1、, INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZATION SECTOR OF ITU G.767 (1 0/98) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Terminal equipments - Principal characteristics of transcoder and digital mu i tipi cat
2、 ion equipment Digital circuit multiplication equipment using i 6 kbits LD-CELP, digital speech interpolation and facsimile demodulation/remodulation ITU-T Recommendation G.767 (Previously CCITT Recommendation) STD=ITU-T RECMN G*7b?-ENGL 1998 = 4862591 0654965 7Tl ITU-T G-SERIES RECOMMENDATIONS TRAN
3、SMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS INTERNA TIONAL A NA LOWE CARRIER SYSTEM GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- TRANSMISSION SYSTEMS IN DIVI DUAL CHARACTERISTICS OF INTERNATIONAL CARRI ER TELEPHON E SYSTEMS ON
4、METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TES TING EQUIPMEN TS TRANSMISSION MEDIA CHA RA CTERIS TICS General Symmetric cable pairs Land
5、coaxial cable pairs Submarine cables Optical fibre cables Characteristics of optical components and sub-systems DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUI PMENTS General Coding of analogue signals by pulse code modulation Coding of analogue signals by methods other than PCM Principal characteristics
6、 of primary multiplex equipment Principal characteristics of second order multiplex equipment Principal characteristics of higher order multiplex equipment G. 1 OO-G. I99 G.200-G.299 G.300-G.399 G.400-G.449 G.450-G.499 G.600-G.609 G.610-G.619 G.620-G.629 G .630-G.649 G.650-G.659 G.660-G.699 G.700-G.
7、799 G.700-G.709 G.710-G.719 G.720-G.729 G.730-G.739 G ,740-G . 749 G.750-G.759 - Operations, administration and maintenance features of transmission equipment Principal characteristics of multiplexing equipment for the synchronous digital Other terminal equipment G.790-G.799 G.770-G.779 G.780-G.789
8、hierarchy DIGITAL NETWORKS G.800-G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900-G.999 For firther details, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION 6.767 DIGITAL CIRCUIT MULTIPLICATION EQUIPMENT USING i6 kbit/s LD-CELP, DIGITAL SPEECH INTERPOLATION AND FACSIMILE DEMO
9、DULATION/REMODULATION Summary This Recommendation specifies the elements of DCME using 16 kbit/s LD-CELP, Digital Speech Interpolation (DSI) and Facsimile DemodulationRemodulation in order to achieve interworking of such equipment. It specifies extensions and deviations for Recommendations G.763 and
10、 G.766 which speci a 32 kbit/s ADPCM DCME, and Facsimile DemodulatiodRemodulation. Source ITU-T Recommendation G.767 was prepared by ITU-T Study Group 15 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 13* of October 1998. Recommendation 6.767 (10/98) 1 FOREWORD ITU (In
11、ternational Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the IT. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recom
12、mendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topi
13、cs. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a coilaborative basis with IS0 and IEC. NOTE In this Recom
14、mendation, the expression “Administration“ is used for conciseness to indicate both a teiecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the
15、 use of a claimed Intellectual Property Right. The 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 process. As of the date of approval of this Recomme
16、ndation, the ITU had 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 strongly urged to consult the TSB patent database. O I
17、TU 1999 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 the ITU. ii Recommendation 6.767 (10/98) CONTENTS Page Scope 1 1 References 1 2 Defin
18、itions 1 3 Abbreviations . 1 4 5 DCME fiame structure . 2 5.1 General . 2 5.1.1 Supported services . 2 5.1.2 PCM fiame 2 5.1.3 DCME fiame 2 5.1.4 DCME multifiame . 2 5.1.5 16 kbit/s DCME frames . 3 6 Bearer fiarne structure 6.1 Cliques. destinations and bearers . 6.1.1 Number of cliques . 6.1.2 Numb
19、er of destinations . 6.1.3 Multiple outgoing bearers . 6.2 Assignment Messages (AM) 6.3 Bearer Channels (BC) . 6.4 Control Channel (CC) . 6.5 BC numbering and the use of the bearer frame 6.5.1 6.5.2 6.5.3 4-bit BCs (8B, FB) . 6.5.4 Normal range 2-bit BCs (LD-CELP voice) . 6.5.5 Overload BCs 6.5.6 Pr
20、e-assigned BCs . %bit (64 kbit/s transparent calls) BCs . 5-bit (VBD optimized 40 kbit/s LD-CELP) BCs 3 3 4 4 Control channel 5 7 7.1 General . 7.2 Number of assignment messages 7.2.1 Singleidouble AM mode criterion . 7.2.2 Total number of assignment messages 7.3.1 CC synchronization . 7.3.2 Assignm
