1、STD-ITU-T RECMN G.7bb-ENGL L7b m 48b257L b32358 475 INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.766 (I 1/96) SERIES G: TRANSMISSION SYSTEMS AND MEDIA Digital transmission systems - Terminal equipments - Principal characteristics of transcoder and dig
2、ital m ulti plication eq ui pmen t Facsimile demodulation/remodulation for digital circuit multiplication equipment ITU-T Recommendation G.766 (Previously CCITT Recommendation) STD-ITU-T RECMN G-7bb-ENGL 197b 48b259L Ob32359 321 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA NTERNATIO
3、NAL TELEPHONE CONNECTIONS AND CIRCUITS NTERNATIONAL ANALOGUE CARRIER SYSTEM RANSMISSION SYSTEMS SENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- NDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES ;ENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE NI
4、TH METALLIC LINES SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION :OORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TRANSMISSION MEDIA CHA RA CTERIS TICS 3IGITAL TRANSMISSION SYSTEMS TERM I NAL EQU I PM ENTS General Coding of analogue signals by pulse code modulation Coding of analogue
5、 signals by methods other than PCM Principal characteristics of primary multiplex equipment Principal Characteristics of second order multiplex equipment Principal characteristics of higher order multiplex equipment G. 100-G. 199 G. 200-G. 299 G. 300-G. 399 G.400-G.449 G.450-G.499 G.700-G.799 G.700-
6、G.709 G.710-G.719 G.720-G.729 G.730-G.739 G. 740-G. 749 G .750-G. 759 Principal characteristics of transcoder and digital multiplication equipment G.760-G.769 Operations, administration and maintenance features of transmission equipment hierarchy G.770-G.779 Principal characteristics of multiplexing
7、 equipment for the synchronous digital G.780-G . 7 89 Other terminal equipment General aspects Design objectives for digital networks Quality and availability targets Network capabilities and functions SDH network characteristics General Parameters for optical fibre cable systems Digital sections at
8、 hierarchical bit rates based on a bit rate of 2048 kbit/s Digital line transmission systems on cable at non-hierarchical bit rates Digital line systems provided by FDM transmission bearers Digital line systems Digital section and digital transmission systems for customer access to ISDN Optical fibr
9、e submarine cable systems Optical line systems for local and access networks DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.790-G.799 G.800-G.899 G ,800-G . 809 G.810-G.819 G.820-G.829 G .830-G. 839 G. 840-G.899 G.900-G.999 G. 900-G. 909 G.910-G.919 G.920-G.929 G.930-G.939 G.940-G .949
10、G.950-G.959 G.960-G. 969 G.970-G.979 G.980-G.999 For further details, please rer to ITU-T List of Recommendations. - STD-ITU-T RECMN G-7bb-ENGL L37b m Lib2591 Ob323b O43 ITU-T RECOMMENDATION 6.766 FACSIMILE DEMODULATION/REMODULATION FOR DIGITAL CIRCUIT MULTIPLICATION EQUIPMENT Source ITU-T Recommend
11、ation G.766 was revised by ITU-T Study Group 15 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of November 1996. STD-ITU-T RECMN G.7bb-ENGL L99b D LiBb259L Ob323bL TBT FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in
12、the field of telecommunications. The IT Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide
13、 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 topics. The approval of Recommendations by the Members of the ITU-T is covered by the
14、 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 collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate bo
15、th a telecommunication 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 use of a claimed Intellectual Property Right. The ITU takes no position concerni
16、ng 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 Recommendation, the ITU haahad not received notice of intellectual property, protected b
17、y 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 ITU 1997 All rights reserved. No part of this publication may be reproduced
18、 or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. 11 Recommendation G.766 (11/96) STD-ITU-T RECMN G-7bb-ENLL L77b 48b257L Ob323b2 7Lb CONTENTS Page 1 1.1 General Abbreviations . 2 Definitions of facsi
19、mile demodulationhemodulation in DCME 3 3 Functions of the facsimile module . 3 4 Facsimile module structure . 5 5 5.1 5.2 Facsimile frame assembler/disassembler blocks 7 7 9 10 11 11 11 Facsimile data channel Facsimile module frame . 5.2.1 Facsimile control channel 5.3 Facsimile blocks . 5.3.1 FEC
20、encoding 5.4 Facsimile transport channels 6 6.1 Facsimile module controller . 13 13 14 14 14 15 15 15 17 17 Common control function . 6.1.1 Communication with the ADF 6.1.2 Other communication functions 6.1.4 FCH management Facsimile Channel Handler (FCH) . 6.2.1 FCH requirements . 6.2.2 FCH protoco
