T G.995.1 (02/2001) CONTENTS 1 2 3 4 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 6 6.1 6.2 7 7.1 7.2 8 Scope . Revision History . Definitions Abbreviations Overview of the Family of DSL Recommendations ITU-T G.992.1: Asymmetric Di
19、gital Subscriber Line (ADSL) Transceivers ITU-T G.992.2: Splitterless asymmetrical digital subscriber line (ADSL) transceivers . ITU-T G.991.1: High bit rate digital subscriber line (HDSL) transceivers ITU-T G.991.2: Single-pair High-speed Digital Subscriber Line (SHDSL) transceivers . ITU-T G.994.1
20、: Handshake procedures for digital subscriber line (DSL) transceivers . ITU-T G.997.1: Physical layer management for digital subscriber line (DSL) transceivers . ITU-T G.996.1: Test procedures for digital subscriber line (DSL) transceivers Relationship among the DSL Recommendations . The Reference C
21、onfiguration for ITU-T G.99-series Recommendations Generic Reference configuration . Relation of the Generic Reference Configuration to the ITU-T G.99- series Recommendations . 6.1.1 Reference Layered Protocol Architecture for ITU-T G.99 Recommendations Illustration of Data Service Using DSL Recomme
22、ndations . End-To-End Data-Centric Connection . Illustration of Service Presentation Options . 7.2.1 Service Presentation at the T interface 7.2.2 Service Presentation at the U interface Glossary of Terms in DSL Recommendations . Appendix I . Bibliography ITU-T G.995.1 (02/2001) Page 1 1 1 1 3 3 4 5
23、 6 7 7 7 7 9 9 10 17 21 21 22 22 23 25 27 . 111 ITU-T Recommendation G.995.1 Overview of digital subscriber line (DSL) Recommendations 1 Scope This Recommendation provides an overview of the family of DSL Recommendations. It describes how the various DSL Recommendations are related. This Recommendat
24、ion also defines a generic system reference and a protocol reference configuration for DSL Recommendations and relates it to the system reference models of the DSL Recommendations. This Recommendation is of informative nature and does not imply any specific requirements. 2 Revision History This revi
25、sion of ITU-T G.995.1 adds more clauses and text with regard to ITU-T G.991.2 and Annex WG.992.2. Specifically, it adds: - - - Text in clause 5.1 that introduces Annex H/G.992.1. Clause 5.4 that introduces ITU-T G.991.2. Text in clause 5.8 that describes relationship of ITU-T G.991.2 and Annex H/G.9
26、92.1 with the existing DSL Recommendations. Clause 6.1.1.4, that discusses the alignment of the G.99 1.2 system reference model with the G.995.1 reference configuration. Text in clause 6.2 that describes the user plane protocol reference architecture for ITU-T G.991.2. - - 3 Definitions This Recomme
27、ndation defines the following terms: 3.1 DSL Recommendations: The family of ITU-T Recommendations G.991.1, G.992.1, G.992.2, G.994.1, G.995.1, G.996.1 and G.997.1. 3.2 XDSL: Any of the various types of digital subscriber lines. 4 Abbreviations This Recommendation uses the following abbreviations: 2B
28、1Q 2 Binary 1 Quaternary ADSL Asymmetric Digital Subscriber Line ATM Asynchronous Transfer Mode ATU ADSL Transceiver Unit ATU-C ATU-R C Common circuitry CAP Carrier-less Amplitude and Phase CO Central Office ADSL Transceiver Unit-Central Office End ADSL Transceiver Unit-Remote Terminal End 1 ITU-T G
29、.995.1 (02/2001) CPE DLL DSL GI1 H HDSL h-P HSS-TC HSTU HSTU-C HSTU-R I ISDN ISP 1-P LTU M MPS-TC NT 1 NT2 NTU PHY PMD PMS-TC POTS REG SM SNI STM TA TC TCM TPS-TC XNI XTU XTU-C XTU-R Customer Premises Equipment Digital Local Line Digital Subscriber Line Global Information Infrastructure HDSL transce
30、iver High Bit Rate Digital Subscriber Line high-pass Handshake Specific-Transmission Convergence Handshake Transceiver Unit Handshake Transceiver Unit-Central office end Handshake Transceiver Unit-Remote terminal end Interface Integrated Services Digital Network Internet Service Provider Low-pass Li
31、ne Termination Unit Mapping Management Protocol Specific-Transmission Convergence Network Termination 1 Network Termination 2 Network Termination Unit Physical Layer Physical Media Dependant Physical Media Specific-Transmission Convergence Plain Old Telephony Service Regenerator Service Module Servi
32、ce Node Interface Synchronous Transfer Mode Terminal Adapter Transmission Convergence Time Compressed Multiplex Transport Protocol Specific-Transmission Convergence Access Network Interface xDSL Transceiver Unit xDSL Transceiver Unit-Central Office End xDSL Transceiver Unit-Remote Terminal End 2 ITU
33、-T 6.995.1 (02/2001) 5 The family of DSL Recommendations includes the following: ITU-T G.992.1, G.992.2, G.99 1.1, G.991.2, G.996.1, G.994.1, G.997.1 and G.995.1. ITU-T G.991.1, G.991.2, G.992.1 and G.992.2 have developed techniques for transmitting a range of bit rates over the existing copper loca
34、l network from relatively short distances at high bit rates, and to long distances at relatively lower bit rates. ITU-T G.994.1, G.996.1, and G.997.1 support ITU-T G.992.1 and G.992.2 by providing common handshake, management and testing procedures. These Recommendations include mandatory requiremen
