1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.107 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2015) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone connections and circuits Transmission planning and the E-model T
2、he E-model: a computational model for use in transmission planning Recommendation ITU-T G.107 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 Transmission planning and the E-model G.100G.109 Gener
3、al 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 the international circuits and national ex
4、tension 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 with long-distance telephone circuits G.160G
5、.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 CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-T
6、RANSMISSION 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 METALLIC LINES G.400G.449 COORDINATION OF RA
7、DIOTELEPHONY 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 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED A
8、SPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.107 (06/2015) i Recommenda
9、tion ITU-T G.107 The E-model: a computational model for use in transmission planning Summary Recommendation ITU-T G.107 gives the algorithm for the so-called E-model as the common ITU-T transmission rating model. This computational model can be useful to transmission planners, to help ensure that us
10、ers will be satisfied with end-to-end transmission performance. The primary output of the model is a scalar rating of transmission quality. A major feature of this model is the use of transmission impairment factors that reflect the effects of modern signal processing devices. In the 2000 version of
11、 this Recommendation, an enhanced version of the E-model was provided in order to better take into account the effects of room noise at the send side and quantizing distortion. With the 2002 version, the impairment due to random packet loss was included in a parametric way for different codecs. Sinc
12、e the 2003 version, an enhanced modelling of quality in the case of low talker sidetone levels is provided. The 2005 version enabled more accurate quality predictions for codecs under (short-term) dependent packet loss. The 2009 version included an Appendix II describing a provisional impairment fac
13、tor framework for wideband speech transmission. In 2011, this appendix was updated in favour of a new Recommendation ITU-T G.107.1. In the current version, the model has been extended to provide an assessment of delay impairments that is also better tailored to less delay-sensitive use cases. Carrie
14、r-grade or enterprise-grade telephony systems must be assessed with the default delay sensitivity parameters, while communication systems with low or very low interactivity requirements can be assessed with different parameters. A reference implementation is given in Appendix III. History Edition Re
15、commendation Approval Study Group Unique ID* 1.0 ITU-T G.107 1998-12-03 12 11.1002/1000/4541 2.0 ITU-T G.107 2000-05-18 12 11.1002/1000/5074 3.0 ITU-T G.107 2002-07-14 12 11.1002/1000/6080 4.0 ITU-T G.107 2003-03-16 12 11.1002/1000/6253 5.0 ITU-T G.107 2005-03-01 12 11.1002/1000/7822 5.1 ITU-T G.107
16、 (2005) Amd. 1 2006-06-13 12 11.1002/1000/8864 6.0 ITU-T G.107 2008-08-29 12 11.1002/1000/9538 7.0 ITU-T G.107 2009-04-29 12 11.1002/1000/9730 8.0 ITU-T G.107 2011-12-14 12 11.1002/1000/11460 8.1 ITU-T G.107 (2011) Amd. 1 2012-06-07 12 11.1002/1000/11707 9.0 ITU-T G.107 2014-02-13 12 11.1002/1000/12
17、120 10.0 ITU-T G.107 2015-06-29 12 11.1002/1000/12505 _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.107 (06/2015) FOREW
18、ORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying
19、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, establishes the topics for study by the ITU-T study groups wh
20、ich, 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 standards are prepared on a collaborative basis with ISO an
21、d IEC. 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 (t
22、o ensure, 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 word
23、s does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU 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 conce
24、rning 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 received notice of intellectual property, protected by patent
25、s, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2015 All rights reserved. No part of this publica
26、tion may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.107 (06/2015) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5
27、 Conventions 2 6 The E-model, a computational model for use in transmission planning 2 6.1 Introduction 2 7 Structure and basic algorithms of the E-model . 3 7.1 Calculation of the transmission rating factor, R . 4 7.2 Basic signal-to-noise ratio, Ro . 4 7.3 Simultaneous impairment factor, Is 5 7.4
28、Delay impairment factor, Id . 5 7.5 Equipment impairment factor, Ie 7 7.6 Advantage factor, A 8 7.7 Default values . 9 Annex A Conditions for using the E-model 11 A.1 Examples of conditions where caution must be exercised when using the E-model 11 A.2 Conditions for which the performance of the E-mo
29、del has been improved by updating from the earlier version 12 Annex B Quality measures derived from the transmission rating factor R 15 Appendix I Calculation of R from MOSCQE values 17 Appendix II Provisional impairment factor framework for wideband speech transmission 18 Appendix III Reference imp
