1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STAN DARD IZATI ON SECT0 R OF ITU G.992.1 (06199) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Digital sections and digital line system - Access networks Asymmetric digital subscrib
2、er line (ADSL) transceivers ITU-T Recommendation G.992.1 (Previously CCITT Recommendation) INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/99) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Digital
3、 sections and digital line system - Access networks Asymmetric digital subscriber line (ADSL) transceivers ITU-T Recommendation G.992.1 (Previously CCITT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AN
4、D CIRCUITS INTERNATIONAL ANALOGUE CARRIER SYSTEM GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- TRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE WITH METALLIC LINES SYSTEMS
5、 ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TESTING EQUIPMENTS TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM General Parameters for optical fib
6、re cable systems Digital sections at hierarchical bit rates based on a bit rate of 2048 kbitis Digital line 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
7、customer access to ISDN Optical fibre submarine cable systems Optical line systems for local and access networks Access networks G. 1 00-G. 199 G .200-G .299 G .300-G. 399 G.4004.449 G.450-G .499 G.600-G.699 G .700-G .799 G.80-G.899 G.900-G.999 G .900-G .909 G.91-G.919 G.920-G.929 G.930-G.939 G .940
8、-G .949 G.950-G.959 G .960-G .969 G.970-G.979 G .98O-G .989 G .99-G ,999 Forjrther details, please refer to TU-T List of Recommendations. ITU-T RECOMMENDATION G.992.1 ASYMMETRIC DIGITAL SUBSCRIBER LINE (ADSL) TRANSCEIVERS Summary This Recommendation describes Asymmetric Digital Subscriber Line (ADSL
9、) Transceivers on a metallic twisted pair that allows high-speed data transmission between the network operator end (ATU-C) and the customer end (ATU-R). This Recommendation provides a variety of bearer channels in conjunction with one of three other services dependent on the environment: 1) ADSL tr
10、ansmission simultaneously on the same pair with voice (band) service; 2) ADSL transmission simultaneously on the same pair with G.961 (Appendix I or 11) ISDN services; or 3) ADSL transmission on the same pair with voiceband transmission and with TCM-ISDN (G.961 Appendix III in an adjacent pair. Syst
11、ems allow approximately 6 Mbits downstream and approximately 640 kbit/s upstream data rates depending on the deployment and noise environment. This Recommendation specifies the physical layer characteristics of the Asymmetric Digital Subscriber Line (ADSL) interface to metallic loops. This Recommend
12、ation has been written to help ensure the proper interfacing and interworking 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 shall be ensured when these two units are manufactur
13、ed and provided independently. A single 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). An ADSL transmission unit can simultaneously convey
14、 all of the following: downstream simplex bearers, duplex bearers, a baseband analogue duplex channel, and ADSL line overhead for framing, error control, operations and maintenance. Systems support a minimum of 6.144 Mbit/s downstream and 640 kbit/s upstream. This Recommendation includes mandatory r
15、equirements, 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. Two categories of performance are specified. Category I performance is requir
16、ed for compliance with this Recommendation; performance enhancement options are not required for category I equipment. Category II is a higher level of performance (i.e. longer lines and greater impairments). Category II performance and characteristics are not required for compliance with this Recom
17、mendation. This Recommendation defines several optional capabilities and features: e echo cancellation; e trellis coded modulation; e dual latency; e transport of a network timing reference; 8 transport of STM andor ATM; 8 reduced overhead framing modes. It is the intention of this Recommendation to
18、 provide, by negotiation during initialization, for U-interface compatibility and interoperability between transceivers complying to this Recommendation and between transceivers that include different combinations of options. Source ITU-T Recommendation G.992.1 was prepared by ITU-T Study Group 15 (
19、1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 22 June 1999. Recommendation G.992.1 (06/99) 1 STD*ITU-T RECMN G-992*L-ENGL 1999 W 48b259L Ob70442 827 W FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunic
20、ations. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The 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 Teleco
