1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.108TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2(03/2004) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone connections and circuits General definitions Application of the E-model: A planning gu
2、ide Amendment 2: New Appendix II Planning examples regarding delay in packet-based networks ITU-T Recommendation G.108 (1999) Amendment 2 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 General de
3、finitions G.100G.109 General Recommendations on the transmission quality 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 internationa
4、l circuits and national extension circuits G.130G.139 General characteristics 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
5、 telephone circuits G.160G.169 Transmission plan aspects of special circuits 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
6、 TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS 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.4
7、00G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE G
8、ENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DIGITAL TERMINAL EQUIPMENTS G.7000G.7999 DIGITAL NETWORKS G.8000G.8999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.108 (1999)/Amd.2 (03/2004) i ITU-T Recommendation G
9、.108 Application of the E-model: A planning guide Amendment 2 New Appendix II Planning examples regarding delay in packet-based networksSource Amendment 2 to ITU-T Recommendation G.108 (1999) was agreed on 31 March 2004 by ITU-T Study Group 12 (2001-2004). ii ITU-T Rec. G.108 (1999)/Amd.2 (03/2004)
10、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 and tariff questions and
11、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 Recommendations on these
12、 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 Recommendation, the expres
13、sion “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. interoperability or applicabilit
14、y) 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 compliance with the Reco
15、mmendation 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, validity or applicability o
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17、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 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written
18、permission of ITU. ITU-T Rec. G.108 (1999)/Amd.2 (03/2004) 1 ITU-T Recommendation G.108 Application of the E-model: A planning guide Amendment 2 New Appendix II Planning examples regarding delay in packet-based networks This appendix provides guidance for the transmission planner on how to deal with
19、 the delay occuring in packet-based networks in conjunction with VoIP terminals and gateways. For the calculations quoted in this appendix, the algorithm of the E-model has been taken from ITU-T Rec. G.107 at the time of publication. In case a later revision of ITU-T Rec. G.107 does contain an impro
20、ved version of the algorithm, this appendix will still provide valid guidance for tutorial purposes. However, for actual transmission planning tasks it should, in any case, be referred to the most recent version of ITU-T Rec. G.107. For illustratory purposes, the following scenarios have been invest
21、igated: 1) two VoIP terminals interconnected via a packet-based network that complies with ITU-T Rec. Y.1541, Class 0; 2) two VoIP islands interconnected via the digital PSTN; 3) a mixed connection between a VoIP terminal (connected to a LAN) and an analogue phone (connected to the PSTN). In additio
22、n, two codecs, G.711 and G.729A, have been considered for each scenario, while no other impairments have been considered (proper echo control assumed). For the E-model calculations, all parameters which are not explicitly mentioned have been set to their default values as per Table 2/G.107. The scen
23、ario in Figure II.1 describes a connection between two VoIP terminals via a packet-based network with a total network delay of 100 ms. The network delay is composed of the fixed delay and the value of the delay variation (jitter). It should be noted that, in this example, the packet-based network pe
24、rforms better than the maximum values set out in ITU-T Rec. Y.1541. 2 ITU-T Rec. G.108 (1999)/Amd.2 (03/2004) Figure II.1/G.108 VoIP terminals with G.711 and WAN according to Y.1541 Class 0 For the E-model calculations, three different cases of terminal delay have been investigated: VoIP terminal se
25、nd delay = 20 ms, VoIP terminal receive delay = 30 ms total delay = Ts + Twan + Tr = (20 + 100 + 30) ms = 150 ms R = 90: Users very satisfied VoIP terminal send delay = 35 ms, VoIP terminal receive delay = 65 ms total delay = Ts + Twan + Tr = (35 + 100 + 65) ms = 200 ms R = 86: Users satisfied VoIP
26、terminal send delay = 50 ms, VoIP terminal receive delay = 100 ms total delay = Ts + Twan + Tr = (50 + 100 + 100) ms = 250 ms R = 79: Some users dissatisfied The quality as perceived by the user in these example calculations is identical for both sides, because the example is symmetrically composed.
