1、ITU-T *RECMN*P.LL 93 m 4862591 058955b 4b7 m I INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STAN DARD IZATION SECT0 R OF ITU P.11 (03/93) TELEPHONE TRANSMISSION QUALITY VOCABULARY AND EFFECTS OF TRANSMISSION PARAMETERS ON CUSTOMER OPINION OF TRANSMISSION QUALITY AND THEIR ASSESSMENT
2、 EFFECT OF TRANSMISSION IMPAIRMENTS ITU-T Recommendation P.11 (Previously “CCITT Recommendation”) ITU-T *RECMN*P.bL 93 m 4862593 0589557 3T3 m FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsib
3、le for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU
4、-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation P.ll was prepared by the ITU-T Study Group XII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunic
5、ation Union (ITU), the CCIIT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to de
6、lay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the n
7、ew ITU structure. 2 telecommunication administration and a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any m
8、eans, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T *RECMN*P.11 93 4862591 0589558 23T 9 CONTENTS 1 Purpose . 2 Effect of individual impairments 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 General Loudness loss Circ
9、uit noise Sidetone Room noise Attenuation distortion . Group-delay distortion Absolute delay . Talker echo . Listener echo . Nonlinear distortion Quantizing distortion Phase jitter Intelligible crosstalk . 3 Effect of multiple impairments and the use of opinion models Annex A - Transmission quality
10、index . A . 1 Introduction A.2 A.3 Basic model for transmission quality index A.4 Typical results . Annex B - Effects of attenuation distortion on transmission performance . Effect of attenuation distortion on loudness and articulation . Examples of attenuation distortion characteristics effect . Ev
11、aluation method using the attenuation distortion unit (adu) . Connection parameters used in the model B . 1 B.2 B.3 B.4 Effect of attenuation distortion on listening and conversation opinion scores . Annex C - Effects of group-delay distortion on transmission performance Annex D - Effects of carbon
12、and linear microphones on transmission performance . Annex E - Quantizing distortion of digital systems Annex F - Effects of nonlinear distortion on transmission performance . Recommendation P.ll (03/93) Page 2 2 3 6 7 7 8 8 8 8 9 9 10 10 10 11 11 11 11 13 17 17 19 23 23 27 29 31 32 32 1 ITU-T *RECM
13、N*P*11 93 48b259L 0589559 17b m Recommendation P.ll EFFECT OF TRANSMISSION IMPAIRMENTS (Geneva, 1980; amended ut Malaga-Torremolinos, 1984; Melbourne, 1988, und Helsinki, 1993) 1 Purpose An essential purpose of the present transmission plan for international connections is to provide guidance on the
14、 control of transmission performance. Such guidance is contained in Recommendations related to complete connections and to the constituent parts of a connection. These Recommendations contain performance objectives, design objectives and maintenance objectives, as defined in Recommendation G. 102 fo
15、r various transmission impairments which affect the transmission quality and customer opinion of transmission quality?) Typical transmission impairments include transmission loss, circuit noise, talker echo, sidetone loss, attenuation distortion, group-delay distortion and quantizing distortion. Alt
16、hough not under the control of the transmission planner, room noise is another important factor which should be considered. This Recommendation is concerned with the effect of transmission parameters, such as those listed above, on customer opinion of transmission quality. It is based on information
17、 contributed in response to specific questions which have been studied by the CCIT. Much of this information is based on the results of subjective tests in which participants have talked, listened or conversed over telephone connections with controlled or known levels of the impairments and rated th
18、e transmission quality on an appropriate scale. General guidance for the conduct of such tests is provided in Recommendation P.80. In addition, Recommendation P.82 provides guidance on the use of telephone user surveys to assess speech quality on international calls. Specific purposes of this Recomm
19、endation are: 1) 2) to provide a general, but concise, summary of the major transmission impairments and their effect on transmission quality which would serve as a central reference for transmission planners; to provide for retention of basic information on transmission quality in support of releva
