1、Union internationale des tlcommunications Place des Nations 1211 GENVE 20 Suisse Switzerland Suiza COVERING NOTE GENERAL SECRETARIAT INTERNATIONAL TELECOMMUNICATION UNION Subject: Erratum Geneva, 7 December 2000 Recommendation ITU-T G.108 (09/99) TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU ITU-T
2、 Recommendation G.108 (09/99) Application of the E-model: A planning guide 1. The following Table of Figures and Table of Tables should be inserted under “Contents“. TABLE OF FIGURES Page Figure 1/G.108 Basic configuration for the interconnection between private and public network. 12 Figure 2/G.108
3、 Standard configuration with a fully digital routing within the private network. 13 Figure 3/G.108 Private Network with 4-wire/2-wire Conversion. 14 Figure 4/G.108 Digitally connected wireless telephone set 14 Figure 5/G.108 Basic connection between the PSTN and an IP network with its H.323 terminal
4、 and a PBX connected via an IWF . 15 Figure 6/G.108 The E-Model in the environment of subjective and objective testing 17 Figure 7/G.108 General configuration for calls via public networks 17 Figure 8/G.108 Example for the addition of impairments on a “Psychological scale“ . 18 Figure 9/G.108 Relati
5、on between OLR and E-Model Rating R . 21 Figure 10/G.108 E-Model Rating R due to talker echo 22 Figure 11/G.108 Relation between absolute delay (Ta) and E-Model Rating R. 23 Figure 12/G.108 Relation between the number of qdu and E-Model Rating R 26 Figure 13/G.108 Reference connection for the calcul
6、ation of SLR and RLR. 36 Figure 14/G.108 Reference connection for echo calculations with one echo path . 39 Figure 15/G.108 Reference connection for echo calculations with two echo paths 40 Figure 16/G.108 Details inside a cordless telephone with respect to echo control . 41 Figure 17/G.108 Basic re
7、ference configuration of the E-Model. 44 Figure 18/G.108 Working configuration for 2-wire/2-wire connections 45 Figure 19/G.108 Working configuration for 4-wire/2-wire connections 47 2 Figure 20/G.108 Working configuration for 2-wire/4-wire connections 48 Figure 21/G.108 Working configuration for fu
8、lly digital connections . 48 Figure 22/G.108 Echo canceller 55 Figure 23/G.108 Application of a pair of echo cancellers within the private network 57 Figure 24/G.108 Options for the location of an echo canceller 58 Figure 25/G.108 Use of echo cancellers in an internetwork or international connection
9、 . 59 Figure 26/G.108 Judgement of a connection on a linear quality scale 63 Figure A.1/G.108 Echo cancellers in a private network and their echo paths. 74 Figure A.2/G.108 Access and routing in public networks 76 Figure A.3a/G.108 Configurations and transmission characteristics for the far-end term
10、ination Europe . 79 Figure A.3b/G.108 Configurations and transmission characteristics for the far-end Termination North America 81 Figure B.1/G.108 Basic structure of the private network 83 Figure B.2/G.108 Reference configuration 1 84 Figure B.3/G.108 Reference configuration 2 84 Figure B.4/G.108 R
11、eference configuration 3 85 Figure B.5/G.108 Use of low bit-rate equipment for a leased line 87 Figure B.6/G.108 Basis for calculation of reference configuration 1 . 89 Figure B.7/G.108 Basis for calculation of reference configuration 2 . 93 Figure B.8/G.108 Basis for calculation of reference config
12、uration 3 . 95 Figure B.9/G.108 Application of echo control devices in the private network. 99 Figure B.10/G.108 Reference configuration 1 100 Figure B.11/G.108 Reference configuration 2 100 Figure B.12/G.108 Reference configuration 3 101 Figure B.13/G.108 Basis for calculation for reference configu
13、ration 1a 102 Figure B.13a/G.108 Analogue set A & analogue set B as perceived side A. 105 Figure B.13b/G.108 Analogue set A & analogue set B as perceived side B. 106 Figure B.14/G.108 Basis for calculation of reference configuration 1b . 107 Figure B.14a/G.108 Digital set A & analogue set B as perce
14、ived side A . 110 Figure B.14b/G.108 Digital set A & analogue set B as perceived side B . 110 Figure B.15/G.108 Basis for calculation of reference configuration 2 . 111 Figure B.15a/G.108 Unlicensed: Wireless processing delay: 7 ms avg 115 Figure B.15b/G.108 Licensed: Wireless processing delay: 100
15、ms avg . 115 Figure B.16/G.108 Basis for calculation of reference configuration 3a 116 Figure B.16a/G.108 Unlicensed: Wireless processing delay: 7 ms avg 120 Figure B.16b/G.108 Licensed: Wireless processing delay: 100 ms avg . 120 Figure B.17/G.108 Basis for calculation of reference configuration 3b
16、 . 121 Figure B.17a/G.108 Unlicensed: Wireless processing delay: 7 ms avg 124 Figure B.17b/G.108 Licensed: Wireless processing delay: 100 ms avg . 125 Figure C.1/G.108 Possible echo paths for a cordless telephone 128 Figure C.2/G.108 Echo control devices in a DECT cordless telephone 129 Figure C.3/G
17、.108 TCLw and artificial echo loss 130 3 TABLE OF TABLES Page Table 1/G.108 Definition of categories of speech transmission quality 19 Table 2a/G.108 Provisional planning values for the equipment impairment factor (Ie) . 27 Table 2b/G.108 Provisional planning values for the equipment impairment fact
18、or (Ie) under conditions of packet loss, codecs G.729-A + VAD and G.723.1-A + VAD. 29 Table 2c/G.108 Provisional planning values for the equipment impairment factor (Ie) under propagation error conditions, GSM codecs 29 Table 3/G.108 Provisional examples for the advantage factor A 30 Table 4/G.108 A
