1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.177 (09/99) 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 voiceband services over hybrid InternetlPSTN connections ITU-T Recommendation G. 177 (Previously CCITT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPH
3、ONE CONNECTIONS AND CIRCUITS General definitions General Recommendations on the transmission quality for an entire international telephone connection General characteristics of national systems forming part of international connections General characteristics of the 4-wire chain formed by the intern
4、ational circuits and national extension circuits General characteristics of the 4-wire chain of international circuits; international transit General characteristics of international telephone circuits and national extension circuits Apparatus associated with long-distance telephone circuits Transmi
5、ssion plan aspects of s eclal circuits and connect rnational telephone conne cp ion network . Protection and restoration of transmission systems Software tools for transmission systems INTERNA TIONA L A NA L OGUE CARRIER SYSTEM GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- TRANSMISSION SYS
6、TEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TESTING EQUIPMENTS TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TRANSMISSION SYS
7、TEMS TERMINAL EQUIPMENTS DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION G. 1004.1 99 G. 1 004. 1 O9 G. 1104.1 19 G. 1204.129 G. 1 304.1 39 G. 1404.149 G. 1504.159 G.160-G. 169 G.17-G.179 G.18O-G.189 G. 1 904.1 99 G.20O-G.299 G
8、.30O-G.399 G.400-G.449 G.450-G.499 G.600-G.699 G.700-G.799 G.800-G.899 G.900-G.999 For firth derails, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION G.177 TRANSMISSION PLANNING FOR VOICEBAND SERVICES OVER HYBRU) INTERNETRSTN CONNECTIONS Summary This Recommendation provides trans
9、mission performance guidelines for voiceband services over networks that are an interconnection of an IP network (e.g. “the Internet“) and the PSTN. As modern telecommunications systems continue to evolve, hybrid networks of various kinds will become more prevalent. This tendency, together with the
10、reality that voiceband communications will be an important source of traffic on such networks, has led ITU-T to develop this Recommendation. The intent is to provide to a wide audience a set of principles on transmission performance aspects of hybrid Int ernet/PSTN connect ions. Source ITU-T Recomme
11、ndation G.177 was prepared by ITU-T Study Group 12 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 30 September 1999. Recommendation G.177 (09/99) 1 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunicati
12、ons. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The 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 Telecommu
13、nication Standardmtion Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-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 laid down in WTSC
14、Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommkdation the term recognized operating agency (ROA) includes any individual, company, corporation or governmen
15、tal organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defined in the Constitution of the ITU (Geneva, 1992). INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recom
16、mendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others ouside of the Recommendation development process. As of the date of
17、approval of this Recommendation, the ITU had not 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 urged to consult
18、the TSB patent database. O ITU 2000 All rights reserved. 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 fiom the ITU. ii Recommendation G.177 (09/99) STDmITU-T RECMN
19、L.177-ENGL 1997 E q8b2591 Obb811i3 175 m 1 1.1 1.2 1.3 2 3 4 5 6 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.1 1 8 9 CONTENTS Page Scope. purpose and application Purpose . Application Terminology Scope Acronyms and Abbreviations . References . Performance of hybrid IntemetPSTN connections . Transmiss
20、ion channel characteristics of IP networks . Speech performance (end-to-end) Speech coder performance . E-Model equipment impairment factors (eifs) 7.1.1 7.1.2 Tandeming performance 7.1.3 . Other considerations for speech coders . Effects of transmission errors and packet loss 7.2.1 Bit errors 7.2.2
