1、ITU-T RECMN*Q.512 95 48b257L Ob00653 077 W INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DIGITAL EXCHANGES Q.512 (02/95) DIGITAL EXCHANGE INTERFACES FOR SUBSCRIBER ACCESS ITU-T Recommendation Q.512 (Previously CCIlT Recommendation”) FOREWORD The -T (Tele
2、communication Standardization Sector) is a permanent organ of the International Telecommunication Union (). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The
3、World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the IT-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 la
4、id down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation 4.512 was revised by ITU-T Study Group 11 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 7th of February 1995. NOTE In this Recommendation, the expression “Administration” is used for c
5、onciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1995 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, el and “Digital local and combined exchanges” - Q.5 10-Series of Recommendations. -
6、 In 1988, CCITT Study Group XI combined the Series Q.500 and Q.510 Recommendations into a single set applicable to digital local, combined, transit and international exchanges in Integrated Digital Networks (IDN) and mixed analogue- digital networks, and also to local, combined, transit and intemati
7、onal exchanges in an Integrated Services Digital Network (ISDN). In 1994, ITU-T Study Group 11 revised the Q.500-Series of Recommendations in order to include a new exchange interface for subscriber access - the V5 interface (Le. the V5.1 interface). The V3 interface is to the case of an ISDN primar
8、y rate access and the case that this interface is used not structured according to the ISDN principles is considered as not subject to ITU-T Recommendations. The V4 interface is marked as not subject to ITU-T Recommendations; reference should be made to interface V5.1 which covers static multiplexed
9、 ISDN basic accesses. The V4 interface was a digital interface used to connect a digital access link which includes a static multiplexer supporting several basic access digital sections. For this interface, the specification (i.e. CV1 channel structure) was not completed. ITU-T will continue to furt
10、her develop and complete these Recommendations in areas where there are unresolved issues and develop additional Recommendations on digital exchanges in the Q.500-Series and other series in the future. The structure for the Q.500-Series of digital switching Recommendations is provided in Recommendat
11、ion 4.500. 11 Recommendation Q.512 (Ol95) ITU-T RECtIN*Q=5L2 95 4862591 Ob00657 712 Recommendation Q.512 DIGITAL EXCHANGE INTERFACES FOR SUBSCRIBER ACCESS (Melbourne, 1988; revised in 1994) 1 Scope It applies to digital local and combined exchanges for telephony in Integrated Digital Networks (IDN)
12、and to local and combined exchanges in an Integrated Services Digital Network (ISDN), and also to mixed (analoguddigital) networks. The field of application of this Recommendation is more fully defined in Recommendation 4.500 B6. Exchange interfaces for subscriber access that have been considered ar
13、e described, and illustrated in Figure 1 and Table 1, but they are not intended to specify every interface. Other interfaces are for further study. This Recommendation is not intended to define any transmission system, network or subscriber equipment in or connected to, a digital exchange via these
14、interfaces. Therefore only the characteristics of the interfaces are described. 2 References The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated w
15、ere valid. All Recommendations and other references are subject to revision: all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Reco
16、mmendations is regularly published. CCITT Recommendation G.703 (199 i), PhysicaVelectrical characteristics of hierarchical digital interfaces. CCITT Recommendation G.704 (1991), Synchronous frame structures used at primary und secondary hierarchical levels. CCIIT Recommendation G.706 (1991), Frame a
17、lignment and Cyclic Redundancy Check (CRC) procedures relating to basic ffame structures defined in Recommendation G.704. ITU-T Recommendation G.960 (1993), Digital section for ISDN basic rate access. ITU-T Recommendation G.961 (1993), Digital transmission system on metallic local lines for ISDN bas
18、ic rate access. ITU-T Recommendation G.962 (1993), Access digital section for ISDN primary rate at 2048 kbitls. IT-T Recommendation G.963 (1993), Access digital section for ISDNprimary rate at 1544 kbitls. IT-T Recommendation G.964 (1994), V Inteqaces at the digital Local Exchange (LE) - V5.l interf
