1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Q.50 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2001) SERIES Q: SWITCHING AND SIGNALLING International automatic and semi-automatic working Signalling for circuit multiplication equipment Signalling between Circuit Multiplication Equipment (CME)
2、and International Switching Centres (ISC) ITU-T Recommendation Q.50 (Formerly CCITT Recommendation) ITU-T Q-SERIES RECOMMENDATIONS SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE Q.1Q.3 INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING Q.4Q.59 Basic Recommendations Q.4Q.9 Nu
3、mbering plan and dialling procedures in the international service Q.10Q.11 Routing plan for international service Q.12Q.19 General Recommendations relative to signalling and switching systems (national or international) Q.20Q.34 Tones for use in national signalling systems Q.35Q.39 General character
4、istics for international telephone connections and circuits Q.40Q.47 Signalling for satellite systems Q.48Q.49 Signalling for circuit multiplication equipment Q.50Q.59 FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN Q.60Q.99 CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Q.100Q.119 SPECIFICAT
5、IONS OF SIGNALLING SYSTEMS No. 4 AND No. 5 Q.120Q.249 SPECIFICATIONS OF SIGNALLING SYSTEM No. 6 Q.250Q.309 SPECIFICATIONS OF SIGNALLING SYSTEM R1 Q.310Q.399 SPECIFICATIONS OF SIGNALLING SYSTEM R2 Q.400Q.499 DIGITAL EXCHANGES Q.500Q.599 INTERWORKING OF SIGNALLING SYSTEMS Q.600Q.699 SPECIFICATIONS OF
6、SIGNALLING SYSTEM No. 7 Q.700Q.799 Q3 INTERFACE Q.800Q.849 DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 Q.850Q.999 PUBLIC LAND MOBILE NETWORK Q.1000Q.1099 INTERWORKING WITH SATELLITE MOBILE SYSTEMS Q.1100Q.1199 INTELLIGENT NETWORK Q.1200Q.1699 SIGNALLING REQUIREMENTS AND PROTOCOLS FOR IMT-2000 Q.1700Q
7、.1799 SPECIFICATIONS OF SIGNALLING RELATED TO BEARER INDEPENDENT CALL CONTROL (BICC) Q.1900Q.1999 BROADBAND ISDN Q.2000Q.2999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. Q.50 (07/2001) i ITU-T Recommendation Q.50 Signalling between circuit multiplication equipm
8、ent (CME) and international switching centres (ISC) Summary This Recommendation contains the Signalling Interface between a International Switching Centre (ISC) and Circuit Multiplication Equipment. Source ITU-T Recommendation Q.50 was revised by ITU-T Study Group 11 (2001-2004) and approved under t
9、he WTSA Resolution 1 procedure on 13 July 2001. ii ITU-T Rec. Q.50 (07/2001) 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
10、-T is responsible 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 Assembly (WTSA), which meets every four years, establishes the topics for stu
11、dy by the ITU-T study groups which, in turn, produce Recommendations on these 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
12、collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “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 i
13、mplementation of this Recommendation may involve the use of a claimed Intellectual 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 pro
14、cess. 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 Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strong
15、ly urged to consult the TSB patent database. ITU 2002 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. ITU-T Rec. Q.50 (07/2001) iii CONT
16、ENTS Page 1 Introduction. 1 2 References. 1 2.1 Normative References. 1 2.2 Bibliography . 1 3 Definitions relating to Circuit Multiplication Equipment. 1 4 Abbreviations 4 5 Requirements 5 5.1 Reasons for use of Circuit Multiplication Equipment (CME) 5 5.2 Integration of Circuit Multiplication Equi
17、pment into the circuit-switched international network 5 5.3 Factors for signalling functions determination . 6 5.3.1 Capabilities and limitations . 6 5.3.2 Connection types supported on Circuit Multiplication Equipment links 6 5.4 Connection types and Circuit Multiplication Equipment techniques in t
18、he context of signalling 6 6 Network aspects 7 6.1 Division of functionality between the International Switching Centre and the Circuit Multiplication Equipment. 7 6.2 Circuit Multiplication Equipment dynamic load control process. 8 6.3 Call set-up process 8 6.3.1 Seizure/select. 9 6.3.2 Release. 9
19、6.3.3 Dual seizure . 10 6.4 Change of connection of type after call set-up . 10 6.5 Inter-dependency between dynamic load control and call set-up process 10 7 Protocol. 10 7.1 Control information elements between International Switching Centre and Circuit Multiplication Equipment. 10 7.2 Information