35、ts, recommendations and options; these are designated by the words “shall“, khould“ and “may“, respectively. The word “will“ is used only to designate events that take place under some defined set of circumstances. In clauses 5.1-5.7, the DSL Recommendations have been introduced. In clause 5.8, the
36、relationship of these Recommendations with each other is described. Overview of the Family of DSL Recommendations 5.1 ITU-T G.992.1 specifies the physical layer characteristics of the Asymmetric Digital Subscriber Line (ADSL) interface to metallic loops. ITU-T G.992.1 has been written to help ensure
37、 the proper interfacing and intenvorking of ADSL transmission units at the customer end (ATU-R) and at the network operator end (ATU-C) and also to define the transport capability of the units. Proper operation is to be ensured when these two units are manufactured and provided independently. A sing
38、le twisted pair of telephone wires is used to connect the ATU-C to the ATU-R. The ADSL transmission units must deal with a variety of wire pair characteristics and typical impairments (e.g. crosstalk and noise). The transmission system is designed to operate on two-wire twisted metallic cable pairs
39、with mixed gauges. ITU-T G.992.1 is based on the use of cables without loading coils, but bridged taps are acceptable in all but a few unusual situations. An ADSL transmission unit can simultaneously convey all of the following: downstream simplex bearers, duplex bearers, a baseband analogue duplex
40、channel, and ADSL line overhead for framing, error control, operations, and maintenance. ITU-T G.992.1 supports a minimum of 6.144 Mbit/s downstream and 640 kbit/s upstream net data rate. Two categories of performance are specified. Category I performance is required for compliance with ITU-T G.992.
41、1; performance enhancement options are not required for category I equipment. Category II is a higher level of performance. Category II performance and characteristics are not required for compliance with ITU-T G.992.1. ADSL provides a variety of bearer channels in conjunction with other services: -
42、 ITU-T G.992.1: Asymmetric Digital Subscriber Line (ADSL) Transceivers ADSL transmission on the same pair with voiceband transmission (including POTS and voiceband data services). ADSL transmission on the same pair with ISDN, as defined in Appendices I and WG.961. The ADSL occupies a frequency band
43、above the ISDN, and is separated from it by filtering. ADSL transmission on the same pair with voiceband transmission (including POTS and voiceband data services), and with ISDN in an adjacent pair as defined in Appendix IIUG.961. In the direction from the network operator to the customer premises (
44、i.e. downstream) the bearer channels may consist of full duplex low-speed bearer channels and simplex high-speed bearer channels; in the other direction (i.e. upstream) only low-speed bearer channels are provided. - - - ITU-T G.995.1 (02/2001) 3 Specifically, ITU-T G.992.1: - defines the combined op
45、tions and ranges of the simplex and full-duplex bearer channels provided; defines the line code and the spectral composition of the signals transmitted by both ATU-C and ATU-R; specifies the transmit signals at both the ATU-C and ATU-R; describes the electrical and mechanical specifications of the n
46、etwork interface; describes the organization of transmitted and received data into frames; defines the functions of the operations channel; defines the ATU-R to service module(s) interface functions; defines the Transmission Convergence Sub-layer for ATM transport. - - - - - - - In separate annexes
47、it also: - describes the transmission technique used to support the simultaneous transport on a single twisted-pair of voiceband services and both simplex and duplex bearer channels; describes the transmission technique used to support the simultaneous transport on a single twisted-pair of ISDN serv
48、ices as defined in Appendices I and IUG.961, and both simplex and duplex bearer channels; describes the transmission technique used to support the simultaneous transport on a single twisted-pair of voiceband services and both simplex and duplex bearer channels when they are subject to cross-talk fro
49、m ISDN as defined in Appendix IWG.96 I ; describes those specifications that are unique to Synchronized Symmetric Digital Subscriber Line (SSDSL) transceivers for use in the same cable binder as TCM-ISDN defined in ITU-T Appendix IIUG.961. This SSDSL transmission method allows symmetric data rates in the range of 192 kbit/s to 1.6 Mbit/s with 32 kbit/s granularity using a scheme synchronized with TCM-ISDN. The 1.544 Mbit/s STM data transport capability is optionally supported. - - - ITU-T G.992.1 defines several optional capabilities and features: - echo cancellation; - trellis code