19、ace (based on 2048 kbitls) for the support of Access Network (AN). ITU-T Recommendation G.965 (1993, V interfaces at the digital Local Exchange (LE) - V5.2 interface (based on 2048 kbitls) for the support of Access Network (AN). CCIT Recommendation M.3603 (1992), Application of maintenance principle
20、s to ISDN basic rate access. CCITT Recommendation M.3604 (1992), Application of maintenance principles to ISDN primary rate access. CCIIT Recommendation M.3605 (1992), Application of maintenance principles to static multiplexed ISDN rate access. Recommendation Q.512 (02/95) 1 II - 1 *I (See b) ET *I
21、 II II T II , i“ . 4 1 . II :i T :i )I . I .I t . ni i c) II Digital access link (static multiplex) i v, . i II 4:yq II Access line configuration Z (static multiplexjng andof concentration) II I II -i4 l II II I I +t II Leased line port f) Z f ;-FI Subscriber analogue line (2-wire) II T1171O95/dOI I
22、I I I I Interface II t Reference point ET Exchange Tenination functions a) Interface T is defined in Recommendation 1.41 1. b, The characteristics of a digital transmission system on metallic local lines for ISDN basic rate access which may ) The differences among V, V, V4 and Vs are essential multi
23、plexing and sigialling requirements. The transmission dl See information prwided in Backgwnd. e) May be bsic rate or primary rate access. Primary rate access oniy supported bys., interface. ) For reserved connections established under control of the local exhange without control plane signalling bet
24、ween form pari of the basic access digital section are defined in Recunmendation G.961. requirements are substantially identical (e.g. Recommendations G.7W and G.704). user and local exchange. NOTE - Not all interfaces will necessarily exist in every implementation. FIGURE UQ.512 nlustration of poss
25、ible access canfigurations 2 Recommendation Q.512 (02/95) ITU-T RECMN*Q-512 95 w 4862593 Ob00659 595 Interface/ reference points I Access type Paragraph Basic access digital v5 Generic digital section 5.6 Primary rate access digital sectionb) Digital access link (Static multiplex) I Access network c
26、onfigurations TABLE UQ.512 Interface references Application to connect Related OAM Recs. Related physical and functional Recs. G.960a) M.3603 G.703 (3.704 None ISDN basic access (2B + D) Digital network equipment, supporting any combination of access types (3.703 (3.704 (3.706 (3.962 G.963 M.3604 No
27、t subject to ITU-T Recommendationsc) G.703 M.3603 G.704 I M.3604d) G.706 G.964 G.965 None I Nonee) A multiple of analogue subscriber lines, ISDN basic accesses and ISDN primary rate accesses with multiplexing andor concentration capability for bearer channels Analogue subscriber lines Recommendation
28、 (3.961 specifies the characteristics of a digital transmission system on metallic local lines which may form part of the basic access digital section. b, cf See information in “Background“. dl e) In the case of ISDN access this is the primary rate access digital section. For ISDN application throug
29、h the V5 interfaces. Characteristics other than those defined in Recommendations Q.551 and Q.552 are not subject to ITU-T Recom- mendations. 3 Terms and definitions For the purposes of this Recommendation, the following definitions apply: 3.1 digital section: A digital section is defined as the whol
30、e of the means of digital transmission of a digital signal of specified rate between two consecutive reference points. A digital link comprises one or more digital sections and may include either a multiplexer or concentrator, but not switching. 3.2 access digital section: The functional requirement
31、s to transmit the information fromlto the user-network interface and to transmit, multiplex, demultiplex and process information required for operation and maintenance fromlto the associated V-reference point related to that particular user-network interface. This excludes the extraction, concentrat
32、ion and multiplexing/demultiplexing of channels with hierarchies other than the one being concerned (as these are considered by the V-reference point). Recommendation Q.512 (OY95) 3 ITU-T RECflN*Q512 75 = 4862571 0600660 207 In addition, this Recommendation uses terms defined in Recommendations G.96
33、2 6, G.963 7, G.964 8, G.965 9 and Q.9 B5. In this Recommendation the term “exchange” or “local exchange” is used for conciseness to indicate both a (digital) local exchange and a (digital) combined exchange. A (digitai) combined exchange is one which includes both local exchange and transi/toll exc
34、hange functions. 4 Abbreviations For the purposes of this Recommendation, the following abbreviations are used: AN Access Network CRC Cyclic Redundancy Check ET Exchange Termination IDN Integrated Digital Network ISDN Integrated Services Digital Network NTl Network Termination Type 1 PABX Private Au
