1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T P.561TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2002) SERIES P: TELEPHONE TRANSMISSION QUALITY, TELEPHONE INSTALLATIONS, LOCAL LINE NETWORKS Objective measuring apparatus In-service non-intrusive measurement device Voice service measurements ITU-
2、T Recommendation P.561 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 stand
3、ards Series 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.
4、900 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. P.561 (07/2002) i ITU-T Recommendation P.561 In-service non-intrusive measurement device Voice service measurements Summary This Recommendation provides specifications for voice service transmission measurement de
5、vices that provide measurements on an in-service and non-intrusive basis. These In-Service, Non-intrusive Measurement Devices (INMDs) are utilised primarily for the measurement of voice-grade parameters such as speech level, noise level, echo loss and speech echo path delay. INMDs may also be used t
6、o measure parameters associated with digital transmission systems, in both circuit switched and packet switched networks, that impact the performance of the voice-grade channels being transported. This Recommendation specifies interfaces, measurement ranges, and accuracy requirements for measuring v
7、oice-grade transmission parameters as well as descriptions of optional functions associated with these parameters. Source ITU-T Recommendation P.561 was revised by ITU-T Study Group 12 (2001-2004) and approved under the WTSA Resolution 1 procedure on 14 July 2002. ii ITU-T Rec. P.561 (07/2002) FOREW
8、ORD 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 and tariff questions and issui
9、ng 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 Recommendations on these topi
10、cs. 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 Recommendation, the expression
11、“Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. 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
12、 Property Right. ITU takes no position concerning 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 not received noti
13、ce of intellectual property, protected by patents, which 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 2003 All rights reserved. No part
14、 of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. P.561 (07/2002) iii CONTENTS Page 1 Scope, purpose, and application . 1 1.1 Scope 1 1.2 Purpose . 1 1.3 Application . 1 2 References. 2 3 Abbreviations and definitions. 3 3.1 Abbr
15、eviations . 3 3.2 Definition 4 4 Interface requirements 6 4.1 Electrical interfaces for class A, B and C INMDs 6 4.1.1 DS1 digital interface. 6 4.2 TMN data transport interfaces for class A, B and C INMDs . 7 4.3 Interfaces for class D INMDs. 7 4.4 Reconstruction of signal for class D INMDs . 7 4.4.
16、1 The de-jitter buffer . 7 4.4.2 The voice decoder. 8 4.4.3 The comfort noise generation. 8 4.4.4 The error concealment process. 8 5 Functional requirements . 9 5.1 Required measurement functions . 9 5.2 Optional functions 10 6 Description of required measurement functions. 10 6.1 Speech measurement
17、s. 11 6.1.1 Speech classification 11 6.1.2 Active speech level measurement 11 6.1.3 Speech level measurement interval 11 6.1.4 Speech activity factor . 11 6.2 Noise measurement 12 6.2.1 Noise level (psophometric weighting) 12 6.2.2 Noise level measurement interval 12 6.2.3 Non-stationary noise class
18、ification and measurement . 12 6.3 Echo measurement 12 6.3.1 Speech echo path delay measurement 12 6.3.2 Echo loss measurement 13 6.3.3 Echo path loss measurement 13 6.3.4 Speech echo path loss measurement. 13 iv ITU-T Rec. P.561 (07/2002) Page 6.4 IP protocol measurements 14 6.4.1 IP delay variatio
19、n measurement . 14 6.4.2 IP packet loss ratio measurement . 14 7 Description of optional functions . 14 7.1 Originating and terminating address digits. 14 7.2 Facility or circuit identification 15 7.3 Time and duration of connection 15 7.4 Signal classification 15 7.5 Customer identification 15 7.6
20、DS1 performance measurements 15 7.7 3 kHz flat noise level 16 7.8 Connection disposition measurements . 16 7.9 Data analysis and reports 16 7.10 Saturation clipping 16 7.11 Measurement interval . 16 7.12 Double talk . 16 7.13 Front-end clipping 16 7.14 One-way transmission 17 7.15 Crosstalk. 17 7.16