19、ssumed analogue access characteristics 32 Table 5/G.108 Assumed digital access characteristics for lines terminated in digital sets 32 Table 6/G.108 Default values and recommended ranges for the parameters 54 Table A.1/G.108 Planning values for wireless telephones European region . 67 Table A.2/G.10
20、8 Planning values for wireless telephones North American region. 67 Table A.3/G.108 Switching equipment connection possibilities 68 Table A.4/G.108 Average values for TBRLw and echo loss (Europe). 70 Table B.1/G.108 Summary of the calculation results . 97 Table B.2a/G.108 E-Model input parameters fo
21、r configuration 1a as perceived at side A. 104 Table B.2b/G.108 E-Model input parameters for configuration 1a as perceived at side B. 105 Table B.3a/G.108 E-Model input parameters for configuration 1b as perceived at side A. 109 Table B.3b/G.108 E-Model input parameters for configuration 1b as perce
22、ived at side B. 109 Table B.4a/G.108 E-Model Input Parameters for Configuration 2 as perceived at side A . 114 Table B.4b/G.108 E-Model input parameters for configuration 2 as perceived at side B. 114 Table B.5a/G.108 E-Model input parameters for configuration 3a (analogue set B) as perceived at sid
23、e A 119 Table B.5b/G.108 E-Model input parameters for configuration 3a (analogue set B) as perceived at side B 119 Table B.6a/G.108 E-Model input parameters for configuration 3b (digital set B) as perceived at side A . 123 Table B.6b/G.108 E-Model input parameters for configuration 3b (digital set B
24、) as perceived at side B 124 Table B.7/G.108 Example E-Model calculations for IP telephony. 126 Table B.8/G.108 E-Model Ratings R for indicated combinations of Ie and end-to-end mean one-way delay 126 2. Item d) of the Introduction should read: “Planning of private networks is more complex than sing
25、le PBX-configurations, therefore sufficient (tutorial) information about the planning and calculation methods needs to be provided.“ 3. Subclause 4.5.3: the second sentence of the 4th paragraph should read: “A variety of multiplexing systems is in use in the existing networks:“ 4. Subclause 7.3.2.3:
26、 the last sentence of the 2nd paragraph should read: “Thus, the maximum delay attributable to codec-related processing in IP based systems operating in real-time is:“ 5. Subclause 7.5: the last sentence of the last paragraph should read: “For coding laws other than A-law/-law (e.g. according to Reco
27、mmendations G.726, G.727 or G.728), the parameter qdu is, for transmission planning, replaced by the equipment impairment factor (Ie) (see 7.6).“ 4 6. Subclause 7.6: 2nd sentence should read: In contrast to the quantization distortion due to the standard 8 bit PCM coding (A-law or -law), these impai
28、rments can not readily be quantified with a number of qdu. 7. Subclause 7.8: 2nd sentence of the second paragraph should read: “Therefore, the advantage factor A should be used with care and with respect to the business interest of the private network customer, where users may judge specific advanta
29、ges in telecommunication with another degree than in the usual private domain.“ 8. Subclause 7.10.4: the last sentence of the first paragraph should read: “For analogue telephone sets, STMR, and to some extent LSTR, depend on the degree of matching between the balance impedance of the telephone circ
30、uit and the input impedance of the terminating line interface in the PBX in conjunction with the impedance of the ports interfacing 2-wire facilities.“ 9. Subclause 7.10.5: 4th sentence should read: “The room noise in normal office environment, as it can be assumed for the business domain of private
31、 networks, can be expected in a range of 30 to 50 dB(A).“ 10. Subclause 7.10.6: 1st sentence of the last paragraph should read: “Nevertheless, it should be observed that these types of artificially generated noise, as stated above, are of a substantially different nature than traditional noise-relat
32、ed parameters which are taken account of by the E-Model.“ 11. Subclause 7.10.7: 1st sentence should read: “In case that a digital sequence, which has been transmitted does not (or with errors) arrive at the destination, it is a common method for data transmission to notify the sender of this fact an
33、d to initiate a second transmission of the same sequence.“ 12. Subclause 7.10.7: 2nd sentence of the second-to-last paragraph should read: “With respect to the first and second type of FEC, as listed afore, their properties are part of the respective Standards and their effectiveness is included in
34、the equipment impairment factor (Ie) for such codecs under errored conditions (see Tables 2b and 2c).“ 13. Subclause 8.2.2: the following sentence should be inserted after the 2nd sentence in the 4th paragraph: “For illustration, the cordless telephone is one conforming to the DECT standard 50, 53.“
35、 14. Subclause 8.2.2: 1st sentence of the 5th paragraph should read: “Cordless telephones conforming to the DECT standard 50, 53 insert an additional mean one-way delay of approximately 14 ms between acoustic interface of the portable part and the network interface of the fixed part (see Table A.1).