20、 elements for Type 1 Circuit Multiplication Equipment 11 7.3 Information elements for Type 2 Circuit Multiplication Equipment 11 7.4 Notification of dynamic load control actions . 11 8 Example systems. 11 Annex A Interface based on time-slot 16 (frame 0-15) 14 iv ITU-T Rec. Q.50 (07/2001) Page Annex
21、 B Interface based on time slot 16 (frame 1-15). 17 B.1 General 17 B.2 Physical level of interface. 17 B.3 Distribution of functions between DCME and ISC 17 B.3.1 DCME functions 17 B.3.2 ISC functions . 18 B.4 Signalling code . 18 B.5 Signalling procedures . 19 B.5.1 Successful call set-up. 19 B.5.2
22、 Unsuccessful call set-up 19 B.5.3 Call release 19 B.5.4 Maintenance procedures 19 ITU-T Rec. Q.50 (07/2001) 1 ITU-T Recommendation Q.50 Signalling between Circuit Multiplication Equipment (CME) and International Switching Centres (ISC) 1 Introduction This Recommendation contains principles and exam
23、ples of signalling between the International Switching Centre (ISC) (exchanges) (see Note) and their associated circuit multiplication equipments. Circuit multiplication equipments may have integral echo control and A/ law converter functions. The information in this Recommendation is compatible wit
24、h the control procedures for such devices. NOTE As Circuit Multiplication Equipment may also be used in national networks, the signalling described here could not only be used in International Switching Centres but also in national exchanges. 2 References 2.1 Normative References The following ITU-T
25、 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 revision: users of this Recommendation
26、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. 1 ITU-T G.703 (1998), Physical/Electrical characteristics of hierarchical
27、digital interfaces. 2 ITU-T G.704 (1998), Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels. 3 ITU-T Q.33 (1988), Protection against the effects of faulty transmission on groups of circuits (Fascicle VI.I of Blue Book). 2.2 Bibliography The documents l
28、isted in this clause provide informative background information for the reader and are not normative within this Recommendation. ITU-T G.763 (1998), Digital circuit multiplication equipment using G.726 ADPCM and digital speech interpolation. ITU-T G.767 (1998), Digital circuit multiplication equipme
29、nt using 16 kbit/s LD-CELP, digital speech interpolation and facsimile demodulation/remodulation. 3 Definitions relating to Circuit Multiplication Equipment For a complete description of additional definitions see ITU-T G.763. 2 ITU-T Rec. Q.50 (07/2001) 3.1 digital circuit multiplication equipment
30、(DCME) and circuit multiplication equipment (CME): DCME and Circuit Multiplication Equipment constitute a general class of equipment which permits concentration of a number of trunks on a reduced number of transmission channels. DCME in particular permits concentration of a number of 64 kbit/s PCM e
31、ncoded trunks on a reduced number of digital transmission channels. 3.2 speech interpolation; digital speech interpolation (DSI): A method of profiting from the time instants when a speaker is not active, which is indicated by a speech detector. The channel is then used by another active connection.
32、 The signals carried by a transmission channel therefore represent interleaved bursts of speech signals derived from a number of different trunks. 3.3 low rate encoding (LRE): Speech coding methods with bit rates less than 64 kbit/s, e.g. the 32 kbit/s transcoding process defined in ITU-T G.721 appl
33、ied to speech coded according to ITU-T G.711. 3.4 speech activity: The ratio of the time speech and corresponding hangover occupies the trunk to the total measuring time, averaged over the total number of trunks carrying speech. 3.5 circuit multiplication equipment gain: The trunk channel to transmi
34、ssion channel multiplication ratio, which is achieved through application of Circuit Multiplication Equipment, including LRE and/or speech interpolation (DSI) (see Figure 1). 3.6 trunk: A bidirectional connection consisting of a forward channel and a backward channel between the International Switch
35、ing Centre and Circuit Multiplication Equipment not subject to LRE or DSI operation. 3.7 transmission channel; bearer channel: One channel of the connection between the transmit unit and receive unit of corresponding Circuit Multiplication Equipment. 3.8 freeze-out: The temporary condition when a tr