21、 Packet loss Loudness ratings and terminal characteristics . Delay and echo 7.4.2 Delay variation 7.4.3 Echo control . Temporal (syllable) clipping . Environmental (acoustic) noise Idle channel noise Noise contrast and comfort noise . Bandwidth . 7.4.1 Delay Stability loss Distortion Speech transmis
22、sion planning in hybrid networks . Non-voice transmission (end-to-end) . Recommendation G.177 (09199) - 2 2 4 5 7 7 8 9 9 9 9 10 10 10 11 11 12 13 14 14 14 14 15 15 15 15 16 . 111 Recommendation G. 177 TRANSMISSION PLANNING FOR VOICEBAND SERVICES OVER HYBRID (Geneva, 1999) INTERNETPSTN CONNECTIONS 1
23、 Scope, purpose and appcation 1.1 Scope This Recommendation provides transmission planning guidelines for voiceband services over connections that include Internet and PSTN segments, i.e. hybrid InternetPSTN connections. In particular, “voice over the Internet“ or “Voice over Internet Protocol“ (VoI
24、P) connections are considered, where at least part of the connection is over an Internet Protocol (IP) network. PSTN-only connections (i.e. connections that begin, end, and are carried only on the PSTN) are considered as the reference against which the performance of other connections is compared. T
25、his Recommendation provides end-to-end transmission performance guidance for hybrid InterneflSTN connections carrying voiceband services. When one of the terminals is attached to an IP network, it is assumed that this terminal has functionality defined in Recommendation H.323. (The terminal need not
26、 be an H.323 terminal, but is assumed to have that fnctionality.) To support these end-to-end guidelines, guidance is given for interworking nctions between Internet and PSTN. The fnctionality provided by InternetPSTN gateways presents special performance issues that must be addressed to ensure high
27、 quality service. Protocol details of IP and higher level protocols (e.g. TCP, UDP, RTP, RSVP) are not considered in this Recommendation. Rather, the impact on perfomance of voiceband services of the packetized aspects of IP networks, such as delay associated with packet assembly, lost or discarded
28、packets, is of primary interest here. The importance of user expectations for voiceband services on hybrid InternetPSTN networks is recognized. However, this Recommendation does not address this subject, nor does it offer detailed suggestions of how to assess the impact of user expectations on the a
29、cceptability of these services. Additional guidance on many of these issues is available in ITU-T P-series and G.lOO-series Recommendations. This Recommendation also includes discussion of issues associated with the interworking functions provided by InternetPSTN gateways. 1.2 Purpose This Recommend
30、ation provides guidance on basic telephony issues involved in providing voiceband services over hybrid InterneflSTN connections. This information will also be useful to equipment manufacturers, VoIP service providers, Internet Service Providers (ISPs), software developers, and PSTN providers where s
31、ervice goes over a gateway to IP networks. Traditional PSTN engineers will be familiar with the telephony aspects of this Recommendation, but will find usefiil the material on Internet-specific features of voiceband services over connections that incorporate an Internet segment. 1.3 Application It i
32、s intended that the guidelines provided in this Recommendation be applied by equipment manufacturers, VoIP service providers, ISPs, software developers, and PSTN providers. Those who provide services where the PSTN interconnects with IP networks through a gateway should find this information useful
33、as they design equipment, software and services for voiceband services over Recommendation G.177 (09/99) 1 hybrid InternetRSTN connections. Application of the guidelines herein by equipment manufkcturers, VoIP service providers, Internet Service Providers, software developers, and PSTN providers sho
34、uld enhance the quality of voiceband services delivmd over hybrid InterneWSTN connections. Furthermore, if widespread customer acceptance of VoIP service is desired, the resulting voiceband service quality should approach that of the PSTN. The guidance in this Recommendation applies to situatiodconn
35、ections where at least part of the connection is on an IP network. Special attention focussed on the “Gatewayhter-Working Function“ (which provides the essential intenvorking capabilities of these hybrid connections). A major application of this Recommendation will be Internet Telephony where the te