21、mmunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in
22、WTSC Resolution No. 1. In some 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 IIAdministrationtl is used for conciseness to indicate both a telecommunication
23、 administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, valid
24、ity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had received notice of intellectual property, protected by patents, which may be requi
25、red to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2000 All rights reserved. No part of this publication may be reproduced or utilized in any form or b
26、y any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. 11 Recommendation G.992.1 (06/99) 1 1.1 1.2 2 3 4 5 5.1 5.2 5.3 6 6.1 6.2 6.3 7 7.1 7.2 , 7.3 7.4 CONTENTS Scope . System reference model Objectives . References . Definitions Abb
27、reviations Reference Models . ATU-C transmitter reference models 5.1.1 ATU-C transmitter reference model for STM transport 5.1.2 ATU-C transmitter reference model for ATM transport . ATU-R transmitter reference models 5.2.1 ATU-R transmitter reference model for STM transport 5.2.2 ATU-R transmitter
28、reference model for ATM transport . ATU-C/R transmitter timing model (Annex C only) Transport capacity . Transport of STM data Transport of ATM data . ADSL system overheads and total bit rates ATU-C functional characteristics . STM Transmission Protocol Specific functionalities . 7.1.1 7.1.2 Downstr
29、eam simplex channels - bit rates . 7.1.3 Downstreamupstream duplex channels - bit rates . 7.1.5 Framing Structure for STM transport ATM Transport Protocol Specific functionalities . 7.2.1 7.2.2 Payload transfer delay 7.2.3 7.2.4 Network timing reference (NTR) 7.3.1 Need for NTR 7.3.2 Transport of th
30、e NTR Framing . 7.4.1 Data symbols . ATU-C input and output V interfaces for STM transport . 7.1.4 Payload transfer delay ATU-C input and output V interface for ATM transport ATM Cell specific functionalities . Framing Structure for ATM transport . Recommendation G.992.1 (06/99) Page 1 2 2 3 3 6 9 9
31、 10 11 12 12 13 13 14 15 16 17 18 19 19 19 19 20 20 20 20 21 21 23 24 24 24 25 25 . 111 7.5 7.6 7.7 7.8 7.9 7.10 7.1 1 I I 7.12 7.13 7.14 7.15 7.16 8 8.1 8.2 7.4.2 Synchronization . 7.4.3 Reduced overhead framing Scramblers Forward error correction . 7.6.1 Reed-Solomon coding . 7.6.2 Reed-Solomon Fo
32、rward Error Correction Superframe Synchronization . 7.6.3 Interleaving 7.6.4 Support of higher downstream bit rates with S = 1/2 (optional) Tone ordering Constellation encoder (trellis code version) . 7.8.1 Bit extraction . 7.8.2 Bit conversion 7.8.3 Coset partition and trellis diagram . 7.8.4 Const
33、ellation encoder Constellation encoder - No trellis coding . 7.9.1 Bit extraction . 7.9.2 Constellation encoder Gain scaling Modulation 7.1 1.1 Subcarriers . 7.1 1.2 Modulation by the inverse discrete Fourier transform (IDFT) 7.1 1.3 Synchronization symbol Cyclic prefix Transmitter dynamic range . 7
34、.13.1 Maximum clipping rate . 7.13.2 Noise/distortion floor . ATU-C Downstream Transmitter spectral masks . 7.1 1.4 Inverse synchronization symbol (Annex C only) Dual Bitmapping and Rate Conversion (Annex C only) FEXT Bitmapping (Annex C only) . ATU-R Functional Characteristics . STM Transmission Pr
35、otocol Specific functionalities . Downstream simplex channels - Transceiver bit rates Framing Structure for STM transport ATM Transport Protocol Specific functionalities . ATU-R input and output T interfaces for ATM transport . 8.1.1 8.1.2 8.1.3 8.1.4 ATU-R input and output T interfaces for STM tran
36、sport Duplex channels - Transceiver bit rates 8.2.1 Page 33 35 37 38 38 38 38 39 40 42 42 43 43 47 50 50 50 50 51 51 51 52 52 53 53 53 53 54 54 54 54 54 54 55 55 55 56 56 iv Recommendation G.992.1 (06199) 8.2.2 8.2.3 ATM Cell specific functionalities . Framing Structure for ATM transport . 8.3 Netwo
37、rk timing reference . 8.4 Framing . 8.4.1 Data symbols . 8.4.2 Synchronization . 8.4.3 Reduced overhead fiaming 8.5 Scramblers 8.6 Forward error correction . 8.7 Tone ordering 8.8 Constellation encoder - Trellis version 8.9 Constellation encoder - Uncoded version 8.10 Gain scaling 8.1 1 Modulation 8
38、.1 1.1 Subcarriers . 8.1 1.2 8.1 1.3 Synchronization symbol 8.1 1.4 Inverse synchronization symbol (Annex C only) 8.12 Cyclic prefix 8.13 Transmitter dynamic range . 8.13.1 Maximum clipping rate . 8.13.2 Noise/distortion floor . Modulation by the inverse discrete Fourier transform . 8.14 8.15 8.16 A
39、TU-R Upstream Transmitter spectral response FEXT Bitmapping (Annex C only) . Dual Bitmapping and Rate Conversion (Annex C only) 9 EOC Operations and Maintenance 9.1 Clear EOC . 9.2 Embedded operations channel (EOC) requirements . 9.2.1 EOC organization and protocol . 9.2.2 EOC message structure 9.2.