35、tomatic Branch Exchange PCM Puise code modulation PSTN Public Switched Telephone Network 5 Characteristics of digital interfaces for subscriber access 5.1 General Digital interfaces for subscriber access are defined at the V-reference point which is the boundary between the Exchange Termination (ET)
36、 and the digital access section or link. These interfaces are designated interface V and are defined to allow flexibility of implementation for different exchange and transmission equipment realizations. However, a physical interface will not be specified for all subscriber access types identified (
37、see Figure 1). As an objective, the characteristics of digital interfaces on the subscriber side of the exchange should be aligned with the characteristics of ISDN userhetwork access structures (see Recommendation 1.41 1 Bi). However, in many countries, digital access arrangements not structured acc
38、ording to ISDN principles are used, e.g. to ensure compatibility with existing networks and services and it is expected that these arrangements will continue to be used for several years. These types of interfaces not structured according to the ISDN principles are not subject to ITU-T Recommendatio
39、ns. 5.2 Interface VI 5.2.1 General Interface V1 may be used at the VI reference point to connect to an ISDN basic access digital section for the provision of a single basic access. The characteristics of the basic access digital section are defined in Recommendation G.960 4 and the characteristics a
40、nd parameters of a digital transmission system which may form part of the digital section for the ISDN basic rate access are given in Recommendation G.961 5. 5.2.2 Functional characteristics The functional description is illustrated in Figure 2 and the following functional requirements are defined:
41、1) (2B + D) channels To provide the bidirectional transmission capability for two B-channels and one 16 kbitfs D-channel as described in Recommendation 1.412 B2. 2) Bittiming To provide bit (signal element) timing to enable the digital section to recover information from the aggregate bit stream. 4
42、Recommendation Q.512 (OW95) 3) Frame timing To provide frame timing to enable digital section and ET to recover the time division multiplexed channels. 4) CV1 channel The CV1 channel provides, for each direction of transmission, the capability to transfer management functions required for the digita
43、l section as specified in Recommendations G.960 4 and M.3603 lo. The CVI channel may carry one or more functional links. These functions include activation from network side, activation request from a digital section, deactivation from ET side, operation and maintenance signals. 5) Powerfeed This fu
44、nction provides for remote power feeding for the digital section and possibly terminal equipment. This function is optional. Basic access digital section 2 B + D-channel Bfi timing Frame timing Exchange functions Activationb) Termination (ET) Deactivationb) Operation and maintenanceb) Power feecia)
45、Vi reference point Ti 164720-Wd02 a) The provision of power feed function is optional. b, These functions are conveyed by the CV, channel. FIGURE UQ.512 Functions at interface V, 5.2.3 Electrical characteristics The electrical characteristics of interface VI are not subject to ITU-T Recommendations.
46、 5.2.4 The channel types associated with interface V, include two B-channels and one D-channel as defined at the user network interface in Recommendation 1.412 B2. In addition, the CV1 channel is required to support the operational and maintenance functions. Channel types, channel allocation and sig
47、nalling The channel allocation is not subject to ITU-T Recommendations. The D-channel signalling procedures are defined in the 4.920 and Q.930-Series Recommendations. Recommendation Q.512 (0295) 5 ITU-T RECMN*Q-512 95 m 4862593 0600bb2 OBT m 5.3 Interface V2 5.3.1 General Interface V2 is a generic d
48、igital interface used to connect remote or local digital network equipment via a first or second order digital section. This network equipment may support any combination of analogue, digital and ISDN subscriber access. The characteristics of this interface may not be structured according to the ISD
49、N principles. 5.3.2 Functional characteristics The functional characteristics depend on the specific application of the V2 interface. These are not generally subject to IT-T Recommendations. 5.3.3 Electrical characteristics The electrical characteristics of interface V2 are described in Recommendation G.703 i. The basic frame structure at interface V2 should be identical to that of the first or second order rate multiplexes described in Recommen- dation G.704 2. 5.3.4 Channel types, channel allocation and signalling The chan