27、 The scenario in Figure II.2 describes a connection between two VoIP islands via the PSTN with a delay in the PSTN of 125 ms. The delays in the LANs are 5 ms each which are composed of the fixed delay and the value of the delay variation (jitter). ITU-T Rec. G.108 (1999)/Amd.2 (03/2004) 3 Figure II.
28、2/G.108 VoIP islands with G.711 and PSTN For the E-model calculations, three different cases of terminal delay (and gateway delay) have been investigated: VoIP terminal send delay = 20 ms, VoIP terminal receive delay = 30 ms VoIP gateway send delay = 20 ms, VoIP gateway receive delay = 30 ms total d
29、elay = Ts + Tlan + Tr + Tpstn + Ts + Tlan + Tr = (20 + 5 + 30 + 125 + 20 + 5 + 30) ms = 235 ms R = 81: Users satisfied VoIP terminal send delay = 35 ms, VoIP terminal receive delay = 65 ms VoIP gateway send delay = 35 ms, VoIP gateway receive delay = 65 ms total delay = Ts + Tlan + Tr + Tpstn + Ts +
30、 Tlan + Tr = (35 + 5 + 65 + 125 + 35 + 5 + 65) ms = 335 ms R = 69: Many users dissatisfied VoIP terminal send delay = 50 ms, VoIP terminal receive delay = 100 ms VoIP gateway send delay = 50 ms, VoIP gateway receive delay = 100 ms total delay = Ts + Tlan + Tr + Tpstn + Ts + Tlan + Tr = (50 + 5 + 100
31、 + 125 + 50 + 5 + 100) ms = 435 ms R = 59: Nearly all users dissatisfied The quality as perceived by the user in these example calculations is identical for both sides, because the example is symmetrically composed. The scenario in Figure II.3 describes a connection between one VoIP island and an an
32、alogue terminal connected to the PSTN with a delay in the PSTN of 25 ms. The delay in the LAN is 5 ms which is composed of the fixed delay and the value of the delay variation (jitter). In addition, the VoIP gateway provides an echo canceller according to ITU-T Rec. G.168 with sufficient tail delay
33、covering the echo path via the local office. 4 ITU-T Rec. G.108 (1999)/Amd.2 (03/2004) Figure II.3/G.108 VoIP terminal with G.711 and PSTN with analogue terminal For the E-model calculations, three different cases of terminal delay (and gateway delay) have been investigated: VoIP terminal send delay
34、 = 20 ms, VoIP terminal receive delay = 30 ms VoIP gateway send delay = 20 ms, VoIP gateway receive delay = 30 ms total delay = Ts + Tlan + Tr + Tpstn = (20 + 5 + 30 + 25) ms = 80 ms R = 91: Users very satisfied VoIP terminal send delay = 35 ms, VoIP terminal receive delay = 65 ms VoIP gateway send
35、delay = 35 ms, VoIP gateway receive delay = 65 ms total delay = Ts + Tlan + Tr + Tpstn = (35 + 5 + 65 + 25) ms = 130 ms R = 90: Users very satisfied VoIP terminal send delay = 50 ms, VoIP terminal receive delay = 100 ms VoIP gateway send delay = 50 ms, VoIP gateway receive delay = 100 ms total delay
36、 = Ts + Tlan + Tr + Tpstn = (50 + 5 + 100 + 25) ms = 180 ms R = 88: Users satisfied The quality as perceived by the user in these example calculations is identical for both sides, because the example is symmetric in its behaviour. The scenario in Figure II.4 describes a connection between two VoIP t
37、erminals via a packet-based network with a total network delay of 100 ms. The network delay is composed of the fixed delay and the value of the delay variation (jitter). It should be noted that, in this example, the packet-based network performs better than the maximum values set out in ITU-T Rec. Y
38、.1541. In addition, low bit-rate coding as per ITU-T Rec. G.729A is deployed; thus, Ie = 11. ITU-T Rec. G.108 (1999)/Amd.2 (03/2004) 5 Figure II.4/G.108 VoIP terminals with G.729A and WAN according to Y.1541 Class 0 For the E-model calculations, three different cases of terminal delay have been inve