40、3 EOC message sets 9.2.4 Data registers in the ATU-R 9.2.5 EOC protocol states . In-service performance monitoring and surveillance 9.3.1 ADSL line related primitives . 9.3.2 9.3.3 9.3.4 9.3 STM data path related primitives ATM data path related primitives Other ADSL indicators, parameters and signa
41、ls Recommendation G.992.1 (06199) Page 56 56 57 57 57 61 63 63 63 63 64 64 64 64 64 65 65 65 65 65 65 65 66 66 66 66 66 67 67 67 68 72 73 80 81 83 83 85 V 9.4 9.5 10 10.1 10.2 10.3 10.4 10.5 10.6 vi Failures and Performance Parameters . Test Parameters . 9.5.1 Near-end test parameters . 9.5.2 Far-en
42、d test parameters Initialization Overview . 1 O . 1 . 1 Basic functions of initialization . 1 O . 1.2 Transparency to methods of separating upstream and downstream signals . . 1 O . 1.3 Implementation of service options for ADSL 1 O . 1.4 Resetting during initialization and data transmission 1 O . 1
43、.5 Initialization with Hyperframe (Annex C only) . Handshake - ATU-C . 10.2.1 CL messages 10.2.2 MS messages . Handshake - ATU-R . 10.3.1 CLR messages . 10.3.2 MS messages . Transceiver training - ATU-C 10.4.1 C-QUIET2 . 10.4.2 C-PILOT1 10.4.3 C-PILOTIA . 10.4.4. C-QUIET3A 10.4.5 C-REVERB1 . 10.4.6
44、C-PILOT2 10.4.7 C-ECT 10.4.8 C-REVERB2 . 10.4.9 C-QUIET5 . 1 0.4.1 O C-PILOT3 10.4.1 1 C-REVERB3 . Transceiver training - ATU-R 10.5.1 R-QUIET2 . 10.5.2 R-REVERB1 . 10.5.3 R-QUIET3 . 10.5.4 R-ECT 10.5.5 R-REVERB2 . Channel analysis (ATU-C) 10.6.1 C-SEGUE1 10.6.2 C-RATES1 . 10.6.3 C-CRCl . Recomrnend
45、a tion G.992.1 (06/99) Page 85 85 85 86 86 86 86 87 87 87 88 88 88 88 89 89 90 91 91 91 92 92 92 93 93 93 93 93 93 93 93 94 94 94 95 95 95 95 96 10.7 10.8 10.9 STD-ITU-T RECMN G.992.1-ENGL 1999 W 48b259L Ob70447 309 Page 10.6.4 C-MSG1 97 10.6.5 C-CRC2 . 98 10.6.6 C-MEDLEY . 98 . Channel analysis (AT
46、U-R) 10.7.1 R-SEGUE1 10.7.2 R-REVERB3 . 10.7.3 R-SEGUE2 10.7.4 R-RATES1 . 10.7.5 R-CRC1 . 10.7.6 R-MSG1 . 10.7.7 R-CRC2 . 1 0.7.8 R-MEDLEY . 10.7.9 R-REVERB4 . Exchange - ATU-C . 10.8.1 C-REVERB4 . 10.8.2 C-SEGUE2 10.8.3 C-RATES-RA 10.8.4 C-CRC-RA1 10.8.5 C-MSG-RA 10.8.6 C-CRC-RA2 10.8.7 C-REVERB- R
47、A . 10.8.8 C-SEGUE-RA . 10.8.9 C-MSG2 . 10.8.10 C-CRC3 . 10.8.1 1 C-RATES2 . 10.8.12 C-CRC4 . 10.8.13 C-B The ADSL occupies a frequency band above the ISDN, and is separated from it by filtering; data services), and with ISDN as defined in Recommendation G.961 Appendix III in an adjacent pair. In th
48、e direction from the network operator to the customer premises (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. The transmission sys
49、tem is designed to operate on two-wire twisted metallic cable pairs with mixed gauges. This Recommendation is based on the use of cables without loading coils, but bridged taps are acceptable in all but a few unusual situations. Specifically, this Recommendation: e e e defines the combined options and ranges of the simplex and full-duplex bearer channels defines the line code and the spectral composition of the signals transmitted by both ATU-C specifies the transmit signals at both the ATU-C and ATU-R; describes the organization of transmitted and received data into frames; defin
