1、 International Telecommunication Union ITU-T I.733TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2009) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK B-ISDN equipment aspects ATM equipment Voice on ATM circuit multiplication equipment Recommendation ITU-T I.733 ITU-T I-SERIES RECOMMENDATIONS INT
2、EGRATED SERVICES DIGITAL NETWORK GENERAL STRUCTURE Terminology I.110I.119 Description of ISDNs I.120I.129 General modelling methods I.130I.139 Telecommunication network and service attributes I.140I.149 General description of asynchronous transfer mode I.150I.199 SERVICE CAPABILITIES Scope I.200I.20
3、9 General aspects of services in ISDN I.210I.219 Common aspects of services in the ISDN I.220I.229 Bearer services supported by an ISDN I.230I.239 Teleservices supported by an ISDN I.240I.249 Supplementary services in ISDN I.250I.259 OVERALL NETWORK ASPECTS AND FUNCTIONS Network functional principle
4、s I.310I.319 Reference models I.320I.329 Numbering, addressing and routing I.330I.339 Connection types I.340I.349 Performance objectives I.350I.359 Protocol layer requirements I.360I.369 General network requirements and functions I.370I.399 ISDN USER-NETWORK INTERFACES Application of I-series Recomm
5、endations to ISDN user-network interfaces I.410I.429 Layer 1 Recommendations I.430I.439 Layer 2 Recommendations I.440I.449 Layer 3 Recommendations I.450I.459 Multiplexing, rate adaption and support of existing interfaces I.460I.469 Aspects of ISDN affecting terminal requirements I.470I.489 INTERNETW
6、ORK INTERFACES I.500I.599 MAINTENANCE PRINCIPLES I.600I.699 B-ISDN EQUIPMENT ASPECTS ATM equipment I.730I.739Transport functions I.740I.749 Management of ATM equipment I.750I.759 Multiplexing aspects I.760I.769 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T I.733
7、(03/2009) i Recommendation ITU-T I.733 Voice on ATM circuit multiplication equipment Summary The purpose of a voice on ATM circuit multiplication equipment (VACME) is to provide a bandwidth efficient means of connecting TDM-based international switching centres (ISCs) and an ATM network. In addition
8、 to providing traditional CME functions, the equipment will have additional capabilities such as ATM multiplexing to optimize bandwidth utilization. VACME is a general switched telephone network (GSTN) trunking equipment using pulse code modulation (PCM) and low rate encoding technique together with
9、 digital speech interpolation (DSI) and facsimile demodulation/remodulation. Recommendation ITU-T I.733 addresses key issues, such as interfaces, signal processing functions, ATM adaptation layer mappings, and OAM functions, to be used in VACME in order to ensure the interworking of this equipment.
10、Source Recommendation ITU-T I.733 was approved on 16 March 2009 by ITU-T Study Group 16 (2009-2012) under Recommendation ITU-T A.8 procedures. This version also includes Corrigendum 1 approved on 14 December 2009. ii Rec. ITU-T I.733 (03/2009) FOREWORD The International Telecommunication Union (ITU)
11、 is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). 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
12、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
13、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
14、“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 applicability) a
15、nd 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 Recommen
16、dation 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 of cl
17、aimed 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 notice of intellectual property, protected by patents, which may be required to implement this Reco
18、mmendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever
19、, without the prior written permission of ITU. Rec. ITU-T I.733 (03/2009) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations and acronyms 3 5 VACME functions 4 6 Reference model . 6 7 VACME functional description 6 7.1 VACME functional model . 6 8 Interfaces. 7 8.1 Transmiss
20、ion interface Trunk side 7 8.2 ATM interface 7 8.3 Local alarms interface 7 9 Signal processing functions 8 9.1 Trunk channels . 8 9.2 Low rate encoding (LRE) . 9 9.3 Digital speech interpolation 11 9.4 Facsimile remodulation 11 9.5 Comfort noise insertion 11 9.6 Packet loss concealment . 12 10 Sign
