1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.993.5 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2015) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Metallic access networks Self-FEXT cancellati
2、on (vectoring) for use with VDSL2 transceivers Recommendation ITU-T G.993.5 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYST
3、EMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND
4、 LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 General G.900G.909 Parameters for optical fibre cable systems G.910G.919 Digital section
5、s at hierarchical bit rates based on a bit rate of 2048 kbit/s G.920G.929 Digital line transmission systems on cable at non-hierarchical bit rates G.930G.939 Digital line systems provided by FDM transmission bearers G.940G.949 Digital line systems G.950G.959 Digital section and digital transmission
6、systems for customer access to ISDN G.960G.969 Optical fibre submarine cable systems G.970G.979 Optical line systems for local and access networks G.980G.989 Metallic access networks G.990G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION M
7、EDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.993.5 (01/2015) i Recommendation ITU-T G.993.5 Self-FEXT can
8、cellation (vectoring) for use with VDSL2 transceivers Summary Vectoring is a transmission method that employs the coordination of line signals for reduction of crosstalk levels and improvement of performance. The degree of improvement depends on the channel characteristics. Vectoring may be for a si
9、ngle user or for multiple users benefit. Recommendation ITU-T G.993.5 is specifically limited to the self-far-end crosstalk (self-FEXT) cancellation in the downstream and upstream directions. It defines a single method of self-FEXT cancellation, in which FEXT generated by a group of near-end transce
10、ivers and interfering with the far-end transceivers of that same group is cancelled. This cancellation takes place between very high-bit-rate digital subscriber line 2 (VDSL2) transceivers, not necessarily of the same profile. This Recommendation is intended to be implemented in conjunction with Rec
11、ommendation ITU-T G.993.2. This version of this Recommendation integrates all of the previous amendments and corrigenda with the 2010 version 1.0 of Recommendation ITU-T G.993.5. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.993.5 2010-04-22 15 11.1002/1000/10414 1.1 ITU
12、-T G.993.5 (2010) Cor. 1 2011-06-22 15 11.1002/1000/11128 1.2 ITU-T G.993.5 (2010) Amd. 1 2011-12-16 15 11.1002/1000/11396 1.3 ITU-T G.993.5 (2010) Cor. 2 2012-06-13 15 11.1002/1000/11643 1.4 ITU-T G.993.5 (2010) Amd. 2 2012-10-29 15 11.1002/1000/11796 1.5 ITU-T G.993.5 (2010) Amd. 3 2013-04-22 15 1
13、1.1002/1000/11889 1.6 ITU-T G.993.5 (2010) Amd. 4 2013-08-29 15 11.1002/1000/11993 1.7 ITU-T G.993.5 (2010) Amd. 5 2014-04-04 15 11.1002/1000/12095 2.0 ITU-T G.993.5 2015-01-13 15 11.1002/1000/12372 _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web
14、 browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.993.5 (01/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communic
15、ation technologies (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 W
16、orld Telecommunication 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.
17、In some areas of 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 rec
18、ognized operating 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
19、 words “shall“ or 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 RIGHTSITU draws attention to the possibility t
20、hat 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 Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommend
21、ation 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. However, implementers are cautioned that this may not represent the latest information and are
22、 therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2015 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 G.993.5 (01/2015) iii Table of Contents Page 1 S
23、cope . 1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 3 5 Reference models 4 5.1 General . 4 5.2 Downstream vectoring 5 5.3 Upstream vectoring 6 6 CO-side requirements in a vectored group . 6 6.1 General . 6
24、6.2 Downstream vectoring requirements for the VTU-O . 8 6.3 Upstream vectoring requirements for the VTU-O 9 6.4 Requirements for the VCE . 9 7 CP-side requirements in a vectored group 9 7.1 General . 9 7.2 Downstream vectoring requirements for the VTU-R . 11 7.3 Upstream vectoring requirements for t
25、he VTU-R 21 7.4 Requirements for the NT system 22 8 Vectoring-specific eoc messages 23 8.1 eoc messages for backchannel configuration . 24 8.2 Pilot sequence update command and response . 28 8.3 Power management commands and responses . 30 9 Activation and deactivation of pairs in a vectored group .
