1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.991.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(07/2004) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital sections and digital line system Access networks Single-pair high-speed digital subscriber line (SHD
2、SL) transceivers Amendment 1 ITU-T Recommendation G.991.2 (2003) Amendment 1ITU-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 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA 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 Digit
5、al sections 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 tra
6、nsmission 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 Access networks G.990G.999 QUALITY OF SERVICE AND PERFORMANCE - GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHA
7、RACTERISTICS G.6000G.6999 DIGITAL TERMINAL EQUIPMENTS G.7000G.7999 DIGITAL NETWORKS G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.991.2 (2003)/Amd.1 (07/2004) i ITU-T Recommendation G.991.2 Single-pair high-speed digital subscriber line (SHDSL) tra
8、nsceivers Amendment 1 Summary This amendment resolves the passing of a target margin in an SHDSL access link with repeaters and introduces the addition of the TU-12/VC-12 framing. The revisions relative to G.991.2 (2003) are indicated with revision marks. Source Amendment 1 to ITU-T Recommendation G
9、.991.2 (2003) was approved on 22 July 2004 by ITU-T Study Group 15 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. G.991.2 (2003)/Amd.1 (07/2004) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicatio
10、ns. 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 Telecommunication
11、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 inform
12、ation 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 operating agenc
13、y. 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 some ot
14、her 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 or impl
15、ementation 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 proces
16、s. 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 urge
17、d to consult the TSB patent database. ITU 2005 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.991.2 (2003)/Amd.1 (07/2004) iii CONTENTS Page 1) Resolution to passing of a target margin in an SHDSL
18、 access link with repeaters 1 2) Addition of TU-12/VC-12 framing 12 ITU-T Rec. G.991.2 (2003)/Amd.1 (07/2004) 1 ITU-T Recommendation G.991.2 Single-pair high-speed digital subscriber line (SHDSL) transceivers Amendment 1 1) Resolution to passing of a target margin in an SHDSL access link with repeat
19、ers Modify Annex D and Appendix III as follows: Annex D Signal regenerator operation In order to achieve data transmission over greater distances than are achievable over a single SHDSL segment, one or more signal regenerators (SRUs) may be employed. In the optional M-pair mode, M-pair regenerators
20、may be used when this reach extension is required. This annex specifies operational characteristics of signal regenerators and the start-up sequence for SHDSL spans containing signal regenerators. Additional explanatory text is included in Appendix III. D.1 Reference diagram Figure D.1 is a referenc
21、e diagram of a SHDSL span containing two regenerators. Up to eight (8) regenerators per span are supported within the EOC addressing scheme (9.5.5.5), and no further limitation is intended herein. Each SRU shall consist of two parts: an SRU-R for interfacing with the STU-C (or a separate SRU-C), and
22、 an SRU-C for interfacing with the STU-R (or a separate SRU-R). An internal connection between the SRU-R and SRU-C shall provide the communication between the two parts during start-up and normal operation. An SHDSL span containing X regenerators shall contain X + 1 separated SHDSL segments, designa
23、ted TR1 (STU-C to SRU1), TR2 (SRUX-C to STU-R), and RRn (SRUn-C to SRUn+1 R, where 1 n X 1). Each segment shall follow the general principles described in 6.2, 6.3 and 7.2 for the preactivation and activation procedures. Additional requirements specific to spans containing regenerators are described