20、nt P-Series and G-Series Recommendations with appropriate reference to these Recommendations and other sources of information such as Supplements and Questions under study; to provide for the interim retention of basic information on transmission quality which is expected to be relevant in the formu
21、lation of future Recommendations. Clause 2 provides a brief description of individual impairments which can occur in telephone connections, typical methods of characterization and general guidance on the acceptable levels of these impairments. More specific information is provided in annexes to this
22、 Recommendation, in other Recommendations and in Supplements. Clause 3 is concerned with the effect of combined impairments on transmission quality and the use of opinion models which permit estimates to be made of customer opinion as a function of combinations of transmission impairments in a telep
23、hone connection. Thus, they can be used to evaluate the transmission quality provided by the present transmission plan, the impact of possible changes in the transmission plan or the consequences of departures from the transmission plan. Such evaluations require certain assumptions concerning the co
24、nstituent parts of a connection, and guidance is provided by the hypothetical reference connections which are the subject of Recommendations G. 103 and G. 104. 3) i) In this Recommendation, the term ?impairment? is used in a general sense to refer to any characteristic or degradation in the transmis
25、sion path which may reduce the performance or quality. It is not used to denote ?equivalent loss? as was the case in some earlier CCIT texts. Recommendation P.ll (03/93) 1 2 Effect of individual impairments Percent “good plus excellent” (dB) 2.1 General Percent “poor plus bad” Ciause 2 describes inv
26、ididually a number of the transmission impairments which can affect the quality of speech transmission in telephone connections. Information is provided on the general nature of each impairment, on methods which have been recommended to measure the impairment and on the acceptable ranges for the imp
27、airment. References are provided to Recommendations where more detailed information on measurement methods and recommended values can be found. 5 to 15 20 2.2 Loudness loss 90 90 12 dB = OLR + 12 - STMR(T)/3 for STMR(T) i 1.5 1 .o 0.5 n 1 “ 50 40 25 20 15 10 5 O dB T1205940-9Yd05 Quantizing distorti
28、on FIGURE A.4P.11 Mean opinion scare as a function of quantizing distortion HGURE A.5/P. 11 Mean opinion score as a function of room and sidetme with a carbon microphone Recommendation P.11 (03/93) 15 ITU-T *RECMN*P.LL 93 m 48b259L 0589574 482 m Lower cutoff frequency FIGURE A.6P. 1 1 Mean opinion s
29、core as a function of her and upper cutoff frequencies 1 O0 90 80 70 60 i 50 a 40 c c P) 30 20 10 O T1205970-93dOs Mean opinion score FIGURE A.7P.11 Opinion relatiomhips for the transmission quality index: percent “G + E” ad percent “P + B” as a function of mean opinion score 16 Recommendation P.ll
30、(03/93) Annex B Effects of attenuation distortion on transmission performance (This annex forms an integral part of this Recommendation) B.l Effect of attenuation distortion on loudness and articulation The effect of attenuation distortion on loudness is marked more at a lower frequency band than at
31、 a higher one. The effect of attenuation distortion on sound articulation is, contrary to loudness, more marked at a higher frequency band than at a lower one. Attenuation distortion equivalent values (IL) and articulation equivalent loss values (IA) are equivalent loss difference values referred to
32、 a system without frequency band restriction. For both attenuation distortion equivalent and articulation equivalent loss values due to bandpass characteristics, it can be assumed that an additivity law of impairment values due to highpass and lowpass characteristics holds true, if each attenuation
33、slope is steeper than 15 dB/octave. These phenomena are induced based on the calculation and subjective test study results as shown in Figures B.l, B.2, B.3 and B.4. NOTE - Attenuation distortion equivalent and articulation equivalent loss described here are determined in reference to a complete tel
34、ephone speech path without attenuation distortion junction. “ 0.2 0.3 0.5 0.8 1 2 3 4 5 kHz TI 205980-931409 Cutoff frequency at 1 O-dB insertion loss O Subjective test wlue Calculated value NOTE - Slope of lowpass and highpass is 48 dB/octave. FIGURE B.lP.11 Cutoff frequency effect on loudness Reco