39、stigated: VoIP terminal send delay = 20 ms, VoIP terminal receive delay = 30 ms total delay = Ts + Twan + Tr = (20 + 100 + 30) ms = 150 ms R = 79: Some users dissatisfied VoIP terminal send delay = 35 ms, VoIP terminal receive delay = 65 ms total delay = Ts + Twan + Tr = (35 + 100 + 65) ms = 200 ms
40、R = 75: Some users dissatisfied VoIP terminal send delay = 50 ms, VoIP terminal receive delay = 100 ms total delay = Ts + Twan + Tr = (50 + 100 + 100) ms = 250 ms R = 68: Many users dissatisfied The quality as perceived by the user in these example calculations is identical for both sides, because t
41、he example is symmetrically composed. The scenario in Figure II.5 describes a connection between two VoIP islands via the PSTN with a delay in the PSTN of 125 ms. The delays in the LANs are 5 ms each which are composed of the fixed delay and the value of the delay variation (jitter). In addition, lo
42、w bit-rate coding as per ITU-T Rec. G.729A is deployed in both VoIP islands; thus, Ie = 2 11 = 22. 6 ITU-T Rec. G.108 (1999)/Amd.2 (03/2004) Figure II.5/G.108 VoIP islands, each with G.729A, and PSTN For the E-model calculations, three different cases of terminal delay (and gateway delay) have been
43、investigated: VoIP terminal send delay = 20 ms, VoIP terminal receive delay = 30 ms VoIP gateway send delay = 20 ms, VoIP gateway receive delay = 30 ms total delay = Ts + Tlan + Tr + Tpstn + Ts + Tlan + Tr = (20 + 5 + 30 + 125 + 20 + 5 + 30) ms = 235 ms R = 59: Nearly all users dissatisfied VoIP ter
44、minal send delay = 35 ms, VoIP terminal receive delay = 65 ms VoIP gateway send delay = 35 ms, VoIP gateway receive delay = 65 ms total delay = Ts + Tlan + Tr + Tpstn + Ts + Tlan + Tr = (35 + 5 + 65 + 125 + 35 + 5 + 65) ms = 335 ms R = 47: Not recommended VoIP terminal send delay = 50 ms, VoIP termi
45、nal receive delay = 100 ms VoIP gateway send delay = 50 ms, VoIP gateway receive delay = 100 ms total delay = Ts + Tlan + Tr + Tpstn + Ts + Tlan + Tr = (50 + 5 + 100 + 125 + 50 + 5 + 100) ms = 435 ms R = 37: Not recommended The quality as perceived by the user in these example calculations is identi
46、cal for both sides, because the example is symmetrically composed. The scenario in Figure II.6 describes a connection between one VoIP island and an analogue terminal connected to the PSTN with a delay in the PSTN of 25 ms. The delay in the LAN is 5 ms which is composed of the fixed delay and the va
47、lue of the delay variation (jitter). In addition, the VoIP gateway provides an echo canceller according to ITU-T Rec. G.168 with sufficient tail delay covering the echo path via the local office. Furthermore, low bit-rate coding as per ITU-T Rec. G.729A is deployed; thus, Ie = 11. ITU-T Rec. G.108 (
48、1999)/Amd.2 (03/2004) 7 Figure II.6/G.108 VoIP terminal with G.729A and PSTN with analogue terminal For the E-model calculations, three different cases of terminal delay (and gateway delay) have been investigated: VoIP terminal send delay = 20 ms, VoIP terminal receive delay = 30 ms VoIP gateway sen
49、d delay = 20 ms, VoIP gateway receive delay = 30 ms total delay = Ts + Tlan + Tr + Tpstn = (20 + 5 + 30 + 25) ms = 80 ms R = 80: Users satisfied VoIP terminal send delay = 35 ms, VoIP terminal receive delay = 65 ms VoIP gateway send delay = 35 ms, VoIP gateway receive delay = 65 ms total delay = Ts + Tlan + Tr + Tpstn = (35 + 5 + 65 + 25) ms = 130 ms R = 79: Some users dissatisfied VoIP terminal send delay = 50 ms, VoIP terminal receive delay = 100 ms VoIP gateway send delay = 50 ms, VoIP gateway receive d