21、alling support . 12 11 ATM adaptation layers . 12 11.1 AAL type 1 mapping 13 11.2 AAL type 2 mapping 14 12 ATM multiplexing and cross-connect 14 12.1 ATM multiplexing 14 12.2 ATM cross-connect (optional) . 15 13 Traffic load control (for further study) . 15 13.1 Dynamic load control (for further stu
22、dy) . 15 14 Operations and maintenance functions . 15 14.1 Facility alarm handling . 15 Bibliography. 19 Rec. ITU-T I.733 (03/2009) 1 Recommendation ITU-T I.733 Voice on ATM circuit multiplication equipment 1 Scope The purpose of a voice on ATM circuit multiplication equipment (VACME) is to provide
23、a bandwidth efficient means of connecting TDM-based international switching centres (ISCs) and an ATM network. In addition to providing traditional circuit multiplication equipment (CME) functions, the equipment will have additional capabilities such as ATM multiplexing to optimize bandwidth utiliza
24、tion. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference 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 r
25、evision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent 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 t
26、his Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.703 Recommendation ITU-T G.703 (2001), Physical/electrical characteristics of hierarchical digital interfaces. ITU-T G.704 Recommendation ITU-T G.704 (1998), Synchronous frame structures used at 1
27、544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels. ITU-T G.711 Recommendation ITU-T G.711 (1988), Pulse code modulation (PCM) of voice frequencies. ITU-T G.723.1 Recommendation ITU-T G.723.1 (2006), Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s. IT
28、U-T G.726 Recommendation ITU-T G.726 (1990), 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM). ITU-T G.728 Recommendation ITU-T G.728 (1992), Coding of speech at 16 kbit/s using low-delay code excited linear prediction. ITU-T G.729 Recommendation ITU-T G.729 (2007), Coding o
29、f speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction. ITU-T G.732 Recommendation ITU-T G.732 (1988), Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s. ITU-T G.733 Recommendation ITU-T G.733 (1988), Characteristics of primary PCM multiplex
30、 equipment operating at 1544 kbit/s. ITU-T G.736 Recommendation ITU-T G.736 (1993), Characteristics of a synchronous digital multiplex equipment operating at 2048 kbit/s. ITU-T G.763 Recommendation ITU-T G.763 (1998), Digital circuit multiplication equipment using G.726 ADPCM and digital speech inte
31、rpolation. ITU-T G.767 Recommendation ITU-T G.767 (1998), Digital circuit multiplication equipment using 16 kbit/s LD-CELP, digital speech interpolation and facsimile demodulation/remodulation. 2 Rec. ITU-T I.733 (03/2009) ITU-T G.775 Recommendation ITU-T G.775 (1998), Loss of Signal (LOS), Alarm In
32、dication Signal (AIS) and Remote Defect Indication (RDI) defect detection and clearance criteria for PDH signals. ITU-T G.803 Recommendation ITU-T G.803 (2000), Architecture of transport networks based on the synchronous digital hierarchy (SDH). ITU-T G.804 Recommendation ITU-T G.804 (2004), ATM cel
33、l mapping into plesiochronous digital hierarchy (PDH). ITU-T I.363.1 Recommendation ITU-T I.363.1 (1996), B-ISDN ATM Adaptation layer specification: Type 1 AAL. ITU-T I.363.2 Recommendation ITU-T I.363.2 (1997), B-ISDN ATM Adaptation layer specification: Type 2 AAL. ITU-T I.366.2 Recommendation ITU-
34、T I.366.2 (2000), AAL type 2 service specific convergence sublayer for narrow-band services. ITU-T Q.50 Recommendation ITU-T Q.50 (2001), Signalling between Circuit Multiplication Equipment (CME) and International Switching Centres (ISC). 3 Definitions This Recommendation defines the following terms
35、: 3.1 circuit multiplication equipment (CME): A generic type of the equipment, including all these types of equipment such as DCME, PCME, IP-CME, VACME and channel transcoder, having a number of 64 kbit/s PCM encoded input trunks, compressing speech signals on channel basis in various ways and sendi
36、ng them out through various types of bearers including STM type, packetized type, ATM type and IP type. 3.2 circuit multiplication system (CMS): A telecommunications network comprised of two or more interoperating CME terminals where each CME terminal contains a transmit unit and a receive unit. 3.3
