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.107.1 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
2、 Wideband E-model Recommendation ITU-T G.107.1 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 General Recommendations on the transmission quality
3、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 extension circuits G.130G.139 General characteris
4、tics 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.169 Transmission plan aspects of special circu
5、its 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-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARA
6、CTERISTICS 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 RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRAN
7、SMISSION 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 ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTE
8、RISTICS 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.107.1 (06/2015) i Recommendation ITU-T G.107.1 Wideband E-model Summary R
9、ecommendation ITU-T G.107.1 gives the algorithm for the wideband (WB) version of the E-model as the common ITU-T transmission rating model for planning speech services that provide WB speech transmission (50-7000 Hz). This computational model can be useful to transmission planners, to help ensure th
10、at users 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 different types of degradations occurring on the en
11、tire transmission path, mouth-to-ear. This WB-E-model is an adapted version of the narrowband (NB) (300-3400 Hz) E-model, typically referred to as “the E-model“, which is described in Recommendation ITU-T G.107. It does not replace the NB E-model. Instead, it describes a separate WB version of the m
12、odel that uses, within limits, similar concepts and input parameters as the NB E-model. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.107.1 2011-12-14 12 11.1002/1000/11453 2.0 ITU-T G.107.1 2015-06-29 12 11.1002/1000/12506 _ * To access the Recommendation, type the URL
13、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.107.1 (06/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the
14、 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 technical, operating and tariff questions and issuing Recommendations on them with a view to standa
15、rdizing 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 turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is cov
16、ered 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. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indi
17、cate both a telecommunication 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 achiev
18、ed 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 not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL P
19、ROPERTY 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 concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asse
20、rted 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, which may be required to implement this Recommendation. However, implementers are cautioned
21、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 publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. R
22、ec. ITU-T G.107.1 (06/2015) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 WB E-model . 3 6.1 Introduction 3 6.2 Transmission rating scale of the WB E-model . 3 7 The structure and basic algorithms of the WB E-model . 4 7.1 Ca
23、lculation of the transmission rating factor, R . 5 7.2 Basic signal-to-noise ratio, Ro,WB 6 7.3 Simultaneous impairment factor, Is,WB 6 7.4 Delay impairment factor, Id,WB 6 7.5 Equipment impairment factor, Ie,WB 8 7.6 Advantage factor, A 8 7.7 Default values . 8 Annex A MOS values derived from the t
24、ransmission rating factor R 10 Bibliography. 11 Rec. ITU-T G.107.1 (06/2015) 1 Recommendation ITU-T G.107.1 Wideband E-model 1 Scope This Recommendation describes the WB version of a computational model, known as the E-model, that has proven useful as a transmission planning tool for assessing the c
25、ombined effects of variations in several transmission parameters that affect conversational1 quality. 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 n
26、etworks. It must be emphasized that the primary output from the model is the “rating 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 agr
27、eed-upon model recommended by the ITU-T). This version is an adapted version of the NB (300-3400 Hz) E-model, typically referred to as “the E-model“, which is described in ITU-T G.107. The WB version addresses scenarios which include WB (50-7000 Hz) transmission. It does not replace the NB E-model.
28、Instead, it describes a separate WB-version of the model that uses, within limits, similar concepts and input parameters as the NB E-model. The current version captures the effects of loudness loss, background noise at the sending side, circuit noise, talker echo, absolute delay, WB speech coding, a
29、nd voice-over-IP packet-loss. Degradations which are covered but have not yet been studied in detail are the background noise at the receiving side and the listener echo. Degradations which are not yet covered are non-optimum sidetone levels and quantizing distortions. For many parameter combination
30、s of high importance to transmission planners, ITU-T G.107.1 can be used with confidence (e.g., loudness loss, send-side noise, coding distortions), but for some parameter combinations of high importance (e.g., the effects of delay in conjunction with other impairments), WB E-model predictions have
31、been questioned and are currently under study. Regarding the interpretation of the WB E-model ratings, note that the current versions of b-ITU-T G.108, b-ITU-T G.108.1 and b-ITU-T G.109 do not refer to the WB version described here, but only to the NB version of the E-model described in ITU-T G.107.