21、l . 6.1.3 Capacity management . 6.1.5 Demodulator/remodulator pool management 6.2 7 7.1 7.2 7.3 8 8.1 Use of the facsimile control channel 24 24 29 30 Message field structure . Message transmission procedure Service channel . Timing and delay requirements Clock difference compensation 8.1.1 Demodula
22、tor side 8.1.2 Remodulator side . Critical time gaps of the T.30 signals . 8.2.1 Demodulator side requirements . 8.2.2 Remodulator side requirements . 30 30 30 31 31 31 31 8.2 . Recommendation 6.766 (11/96) 111 8.3 9 10 10.1 10.2 10.3 10.4 11 11.1 11.2 STD.ITU-T RECMN G-ibb-ENGL L77b q8b2591 Ob323b3
23、 852 Front-End Delay (FED) buffer . Multi-clique and multi-destination operation . Facsimile module operation and maintenance Facsimile module statistics . Facsimile module configuration data . Error count FEC activation Required DCME modifications Facsimile data handling Changes in the DCME process
24、es Annex A . Examples of FCH protocol exchanges SF-T.30 cases with matched capabilities NSF-T.30 proprietary cases with matched capabilities SF-T.30 cases with unmatched capabilities Annex B - Formal description of the facsimile module controller . B . 1 Introduction B.2 FMC interfaces . B . 3 Inter
25、nal structure of the FMC . B.4 Common control function (CCF) . B.5 FCH Supplement No . 1 - Dimensioning example for facsimile compression . S . 1 Introduction S.2 Assumptions . S.3 Method A.l A.2 A.3 A.4 NSF-T.30 proprietary cases with unmatched capabilities Page 32 32 32 32 34 34 34 35 35 35 36 36
26、55 58 62 64 64 64 70 72 73 100 100 100 100 v Recommendation G.766 (11196) STD-ITU-T RECMN G.7bb-ENGL L77b 48b2591 Ob323b4 797 W Recommendation G.766 FACSIMILE DEMODULATIONlREMODULATION FOR DIGITAL CIRCUIT MULTIPLICATION EQUIPMENT (revised in 1996) i General This Recommendation for a Digital Circuit
27、Multiplication Equipment (DCME) facsimile module is intended to be as flexible as possible in an open-network environment, while providing manufacturers of equipment the license to invent, whilst maintaining equipment interoperability . Use of the facsimile module provides a solution to the DCME tra
28、ffic loading problem created by the rapid growth of facsimile traffic, which is transmitted via DCME using 40 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) encoding, that rapidly depletes DCME bearer capacity resulting in reduced speech quality. The facsimile module (see Figure 1) is a
29、functional unit which permits adding the facsimile compression feature to the DCME. The basic function of the facsimile module is to detect facsimile calls, demodulate the facsimile signals and transmit the demodulated data to the remote facsimile module via the DCME. At the remote facsimile module,
30、 the voiceband signai is reconstructed to its original format for transmission to the local terminal equipment. Calls which cannot be demodulated are routed through the G.726 40 kbits ADPCM channels of the DCME. It is recognized that Group 3 facsimile demodulatiodremodulation is only the first featu
31、re of a series of voiceband data demodulatiodremodulation capabilities which will in all likelihood be extended to the next generation of voiceband data modems operating at bit rates greater than 9600 bits. It is anticipated that the modulation schemes for high speed modems will also be incorporated
32、 into facsimile machines and such traffic, when presented to DCMEs, must be accommodated. The design of the DCME facsimile module has been structured to carry demodulated data at bit rates up to 24 kbits to permit future flexibility. The DCME facsimile module is fully compatible with all of the oper
33、ating modes of Recommendation G.763 which includes, point-to-point, multi-clique and multi-destination operating modes. Careful consideration has been given to error protection. The Forward Error Correction (FEC) provided in the DCME facsimile module is robust against randomly distributed single bit
34、 errors. It also fully protects against errors as long as the error event is less than one frame of the primary multiplex multifiame or provided that only one error burst event occurs within a single DCME frame (2 ms). There have been two approaches integrated into the DCME facsimile module, a Proto
35、col Analysis (PA) approach and a Waveform Analysis (WA) approach. In order to retain the interoperability objective, compromises were introduced which slightly increased the equipment complexity. If one were to consider only a PA approach or only a WA approach, some simplification would be possible.
