1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T P.562TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2004) SERIES P: TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS Objective measuring apparatus Analysis and interpretation of INMD voice-service measurements ITU-T Recomm
2、endation P.562 ITU-T P-SERIES RECOMMENDATIONS TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS Vocabulary and effects of transmission parameters on customer opinion of transmission quality Series P.10 Subscribers lines and sets Series P.30 P.300 Transmission standards Ser
3、ies P.40 Objective measuring apparatus Series P.50 P.500 Objective electro-acoustical measurements Series P.60 Measurements related to speech loudness Series P.70 Methods for objective and subjective assessment of quality Series P.80 P.800 Audiovisual quality in multimedia services Series P.900 Tran
4、smission performance and QoS aspects of IP end-points Series P.1000 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. P.562 (05/2004) i ITU-T Recommendation P.562 Analysis and interpretation of INMD voice-service measurements Summary This Recommendation provides advi
5、ce on the analysis and interpretation of INMD voice-service measurements. It describes methods to analyse individual measurement parameters over single and multiple calls. The effects of the location of an INMD on measurements are discussed and the use of customer opinion models, and how these can b
6、e used with INMD measurements, described. This Recommendation also looks at how INMD measurements can be applied to network planning and maintenance. Source ITU-T Recommendation P.562 was approved on 14 May 2004 by ITU-T Study Group 12 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU
7、-T Rec. P.562 (05/2004) 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 technical, operating a
8、nd 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 turn, produce
9、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. NOTE In this Re
10、commendation, 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 ensure e.g. interope
11、rability 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 not suggest that
12、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 the evidence, val
13、idity 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 patents, which may be require
14、d 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 2005 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, withou
15、t the prior written permission of ITU. ITU-T Rec. P.562 (05/2004) iii CONTENTS Page 1 Scope 1 2 Normative references 1 3 Abbreviations and definitions. 2 3.1 Abbreviations . 2 3.2 Definitions 3 4 Interpreting INMD measurements 3 4.1 Single call measurements . 3 4.2 Multiple call measurements 5 4.3 S
16、ample size. 6 5 Impact of Class C INMD location in the network 7 5.1 Context . 7 5.2 INMD location at the outgoing side of the international gateway . 8 5.3 INMD location at the incoming side of the international gateway 9 5.4 Comparative impact of both scenarios on the measures recommended in ITU-T
17、 Rec. P.561 . 9 5.5 Discussion. 10 5.6 Conclusion 11 6 Using INMD measurements to predict average customer opinion. 12 6.1 Using a model to predict customer opinion 12 6.2 Assumptions . 13 6.3 Model 14 6.4 Predictions 16 6.5 Diagnostics using an opinion model for INMDs of classes A, B or C. 17 7 Usi
18、ng INMD measurements for network planning 18 8 Using INMD measurements to maintain networks 18 8.1 Objectives provided by Recommendations in the G series 19 8.2 Additional thresholding techniques used to direct maintenance 21 Annex A Call Clarity Index model description 22 A.1 Introduction 22 A.2 Mo
19、del equations . 24 A.3 Model output 31 A.4 Weighting values 32 A.5 Assumptions/Data files. 33 A.6 Miscellaneous equations. 37 Annex B Mapping INMD measurements to the E-model. 38 B.1 Algorithms relating INMD measurements to E-model parameters 38 Appendix I Details on the comparison of class C INMD l
20、ocation within the network 43 iv ITU-T Rec. P.562 (05/2004) Page Appendix II Statistical techniques for use on multiple INMD measurements . 46 II.1 Confidence intervals. 46 II.2 Hypothesis test for the mean of a set of measurements versus a fixed value . 46 II.3 Hypothesis test for the means of two
21、sets of measurements 47 Appendix III Statistical techniques for use on INMD threshold calculations 48 III.1 Introduction 48 III.2 Theoretical approach 48 III.3 Approximation 50 ITU-T Rec. P.562 (05/2004) 1 ITU-T Recommendation P.562 Analysis and interpretation of INMD voice-service measurements 1 Sc
22、ope This Recommendation provides advice on the analysis and interpretation of voice-service measurements as produced by an in-service non-intrusive measurement device (INMD). It should be used in association with ITU-T Rec. P.561, In-service, non-intrusive measurement device Voice service measuremen
23、ts 1. INMDs are utilized primarily for the measurement of voice-grade parameters such as speech, noise and echo. INMDs may also be used to measure parameters associated with digital transmission systems, in both circuit switched and packet switched networks, that impact the performance of the voice-
24、grade channels being transported. The INMD is used as a stand-alone device or can be used as part of a network element. They may be deployed at selected switch and facility nodes in telecommunication networks to measure the in-service performance parameters of voice grade services, and to locate and
25、 analyse network anomalies. For the circuit-switched network (i.e., using INMDs of classes A, B or C 1), analysis of network anomalies is made easier when the connection information such as calling and called address digits, circuit assignments involved, etc., are known, together with the measured p
26、erformance. This stands also for the packet-switched networks (i.e., using INMDs of class D 1), with connection information as well as protocol information. This Recommendation is divided into the following clauses. Clause 2 gives a list of references to related standards. Clause 3 provides abbrevia
27、tions and definitions used within this Recommendation. Clause 4 describes how individual INMD measurements should be interpreted and describes limitations of this method. Clause 5 discusses the impact of Class C INMD location within the network on measurements. Clause 6 shows how INMD measurements c