24、 in this annex. Figure D.1/G.991.2 Block diagram of a SHDSL span with two signal regenerators 2 ITU-T Rec. G.991.2 (2003)/Amd.1 (07/2004) D.2 Startup procedures D.2.1 SRU-C Figure D.2 shows the state transition diagram for SRU-C start-up and operation. The SRU-C begins in the “Idle0“ state and, in t
25、he case of an STU-R initiated start-up, transitions first to the “Wait for STU-CIdle0a“ state. If line probe is disabled, the STU-C shall transition from the “Idle0a“ state to the “Wait for STU-C“ state; otherwise the STU-C will return to “Idle0“ and wait for target margins to be passed across the i
26、nternal regenerator interface with the indication that they originated at the STU-C. In this annex, the term “target margin“ refers to both the current condition target margin and the worst-case target margin as described in 6.3.6 and 6.4.1. For an STU-C initiated start-up, the SRU-C moves from “Idl
27、e0“ to the “G.994.1 Session 1Idle0b“ state. If target margins have been received across the internal regenerator interface with the indication that they originated at the STU-C, the SRU-C will transition from “Idle0b“ to Check “G.994.1“ and the SRU-C will use these target margins in subsequent capab
28、ilities exchanges with its “CO target margin“ capability bit set to a one. An SRU initiated start-up shall function identically to an STU-C initiated start-up from the perspective of the SRU-C. The SRU-C shall communicate “Capabilities Available“ status and transfer a list of its capabilities to the
29、 SRU-R across the regenerators internal interface upon entering the “Wait for STU-C“ or “Idle0a“ state. The SRU-Cs capabilities list, as transferred to the SRU-R, shall be the intersection of its own capabilities, the capabilities list it received from the STU-R (or SRU-R) in its G.994.1 session, an
30、d the segment capabilities determined by the line probe, if used. The SRU-C shall receive mode selection information from the SRU-R in association with the “SRU-R Active“ indication. In the subsequent G.994.1 session, the SRU-C shall select the same mode and parameter settings for the SHDSL session.
31、 The timer TSRUCshall be set to 4 minutes. If TSRUCexpires before the SRU-C reaches the “Active“ state, the SRU-C shall return to the “Idle“ state and shall indicate link failure to the SRU-R across the internal interface. The SRU-C shall also indicate failure and return to the “Idle“ state if a G.9
32、94.1 initiation is unsuccessful after 30 s. The “Diagnostic Mode“ bit, if set in the G.994.1 Capabilities Exchange, shall cause an SRU-C to function as an STU-C if the subsequent segment fails. This implies that an internal failure indication received while in the “Wait for STU-C“ state shall cause
33、the SRU-C to select an operational mode, initiate a G.994.1 session, and transition to state “G.994.1 Session 2“. ITU-T Rec. G.991.2 (2003)/Amd.1 (07/2004) 3 IdleReceive InternalInitiate G.994.1 SessionCapabilities Exchange“Link Initiation“ IndicationConnected to SRU-RReceive MSwith “Silent Period“
34、= 1Complete G.994.1 SessionStart TSRURCheck G.994.1G.994.1FailureG.994.1 Session 2ActiveReceive InternalInitiate G.994.1 Session“SRU-R Active“ IndicationConnected to STU-R(Line Probe)(Second G.994.1 Session)(Capabilities Exchange) Send MS with “Silent Period“ = 1Start TSRUCReceive G.994.1 initiation
35、G.994.1 SessionCapabilities Exchange(Line Probe)(Second G.994.1 Session)(Capabilities Exchange)Send MS with “Silent Period“ = 1Start TSRUCInternal FailureIndication andInitiate G.994.1SessionDiagnostic ModeTTimeoutSRUCTTimeoutSRUCInternal FailureIndication andnot DiagnosticModeReceive G.994.1 initia
36、tionG.994.1 SessionCapabilities Exchange(Line Probe)(Second G.994.1 Session)(Capabilities Exchange)Send MS with “Silent Period“ = 1Start TSRUCReceive G.994.1 InitiationG.994.1 SessionMS with “Silent Period“ = 1Receive Internal“SRU-R Active” IndicationInitiate G.994.1 SessionComplete G.994.1 Sessionn
