1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.108TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(09/2003) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone connections and circuits General definitions Application of the E-model: A planning gu
2、ide Amendment 1: New Appendix I: The relationship between and interaction of talker echo and absolute delay ITU-T Recommendation G.108 (1999) Amendment 1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100
3、G.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 of the 4-wire chain formed by
4、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.150G.159 Apparatus associated wi
5、th 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 systems G.190G.199 GENERAL CHARAC
6、TERISTICS 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 LINKS AND INTERCONNECTION WITH ME
7、TALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND 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 QUALITY OF SERVICE A
8、ND PERFORMANCE - GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS 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.108 (1999)/Amd.1 (09/2003) i ITU-
9、T Recommendation G.108 Application of the E-model: A planning guide Amendment 1 New Appendix I: The relationship between and interaction of talker echo and absolute delay Source Amendment 1 to ITU-T Recommendation G.108 (1999) was agreed by ITU-T Study Group 12 (2001-2004) on 30 September 2003. ii I
10、TU-T Rec. G.108 (1999)/Amd.1 (09/2003) 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 permanent organ of ITU. ITU-T is responsible for studying technic
11、al, 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, establishes the topics for study by the ITU-T study groups which, in
12、 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 standards are prepared on a collaborative basis with ISO and IEC.
13、NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensur
14、e 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 other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does no
15、t suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning th
16、e 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 received notice of intellectual property, protected by patents, w
17、hich 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. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means
18、 whatsoever, without the prior written permission of ITU. ITU-T Rec. G.108 (1999)/Amd.1 (09/2003) 1 ITU-T Recommendation G.108 Application of the E-model: A planning guide Amendment 1 New Appendix I: The relationship between and interaction of talker echo and absolute delay This appendix is intended
19、 to provide guidance on the relationship between and interaction of talker echo and absolute delay by means of graphs which result from calculations with the E-model as contained in ITU-T Rec. G.107 (03/2003). Figure I.1 illustrates the combined effects of talker echo in the presence of absolute del
20、ay, whereas Figures I.2a and I.2b illustrate the effects of talker echo only (all three figures have been taken from ITU-T Rec. G.131). It should be noted that, the upper graph in Figure I.1 illustrates the effect of absolute delay in the absence of any echo (see also Figure 1 of ITU-T Rec. G.114).
21、Figures I.3 through I.7 illustrate the comparison of the effects of talker echo only with the combined effects of talker echo and absolute delay; each for a given value of talker echo loudness rating TELR. NOTE All graphs are based on the 2003 version of the E-model. The graphs depicting the effects
22、 of talker echo have been calculated with Ta = 0, T = Tr/2 by means of recursive calculation; whereas the graph for absolute delay, in the absence of echo, is based on Ta = 0, Tr = 0 as provided in ITU-T Rec. G.114. From a transmission planners perspective, it is important to understand that the eff
23、ects of talker echo may be eliminated by the proper deployment of an echo cancelling device, which performs in accordance with, or even exceeds, the requirements given in ITU-T Rec. G.168. In addition, it is also very important to understand that the effect of absolute delay cannot be eliminated by
24、the deployment of technology. Talker echo and absolute delay may effect different sequences of the same conversation, which is the reason why, under normal circumstances, the combination of both effects has to be taken as the basis for transmission planning. However, the differences, as shown in Fig
25、ures I.3 through I.7, may be taken as useful brackground information for tutorial purposes; any application, in exceptional cases, is left to the individual transmission planners discretion. 2 ITU-T Rec. G.108 (1999)/Amd.1 (09/2003) 0 50 100 150 200 250 300 350 400 450 5005060708090100G.108AMD.1_FI.
26、1Mouth-to-ear-delay/msE-modelrating RNo talker echoTELR = 65 dBTELR = 55 dBTELR = 45 dBTELR = 35 dBTELR = 25 dBFigure I.1/G.108 Combined effects of talker echo in the presence of absolute delay 250R = 90R = 80R = 74R = 70R = 60R = 50100 200 300 400 50030354045505560657075G.108AMD.1_FI.2aMean one-way
27、 delay of the echo path (ms)Talker echoloudness ratingTELR(dB)Figure I.2a/G.108 Effects of talker echo based on E-model ITU-T Rec. G.108 (1999)/Amd.1 (09/2003) 3 100R = 90R = 80R = 74R = 70R = 60R = 5010 20 30 40 5012141618202224262830G.108AMD.1_FI.2bMean one-way delay of the echo path (ms)Talker ec
28、holoudness ratingTELR(dB)Figure I.2b/G.108 Effects of talker echo based on E-model 0 50 100 150 200 250 300 350 400 450 5005060708090100G.108AMD.1_FI.3Mouth-to-ear-delay/msE-modelrating RTalker echoTalker echo plus absolute delayFigure I.3/G.108 Comparison of the effects of talker echo with the comb
29、ined effects of talker echo and absolute delay; for TELR = 65 dB 4 ITU-T Rec. G.108 (1999)/Amd.1 (09/2003) 0 50 100 150 200 250 300 350 400 450 5005060708090100G.108AMD.1_FI.4Mouth-to-ear-delay/msE-modelrating RTalker echoTalker echo plus absolute delayFigure I.4/G.108 Comparison of the effects of t
30、alker echo with the combined effects of talker echo and absolute delay; for TELR = 55 dB 0 50 100 150 200 250 300 350 400 450 5005060708090100G.108AMD.1_FI.5Mouth-to-ear-delay/msE-modelrating RTalker echoTalker echo plus absolute delayFigure I.5/G.108 Comparison of the effects of talker echo with th
31、e combined effects of talker echo and absolute delay; for TELR = 45 dB ITU-T Rec. G.108 (1999)/Amd.1 (09/2003) 5 0 50 100 150 200 250 300 350 400 450 5005060708090100G.108AMD.1_FI.6Mouth-to-ear-delay/msE-modelrating RTalker echoTalker echo plus absolute delayFigure I.6/G.108 Comparison of the effect
32、s of talker echo with the combined effects of talker echo and absolute delay; for TELR = 35 dB 0 50 100 150 200 250 300 350 400 450 5005060708090100G.108AMD.1_FI.7Mouth-to-ear-delay/msE-modelrating RTalker echoTalker echo plus absolute delayFigure I.7/G.108 Comparison of the effects of talker echo w
33、ith the combined effects of talker echo and absolute delay; for TELR = 25 dB Printed in Switzerland Geneva, 2004 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series B Means of expression: definitions, symbols, classification Series C General telecommunication statistics
34、 Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I
35、Integrated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia signals Series K Protection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M TMN and network
36、maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone in
37、stallations, local line networks Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks and open system communications Series Y Global information infrastructure, Internet protocol aspects and Next Generation Networks Series Z Languages and general software aspects for telecommunication systems