21、ent messages 7.3 Control channel content 5 . Recommendation G.767 (10/98) 111 7.4 8 8.1 8.2 8.3 9 1 o . 11 11.1 11.2 11.3 11.4 11.5 12 7.3.3 Asynchronous data word . 7.3.4 Error correction . CC message transmission scheme 7.4.2 CC bit mapping . Variable bit rate and overload channel creation . Princ
22、iples 8.1.1 Creation of 16 kbit/s channels . 8.1.2 Creation of 12.8 kbitk channels 8.1.3 Creation of 9.6 kbit/s channels Overload channel creation 8.2.1 Notations . 8.2.2 Packaging schemes Overload channel creation process - The VBR scheme . 8.3.1 VBR lists . 8.3.2 Notations . 7.4.1 Control channel
23、structure 8.3.3 VBR not required 8.3.4 VBR required ABPS calculations Channel check procedure Facsimile demodulationremodulation . General . Facsimile blocks, facsimile transport channels and fax banks . Facsimile data channel . Facsimile control channel and forward error correction . FCC location o
24、n the bearer . System statistics measurement . Page 8 10 11 11 11 16 16 16 16 16 16 16 16 17 17 18 18 18 20 20 20 20 20 21 22 23 23 iv Recommendation 6.767 (10/98) STD-ITU-T RECMN G-767-ENGL 1998 M 4862593 Ob54970 Ob9 Introduction The introduction of the 16 kbit/s LD-CELP speech compression algorith
25、m by ITU-T (Recommendation G.728), with its expansions to variable bit rates below and above 16 kbits, has enabled the enhancement of circuit multiplication equipment performance in both speech quality and multiplication gain. Third generation DCME follows the operation principles of the second gene
26、ration DCME (DCME in accordance with Recommendations G.763 and G.766), with modifications dictated by the transition from ADPCM, which is a single sample based speech compression algorithm, to LD-CELP, which operates on a 5-sample vector. This Recommendation is, therefore, an extension to Recommenda
27、tions G.763 (Digital Circuit Multiplication Equipment Using 32 kbit/s ADPCM and Digital Speech Interpolation) and G.766 (Facsimile DemodulationRemodulation for DCME), as it specifies only the deviations of the third generation DCME from its predecessor. Recommendation 6.767 (10/98) V STD-ITU-T RECMN
28、 G.7b7-ENGL 3998 = 48b2593 Ob54973 TT5 m Recommendation 6.767 DIGITAL CIRCUIT MULTIPLICATION EQUIPMENT USING 16 kbith LD-CELP, DIGITAL SPEECH INTERPOLATION AND FACSIMILE DEMODULATION/REMODULATION (Geneva, 1998) 1 Scope This Recommendation specifies the elements of DCME using 16 kbits LD-CELP, Digita
29、l Speech Interpolation (DSI) and facsimile demodulationhemodulation (namely a 16 kbit/s DCME) in order to achieve intenvorking of such equipment. It is an extension to Recommendations G.763 (Digital Circuit Multiplication Equipment Using 32 kbit/s ADPCM and Digital Speech Interpolation) and G.766 (F
30、acsimile DemodulationRemodulation for DCME), as it specifies only the deviations of the 16 kbit/s DCME from the G.763 32 kbits DCME. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommend
31、ation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other refere
32、nces listed below. A list of the currently valid ITU-T Recommendations is regularly published. - ITU-T Recommendation G.763 (1 998), Digital circuit multiplication equipment using ADPCM (Recommendation G. 726) and digital speech interpolation. ITU-T Recommendation G.766 (1 996), Facsimile demodulati
33、on/remodulation for digital circuit multiplication equipment. - 3 Definitions The same definitions of Recommendations G.763 and G.766 are used in this Recommendation. 4 Abbreviations The abbreviations used in the above-referenced Recommendations are also used in this Recommendation as well. This Rec
34、ommendation uses also the following abbreviations. ABPS Averaged Bit Per Sample AM Assignment Message BB Bit Bank BCH B ose-Chaudhuri-Hocquenghem FB Fax Bank FCC Facsimile Control Channel FDC Facsimile Data Channel Recommendation 6.767 (10/98) 1 STDBITU-T RECMN Ge7b7-ENGL 1778 4Bh259L Oh54912 933 W
35、FTC Facsimile Transport Channel Info Information LD-CELP PCM Pulse Code Modulation QB Quarter Byte Rx Receive Tx Transmit VBD Voice-Band Data Low-Delay Code Excited Linear Prediction 5 DCME frame structure 5.1 General 5.1.1 Supported services The 16 kbit/s DCME frame structure accommodates the follo
