1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.995.1 Amendment I (11/2001) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system - Access networks Overview of digital subscriber line (DSL) Recomm
2、endations Amendment I ITU-T Recommendation G.995.1 (2001) - Amendment I INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.995.1 Amendment 1 (1 1/2001) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line
3、system - Access networks Overview of digital subscriber line (DSL) Recommendations Amendment I ITU-T Recommendation G.995.1 (2001) - Amendment 1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS TRANSMISSION S
4、YSTEMS GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES COORDINA
5、TION OF RADIOTELEPHONY AND LINE TELEPHONY TESTING EQUIPMENTS TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TERMINAL EQUIPMENTS DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM General Parameters for optical fibre cable systems Digital sections at hierarchical bit rates based on a bit rate of 2
6、048 kbit/s 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 customer access to ISDN Optical fibre submarine cable systems Optical line systems f
7、or local and access networks Access networks G.1004.199 G.200-G.299 G.3004.399 G.4004.449 G.450-G.499 G.500-G.599 G.600-G.699 G .700-G .799 G.8004.899 G.900-G.909 G.9204.929 G.930-G.939 G.94cG.949 G.9504.959 G.97M.979 G.98M.989 G.990-G.999 G.900-G.999 G .9 10-G.9 19 G.960-G.969 For further details,
8、please refer to the list of ITU-T Recommendations. ITU-T Recommendation G.995.1 Overview of digital subscriber line (DSL) Recommendations Amendment 1 Source Amendment 1 to ITU-T Recommendation G.995.1 (2001) was prepared by ITU-T Study Group 15 (200 1-2004) and approved under the WTSA Resolution 1 p
9、rocedure on 29 November 200 1. ITU-T Rec. G.995.1 (2001)/Amd.l (11/2001) 1 FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T
10、 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 Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study
11、 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 information technology which fall within ITU-Ts purview, the necessary standards are prepared on a co
12、llaborative 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 operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or imp
13、lementation 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 development proce
14、ss. 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. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urg
15、ed to consult the TSB patent database. O ITU 2002 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. 11 ITU-T Rec. G.995.1 (200l)/Amd.1 (11/2001) CONTENTS Page 1) Clause 5.8 . 1 2) New clause 5.9 1 3) New subclaus
16、e 6.1.1.8 2 ITU-T Rec. G.995.1 (2001)/Amd.l (11/2001) iii ITU-T Recommendation G.995.1 Overview of digital subscriber line (DSL) Recommendations Amendment 1 1) Clause 5.8 Add the following text as the 7thparagraph of clause 5.8: G.99 DSL Recommendations facilitate transmission of digital data over t
17、he copper pair. G.993.1 provides a foundation for transceivers that may support both asymmetric and symmetric operations at much higher data rates when compared to G.991.1 and G.991.2 for symmetric date rates and G.992.1 and G.992.2 for asymmetric data rates. In the Fibre-to-the-exchange (FTTEx) typ
18、e of deployment, G.993.1 transceivers would provide less loop plant coverage than the G.991.1, G.991.2, G.992.1 and G.992.2 transceivers. The coverage can however be increased using the Fibre-to-the-cabinet (FTTCab) type of deployment. G.993.1 based transceivers would be able to coexist with underly
19、ing narrow-band POTS or ISDN services, as is the case with G.992.1 and G.992.2. The Network Operators would also be able to choose to provide VDSL on access lines without any narrow-band services. 2) New clause 5.9 Add new clause 5.9 as follows: 5.9 ITU-T G.993.1 VDSL (Very high speed Digital Subscr
20、iber Lines) permits the transmission of asymmetric and symmetric aggregate data rates up to tens of Mbits on twisted pairs. G.993.1 is an access technology that exploits the existing infrastructure of copper wires that were originally deployed for POTS services. While POTS uses approximately the low
21、er 4 kHz and ADSL/HDSL use approximately 1 MHz of the copper wire spectrum, G.993.1 uses up to 12 MHz of the spectrum. G.993.1 includes worldwide frequency plans that allow asymmetric and symmetric services in the same group of wire pairs (known as a binder). This is accomplished by designating band
22、s for the transmission of upstream and downstream signals. G.993.1 transceivers must overcome many types of ingress interference from radio and other transmission techniques that occur in the same frequencies of typical deployment scenarios. Similarly, G.993.1 transmission power transmission levels
23、have been designed to minimize potential egress interference into other transmission systems. As with other Recommendations in the G.99 series, G.993.1 uses G.994.1 to handshake and initiate the transceiver training sequence. ITU-T G.993.1 supports a Fibre to the Node deployment architecture with an
24、 Optical Network Unit (ONU) appropriately placed in the existing metallic access network and the Local Exchange or Central Office deployment architecture without an ONU. The first architectural model covers Fibre- to-the-cabinet (FTTCab) type of deployment; the second one is Fibre-to-the-exchange (F
25、TTEx) type of deployment. Existing unscreened twisted metallic access wire-pairs are used to convey the signals to and from the customers premises. ITU-T G.993.1 provides two or four data paths with bit rate under the control of the network operator, consisting of one or two downstream and one or tw
26、o upstream data paths. A single path in each direction can be of high latency (with lower BER expected) or lower latency (with higher BER expected). Dual paths in each direction provide one path of each type. The dual latency ITU-T G.993.1: Very high speed digital subscriber line foundation ITU-T Re
27、c. G.995.1(2001)/Amd.l (11/2001) 1 configuration is thought to be the minimum that is capable of supporting a sufficient full service set, although it is possible to support both the single latency model with programmable latency, or two pathslatencies. The model assumes that Forward Error Correctio