36、unk channel becomes active and cannot immediately be assigned to a transmission channel, due to lack of available transmission capacity. 3.9 freeze-out fraction: The ratio of the sum of the individual channel freeze-outs to the sum of the active signals and their corresponding hangover times and fro
37、nt end delays, for all trunk channels over a fixed interval of time, e.g. one minute. 3.10 transmission overload: The condition when the freeze-out fraction or average bits per sample goes beyond the value set in accordance with speech quality requirements. T1155420-93.Input trunks Transmission chan
38、nels (64 kbit/s)CME(DCME)Bearer channels 64 kbit/s40 kbit/s32 kbit/s32/24 kbit/sFigure 1/Q.50 Circuit Multiplication Equipment gain ITU-T Rec. Q.50 (07/2001) 3 Operating modes 3.11 Point-to-point mode (see diagrams a) and b) of Figure 2) Using diagram a) of Figure 2 for reference, the transmit side
39、Circuit Multiplication Equipment concentrates N trunks into N/G transmission channels, where G is the Circuit Multiplication Equipment gain. At the receive side, the receiving Circuit Multiplication Equipment simply reconstitutes the N trunks from the N/G transmission channels. The example in diagra
40、m b) of Figure 2 also shows a point-to-point mode. From the switching point of view there could be a difference between the configurations in diagrams a) and b) of Figure 2. For transmission of alarms it has also to be considered that different exchanges may be connected to one Circuit Multiplicatio
41、n Equipment. 3.12 Multi-clique mode (see Figure 3) In this mode the pool of transmission channels is sub-divided into several independent pools (cliques) of fixed capacity, each destination specific. If a part of the cliques capacity is not used, it cannot be used for another destination (see Figure
42、 3). 3.13 Multi-destination mode A DCME operational mode where input trunk channel traffic is interpolated over a pool of available transmission channels for all destinations having traffic in the pool. The transmit trunk channels are designated to receive trunk channels at corresponding locations.
43、Figure 4 shows a unidirectional system block diagram for a multi-destination mode with two transmit and two receive DCME units. T1155430-93Exchange ACME 1transmitCME 2receiveExchange BExchange AExchange BCME 1 CME 2 Exchange CN inputtrunk channelsN ouputtrunk channelsN/G transmissionchannels whereG
44、= CME gainInputtrunk channelsnumbers 0 to MN/G transmissionchannelsN ouputtrunk channelsInputtrunk channelsnumbers M + 1 to Nb) Point-to-point two origins unidirectionala) Point-to-point unidirectionalFigure 2/Q.50 Multi-clique for two origins and two destinations unidirectional 4 ITU-T Rec. Q.50 (0
45、7/2001) T1155440-93(N2 = N2A + N2B)N2AG2AN2BG2B+N1AG1AN1BG1B+N1AG1AN2AG2A+(N1 = N1A + N1B)(NA = N1A + N2A)Tx unitTx unitRx unitTransmitting stations Receiving destinationStatic TSIor pre-sorterTransmissionchannelsTransmissionchannelsN1 trunkchannels fromexchange AN2 trunkchannels fromexchange BNA tr
46、unkchannels toexchange CTo station BDCME No. 1DCME No. 2DCME No. AFigure 3/Q.50 Multi-clique mode (only one direction shown) T1155450-93DCME A(N2 = N2A + N2B)N1G1N2G2Tx unitDCME No. 1DCME No. 2Tx unitRx unitRx unitDCME BTransmission channelsTransmission channelsN1A + N2Aoutput trunkchannelsN1B + N2B
47、output trunkchannelsN1 inputtrunkchannelsN2 inputtrunkchannelsPre-selectorPre-selector(N1 = N1A + N1B)Figure 4/Q.50 Multi-destination mode (only one direction shown) 4 Abbreviations This Recommendation uses the following abbreviations: CCF Call Control Function CME Circuit Multiplication Equipment C
48、MECF CME Control Function CMESF CME Switching Function ITU-T Rec. Q.50 (07/2001) 5 DCME Digital Circuit Multiplication Equipment DSI Digital Speech Interpolation ISC International Switching Centre LRE Low Rate Encoding TASI Time Assignment Speech Interpolation TRM Transmission Resource Management 5
49、Requirements 5.1 Reasons for use of Circuit Multiplication Equipment (CME) Circuit Multiplication Equipment is used in order to reduce the bandwidth required for transmission of a given set of calls. This can be achieved by reducing the redundancy which is inherent in speech communications. Circuit Multiplication Equipment gains of up to 5:1 can be achieved using DSI + LRE with subjectively acceptable quality. Thus, the amount of line plant required between switching points and hence the cost of provision can be minimized. 5.2 I