36、wing services: o %bit channels to support 64 kbit/s transparent calls. 2-bit channels to support voice calls at LD-CELP 16 kbit/s, 12.8 kbit/s, 9.6 kbit/s according 5-bit channels to support VBD calls at 40 kbit/s according to Recommendation G.728 and its o 4-bit channels to support fax banks carryi
37、ng demodulated fax calls similar to 8-, 5-, 2-bit channels to support 64 kbit/s, 40 kbit/s, 16 kbit/s, 12.8 kbit/s and 9.6 kbit/s o to Recommendation G.728 and its Annex H. draft Annex J. Recommendations G.763 and G.766. pre-assigned channels. o o 5.1.2 PCM frame As in Recommendation G.763, the bear
38、er structure of the 16 kbit/s DCME retains compatibility with Recommendation G.704, so it contains 32 consecutively numbered 8-bit time slots, from O to 3 1 1. 5.1.3 DCME frame The low rate encoding algorithm used in the 16 kbit/s DCME is LD-CELP according to Recommendation G.728. The LD-CELP algori
39、thm handles a speech vector of 5 consecutive PCM samples (at 64 kbit/s) and results in a vector of 10, 8 or 6 bits (at 16, 12.8 or 9.6 kbit/s respectively). The encoding rate can be altered once every 4 speech vectors, i.e. every 2.5 ms. A DCME frame of 2.5 ms, which contains 20 G.704 PCM frames, is
40、 used in the 16 kbit/s DCME. 5.1.4 DCME multiframe The IT related circuit supervisiodalm condition field of the asynchronous word supports up to 360 ITS, carried over up to 12 primary rate interfaces. The G.767 DCME multiframe of 72 DCME frames is used to accommodate that. The case of T1 bearer inte
41、rface is similar to El and handled as in Recommendation G.763. 2 Recommendation 6.767 (10/98) STD.ITU-T RECMN G-767-ENGL I1998 4862593 Ob54973 878 5.1.5 16 kbit/s DCME frames The 16 kbits DCME fiame and multiframe structures are depicted in Figure 1. Figure 1/6.767 - 16 kbit/s frame and multiframe s
42、tructures 6 Bearer frame structure 6.1 Cliques, destinations and bearers 6.1.1 Number of cliques With LD-CELP, small cliques (compared to G.763 DCME) can support a fairly large amount of traffic. Therefore the maximum number of cliques (pools) carried on a single bearer in 16 kbit/s DCME is increase
43、d to 4. Each pool starts and ends on TS boundaries (and therefore occupies an integral number of time slots). 6.1.2 Number of destinations The maximum number of destinations is 4 including the cases of mixed operation between multi-clique and multi-destination modes. 6.1.3 Multiple outgoing bearers
44、Optionally, a 16 kbWs DCME will support up to 4 outgoing bearers. A single bearer will be able to carry up to 4 cliques. A clique shall not be split across bearers. 6.2 Assignment Messages (AM) When using LD-CELP, the DCME gain increases significantly and the number of supported ITS is increased acc
45、ordingly (compared to ADPCM). As a result, the number of activity events (and assignment messages) increases. Taking into account the fact that the DCME frame is extended (from 2 ms to 2.5 ms), the control channel can support up to two assignment messages (namely double AM) every DCME frame, so as t
46、o avoid long queues and freeze-out due to limited control channel capacity. The option of operating with a single Assignment Message (single AM), when smaller configurations are applied, is maintained. Recommendation G.767 (10/98) 3 STDmITU-T RECMN G.7b7-ENGL 1998 li8b259L Ob54974 704 W r- 6.3 Beare
47、r Channels (BC) BC BC BC BC m-4 m-3 m-2 m-1 I, cc BC BC BC BC . . . BC BC / cc BCBC n-1 n :i (2QBs) i 2 I TSo (3QBs) 2 3 4 5 16 kbit/s LD-CELP encoded voice calls use 2 bits every PCM frame. Therefore the 16 kbit/s DCME bearer channels occupy 2 bits each. These basic Bearer Channels (BCs) shall be r
48、eferred to as Quarter Bytes (QBs) in this Recommendation. Each QB occupies 40 bits every DCME fiame2. BC m 6.4 Control Channel (CC) A single AM control channel of the 16 kbits DCME occupies 4 bits every PCM frame, i.e. 2 QBs. The single AM control channel holds the synchronization word, an assignmen
49、t message (IT and BC numbers and synchronous data word), the asynchronous data word and some error correction bits. When an additional assignment message in the same DCME fiame is required (double AM), one additional QB supports it. 6.5 Each time slot is subdivided into 4 QBs. The leftmost two or three QBs of each pool carries the control channel (single or double AM, respectively). The remaining QBs of the pool are the Bearer Channels (BCs) and are used to carry traffic. The normal range BCs are consecutively numbered. When a single AM control channel is used, the BC that fol