21、 Stability loss . 17 7.17 Distortion 17 7.18 Single-ended speech quality. 17 7.19 IP round-trip delay 17 7.20 IP one-way connectivity. 18 7.21 Out-of-order IP packets 18 7.22 IP packets loss pattern 18 7.23 Type and configuration of voice coder. 18 7.24 Quantity of transmitted data in IP packets . 1
22、8 7.25 Packet Arrival Descriptors . 18 8 Requirements for performance of measurements . 19 8.1 Description of different classes 19 8.1.1 Class A Local (National for many countries) circuit switched networks 19 8.1.2 Class B Medium-delay circuit switched networks 20 8.1.3 Class C Long-delay circuit s
23、witched networks . 20 8.1.4 Class D Packet switched networks 21 8.2 Measurement specification. 22 8.3 Requirements for accuracy. 22 8.4 Description of reference circuits 24 8.4.1 Reference circuit 1 24 ITU-T Rec. P.561 (07/2002) v Page 8.4.2 Reference circuit 2 25 8.4.3 Reference circuit 3 26 8.5 Re
24、ference measurements 26 8.5.1 Analogue versus digital measurements 26 8.5.2 Reference Speech Level (RSL) 26 8.5.3 Reference Noise Level (RNL) 27 8.5.4 Reference Speech Activity Factor (RSAF) 27 8.5.5 Reference Echo Loss (REL). 27 8.5.6 Reference Echo Path Loss (REPL). 27 8.5.7 Reference Speech Echo
25、Path Loss (RSEPL) 27 8.5.8 Reference Speech Echo Path Delay (RSEPD) . 27 9 Test conditions for Class A, B and C devices 28 9.1 Test design 28 9.2 Multiple measurements 28 9.3 Circuit conditions for Class A device. 28 9.4 Circuit conditions for Class B device. 28 9.4.1 Description of test elements .
26、29 9.4.2 Circuit conditions . 29 9.4.3 Circuit conditions with echo cancellers 30 9.5 Circuit conditions for Class C device. 31 9.5.1 Description of test elements . 32 9.5.2 Circuit conditions . 32 9.5.3 Circuit conditions with echo cancellers 32 9.5.4 Circuit conditions with DCME. 33 Annex A Speech
27、 material . 34 A.1 Parameters 34 A.1.1 Subjects. 34 A.1.2 Conversations . 34 A.1.3 Language 34 A.1.4 Duration of conversations. 34 A.1.5 Activity factor of conversations . 34 A.2 Telephone connection. 35 A.3 Source recordings . 35 A.3.1 Recording environment 35 A.3.2 Recording system . 35 A.3.3 Reco
28、rding procedure 35 A.3.4 Speech level 35 A.3.5 Subjects. 35 A.3.6 Conversation task . 36 vi ITU-T Rec. P.561 (07/2002) Page A.3.7 Calibration signal 36 Appendix I Review of measurement techniques. 36 I.1 Speech echo path delay 36 I.1.1 Correlation analysis 36 I.1.2 Adaptive filter analysis. 36 I.2 V
29、erification of delay measurements. 38 I.3 Failure of delay measurement 38 Appendix II Degradation of telephone transmission quality due to non-stationary noise 39 II.1 Introduction 39 II.2 Classification of non-stationary noise 40 II.2.1 The noise signal database and its analysis 41 II.3 Noise class
30、ification and measurement algorithm (example) 42 II.3.1 Main features 43 II.3.2 Stationarity algorithm. 43 II.3.3 Stationary noise 44 II.3.4 Non-stationary noise. 44 II.4 Psophometric measure 44 II.5 Performance evaluation (example). 44 II.5.1 Analysis of the results 45 II.6 Conclusion 45 Bibliograp
31、hy. 45 ITU-T Rec. P.561 (07/2002) 1 ITU-T Recommendation P.561 In-service non-intrusive measurement device Voice service measurements 1 Scope, purpose, and application 1.1 Scope This Recommendation provides specifications for voice service transmission measurement devices that provide measurements o
32、n an in-service and non-intrusive basis. These In-Service Non-intrusive Measurement Devices (INMDs) are utilized primarily for the measurement of voice-grade parameters such as speech level, noise level, echo loss and speech echo path delay. INMDs may also be used to measure parameters associated wi
33、th digital transmission systems, in both circuit switched and packet switched networks, that impact the performance of the voice-grade channels being transported. This Recommendation specifies interfaces, measurement ranges, and accuracy requirements for measuring voice-grade transmission parameters
34、, as well as descriptions of optional functions associated with these parameters. It does not specify the measurement algorithms to be used, nor the application of the resulting measurement. 1.2 Purpose The INMD in this Recommendation is intended for in-service (maintenance) application, to detect n