32、 2 References The following ITU-T Recommendations and other 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 revisi
33、on; users of this Recommendation are therefore encouraged 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 R
34、ecommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.107 Recommendation ITU-T G.107 (2015), The E-model: a computational model for use in transmission planning. _ 1 Conversational quality in this context refers to transmission characteristics, e.g., long
35、 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.107.1 (06/2015) ITU-T G.113 Recommendation ITU-T G.113 (2007), Transmission impairments due t
36、o speech processing. ITU-T G.722 Recommendation ITU-T G.722 (2012), 7 kHz audio-coding within 64 kbit/s. ITU-T O.41 Recommendation ITU-T O.41 (1994), Psophometer for use on telephone-type circuits. ITU-T P.800 Recommendation ITU-T P.800 (1996), Methods for subjective determination of transmission qu
37、ality. ITU-T P.833 Recommendation ITU-T P.833 (2001), Methodology for derivation of equipment impairment factors from subjective listening-only tests. ITU-T P.833.1 Recommendation ITU-T P.833.1 (2009), Methodology for the derivation of equipment impairment factors from subjective listening-only test
38、s for wideband speech codecs. ITU-T P.834 Recommendation ITU-T P.834 (2015), Methodology for the derivation of equipment impairment factors from instrumental models. ITU-T P.834.1 Recommendation ITU-T P.834.1 (2015), Methodology for the derivation of equipment impairment factors from instrumental mo
39、dels for wideband speech codecs. 3 Definitions This Recommendation does not define any new terms. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: LSTR Listener Sidetone Rating MOS Mean Opinion Score NB Narrowband OLR Overall Loudness Rating RLR Receive
40、 Loudness Rating SLR Send Loudness Rating STMR Sidetone Masking Rating TELR Talker Echo Loudness Rating WB Wideband WEPL Weighted Echo Path Loss 5 Conventions None. Rec. ITU-T G.107.1 (06/2015) 3 6 WB E-model 6.1 Introduction The complexity of modern networks requires that, for transmission planning
41、, the many transmission parameters be not only considered individually, but also that their combined effects be taken into account. This can be done by “expert, informed guessing“, but a more systematic approach is desirable, such as by using a computational model. The output from the model describe
42、d here is a scalar transmission rating value, R, which varies directly with the overall conversational quality. ITU-T G.113 gives guidance about specific impairments, including combined effects based upon a simplification of the model. 6.2 Transmission rating scale of the WB E-model For the narrowba
43、nd (NB) case described in ITU-T G.107, the transmission rating scale ranges from R = 0 (lowest possible quality) to R = 100 (optimum quality). On this scale, a default NB transmission channel including logarithmic PCM coding and a noise floor (default parameter values according to Table 2 of ITU-T G
44、.107) obtains a rating of R = 93.2. For a WB speech transmission channel, the quality is generally judged better than that for a NB channel. Thus, this scale range was extended in order to be also applicable to WB transmission scenarios. In the present WB version, the E-model is defined for a WB tra
45、nsmission channel of 50-7000 Hz, as it is defined in ITU-T G.722. Unfortunately, it is not possible to obtain direct human judgements on the R-scale, as this scale has additivity properties which are not reflected by ordinary rating scales. Instead, for NB conditions, ITU-T recommends collecting jud
46、gements on a 5-point absolute category rating scale (see ITU-T P.800). The mean rating, averaged over all test participants and stimuli reflecting the same circuit condition, is then called a mean opinion score (MOS). It has been shown that MOS ratings differ between tests where only NB stimuli are
47、presented, and tests where both NB/WB or purely WB stimuli are presented, as the use of the scale is largely influenced by the stimulus set. On the other hand, there is also experimental evidence that judgements for WB samples collected in a purely WB context do not differ significantly from those c
48、ollected in a mixed NB/WB context (see b-Barriac and b-Takahashi). In addition to the stimulus bandwidth, test results are influenced by the test participant group, the language, the participants native country, etc. b-Mller-01. For a NB context, an average S-shaped relationship is defined between t
49、he R-scale (range 0;100) and MOS ratings (range 1;4.5) collected from “average“ test participants in an “average“ experimental setting, see Annex B and Appendix I of ITU-T G.107. For a WB or a mixed NB/WB context, the R-scale was extended in a way which leaves the NB use of the scale unaffected, including the position of the reference connection (default parameter settings according to Table 2 of ITU-T G.107). Such an extension can be based on pairs of
