1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.175TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2000) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone connections and circuits Transmission plan aspects of special circuits and connections using the
2、international telephone connection network Transmission planning for private/public network interconnection of voice traffic ITU-T Recommendation G.175 (Formerly CCITT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE
3、CONNECTIONS AND CIRCUITS G.100G.199 General definitions G.100G.109 General Recommendations on the transmission quality for an entire international telephone connection G.110G.119 General characteristics of national systems forming part of international connections G.120G.129 General characteristics
4、of the 4-wire chain formed by the international circuits and national extension circuits G.130G.139 General characteristics of the 4-wire chain of international circuits; international transit G.140G.149 General characteristics of international telephone circuits and national extension circuits G.15
5、0G.159 Apparatus associated with long-distance telephone circuits G.160G.169 Transmission plan aspects of special circuits and connections using the international telephone connection network G.170G.179 Protection and restoration of transmission systems G.180G.189 Software tools for transmission sys
6、tems G.190G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS 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 LIN
7、KS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA CHARACTERISTICS G.600G.699 TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.99
8、9 For further details, please refer to the list of ITU-T Recommendations. ITU-T G.175 (05/2000) i ITU-T Recommendation G.175 Transmission planning for private/public network interconnection of voice traffic Summary This ITU-T Recommendation deals with the digital interconnection of public ISDN/PSTN
9、and private networks. The primary application is to the overall quality of speech transmission for 3.1 kHz voiceband telephony using handsets, independent of all other types of services (e.g. facsimile and voiceband data) provided by those networks. The intention is to give guidance for transmission
10、 planning purposes, not only for a given network operator, but also for negotiations between the involved network operators. Source ITU-T Recommendation G.175 was revised by ITU-T Study Group 12 (1997-2000) and approved under the WTSC Resolution 1 procedure on 18 May 2000. ii ITU-T G.175 (05/2000) F
11、OREWORD 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 is responsible for studying technical, operating and tariff questions and i
12、ssuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on thes
13、e topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSC Resolution 1. 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 expre
14、ssion “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 implementation of this Recommendation may involve the use of a claimed Intell
15、ectual 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 process. As of the date of approval of this Recommendation, ITU had not receive
16、d 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 urged to consult the TSB patent database. Ge3 ITU 2001 All rights reserve
17、d. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T G.175 (05/2000) iii CONTENTS Page 1 Scope. 1 2 Normative references 1 3 Abbreviations 2 4 Defini
18、tions 2 5 Reference configurations 4 6 Basic planning principle the impairment factor method in conjunction with the E-Model 7 7 Planning method and limits 9 7.1 Planning method . 9 7.2 Main parameters 11 7.3 Quality expectation and absolute upper planning limits. 12 7.4 Use of the E-Model. 12 7.4.1
19、 Input parameters 13 7.4.2 Performing the calculation. 14 7.4.3 Default values 15 8 Implementation of echo cancellers . 15 ITU-T G.175 (05/2000) 1 ITU-T Recommendation G.175 Transmission planning for private/public network interconnection of voice traffic 1 Scope Most of the ITU-T Recommendations in
20、 the G-series are presently based on configurations where the national part of an international connection is usually terminated by a single analogue telephone set or by a digital terminal. Consequently, these ITU-T Recommendations do not take into account PABXs (Private Automatic Branch Exchange) o
21、r private networks. However, modern private networks, mainly those of large size and/or using new technologies, will contribute in a specific, possibly significant amount to the overall transmission quality. This ITU-T Recommendation deals with the digital interconnection of public ISDN/PSTN and pri
22、vate networks. The primary application is to the overall quality of speech transmission for 3.1 kHz voiceband telephony using handsets, independent of all other types of services (e.g. facsimile and voiceband data) provided by those networks. The intention is to give guidance for transmission planni
23、ng purposes, not only for a given network operator, but also for negotiations between the involved network operators. For the purpose of this ITU-T Recommendation, only call paths between the private network and other networks (private or public) including telephone sets or other speech terminals ar
24、e considered. Consequently, the provision of through-connections between two interfaces to other networks, or a call path between two terminals inside the same network are not covered by this ITU-T Recommendation. NOTE Although in principle the planning of internal- and through-connections of the Pr
25、ivate Network is not covered here, the methods and rules described in this ITU-T Recommendation may be used for those applications as well. 2 Normative references The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions
26、of this Recommendation. At the time of publication, the editions indicated were 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
27、 and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. 1 ITU-T Recommendation G.100 (1993), Definitions used in Recommendations on general characteristics of international telephone connections and circuits. 2 ITU-T Recommendation G.101 (1996)
28、, The transmission plan. 3 ITU-T Recommendation G.107 (2000), The E-Model, a computational model for use in transmission planning. 4 ITU-T Recommendation G.108 (1999), Application of the E-model: A planning guide. 5 ITU-T Recommendation G.109 (1999), Definition of categories of speech transmission q
29、uality. 6 ITU-T Recommendation G.113 (1996), Transmission impairments. 7 ITU-T Recommendation G.122 (1993), Influence of national systems on stability and talker echo in international connections. 2 ITU-T G.175 (05/2000) 8 ITU-T Recommendation G.165 (1993), Echo cancellers. 9 ITU-T Recommendation G.
