1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU SERIES Q: SWITCHING AND SIGNALLING Digital exchanges - Transmission characteristics Q.551 (01/2002) Transmission characteristics of digital exchanges ITU-T Recommendation Q.551 ITU-T Q-SERIES RECOMMENDATIONS
2、SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN SPECIFICATIONS OF SIGNALLING SYSTEM No. 4 SPECIFICATIONS OF SIGNALLING SYSTEM No. 5 SPECIFICATIONS OF SIGNALLING SYSTEM No. 6 SPECIFICATIONS OF SIGNALLING SYSTEM R1 SPECIF
3、ICATIONS OF SIGNALLING SYSTEM R3 DIGITAL EXCHANGES INTERNATIONAL AUTOMATIC AND SEMI- AUTOMATIC WORKING CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Introduction and field of application Exchange interfaces, functions and connections Design objectives and measurement Transmission characteristics INTE
4、RWORKING OF SIGNALLING SYSTEMS SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 43 INTERFACE DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 PUBLIC LAND MOBILE NETWORK INTERWORKING WITH SATELLITE MOBILE SYSTEMS INTELLIGENT NETWORK SPECIFICATIONS OF SIGNALLING RELATED TO BEARER INDEPENDENT CALL BROADBAND ISDN SI
5、GNALLING REQUIREMENTS AND PROTOCOLS FOR Ih4T-2000 CONTROL (BICC) Q. 1-4.3 Q.4-Q.59 4.60-4.99 Q. 100-Q. 1 19 Q. 120-Q. 139 Q. 140-Q. 199 Q.250-Q.309 Q.310-Q.399 Q.400-Q.499 Q.500-Q.599 Q.500-Q.509 Q.5 10-Q.539 Q.540-Q.549 Q.55O-Q.599 Q .600-Q.699 Q.700-Q.799 Q. SOO-Q. 849 Q.850-Q.999 Q. 1 OWQ. 1 O99
6、Q.1100-Q.1199 Q. 1200-4.1699 Q.17WQ.1799 Q. 1900-Q. 1999 Q.2000-Q.2999 For further details, please refer to the list of iTU-T Recommendations. ITU-T Recommendation Q.551 Transmission characteristics of digital exchanges summary This Recommendation gives values for transmission characteristics relate
7、d to the path fi-om an exchange test point to an exchange interface and vice-versa. The overall characteristics for connections involving two interfaces can, in most cases, be obtained by suitably combining these values. Source ITU-T Recommendation Q.551 was prepared by ITU-T Study Group 15 (2001-20
8、04) and approved under the WTSA Resolution 1 procedure on 6 January 2002. ITU-T Rw. QS51(01/2002) i 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 perm
9、anent 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 Standardization Assembly (WTSA), which meets every four years, establi
10、shes 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 information technology which fall within ITU-Ts purview, the necessary stand
11、ards are prepared on a collaborative basis with IS0 and LEC. 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
12、 that 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 Recomme
13、ndation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implenientors are cautioned that this may not represent the latest information
14、and are therefore strongly urged 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 Rw. Q.551 (OY2002) CONTENTS 3.1 3.2 3.3 3.3.1 3.3.2 3.4 3.4.1 3.4.2 3.5 3
15、.6 3 -7 3.8 1 Introduction 1.1 General . 1.2 Definitions 2 Characteristics of interfaces . 2.1 Two-wire analogue interfaces 2.1.1 Interface Z 2.1.2 Interface Cz . 2.2 Four-wire analogue interfaces 2.2.1 Interface Cl . 2.3 Digital interfaces 2.3.1 Interface A 2.3.2 Interface B 2.3.3 V-type interfaces
16、 Voice-frequency parameters of a connection between two interfaces of the same exchange . 3 General . Transmission loss through the exchange Group delay Absolute group delay . Group delay distortion Noise and total distortion . Weighted noise . Crosstalk . Total distortion including quantizing disto
17、rtion . Discrimination against out-of-band signals applied to the input interface . Spurious out-of-band signals received at the output interface . Echo and stability . 4 Exchange transfer function -jitter and wander Annex A . Information on the formulae used in this Recommendation to calculate weig
18、hted noise and signal-to-total distortion ratio . A . 1 General . A.2 Weighted noise . A.2.1 A.2.2 A.2.3 Weighted noise for an input connection originating from a Z-interface Weighted noise for an output connection terminating in a Z-interface Weighted noise for a whole connection originating from a
19、nd terminating in a Z-interface . Page 1 1 4 7 7 7 8 8 8 8 8 8 8 9 9 9 9 9 11 11 12 14 15 16 16 16 17 17 17 18 18 18 19 ITU-T Rec . 4.551 (01/2002) iii Page A.2.4 A.2.5 A.2.6 A.2.7 A. 3 A.3.1 A.3.2 A.3.3 A.3.4 A.3.5 A.3.6 Weighted noise for an input connection originating from a 2-wire or 4- wire C-