28、n (FEC) will be needed for part of the payload and that deep interleaving will be required to provide adequate protection against impulse noise. G.993.1 provides for service-splitter functional blocks to accommodate shared use of the physical transmission media for VDSL and either POTS or ISDN-BA. T
29、he rationale behind this is to provide network operators freedom to evolve their networks in one of two ways: complete change out or overlay. Support for active Network Termination (NT) in G.993.1 provides termination of the point- to-point VDSL transmission system and presents a standardized set of
30、 User Network Interfaces (UNI) at the customers premises. The NT provides the network operator with the ability to test the network up to the UNI at the customers premises in the event of a fault condition or via nighttime routine checks. The home wiring transmission system is outside the scope of G
31、.993.1. It is envisaged that G.993.1 will find applications in the transport of various protocols. For each transport protocol, different functional requirements must be developed for the Transport Protocol Specific - Transmission Convergence Layer (TPS-TC). This specification covers the functional
32、requirements for the transport of Asynchronous Transfer Mode (ATM) and Packet Transfer Mode (PTM). However the G.993.1 core transceiver would be capable of supporting future additional transport protocols. VDSL service would non-invasively coexist with the narrow-band services on the same pair. Fail
33、ure of power to the VDSL NT or failure of the VDSL service shall not affect any existing narrow-band services. This may imply that the splitter filter is of a passive nature not requiring external power in order to provide frequency separation of the VDSL and existing narrow-band signals. POTS, if p
34、resent, shall continue to be powered from the existing exchange node and a DC path is required from the local exchange to the customer telephone. Similarly a DC path is required for ISDN-BA in order to provide remote power feeding to the ISDN-BA NT. POTS and ISDN-BA cannot exist simultaneously on th
35、e same pair at present. Network Operators may provide one or the other but not both over a single wire-pair. Network Operators may choose to provide VDSL on access lines without any narrowlband services. The VDSL NT is not required to be powered remotely. Also, repeatered operation is not required f
36、or G.993.1. 3) New subclause 6.1.1.8 Add new subclause 6.1.1.8 as follows: 6.1.1.8 Relation with ITU-T G.993.1 Figure 8 bis illustrates the G.993.1 system reference model aligned with the reference configuration shown in Figure 1. 2 ITU-T Rec. 6.995.1 (2001)/Amd.l (11/2001) V U T S R j i qh- - Signa
37、l lines Interfaces Figure 8 bislG.995.1- 6.993.1 system reference model and its alignment with the generic reference configuration The G.993.1 system reference model shows the functional blocks necessary to illustrate a VDSL transmission system. With reference to the alignment with the generic refer
38、ence configuration, the Core Network may contain the following functions: o Concentrator and/or switch. o Interface to the Broadband and Narrow-band network. The VDSL Access Network consists of the following: o VDSL Transceiver Unit-ONU (VTU-O). o Copper Loop Plant. o POTS splitter to separate the P
39、OTS and VDSL channels. The VDSL-NT1 may consist of the following functions: o VDSL Transceiver Unit - Remote Terminal end (VTU-R). o Multiplexer/Demultiplexer. o Higher layer functions. o Interface to the User terminal or a Home Network. The VDSL-NT2, Terminal Adapter and User Terminal may share som
40、e or all of the NT1 fnctionalities. In G.993.1, interfaces are defined at the V, U and T reference points namely U-O, U-R, V-O, and T-R interfaces. The U-O and U-R interfaces are fully defined in G.993.1. Due to the potential asymmetry of the signals on the line, the transmitted signals are distinct
41、ly specified at the U-R and U-O reference points. ITU-T Rec. G.995.1(2001)/Amd.l (11/2001) 3 The V-O and T-R interfaces are defined only in terms of logical functions. The V-O interface may consist of interfaces to one or more (PTM or ATM) switching systems. Implementation of the V-O and T-R interfa
42、ces is optional when interfacing elements are integrated into a common element. One or other of the high-pass filters, which are part of the splitters, may be integrated into either of the VTU-O or VTU-R; if so, then the U-O2 and U-R2 interfaces become the same as the U-O and U-R interfaces, respect
43、ively. The T/S interface is not defined in G.993.1. The nature of the customer installation distribution and customer premises network may be varied, e.g. bus or star, or type of media. Therefore, more than one type of T-R interface may be used, and more than one type of T/S interface may be provide
44、d from a VDSL NT (e.g. NT1 or NT2 types of functionalities). 4 ITU-T Rec. G.995.1 (2001)/Amd.l (11/2001) SERIES OF ITU-T RECOMMENDATIONS Series A Series B Series C Series D Series E Series F Series G Series H Series I Series J Series K Series L Series M Series N Series O Series P Series Q Series R S
45、eries S Series T Series U Series V Series X Series Y Series Z Organization of the work of ITU-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall network operation, telephone service, service operation and human factors N
46、on-telephone telecommunication services Transmission systems and media, digital systems and networks Audiovisual and multimedia systems Integrated services digitai network Cable networks and transmission of television, sound programme and other multimedia signals Protection against interference Cons
47、truction, installation and protection of cables and other elements of outside plant TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Maintenance: international sound programme and television transmission circuits Specifica
48、tions of measuring equipment Telephone transmission quality, telephone installations, local line networks Switching and signalling Telegraph transmission Telegraph services terminal equipment Terminals for telematic services Telegraph switching Data communication over the telephone network Data networks and open system communications Global information infrastructure and Internet protocol aspects Languages and general software aspects for telecommunication systems Printed in Switzerland Geneva, 2002