30、168 (2000), Digital network echo cancellers. 10 ITU-T Recommendation G.703 (1998), Physical/electrical characteristics of hierarchical digital interfaces. 11 CCITT Recommendation G.711 (1988), Pulse code modulation (PCM) of voice frequencies. 3 Abbreviations This ITU-T Recommendation uses the follow
31、ing abbreviations: ATM Asynchronous Transfer Mode DCME Digital Circuit Multiplication Equipment ETSI European Telecommunication Standards Institute %GoB Percentage Good or Better ICP International Connection Point ISDN Integrated Services Digital Network LSTR Listener SideTone Rating MOS Mean Opinio
32、n Score OLR Overall Loudness Rating PABX Private Automatic Branch eXchange PCM Pulse Code Modulation %PoW Percentage Poor or Worse PSTN Public Switched Telephone Network qdu Quantizing Distortion Unit RLR Receiving Loudness Rating SLR Sending Loudness Rating STMR SideTone Masking Rating TELR Talker
33、Echo Loudness Rating VPN Virtual Private Network WEPL Weighted Echo Path Loss 4 Definitions This ITU-T Recommendation defines the following terms: 4.1 private network: The term “private“ is normally used in conjunction with several PABXs forming a network, mainly in an application for a restricted u
34、ser group. In complement, the term “public“ is usually used to describe main national or regional telecommunication networks providing services to general public. The following list, specifying in more detail the definition of a private network, is also based on the assumption that the call path wit
35、hin the private network is contributing a possibly significant amount of transmission impairments to the overall transmission quality, such as loss, transmission time, number of qdus, etc. ITU-T G.175 (05/2000) 3 The term “private network“ is defined as follows: 1) It consists normally of more than
36、one switching equipment (PABX), connected via private or leased lines, forming a network, independent of its structure and hierarchy. Switching equipment and leased lines can be either digital or analogue. 2) It provides switching functions and all other features only to a single customer or a group
37、 of customers, but is not accessible to everyone. 3) There is no limitation by its geographical size, it is not restricted to the national area and it is not limited on the number of extensions and access points to other networks. A private network consists of private local exchanges providing inter
38、faces for all types of terminal elements and for transmission elements to other private local or private transit exchanges and private transit exchanges with interfaces for transmission elements to other private transit or private local exchanges. 4.2 public network: The term “public network“ is use
39、d in this ITU-T Recommendation for all networks providing their switching functions and features not only to a specific user group, but also to the general public. The word “public“ is not related to the legal status of the network operator. Public networks can be restricted to only a limited size o
40、f specific features and switching functions. Furthermore, public networks may provide access points only in a specific geographical area. From the point of view of a connection, public networks are mainly “transit networks“. However, they may also be considered as a combination of “transit and termi
41、nating networks“ in cases where the public network operator is also providing terminal equipment such as telephone sets, PABXs, or PABX-Features. 4.3 network elements: All the components forming a connection can be divided into three main groups. The interconnection between private and public networ
42、k is shown in the reference configurations of Figures 1 through 4. The private network is comprised of terminal elements, switching elements and transmission elements. 4.4 types of traffic: In the case of some private networks, the “main types of traffic“ via other networks (mainly public networks)
43、may be taken into account for a possible higher amount of permitted impairments within the private network. The inclusion of the type of external traffic into planning enables the planner, wherever this is possible, to extend the limits for specific parameters (e.g. transmission time) within the pri
44、vate network, resulting in a more economical design of the network. As a basic distinction for the traffic via public networks, three different types can be identified for planning purposes and with respect to the amount of transmission impairments. Referred to the switching element (local exchange)
45、 of the public network providing the access to the private network, Local Traffic means all connections in the local public network or in a restricted geographical area of the public network. A second type of traffic is the National Long Distance Call Traffic, which designates all calls in the entir
46、e area of a country. Usually this area is identical to the area of coverage of the major public network(s) in this country. Finally, International Calls must be considered to contribute in most cases with a higher amount of transmission impairments than national calls. The distinction into these typ
47、es of traffic may support negotiations between public and private network operators, not only for the partitioning of transmission impairments, but also in conjunction with other technical aspects, such as the correct insertion of echo cancellers, the use of ATM with nodes in different networks, etc
48、. 4 ITU-T G.175 (05/2000) 4.5 access to the public network: Among others, the type of access to a public network may also influence the transmission planning of the private network and may be helpful for negotiations between the network operators. “Access“ in this context means not only the physical
49、 characteristics of the interfaces between public and private networks, but also the point of access with respect to the hierarchy of the public network and to additional features for private networks, provided by the public network. For large private networks, the point of access does not need to be identical to the access for single subscribers. According to the scope of this ITU-T Recommendation, only digital interfaces for the access to public networks are considered. 4.5.1 digital access at the local exchange: In most cases the access to th
