1、 International Telecommunication Union ITU-T G.109TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1(01/2007) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone connections and circuits General definitions Definition of categories of speech transm
2、ission quality Amendment 1: New Appendix I The E-model-based quality contours for predicting speech transmission quality and user satisfaction from time-varying transmission impairments ITU-T Recommendation G.109 (1999) Amendment 1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGIT
3、AL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE 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
4、 connections G.120G.129 General characteristics 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 telepho
5、ne circuits and national extension circuits G.150G.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 system
6、s G.180G.189 Software tools for transmission systems 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 T
7、ELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGI
8、TAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999ACCESS NETWORKS G.9000G.9999 For
9、 further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.109 (1999)/Amd.1 (01/2007) i ITU-T Recommendation G.109 Definition of categories of speech transmission quality Amendment 1 New Appendix I The E-model-based quality contours for predicting speech transmission quality a
10、nd user satisfaction from time-varying transmission impairments Source Amendment 1 to ITU-T Recommendation G.109 (1999) was agreed on 25 January 2007 by ITU-T Study Group 12 (2005-2008). ii ITU-T Rec. G.109 (1999)/Amd.1 (01/2007) FOREWORD The International Telecommunication Union (ITU) is the United
11、 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 issuing Recommendations on them with a view to standardizing telecommu
12、nications 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 turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the proce
13、dure 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. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telec
14、ommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of thes
15、e 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 not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU
16、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 the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU member
17、s 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, which may be required to implement this Recommendation. However, implementers are cautioned that this may not
18、represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.109 (1
19、999)/Amd.1 (01/2007) iii CONTENTS Page New Appendix I The E-model-based quality contours for predicting speech transmission quality and user satisfaction from time-varying transmission impairments 1 I.1 Abstract. 1 I.2 The E-model reduced to the transport layer . 1 I.3 Contours of speech transmissio
20、n quality (contours of user satisfaction) . 3 I.4 Predicting speech transmission quality from time-varying transmission impairments with the use of quality contours. 6 I.5 Appendix I references. 9 ITU-T Rec. G.109 (1999)/Amd.1 (01/2007) 1 ITU-T Recommendation G.109 Definition of categories of speech
21、 transmission quality Amendment 1 New Appendix I The E-model-based quality contours for predicting speech transmission quality and user satisfaction from time-varying transmission impairments (This appendix does not form an integral part of this Recommendation) I.1 Abstract This appendix introduces
22、contours of speech transmission quality (or contours of user satisfaction) that can be used to predict speech transmission quality from time-varying transmission impairments. Quality contours are derived from the ITU-T E-model ITU-T G.107 upon reducing it to the transport layer only (i.e., with assu
23、med default values characterizing perfect terminals). The shape of quality contours is determined by the Delay Impairment Iddthat covers loss of interactivity and the Effective Equipment Impairment Ie-effthat covers information loss due to encoding scheme and packet loss. The proposed quality contou
24、rs determine the rating factor R for all possible combinations of packet loss (assuming a given encoding scheme) and mouth-to-ear delay (assuming echo-free connections). Quality contours can be used in cross-layer optimization of various communications layers (e.g., adaptive playout scheduling at th
25、e application layer, traffic differentiation at the MAC layer) when predicting end-to-end speech transmission quality from time-varying transmission impairments. I.2 The E-model reduced to the transport layer The ITU-T E-model combines individual impairments (loss, delay, echo, codec type, noise, et
26、c.) due to both the signals properties and the network characteristics into a single, overall measure of conversational voice quality called the R factor: AIIIRReffedso+=(I-1) The calculations of the rating factor R are based on a number of input parameters and include complex mathematical formulas.