26、 30 9.1 Orderly shutdown event . 30 9.2 Disorderly shutdown event . 30 10 Initialization of a vectored group 31 10.1 Overview 31 10.2 ITU-T G.994.1 Handshake phase . 35 10.3 Channel Discovery phase . 41 10.4 Training phase 51 10.5 Channel Analysis and Exchange phase 61 10.6 Transition from initializ
27、ation to Showtime 61 10.7 Loop diagnostic mode procedures 62 11 Configuration and test parameters 64 11.1 Configuration parameters . 64 iv Rec. ITU-T G.993.5 (01/2015) Page 11.2 Test parameters . 66 Appendix I Crosstalk channel modelling 70 I.1 Scope 70 I.2 Purpose . 70 I.3 MIMO crosstalk channel mo
28、del A . 70 I.4 MIMO crosstalk channel model C . 70 Appendix II Examples of VCE control of initialization process in the activation of multiple lines in the vectored group . 74 II.1 Introduction 74 II.2 VCE handling two groups of initializing lines . 74 II.3 VCE using handshake capabilities . 77 Appe
29、ndix III SNR-based FEXT channel estimation method 78 III.1 Tools . 78 III.2 Estimation of FEXT channels from a new line into existing lines . 78 III.3 Estimation of FEXT channels from existing lines into a new line . 84 Bibliography. 89 Rec. ITU-T G.993.5 (01/2015) 1 Recommendation ITU-T G.993.5 Sel
30、f-FEXT cancellation (vectoring) for use with VDSL2 transceivers 1 Scope Vectoring is a transmission method that employs the coordination of line signals for reduction of crosstalk levels and improvement of performance. The degree of improvement depends on the channel characteristics. Vectoring may b
31、e for a single user or for multiple users benefit. This Recommendation is specifically limited to the self-far-end crosstalk (self-FEXT) cancellation in the downstream and upstream directions. This Recommendation defines a single method of self-FEXT cancellation, in which far-end crosstalk (FEXT) ge
32、nerated by a group of near-end transceivers and interfering with the far-end transceivers of that same group is cancelled. This cancellation takes place between very high-bit-rate digital subscriber line 2 (VDSL2) transceivers, not necessarily of the same profile. This Recommendation is intended to
33、be implemented in conjunction with ITU-T G.993.2. Multi-pair digital subscriber line (DSL) bonding (b-ITU-T G.998.1, b-ITU-T G.998.2 and b-ITU-T G.998.3) may be implemented in conjunction with vectoring. The techniques described in this Recommendation provide means of reducing self-FEXT generated by
34、 the transceivers in a multi-pair cable or cable binder. Self-FEXT cancellation techniques are particularly beneficial with short cable lengths ( 0 for band number vb), and report(vb) = 0 if the VBB-vb is not included in the ERB (i.e., L_w = 0 for band number vb). The backchannel data rate (BDR) for
35、 transmission of the error report block for each sync symbol is: 257/_8 D M TfERBNB D R where DMTf is the symbol rate (in symbols/s) defined in clause 10.4.4 of ITU-T G.993.2. The BDR is not defined when padding is not used. In that case, N_ERB varies from error report to error report. 7.2.4 Identif
36、ication of the ERB during Showtime At each of the sync symbol counts indicated by the VTU-O, the VTU-R shall transmit a single ERB. With each ERB, the VTU-R shall also transmit the downstream sync symbol count (as defined in clause 7.3.2) as identification of the downstream sync symbol the ERB corre
37、sponds to. The VTU-O shall indicate such sync symbol counts using the following time identification control parameters: the error sample update period (m); the error sample shift period (z). The error sample update period gets value of m if the error sample has to be reported on every m-th sync symb
38、ol, i.e., on the sync symbol positions with sync symbol counts SSC = mP+k, where P is any integer in the range from 0 to mkSSCN /1_ , and k is the offset, which is an integer in the range from 0 to m1. which is an integer in the range from 0 to m1. After the SSC counter wraps around at the value of
39、N_SSC-1, the next sync symbol count at which ERB shall be reported is SSC = k (this count is obtained by setting P=0). The VTU-R shall set k=0 for the first report after the VTU-Os Error Feedback request. This report shall be sent for the first available sync symbol with SSC count that is a multiple
40、 of m after reception of the ERB request (see clause 8.1). If z 0, the VTU-R shall increase k by 1 after each error sample shift period of z reports, wrapping around k at m-1. If m = 1, the VTU-R shall report on each sync symbol. The error sample update period value of m = 0 is special and shall be
41、used to indicate that the VTU-R shall stop error sample reporting. The non-zero error sample shift period z is valid only for m 1. The error sample shift period value of z = 0 shall be used if no error sample shift is to be done and if m=1. NOTE 1 The parameters m and z should be selected such that
42、the error samples are reported at least once for all the bits of the pilot sequence after a certain time. NOTE 2 For example, with N_SSC = 1024, m = 3, and the first report sent at SSC = 6, the reports are on the following sync symbol counts: m = 3 and z = 0 then SSC = 6, 9, , 1020, 1023, 0, 3, 6, 9
43、, m = 3 and z = 128 then SSC = 6, 9, , 128 3, 1293, 1303+1, 1313+1, 257 3+1, 2583+2, 2593+2,. 340 3+2, 2, 5, .44 3+2, 453, 463, 473, Rec. ITU-T G.993.5 (01/2015) 21 The values for the time identification control parameters are defined in Table 7-4. Table 7-4 Values of time identification control par
44、ameters Parameter Valid values for VCE Mandatory values for VTU-R to support m 0, 1, 2, , 63, 64 All valid values z If m 1: 0, 2, , 254, 255, 256 If m 1: 0 All valid values 7.3 Upstream vectoring requirements for the VTU-R The VTU-R shall comply with ITU-T G.993.2, with the exceptions and additional
45、 requirements contained in this Recommendation. In order to enable the VCE to fulfil the tasks described in clause 6.1, the VTU-R shall support the requirements in the following clauses. 7.3.1 Symbol alignment Under VCE control, all VTU-Rs in the vectored group shall use the same subcarrier spacing
46、and symbol rate. NOTE The VCE may control the alignment of symbols from different lines of the vectored group at the U-O2 reference point (defined in Figure 5-4 of ITU-T G.993.2) by adjusting the timing advance (TA) of these lines during initialization (see clause 10). 7.3.2 Sync symbol position The
47、 VTU-R shall have the capability to transmit sync symbols as defined in clause 10.2 of ITU-T G.993.2. The VTU-R shall transmit sync symbols at time positions assigned by the VCE and communicated to the VTU-R during initialization. The time position of upstream sync symbols is defined by an offset be
48、tween upstream and downstream sync symbol positions. The offset between the upstream and downstream sync symbol time positions is set by the VCE and sent to the VTU-R in the O-SIGNATURE message. The VCE may configure all VTU-Rs in the vectored group to transmit upstream sync symbols at the same time
49、 positions or at different time positions for one or more VTU-Rs in the vectored group. The VTU-R shall keep a downstream sync symbol counter (MODULO N_SSC), counting continuously over Showtime. The counter value of the first downstream sync symbol transmitted in Showtime shall be set by the VTU-R to the value of the field First SSC of the first received Error Feedback command (see Table 8-3). Before receiving the first Error Feedback
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