35、mmendation P.ll (03/93) 17 dB ITU-T *RECMN*P.LL 93 M 4862591 0589576 255 cutoff irequeniy at lCkdB insertion loss I C .- 54 I I Ig m .- - - 2500 4000 .I- -4 - - 3000 O 10 20 30 40 50 O Slope (dB/cctave) a) Lowpass filter effect I I Cutoff frequency at 1BdB insertion loss l I 400 300 200 10 20 30 40
36、50 Slope (dB/octave) T1205990-93d10 b) Highpacc fiiter effect Width 0.4-mm copper subscriber line (7-dB image loss at 1500 Hz) - Without subscriber line FIGURE B.2P.11 Lowpass and highpass filter dope effect on loudness dB 0.2 0.3 0.5 0.8 1 2 3 4 5 8 10 kHz T1206000-93/dll Cutoff frequency at 10-dB
37、insertion lcss O Subjective test value Calculated value for the telephone system Calculated value for ARAEN system -I-. FIGURE B.3P.11 Cutoff frequency effect on articulation 18 Recommendation P.11 (03/93) 10 20 30 40 50 60 Siope rate (dBioctave) a) bpass filter effect Cutoff frequency at 1 GdB inse
38、rtion loss i- 10 20 30 40 50 60 Slope rate (dB/octave) T1206010-93d12 b) Highpass filter effect Calculated value for the telephone system Calculated value for ARAEN system - FIGURE B.4P.11 Lowpass and highpass filter slope on articulation B.2 The effect of attenuation distortion on listening and con
39、versation opinion scores increases noticeably as the overall loudness loss of a connection decreases. This tendency can be more marked when circuit noise exists. The effect of attenuation distortion on opinion scores is somewhat less than that of loudness loss, which is always dominant at any, parti
40、cularly high overall loudness loss. However, its effect seems to be comparable to, or even larger than, that of noise under certain conditions, especially in connections of lower overall loudness loss. Effect of attenuation distortion on listening and conversation opinion scores See Figures B.5, B.6
41、, B.7 and Table B.l. Recommendation P.ll (03/93) 19 ITU-T *RECMN*P.LL 93 di3 48b259L 0589578 028 20 15 10 - is“ ri 5 z - O -5 c e I 1 I I I I I # o. 1 0.2 0.3 0.4 0.5 0.6 0.8 1 2 3 4 5 kHz T1206020-93/d13 Frequency D1 D2 03 D4 12 4-wire circuits chain 95% limit characteristics, based on Figure VG.23
42、2, Graph No. 28 12 4-wire circuits chain characteristics, based on Figure VG.132 Average characteristics of D4 and D2 SRAEN filter (see Recommendation G.lll and this Recommendation) FIGURE B.5P.11 Junction attenuation distortion characteristics for test conditions 20 Recommendation P.ll (03/93) 4 h
43、Room noise = 50 dBA O 5 10 15 20 25 30 dB T1206030-93/414 Jonction locs FIGURE B.6P.11 Attenuation distortion effect on conversation opinion score Yo O0 I I O I I Room noise = 50 dBA ICN,= -54.5 dBmp I I -5 O 5 10 15 20 25 30 dB T1206040-93idl5 Jonction loss FIGURE B.7P.11 Attenuation distortion eff
44、ect on percent F, G and E conversation test Recommendation P.11 (03/93) 21 No. 1 2 3 4 5 TABLE B.lP.11 Opinion test conditions Item Junction loss Circuit noise level Room noise Sending and receiving end Attenuation distortion Conditions of conservation opinion test using local telephone systems 3, 1
45、3,23, 29 dB ICN, a) = -48.5 dBmp -54.5 dBmp -60.5 dBmp -78.5 dBmp (14 000 PWP) (3500 PWP) (900 PWP) (14 PWP) 50 dBA Local telephone systems Telephone: Model 600 Subscriber line: 0.4 mm 0, 7 dB at 1500 Hz Feeding bridge: XB exchange (220 + 220 n) Junction impedance: 600 C2 D1, D2, D3, D4 (see Figure
46、ES) (Note) Measured at 800 Hz Including exchange noise: -8 dB/octave spectrum characteristics SCRE + RCRE = 9.3 dB b, a) Injected circuit noise referred to the input of a telephone receiving end with O dB receive corrected reference equivalent. b, SCRE Sending corrected reference equivalent RCRE Rec
47、eiving corrected reference equivalent. 22 Recommendation P.ll (03193) ITU-T *RECMN*P.LL 93 4862593 0589581 b12 B.3 Examples of attenuation distortion characteristics effect Characteristic parameters Equivalent loss (dB) Attenuation distortion D4 D3 D2 D1 B.4 The attenuation distortion unit (adu) may
48、 be used for evaluation of the attenuation distortion effect. However, a planning rule based on using an adu is not required. NOTE - The attenuation distortion of a digital system is controlled by the existing planning rule based on using a quantizing distortion unit (qdu) because the methods used t
49、o assign qdus to a digital system account for the effect of attenuation distortion. Therefore, there is no need for a planning rule based on using an adu. The definition of attenuation distortion for one adu is shown in Table B.3. Evaluation method using the attenuation distortion unit (adu) Aspect 1 Aspect 2 Aspect 3 Slope Insertion loss Cutt-off frequency (Hz) (dB/oc t ) (dB) at at fLIO fHIO fLIO fHIO 300 Hz 3.4Hz IL IA I2.5 IY FGE 150 3500 7.0 300 3.8 0 O O O O O 210 3400 10.0 31.5 5.2 10 0.8 0.3 - 2.3 1.8 280 3300 10.7 29.1 8.