27、 To assist with calculations, ITU has established a number of default parameters (Table 2 in ITU-T G.107). If all parameters that do not depend on the transmission over the network are set to the default values (i.e., assuming perfect terminals) or ideal ones (e.g., TELR which is set to infinity), t
28、he expression for the R factor can be reduced to the transport layer as follows: effeddoIIRR= (I-2) In this equation, Idd is the Delay Impairment factor which captures the effect of transmission delay (mouth-to-ear) in echo-free connections and Ie-eff is the Effective Equipment Impairment factor whi
29、ch captures the effect of information loss due to both encoding scheme and packet loss. In the context of VoIP transmission assessment, both impairments are relevant. Since both impairments are isolated, their contributions to the quality degradation can be studied separately. NOTE All figures displ
30、ayed in this appendix have been calculated with the current (2005) version of the E-model. The most recent version should be used in conjunction with this appendix. 2 ITU-T Rec. G.109 (1999)/Amd.1 (01/2007) I.2.1 Delay Impairment Idd Delay Impairment Iddrepresents impairment due to absolute transmis
31、sion delay (e.g., mouth-to-ear) in echo-free connections. ITU-T G.107 gives a fully analytical expression for calculating Idd. Figure I.1 shows calculated Delay Impairment Iddas a function of absolute transmission delay Ta. G.109(99)Amd1_FI.1Idd40302010050100 200 300 400 5000TamsDelay impairment due
32、 to absolute delay G.107 (03/2005)Figure I.1 Delay impairment Iddas a function of absolute transmission delay TaI.2.2 Effective Equipment Impairment Ie-eff The Effective Equipment Impairment Ie-effcaptures the effect of information loss due to both encoding scheme and packet loss. The current versio
33、n of the E-model is able to quantify the effect of random (and for general predictions also bursty) packet loss in narrow-band speech transmission ITU-T G.107 and ITU-T G.113ApI. Figure I.2 shows for several codecs how the Effective Equipment Impairment increases as packet loss increases. This figur
34、e deals only with one specific packetization interval per codec: 10 ms for G.711 random loss, 20 ms for G.711 bursty loss, G.729A/E (both bursty and random loss), GSM-EFR, and 30 ms for G.723.1 (random loss only). G.109(99)Amd1_FI.2504540353025201510502 4 6 8 101214161820Ie-effPpl%G.711 w. PLC-burst
35、y lossG.711 w/o PLC-random lossG.729E w. PLC-bursty lossGSM-EFR w. PLC-random lossG.729A+VAD w. PLC-bursty lossG.723.1+VAD w. PLC-random lossG.729A+VAD w. PLC-random lossG.711 w. PLC-random lossEffective equipment impairment G.113/App. I (05/2002)Figure I.2 Effective Equipment Impairment Ie-effas a
36、function of packet loss PplITU-T Rec. G.109 (1999)/Amd.1 (01/2007) 3 I.3 Contours of speech transmission quality (contours of user satisfaction) The R factor reduced to transmission layer can be calculated from transmission impairments (e.g., Iddand Ie-eff) described in clause I.2 as follows: )()(0
37、pleffeaddPITIRR= (I-3) Equation I-3 can be viewed as a function of two variables: absolute transmission delay Ta(e.g., mouth-to-ear delay) and Packet-loss Probability Ppl(with assumed encoding scheme). By placing Taon the X-axis and Pplon the Y-axis it is possible to draw values of R for all possibl
38、e combinations of loss and delay. Figure I.3 shows the contours of Rating Factor R calculated for the G.711 encoding scheme (random packet loss) with Packet Loss Concealment (PLC) implemented. G.109(99)Amd1_FI.36070809050505090807070606060181614121086420010 3040200Ppl%TamsFACTOR R CONTOURS: G.711 w.