30、lementation of the E-model in ITU-T G.107 . 19 Appendix IV Use of the E-model in conjunction with noise reduction or echo canceller systems in the network or the terminal equipment . 20 Bibliography. 22 Rec. ITU-T G.107 (06/2015) 1 Recommendation ITU-T G.107 The E-model: a computational model for us
31、e in transmission planning 1 Scope This Recommendation describes a computational model, known as the E-model, that has proven useful as a transmission planning tool for assessing the combined effects of variations in several transmission parameters that affect the conversational1 quality of 3.1 kHz
32、handset telephony. This computational model can be used, for example, by transmission planners to help ensure that users will be satisfied with end-to-end transmission performance whilst avoiding over-engineering of networks. It must be emphasized that the primary output from the model is the “ratin
33、g factor“ R but this can be transformed to give estimates of customer opinion. Such estimates are only made for transmission planning purposes and not for actual customer opinion prediction (for which there is no agreed-upon model recommended by the ITU-T). The E-model can be used with confidence fo
34、r many combinations of high importance to transmission planners, but for some parameter combinations of high importance, E-model predictions have been questioned and are currently under study. Annex A provides further information in this regard. 2 References The following ITU-T Recommendations and o
35、ther references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encourag
36、ed to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone docume
37、nt, the status of a Recommendation. ITU-T G.107.1 Recommendation ITU-T G.107.1 (2015), Wideband E-model. ITU-T G.108 Recommendation ITU-T G.108 (1999), Application of the E-model: A planning guide. ITU-T G.109 Recommendation ITU-T G.109 (1999), Definition of categories of speech transmission quality
38、. ITU-T G.113 Recommendation ITU-T G.113 (2007), Transmission impairments due to speech processing. ITU-T P.833 Recommendation ITU-T P.833 (2001), Methodology for derivation of equipment impairment factors from subjective listening-only tests. _ 1 Conversational quality in this context refers to tra
39、nsmission characteristics, e.g., long transmission times, effects of talker echoes, etc. However, the E-model, as described in this Recommendation, is not intended to model transmission impairments during double talk situations. 2 Rec. ITU-T G.107 (06/2015) ITU-T P.834 Recommendation ITU-T P.834 (20
40、15), Methodology for the derivation of equipment impairment factors from instrumental models. ITU-T P.863 Recommendation ITU-T P.863 (2014), Perceptual objective listening quality assessment. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation None. 4 Abbreviatio
41、ns and acronyms This Recommendation uses the following abbreviations and acronyms: BurstR Burst Ratio GoB Good or Better LSTR Listener Sidetone Rating MOS Mean Opinion Score MNRU Modulated Noise Reference Unit OLR Overall Loudness Rating OPINE Overall Performance Index model for Network Evaluation P
42、LC Packet Loss Concealment PoW Poor or Worse qdu quantization distortion unit RLR Receive Loudness Rating SLR Send Loudness Rating STMR Sidetone Masking Rating TELR Talker Echo Loudness Rating WEPL Weighted Echo Path Loss 5 Conventions None. 6 The E-model, a computational model for use in transmissi
43、on planning 6.1 Introduction The complexity of modern networks requires not only that, for transmission planning, each of the many transmission parameters be considered individually but also that their combined effects be taken into account. This can be done by “expert, informed guessing“, but a mor
44、e systematic approach is desirable, such as by using a computational model. The output from the model described here is a Rec. ITU-T G.107 (06/2015) 3 scalar quality rating value, R, which varies directly with the overall conversational quality. ITU-T G.113 gives guidance about specific impairments,
45、 including combined effects based upon a simplification of the model. However, the output can also give nominal estimates of the user reactions, for instance in the form of percentages finding the modelled connection good or better (GoB) or poor or worse (PoW), as described in Annex B. Furthermore,
46、detailed guidance on the proper application of the E-model, as described in this Recommendation, is provided in ITU-T G.108. In addition, the definition of categories of speech transmission quality can be found in ITU-T G.109. 7 Structure and basic algorithms of the E-model The E-model is based on t
47、he equipment impairment factor method, following previous transmission rating models. It was developed by an ETSI ad hoc group called “Voice Transmission Quality from Mouth to Ear“. The reference connection, as shown in Figure 1, is split into a send side and a receive side. The model estimates the
48、conversational quality from mouth to ear as perceived by the user at the receive side, both as listener and talker. Figure 1 Reference connection of the E-model The transmission parameters used as an input to the computation model are shown in Figure 1. Values for room noise and for the D-factors ar
49、e handled separately in the algorithm for the send side and receive side and may be of different amounts. The parameters send loudness rating (SLR), receive loudness rating (RLR) and circuit noise Nc are referred to a defined 0 dBr point. All other input parameters are either considered as values for the overall connection, such as overall loudness rating (OLR), i.e., the sum of SLR and RLR, number of qdu, equipment impairment factors Ie and advantage factor A, or refer