20、interface with or without signalling on the speech wires Weighted noise for an output connection terminating at a 2-wire C- interface with Lo 2 -5 dBr or a 4-wire C-interface both with or without signalling on the speech wires . Weighted noise for an output connection terminating at a 2-wire C- inte
21、rface with Lo -5 dBr and with or without signalling on the speech wires. 20 21 22 Weighted noise for a whole connection originating from and terminating in 2-wire or 4-wire C-interfaces with or without signalling on the speech wires . 23 Total distortion including quantizing distortion. 24 Total dis
22、tortion including quantizing distortion for an input connection originating from a Z-interface . 24 Total distortion including quantizing distortion for an output connection terminating in a Z-interface. 25 Total distortion including quantizing distortion for a whole connection originating from and
23、terminating in a Z-interface 26 Total distortion including quantizing distortion for an input connection originating from a 2-wire or a 4-wire C-interface 27 Total distortion including quantizing distortion for an output connection terminating in a 2-wire or a 4-wire C-interface 28 Total distortion
24、including quantizing distortion for a whole connection originating from and terminating in 2-wire or 4-wire C-interfaces . 29 . iv ITU-T RW. Q.551 (OV2002) ITU-T Recommendation Q.551 Transmission characteristics of digital exchanges 1 Introduction 1.1 General The field of application of this Recomme
25、ndation is found in ITU-T Rec. Q.500. A high percentage of international calls will have a digital PABX included in the connection. Therefore, ITU-T Recs. Q.551-Q.554 are applicable also for digital PABXs with regard to those specific transmission parameters affecting the transmission quality of an
26、international call, for instance, Loudness Ratings, noise, talkers and listeners sidetone, echo and stability. These Recommendations primarily concern digital PABXs connected digitally to the international network. However, network operators may find some of the specification details useful for digi
27、tal PAl3Xs connected by analogue means to the international network. The signals taken into consideration are passed through the following interfaces as described in ITU-T Recs. Q.511 and 4.512 and Figures 1 and 2: - - - Interface A is for primary digital signals at 2048 kbit/s or 1544 kbit/s. Inter
28、face B is for secondary digital signals at 8448 kbit/s or 63 12 kbit/s. Interface C comprises both 4-wire and 2-wire analogue trunk interfaces. Interfaces Cl 4-wire and C2 2-wire represent possible applications of interface C in Figure UQ.5 1 1. Interface Cl represents a 4-wire and interface C2 a 2-
29、wire analogue trunk interface. For practical reasons, Cl and C2 are further subdivided into C11, C12, C13, C21 and C22. Cl1 interfaces channel translating equipment. C12 and Cl3 interface 4-wire analogue exchanges; C12 via the relay sets, cl3 directly to the switching stages. C21 is an interface app
30、licable when a 2-wire circuit connects a digital transit exchange with a exchange, analogue or digital. C22 is an interface applicable when a 2-wire circuit connects exchanges, analogue and/or digital. See Figures 1 and 2 for illustration of the principles. - - Interface type V is for digital subscr
31、iber line access. Interface type Z is for analogue subscriber line access. local local It should be noted that the ITU-T only recommends the C interfaces with certain reservations. The most important disadvantages, namely the reduction in flexibility and multiplicity, are mentioned in 4. UQ.5 1 1. N
32、OTE 1 - Remote analogue exchange concentrators and analogue PABXs may use interface Z for access to a digital exchange. NOTE 2 - In the future, differences in circuit configurations with respect to transmission parameters may cause a subdivision of the Z interface. Also, for interfaces other than th
33、ose designated Z, there can exist types whose transmission characteristics have not been defined, even though they may be recognized as being in practical operation. This may be due to ITU-T not having considered their international standardization justified, e.g. because of their limited use, or be
34、cause their function is to coordinate with pre-existing national standards. However, later additions to recommended interfaces are not ruled out (e.g. 4-wire subscriber interface). ITU-T RW. Q.551 (OU2002) 1 Distribution fraine Digital exchange Distribution frame Subscriber lines Trunk lines O dBr A
35、nalogue subscriber I I I I I su bscriber line I w I I I I Concentrator I Digital subscriber line I I - - - - - - Digital path Analogue path Analoguepad -+ - - ND or DIA converter (Note 1) ! v, Reference point test points To Ti ?Y I I / / -d *- d Digital switching network e- -* Ir- / , - Line PCM ter