39、 PLC, random loss G.113/App. I (05/2002)Figure I.3 Contours of rating factor R calculated for G.711 encoding scheme (random packet loss, PLC) ITU-T G.109 defines categories of speech transmission quality and categories of user satisfaction in terms of ranges of R. Consequently, it is possible to dra
40、w contours of speech transmission quality to be expected by end user (contours of user satisfaction) as shown in Figure I.4. G.109(99)Amd1_FI.4not recommendedalmost all users dissatisfiedmany users dissatisfiedsatisfiedsome users dissatisfiedvery satisfied1816141210864200 100 300 400200Ppl%TamsQUALI
41、TY CONTOURS: G.711 w. PLC, random loss G.113/App. I (05/2002)Figure I.4 Contours of user satisfaction (contours of speech transmission quality) for G.711 encoding scheme (random packet loss, PLC) 4 ITU-T Rec. G.109 (1999)/Amd.1 (01/2007) Figures I.5 to I.12 show contours of quality calculated for a
42、number of encoding schemes. They are based on the ITU-T E-model analytical formulas (Equations 3-27, 3-28, 3-29 in ITU-T G.107) and tabulated values (Tables I.3, I.4 in ITU-T G.113ApI) for calculating Idd and Ie-eff. G.109(99)Amd1_FI.5not recommendedalmost all users dissatisfiedmany users dissatisfi
43、edsatisfiedsome users dissatisfiedvery satisfied1816141210864200 100 300 400200Ppl%TamsQUALITY CONTOURS: G.711 w/o PLC, random loss G.113/App. I (05/2002)Figure I.5 Quality contours calculated for G.711 encoding scheme (random packet loss) without PLC G.109(99)Amd1_FI.6not recommendedalmost all user
44、s dissatisfiedmany users dissatisfiedsatisfiedsome users dissatisfiedvery satisfied1816141210864200 100 300 400200Ppl%TamsQUALITY CONTOURS: G.711 w. PLC, bursty loss G.113/App. I (05/2002)Figure I.6 Quality contours calculated for G.711 encoding scheme (bursty packet loss) with PLC ITU-T Rec. G.109
45、(1999)/Amd.1 (01/2007) 5 G.109(99)Amd1_FI.7not recommendedalmost all users dissatisfiedmany users dissatisfiedsatisfiedsome users dissatisfiedvery satisfied1816141210864200 100 300 400200Ppl%TamsQUALITY CONTOURS: G.729A+VAD w. PLC, random loss G.113/App. I (05/2002)Figure I.7 Quality contours calcul
46、ated for G.729A encoding scheme (random packet loss) with PLC G.109(99)Amd1_FI.8not recommendedalmost all users dissatisfiedmany users dissatisfiedsatisfiedsome users dissatisfiedvery satisfied1816141210864200 100 300 400200Ppl%TamsQUALITY CONTOURS: G.729A+VAD w. PLC, bursty loss G.113/App. I (05/20
47、02)Figure I.8 Quality contours calculated for G.729A encoding scheme (bursty packet loss) with PLC G.109(99)Amd1_FI.9not recommendedalmost all users dissatisfiedmany users dissatisfiedsatisfiedsome users dissatisfied181614121086420010 3040200Ppl%TamsQUALITY CONTOURS: G.729E+VAD w. PLC, bursty loss G
48、.113/App. I (05/2002)very satisfiedFigure I.9 Quality contours calculated for G.729E encoding scheme (bursty packet loss) with PLC 6 ITU-T Rec. G.109 (1999)/Amd.1 (01/2007) G.109(99)Amd1_FI.10not recommendedalmost all users dissatisfiedmany users dissatisfiedsatisfiedsome users dissatisfiedvery sati
49、sfied1816141210864200 100 300 400200Ppl%TamsQUALITY CONTOURS: G.723.1+VAD w. PLC, random loss G.113/App. I (05/2002)Figure I.10 Quality contours calculated for G.723.1 encoding scheme (random packet loss) with PLC G.109(99)Amd1_FI.11not recommendedalmost all users dissatisfiedmany users dissatisfiedsatisfiedsome users dissatisfied181614121086420010 3040200Ppl%TamsQUALITY CONTOURS: GSM-EFR w. PLC, random loss G.113/App. I (05/2002)very satisf