37、SHDSL Activationwith Mode SelectioDisconnect,Failure, or RetrainG.994.1FailureIdle0bIdle0(no CO margins)Line Probe Not EnabledORCO Margins ReceivedReceive G.994.1 InitiationG.994.1 SessionCapabilities Exchange(default margins)Idle0aLine Probe EnabledSend MS with“Silent Period”=1Receive Internal “Lin
38、kInitiate G.994.1 SessionCapabilities ExchangeInitiation” IndicationLine Probe EnabledANDCO Margins Not ReceivedLine Probe Not Enabled Send MS with“Silent Period”=1Start TSRUCFigure D.2/G.991.2 SRU-C state transition diagram 4 ITU-T Rec. G.991.2 (2003)/Amd.1 (07/2004) D.2.2 SRU-R Figure D.3 shows th
39、e state transition diagram for SRU-R start-up and operation. The SRU-R begins in the “Idle0“ state and, in the case of an STU-R initiated train, transitions first to the “G.994.1 Session 1Idle0a“ state. For an STU-C initiated train, the SRU-C moves from “Idle0“ to the “G.994.1 Session 2Idle0b“ state
40、. If line probe is enabled, the SRU-R will transition to the “G.994.1 Session 1“ state once the target margins are received from the STU-C, or once the target margins are received from the SRU-C with the “CO target margin“ capability bit set to a one. In this annex, the term “target margin“ refers t
41、o both the current condition target margin and the worst-case target margin as described in 6.3.6 and 6.4.1. The SRU-R shall communicate “Link initiation“ status to the SRU-C across the regenerators internal interface upon entering the “Wait for STU-R“ or “Idle0b“ state. If the SRU-R exchanges capab
42、ilities with a STU-C, it shall communicate the target margins from the STU-C across the regenerators internal interface. If the SRU-R exchanges capabilities with a SRU-C, and the SRU-C has the “CO target margin“ capability bit set to a one, then it shall communicate the target margins from the SRU-C
43、 across the regenerators internal interface. Upon entering the “Active“ state, it shall communicate “SRU-R Active“ status to the SRU-C. If plesiochronous operation (Clock Mode 1; see clause 10) is selected, the SRU-R may optionally indicate its entry into the “Active“ state to the SRU-C prior to the
44、 completion of the SHDSL activation sequence. If synchronous or network referenced plesiochronous clocking is selected (Clock Modes 2, 3a or 3b; see clause 10), the SRU-R shall not indicate entry into the “Active“ state until the SHDSL activation sequence has been completed. The SRU-R shall receive
45、a list of capabilities from the SRU-C across the regenerators internal interface in association with the “Capabilities available“ indication. The SRU-Rs capabilities list, as indicated in the subsequent G.994.1 session, shall be the intersection of its own capabilities with the capabilities list it
46、received from the SRU-C. The SRU-R shall provide mode selection information to the SRU-C in association with the “SRU-R active“ indication, based on the selections it has received in the G.994.1 session. The timer TSRURshall be set to 4 minutes. If TSRURexpires before the SRU-R reaches the “Active“
47、state, the SRU-R shall return to the “Idle“ state and shall indicate link failure to the SRU-C across the internal interface. The SRU-R shall also indicate failure and return to the “Idle“ state if a G.994.1 initiation is unsuccessful after 30 s. The “Diagnostic mode“ bit, if set in the G.994.1 capa
48、bilities exchange, shall cause an SRU-R to function as an STU-R if the subsequent segment fails. This implies that an internal failure indication received while in the “Wait for STU-R“ state shall cause the SRU-R to initiate a G.994.1 session and transition to state “G.994.1 Session 2“. ITU-T Rec. G
49、.991.2 (2003)/Amd.1 (07/2004) 5 IdleG.994.1 Session 1G.994.1 Session 2ActiveTSRURtimeoutInternal failureindication andnot diagnosticmodeG.994.1failureReceive mode selectionSHDSL activationStart G.994.1 session normallyCapabilities exchange(Line probe)(Second G.994.1 session)(Capabilities exchange)Receive Ack(1)Complete G.994.1 sessionStart TSRURInternal failure indicationInitiate G.994.1 sessionand diagnostic modeReceive REQ-MRselect modeSHDSL activationWait for STU-CReceive MS withStart T“Silent period“ = 1SRURReceive G.994.1 initiationSelect m