36、mination - I w I I L,dBr Interface (Note2) . i 1 I I 1 lLidBr b- C, I I I . I I I I m I I I I Loar + Interface (Note 3) . LidBr c, . I I I T1524010-O2 NOTE 1 - Digital loss pads, if required, may be located in the switching network or the exchange terminals (see 1.2.4.1). NOTE 2 - Termination of int
37、ernational long-distance switched connections (see Figure 2). NOTE 3 - Termination of local 2-wire trunk switched traffic (see Figure 2). NOTE 4 - Virtual international connecting point (see ITU-T Rec. G.101). NOTE 5 - This figure shows typical examples utilizing the defined interfaces. NOTE 6 - For
38、 different interfaces, the values of Li and Lo are, in general, not equal. NOTE 7 - For details, refer to Figure UQ.512 and Fi,- 2/G.960. Figure YQ.551- Interfaces, transmission levels and test points at a digital exchange 2 ITU-T Rw. Q.551 (Oll2002) International long distance connection Analogue e
39、xchange , transit /, c, A Cl transit C?l CZ 1 Digital exchange A T15153OC-O2 - 4-wire Analogue lines 2-wire digital lines _ -c -* - -*- NOTE - The trunk between local exchanges carry local traffic only. C?, C?l Digital Analogue Digital local local u C?, local C?, u exchange exchange exchange Figure
40、2/Q.551- Interfaces in possible network interconnections A Digital exchange czz local Interface types V and Z may appear remote from the exchange through the use of digital transmission facilities. When this occurs, there should be no impact on transmission parameters other than delay. Transmission
41、parameters associated with interface Z include the effects of the equipment provided for interfacing the analogue subscriber line to the digital switching network of the exchange. It is necessary to ensure that representative DC currents are flowing during the measurements of all of these transmissi
42、on parameters. These DC currents can contribute to noise, distortion, crosstalk, variation of gain with input level, etc. Therefore, appropriate allowances for this must be made. In some cases, where indicated, the permissible limits quoted include these allowances. Detailed transmission characteris
43、tics for these interfaces are provided in the following Recommendations: - - - In the present Recommendations, values given for transmission characteristics relate to the path the overall characteristics for connections involving two interfaces can, in most cases, be obtained by suitably combining t
44、hese values (see clause 3). In the future, other interfaces may be defined. These Recommendations consider analogue signals which are encoded in accordance with ITU-T Rec. G.7 1 1. The transmission characteristics of voice-frequency (VF) connections through a digital transit exchange should in princ
45、iple provide performance in accordance with ITU-T Rec. G.712 and, where applicable, ITU-T Rec. Q.45 bis (see also ITU-T Rec. G. 142). ITU-T Rec. Q.552 for 2-wire analogue interfaces; ITU-T Rec. Q.553 for 4-wire analogue interfaces; ITU-T Rec. Q.554 for digital interfaces. ITU-T RC. Q.551 (OlL2002) 3
46、 The principles of ITU-T Rec. G.142 and the limits of ITU-T Rec. G.712 have been used as a basis for establishing the transmission characteristics for analogue voice-frequency connections specified in 2Q.552 and 3/Q.553. The limit values are not necessarily identical with those specified in the G-se
47、ries, since in the case of a connection through the exchange, additional allowances generally have been made for cabling (see clause 2). The values given are to be considered as either “design“ or “performance objectives“ according to the explanations of the terms given in ITU-T Rec. G.102 and the p
48、articular context. The specification clauses in this Recommendation exclude the effects of auxiliary functions such as echo suppression, echo cancellation or transmission to the subscriber of metering impulses, or of non-telephony functions such as telemetering over the subscriber pair. 1.2 Definiti
49、ons 1.2.1 Exchange test points, exchange input and output and half-connections 1.2.1.1 exchange test points: The exchange test points shown in Figure 1 are defined for specification purposes. They generally do not physically exist in an exchange but are accessed via the digital switching network. In this case, some or ail of the switching network will be included in the path from the exchange interface to the access points. The transmission parameters affected by this means of access are the absolute group delay and possibly jitter and wander and bit er