36、rminal (e.g. a PC) enjoys H.323 stack functionality. As noted above, this Recommendation will use PSTN-only connections as the reference against which the performance of other connections will be compared. This Recommendation applies to connections where the data transfer phase occurs over hybrid In
37、ternetRSTN connections. Issues of call Set-up, number translation (between PSTN and IP numbering), etc., are not considered in this Recommendation. This Recommendation applies to IP networks that provide voice telephony in accordance with any of the scenarios described in clause 5, Performance of hy
38、brid InterneflSTN connections. This Recommendation contains general information on end-to-end quality and the way in which quality is affected by various components in the VoIP system. A description of the relationship of the performance of terminals and of the network is also included. 2 Terminolog
39、y This Recommendation defines the following terms: 2.1 hybrid PSTNAnternet: A connection that includes at least one segment where trac is carried on the PSTN and at least one segment where trafc is carried on a network that uses the Internet Protocol suite. 2.2 gateway/IWF: A connection element that
40、 interconnects different networks and performs the necessary translation between the protocols used on those networks. 2.3 interwork The ability of two networks to be connected and transfer traffic fiom one to the other. 2.4 H.323-based terminal: A terminal that is either dedicated (e.g. a telephone
41、 set) or general purpose (e.g. a computer running an application that performs the terminal fiinction) and that: - is intended for connection to an IP network; - provides the hctionality defined in Recommendation H.323. 3 Acronyms and Abbreviations This Recommendation uses the following abbreviation
42、s: %GOB Per cent Good-or-Better %POW Per cent Poor-or-Worse ACELP Algebraic-Code-Excited Linear-Prediction ACR Absolute Category Rating ADPCM ADSL Asymmetric Digital Subscriber Line ATM Asynchronous Trarisfer Mode Adaptive Differential Pulse Code Modulation 2 Recommendation G.177 (09/99) BER CNG CS-
43、ACELP dB(A) dBm TU-T RECHN G-277-ENGL L999 48b259L Obb8122 blab UDP User Datagram Protocol WD Voiceband Data VDSL VOIP Voice 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
44、 below. A list of the currently valid ITU-T Recommendations is regularly published. ITU-T Recommendation G. 1 O 1 (1 996), The transmission plan. ITU-T Recommendation G. 107 (1998), The E-model, a computational model for use in transmission planning. ITU-T Recommendation G. 1 O8 (1 999), Application
45、 of the E-model - A planning guide. ITU-T Recommendation G. 109 (1999), Definition of categories of speech transmission quality. ITU-T Recommendation G. 1 13 (1 996), Transmission impairments. ITU-T Recommendation G. 1 14 (1996), One-way transmission time. ITU-T Recommendation G. 1 16 (1999), Transm
46、ission perjormance objectives applicable to end-to-end international connections. ITU-T Recommendation G. 13 1 (1996), Control of talker echo. ITU-T Recommendation G. 168 (1997), Digital network echo cancellers. ITU-T Recommendation G. 173 (1993), Transmission planning aspects of the speech service
47、in digital public land mobile networks. ITU-T Recommendation G. 174 (1 994), Transmission peflormance objectives for terrestrial digital wireless systems using portable terminals to access the PSW. ITU-T Recommendation G. 175 (1 997), Transmission planning for privatdpblic network interconnection of
48、 voice trafic. ITU-T Recommendation G. 176 (1997), Planning guidelines for the integration of ATM technology into networh supporting voiceband services. CCITT Recommendation G.7 1 1 (1 988), Pulse code modulation (PCM) of voice frequencies. ITU-T Recommendation G.723.1 (1996), Speech coders: Dual ra
49、te speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s. CCITT Recommendation G.726 (1990), 40, 32, 24, 16 kbit/s adaptive dzyerential plse code modulation (ADPCIY) . CCITT Recommendation G.728 (1992), Coding of speech at 16 kbith using low-delay code excited linear prediction. Recommendation G.177 (09/99) STD=ITU-T RECMN G.177-ENGL 1999 VBb259L Obb8123 552 - ITU-T Recommendation G.729 (1996), Coding of speech at 8 kbit/s using Conjugate- Structure Algebraic-Code-Excited Linear-Prediction (CS-A CELP). ITU-T Recommendation G.729