36、 However, such simplification is not recommended as the open-network interoperability would then be lost. 1.1 Abbreviations This Recommendation uses the following abbreviations: ADF ADPCWDSI Function ADPCM Adaptive Differential Pulse Code Modulation Recommendation G.766 (11/96) 1 STD-ITU-T RECMN Ge7
37、bb-ENGL 1996 48b254L Ob323b5 b25 W BC CCF CRC DCME DCN DCOA DCS DIS DSI DTC EOM EOP EPT FA FCC FCH FCM FD FDC FEC FED FMC FSTI FTC HDLC HSC IT LRE NSF-T.30 NSS O&M PA RAG Rx RUD SDL SF-T.30 Tx WA Bearer Channel Common Control Function Cyclic Redundancy Check Digital Circuit Multiplication Equipment
38、Disconnect Digital Channel Occupancy Analyser Digital Command Signal Digital Identification Signal Digital Speech Interpolation Digital Transmit Command End of Message End of Procedure Echo Protection Tone Frame Assembler Facsimile Control Channel Facsimile Channel Handler Facsimile Compression Modu
39、le Frame Disassembler Facsimile Data Channel Forward Error Correction Front-End Delay Facsimile Module Controller Facsimile Statistical Time Interval Facsimile Transport Channel High level Data Link Control Hangover control and Signal Classification Intermediate Trunk Low Rate Encoding Non-Standard
40、Facility-T.30 Non-Standard Set-up Operation and Maintenance Protocol Analysis Resource management and Assignment Generation Receive Receive channel status Update and overload channel Decoding Specification and Description Language Standard Facility-T. 3 O Transmit Waveform Analysis 2 Recommendation
41、G.766 (1 1/96) STD-ITU-T RECMN G-7bb-ENGL L79b D 48b257L Ob323bb 5bL 2 This Recommendation defines the following terms: 2.1 facsimile module: A functional unit performing the demodulatiodremodulation of the facsimile signal and transmissionheception of control codes and demodulated image information
42、 via the associated ADPCM/DSI function of the DCME. 2.2 ADPCM/DSI function (ADF): The ADPCM/DSI Function (ADF) of the DCME encompasses all the traffic handling functions specified in Recommendation G.763. 2.3 facsimile control channel (FCC): An unidirectional 32-bit channel (21 information bits, 10
43、parity bits and 1 dummy bit) used between the transmit unit of one facsimile module to the receive unit of one or more associated facsimile modules which is dedicated primarily to carrying channel assignment messages and control messages. 2.4 facsimile data channel (FDC): A variable length data bloc
44、k containing bits of the demodulated image information or procedural signals, accumulated over a period of 2 ms from one intermediate hunk (IT) (see 2.10/G.763), and clock alignment overhead bits. 2.5 facsimile module frame: A bit sequence consisting of the FDCs ordered by ascending IT number. The s
45、equence starts with the facsimile control channel. 2.6 facsimile block: This is a 32-bit block consisting of either 32 contiguous bits of the facsimile module frame or 21 contiguous bits of the fiame FEC encoded with the addition of 10 parity bits and 1 dummy bit. 2.7 facsimile transport channel (FT
46、C): A 32-kbit/s channel that carries a facsimile block frordto the facsimile module tolfiom the ADF where the facsimile block is placed intohemoved (from) a 32-kbitIs bearer channel (see 2.8/G.763). 2.8 facsimile compression: The real time process of demodulating the facsimile signal to its basic di
47、gital rate for transparent transmission and subsequent remodulation at the remote end of the DCME link. 2.9 facsimile data interface: The functional interface which permits the transfer of FTC information between the facsimile module and the ADF. Definitions of facsimile demodulation/remodulation in
48、 DCME 3 The facsimile module (see Figure 1) is a functional unit which permits adding the facsimile compression feature to the DCME. The basic function of the facsimile module il DCME control controi 2 7 Path ADPCM ADPCM - b b a, % Signai C analysis and s3 demodulation a b Delay Set switches 5 : FMC
49、 Set switches ? Delay C and decode -I u i ADPCM ADPCM a DCME control DCME control i T1522210-96 FA Fax frame assembler FD sl, s2, s3, s4 Switches a, b, c Switch positions A, B Connection points Fax frame disassembler (+V.21 decode in PA) dt ao tn ae Fa1 s a Figure 11/G.766 - An example of FCH functional decomposition Table 4G.766 - An FCH interworking example using the FCH functional decomposition of Figure 11 I I (Called) WA Path 22 Recommendation G.766 (1196) STD-ITU-T RECMN G.7bb-ENGL 1776 LiBb2591 Ob323Bb 35T W Table 4G.766 - An FCH