37、 comfort noise: Artificially generated noise signal at the receive side to compensate for the silent part of conversation that was removed by the send side and that gives a comfortable feeling to the receiver when silence elimination is introduced. It is desirable for a comfort noise to have the cha
38、racteristics similar to those of the original background noise signal that was suppressed (e.g., in terms of its level and spectrum). 3.4 digital circuit multiplication equipment (DCME): A general class of equipment which permits concentration of a number of 64 kbit/s PCM encoded trunk circuits on a
39、 reduced number of transmission circuits. 3.5 digital speech interpolation (DSI): A process which, when used in the transmit unit of a VACME, causes digital voice signals of a trunk channel to be mapped into ATM cells transferred through an ATM network only when activity is actually present on the t
40、runk channel. This, by exploiting the probability of the speech activity factor of trunk channels being less than 1.0, enables the traffic from a number of trunk channels to be concentrated and carried by a lesser number of ATM cells compared with the number of cells necessary for continuous connect
41、ions. NOTE A similar concept is defined in ITU-T G.763, ITU-T G.767, and b-ITU-T G.768, however, in specific terms as applicable to these Recommendations. 3.6 facsimile demodulation/remodulation: A processing introduced in a VACME where facsimile traffic is discriminated from voiceband data; subsequ
42、ently demodulated to recover the baseband digital signal; mapped into ATM cells; demultiplexed in the VACME receive unit; and Rec. ITU-T I.733 (03/2009) 3 remodulated using the same modulation scheme as used on the original signal received by the VACME transmit unit. NOTE A similar concept is define
43、d in ITU-T G.763, ITU-T G.767, and b-ITU-T G.768, however, in specific terms as applicable to these Recommendations. 3.7 low rate encoding (LRE): A voiceband signal encoding method which results in a bit rate less than 64 kbit/s. Conversion between voiceband signals encoded in PCM at 64 kbit/s and t
44、hose encoded at the lower rates will be carried out by the means specified in the referred ITU-T Recommendations. NOTE In ITU-T G.763, ITU-T G.767, and b-ITU-T G.768, LRE is defined in slightly different terms, as specifically needed in these Recommendations. 3.8 silence elimination: A process that
45、suppresses the transmission of the inactive part of the silent part of conversation to attain efficient transmission of a voice conversation. When silence elimination is introduced, it is necessary to insert comfort noise at the receive side, to compensate for the suppressed silence periods present
46、during listening and pause time intervals. This process is also sometimes called silence suppression. NOTE A similar concept is used in ITU-T G.763, ITU-T G.767, and b-ITU-T G.768, however, in specific terms as applicable to these Recommendations. 3.9 trunk channel (TC): A unidirectional, digital tr
47、ansmission path (generally short distance) used for carrying traffic and which connects a VACME to other equipment, e.g., an ISC. Two such trunk channels (transmit and receive) are needed by 4-wire telephone circuits and constitute a trunk circuit. NOTE 1 Signals carried by a trunk channel are trans
48、mitted at a bit rate of 64 kbit/s. NOTE 2 A number of trunk channels in each direction of transmission are required between a VACME CME and, for instance, an ISC. These trunk channels may be carried by a number of 2048 or 1544 kbit/s systems for example. 3.10 voice on ATM circuit multiplication equi
49、pment (VACME): A class of equipment which allows for the concentration of a number of 64 kbit/s PCM encoded input trunk circuits onto a reduced amount of bandwidth in the ATM domain. ATM cross-connection and multiplexing functions allow for a more efficient use of bandwidth. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations: AAL ATM Adaptation Layer ADPCM Adaptive Differential Pulse Code Modulation AIS Alarm Indication Signal AMI Altern
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