35、etwork anomalies affecting transmission performance on voice services. 1.3 Application The INMDs are used as stand-alone devices or can be used as parts of network elements. They may be deployed at selected switch and facility nodes in telecommunications networks to measure the in-service performanc
36、e parameters of voice grade services, and to locate and analyze network anomalies. The 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 performance. Record
37、ing of such information does not constitute intrusion of privacy, since speech intelligence is not monitored. Other optional functions may be added to make the INMD more useful. The INMD can only be used at a four-wire point. In order to study conditions on the two-wire part of a subscriber line, th
38、e INMD must be connected via a four-wire trunk on the network element (that connects to the subscribers line under study); thus, to isolate a problem to the particular subscribers line, some means of conveying connection information from the network element to the INMD must be employed. The INMD mea
39、sures transmission on the path including the customer-provided equipment to the point of INMD measurement access. In this way, the INMD can detect transmission anomalies on the built-up connection. These anomalies can be caused by the customer environment, subscriber line, switches and trunks, inclu
40、ding anomalies at interfaces between these network elements. In particular, the INMD can, potentially, observe anomalies that are not detectable by traditional out-of-service tests. Examples of these difficult-to-detect anomalies are: intermittent fading; acoustical feedback; room noise; defective c
41、ustomer equipment; intermittent leakage on metallic circuits; 2 ITU-T Rec. P.561 (07/2002) intermittent noise; design violations; pair gain system problems; digital switch level and echo control problems; echo problems at the line-to-trunk interface; tones and announcement level control problems; an
42、d switch translation problems that cause violations in network loss plans. Although the INMD is potentially able to detect such anomalies, it should be noted that the INMD cannot specifically separate combined signals, e.g. room noise and cable noise, or acoustical feedback and hybrid mismatch. Simi
43、larly, the INMD cannot distinguish between a trouble on a trunk, on a switch, on the terminating subscriber line, or on the terminal equipment. Network anomalies detected by the INMD may be subsequently isolated to the affecting network element, by applicable out-of-service tests, or facility perfor
44、mance monitoring. Alternatively, the use of advanced signal processing techniques, such as pattern recognition, may enable the INMD to infer the source of an anomaly, e.g. by recognizing particular types of noise. As an alternative to routine testing of network elements, for the detection of network
45、 anomalies, the INMD is effective when used in call sampling mode. In this way, there is no need to maintain large routine testing databases. For post active detection, the INMD is most effective when used as a portable device for detecting intermittent problems. Stand-alone, facility access INMD sy
46、stems, complete with proprietary interfaces to data collection and analysis software, currently exist and are being used by service providers. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this
47、 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 recent edition of the Recommendations and other
48、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 Recommendation P.10 (1998), Vocabulary of terms on telephon
49、e transmission quality and telephone sets. 2 ITU-T Recommendation G.100 (2001), Definitions used in Recommendations on general characteristics of international telephone connections and circuits. 3 ITU-T Recommendation P.56 (1993), Objective measurement of active speech level. 4 ITU-T Recommendation G.122 (1993), Influence of national systems on stability and talker echo in international connections. 5 ITU-T Recommendation G.703 (2001), Physical/electrical characteristics of hierarchical digital interfaces. 6 ITU-T Recommendation G.