28、an be used to predict average customer opinion, and how these customer opinion predictions should be interpreted. Clause 7 looks at how INMD measurements can be applied to network planning through the use of the E-model 2. Clause 8 shows how INMD measurements can be used for network maintenance. Ful
29、l details of the recommended model for predicting average customer opinion are given in Annex A and details of how to map INMD measurements into the E-model are given in Annex B. 2 Normative references The following ITU-T Recommendations and other references contain provisions which, through referen
30、ce 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 encouraged to investigate the possibility of applying the most re
31、cent 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 document, the status of a Recommendation. 1 ITU-T Recommendatio
32、n P.561 (2002), In-service, non-intrusive measurement device Voice service measurements. 2 ITU-T Recommendation G.107 (2003), The E-model, a computational model for use in transmission planning. 3 ITU-T Recommendation G.100 (2001), Definitions used in Recommendations on general characteristics of in
33、ternational telephone connections and circuits. 4 ITU-T Recommendation G.131 (2003), Talker echo and its control. 2 ITU-T Rec. P.562 (05/2004) 5 ITU-T Recommendation G.169 (1999), Automatic level control devices. 6 ITU-T Recommendation P.800 (1996), Methods for subjective determination of transmissi
34、on quality. 7 ITU-T Recommendation G.108 (1999), Application of the E-mode: A planning guide. 8 ITU-T Recommendation G.109 (1999), Definition of categories of speech transmission quality. 9 ITU-T Recommendation G.113 (2001), Transmission impairments due to speech processing. 10 ITU-T Recommendation
35、G.114 (2003), One-way transmission time. 11 ITU-T Recommendation G.120 (1998), Transmission characteristics of national networks. 12 ITU-T Recommendation G.121 (1993), Loudness ratings (LRs) of national systems. 13 ITU-T Recommendation G.122 (1993), Influence of national systems on stability and tal
36、ker echo in international connections. 14 ITU-T Recommendation P.79 (1999), Calculation of loudness ratings for telephone sets. 15 ITU-T Recommendation P.76 (1988), Determination of loudness ratings; fundamental principles. 16 ITU-T Recommendation G.223 (1988), Assumptions for the calculation of noi
37、se on hypothetical reference circuits for telephony. 17 ITU-T Recommendation G.212 (1988), Hypothetical reference circuits for analogue systems. 3 Abbreviations and definitions 3.1 Abbreviations This Recommendation uses the following abbreviations: ALC Automatic Level Control CCI Call Clarity Index
38、CDR Call Data Record CME Circuit Multiplication Equipment CMS Circuit Multiplication System EC Echo Canceller EL Echo Loss EPL Echo Path Loss INMD In-service Non-intrusive Measurement Device ISC International Switching Centre LE Local Exchange MOS Mean Opinion Score OLR Overall Loudness Rating PCM P
39、ulse Code Modulation RLR Receiving Loudness Rating ITU-T Rec. P.562 (05/2004) 3 SEPL Speech Echo Path Loss SLR Sending Loudness Rating TELR Talker Echo Loudness Rating TSG Trunk SubGroup 3.2 Definitions For definitions not listed here, please refer to ITU-T Recs P.561 1 and G.100 3. 3.2.1 customer o
40、pinion model: Customer opinion models aim to predict the average subjective opinion of customers using objective measures. 3.2.2 subjective opinion: A subjective opinion is a personal view and varies from person-to-person. A subjective opinion will not necessarily be the same when repeated under the
41、 same external conditions. Call quality is an example of a subjective measure. 3.2.3 objective measurement: An objective measurement is made using measurement equipment and is repeatable given the same external conditions. Active speech level is an example of an objective measure. 3.2.4 E1: A G.703
42、interface operating at 2048 kbit/s capable of carrying 32 channels of 64 kbit/s each. 3.2.5 T1: A G.703 interface operating at 1544 kbit/s capable of carrying 24 channels of 64 kbit/s each. 4 Interpreting INMD measurements INMDs continuously monitor the network and have the potential to generate vas
43、t amounts of data. Interpreting this data is crucial to understanding the performance of the network being monitored. This clause provides guidelines on how individual voice-service measurements should be interpreted and how measurements from many calls can be collated. For each case the application
44、s, benefits and limitations are described. 4.1 Single call measurements Voice-service measurements made by an INMD are described in ITU-T Rec. P.561 1, the minimum required measurements being: speech level, noise level, echo path delay and at least one type of echo loss measurement, plus IP delay va
45、riation and IP packet loss ratio for Class D INMDs. Each of these parameters allows some aspect (or aspects) of network performance to be determined or predicted for that particular call. The parameters measured by an INMD characterize the network connection from each talker to the INMD equipment in
46、 that direction only. The network connection in the opposite direction, INMD to listener, is not measured. The only exception to this is the measurement of the echo-path which provides some information about the network connection from the INMD to source of reflected echo (usually the 4-wire to 2-wi
47、re hybrid) and back to the INMD. This means that the majority of impairments in the receive path, INMD to listener, cannot be detected by an INMD. Some aspects of network performance that can be derived from single voice-service measurement parameters are shown in Table 1. Any assumptions made in de
48、riving network performance are also listed. 4 ITU-T Rec. P.562 (05/2004) Table 1/P.562 Aspects of network performance derived from INMD measurement parameters Parameter Aspect of network performance Assumptions made Active speech level Network SLR Speakers vocal level Psophometric noise level Circui
49、t noise level introduced by the network Room noise level Echo loss Echo path loss Speech echo path loss Operation or presence of echo cancellers Hybrid performance Echo path delay Transmission delay of the connection Local delay Speech activity factor Accuracy of other parameters (e.g., 90% activity in both directions could mean noise is being classified as speech) Type of call (e.g., recorded message) Normal conversational habits Front end clipping Performance of voice activity detectors (e.g., in CMEs) Saturation clipping A