36、“ 15. Subclause 8.2.2: 3rd sentence of the 5th paragraph should read: “Therefore, the DECT standard requires precautions to suppress the reflected signal, via the use of an Echo Canceller (EC), together with a Soft Suppressor (SS).“ 16. Subclause 8.2.2: the last sentence of the 5th paragraph should
37、read: “More detailed information about echo control in DECT cordless telephones is provided in Annex C.“ 17. Subclause 8.2.2: 2nd sentence of 6th paragraph should read: “Figure 16 shows in more detail the relevant components for echo control in a DECT terminal, most of which reside in the fixed part
38、.“ 18. Subclause 8.5: 2nd sentence should read: “In contrast to the standard PCM coding and decoding according to the A-law or -law (Recommen-dation G.711 15), these impairments are expressed in terms of “equipment impairment factor“ (Ie), instead of Quantization distortion units (qdu).“ 19. Subclau
39、se 9.5: the brackets should be removed in the 13th paragraph to read as follows: “Calculations for the configuration and values of Figure 15 result in values for the round-trip delay, Tr = 28 ms and for the weighted echo path loss WEPL = 54 dB.“ 5 20. Subclause 9.5: the brackets should be removed in
40、 the 14th paragraph to read as follows: “As explained in 7.3, the absolute one-way delay (Ta) causes major impairments only when the delay exceeds 150 ms, i.e. the value for the absolute delay, Ta = 28 ms, for the configuration of Figure 15 will have no influence on the result.“ 21. Subclause 9.5: t
41、he 4th sentence of the last paragraph should read: “The minimum value of echo loss enhancement according to the DECT Standard 50, 53, for example, is 6.5 dB.“ 22. Subclause 9.7: the 1st sentence of Note 1 should read: “For the calculations shown in this Recommendation the algorithm of the E-Model ha
42、s been taken from Recommendation G.107 3 (12/98) at the time of publication.“ 23. Subclause 10.2: the last sentence should read: “A preference should be given to those echo cancellers, which are in accordance with accepted standards, such as Recommendations G.168 12 or G.165 11. 24. Subclause 10.5:
43、the 2nd sentence should read: “For a specific type of echo canceller, which may be inserted into the network subject to planning, there are two feasible approaches how this echo canceller can be considered in the E-Model calculations:“ 25. Table A.2: the title of the first column should read: “Licen
44、sed: TDMA 48“ 26. Subclause A.1.8: second sentence of the first bullet should read: “These coders employ mainly the different ADPCM algorithms described in Recommendation G.721 (1988), G.726, and G.727.“ 27. Subclause A.1.10: the last sentence of the second-to-last paragraph should read: “In general
45、, the speech level is sufficiently low if the send loudness rating at the echo canceller input is SLR 7 dB.“ 28. Annex B: the first sentence of Note 2 should read: “For the calculation of the following examples the algorithm of the E-Model has been taken from Recommendation G.107 3 (12/98) at the ti
46、me of publication.“ 29. Subclause B.1.3: the last sentence of the last paragraph should read: “It should be noted, that these echo cancellers are, with the exception of the permitted echo path delay, nearly identical with those according to Recommendations G.165 11 or G.168 12.“ 30. Subclause B.1.4:
47、 replace Figure B.7/G.108 Basis for calculation of reference configuration 2 with the following: 110T1211400-99117144 dBABDSLR = 8 dBRLR = 3 dB24 dBAE =24 dBSLR = 7 dBRLR = 3 dBPrivate networkPublic networknational long distance pathFar end terminationMean one-way delay in msEcho path 1Echo path 2li
48、ne 1.5 Low bit-rateequipment0 dBrpointequipment20 msAE Artificial echo loss0.5 6 31. Subclause B.2.2.1: the second sentence should read: “An advantage factor of A = 5 has been assigned to unlicensed technology (PACS, WUPE, PCI, PWT) whereas an advantage factor of A = 10 has been assigned to licensed
49、 technology (TDMA 48).“ 32. Subclause B.2.6.3.2: the title should read: “Licensed: Wireless processing delay: 100 ms average (TDMA 48)“ 33. Subclause B.2.7.3.2: the title should read: “Licensed: Wireless processing delay: 100 ms average (TDMA 48)“ 34. Subclause B.2.8.3.2: the title should read: “Licensed: Wireless processing delay: 100
