1、- STD-ITU-T RECMN G.704-ENGL L998 4862593 ObSb382 17“ m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.704 (1 0/98) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Terminal equipments - General Synch
2、ronous frame structures used at 1544, 6312,2048, 8448 and 44 736 kbit/s hierarchical levels ITU-T Recommendation G.704 (Previously CClTT Recommendation) ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NEWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS INTERNA
3、TIONAL ANALOGUE CARRIER SYSTEM INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TESTING EQUIPMENTS TRANSMISSION MEDIA CHARACTERISTIC
4、S DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION , ,. , Genera!;:; I, I:, ,:.G ,:,;: . ., , , .r,. , ,. 1,1, “:,$:, ,. , ,. _, , , ;.?,:,., : , , , : , ,. i , , . , . ,. ,. .,I , , ., , : , , , Coding of analogue signals by pulse code m
5、odulation Coding of analogue 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 Principal characteristics of transcoder and digital mult
6、iplication equipment Operations, administration and maintenance features of transmission equipment Principal characteristics of multiplexing equipment for the synchronous digital hierarchy Other terminal equipment DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G. 1 OO-G. 199 G.300-G.399 G
7、.400-G.449 G.450-G.499 G.700-G.799 G.700-G.?09 :.:ft G.710-G.719 G.720-G.729 G.730-G.739 G.740-G.749 G.750-G.759 G.760-G.769 G.770-G.779 G.780-G.789 G.790-G.799 G.800-G.899 G.900-G.999 Forjuther details, please rejr to ITU-T List of Recommendations. STD-ITU-T RECMN G-704-ENGL L998 W 48b2591 0b5b384
8、T42 = ITU-T RECOMMENDATION G.704 SYNCHRONOUS FRAME STRUCTURES USED AT 1544,6312, 2048,8448 AND 44 736 kbit/s HIERARCHICAL LEVELS Summary This Recommendation gives functional characteristics of interfaces associated with: - network nodes, in particular, synchronous digital multiplex equipment and dig
9、ital exchanges - PCM multiplexing equipment. in IDNs for telephony and ISDNs; and Clause 2 deals with basic frame structures, including details of frame length, frame alignment signals, Cyclic Redundancy Check (CRC) procedures and other basic information. Clauses 3 to 6 contain more specific informa
10、tion about how certain channels at 64 kbit/s and at other bit rates are accommodated within the basic fiame structures described in clause 2. Source ITU-T Recommendation G.704 was revised by ITU-T Study Group 15 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 1 3h of Oc
11、tober 1998. Recommendation G.704 (10/98) 1 - FOREWORD ITU (International 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 ITU. The ITU-T is responsible for studyi
12、ng technical, operating and tariff questions and issuing Recommendations 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 Grou
13、ps which, in their turn, produce Recommendations on these topics. 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
14、 on a collaborative basis with IS0 and IEC. NOTE In this Recommendation the term recognized operating agency (ROA) includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are def
15、ined in the Constitution of the ITU (Geneva, 1992). 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 concerning the evidence, vali
16、dity 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 had not received notice of intellectual property, protected by patents, which may be
17、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 1999 All rights reserved. No part of this publication may be reproduced or utilized in any form
18、 or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. II Recommendation G.704 (10/98) 2.2 2.3 2.4 2.5 3.2 CONTENTS Page Scope Basic frame structures Basic frame structure at 1544 kbit/s . 2.1.1 Frame length 2.1.2 F-bit . 2.1.3 A
19、llocation of F-bit . Basic frame structure at 63 12 kbit/s . 2.2.1 Frame length 2.2.2 F-bits . 2.2.3 Allocation of F-bits . Basic frame structure at 2048 kbit/s . 2.3.1 Frame length 2.3.2 Allocation of bits number 1 to 8 of the frame . 2.3.3 Description of the CRC-4 procedure in bit 1 of the frame 2
20、.3.4 Synchronization Status: Sa, . Basic frame structure at 8448 kbit/s . 2.4.1 Frame length 2.4.2 Frame alignment signal . 2.4.3 Service digits . Basic frame structure at 44 736 kbit/s 2.5.1 Multiframe length 2.5.2 Multiframe overhead bits 2.5.3 Allocation of the multiframe overhead bits . Characte
21、ristics of frame structure carrying channels at various bit rates in 1544 kbit/s Interface at 1544 kbit/s carrying 64 kbit/s channels . 3.1.1 Frame structure . 3.1.2 Use of 64 kbit/s channel time slots 3.1.3 Signalling Interface at 1544 kbit/s carrying 32 kbit/s channel time slots (see Note) . 3.2.1
22、 Frame structure 3.2.2 Use of 32 kbit/s channel time slot . 3.2.3 3 84 kbit/s 12-channel time slot grouping 3.2.4 32 kbit/s signalling grouping channel multiframe structure 3.2.5 Signal grouping channel unused bits . 3.2.6 Loss and recovery of signalling channel multiframe alignment . Recommendation
23、 G.704 (10/98) 1 9 9 9 10 13 14 14 14 14 14 14 15 15 22 22 22 22 22 24 24 24 24 25 27 27 . 111 STDOITU-T RECMN G-704-ENGL L998 3.3 4 4.1 4.2 5 5.1 5.2 6 6.1 6.2 Interface at 1544 kbit/s carrying n x 64 kbit/s Characteristics of frame structures carrying channels at various bit rates in 63 12 kbit/s
24、interfaces Interface at 63 12 kbit/s carrying 64 kbit/s channels . 4.1.1 Frame structure 4.1.2 Use of 64 kbit/s channel time slots 4.1.3 Signalling Interfaces at 63 12 kbit/s carrying other channels than 64 kbit/s Characteristics of fiame structures carrying channels at various bit rates in 2048 kbi
25、t/s interfaces Interface at 2048 kbit/s carrying 64 kbit/s channels . 5.1.1 Frame structure 5.1.2 Use of other 64 kbit/s channel time slots 5.1.3 Signalling Interface at 2048 kbit/s carrying n x 64 kbit/s 5.2.1 One n x 64 kbit/s signal on the tributary side of a multiplex equipment 5.2.2 One or more
26、 n x 64 kbit/s signal on the multiplexed signal side of a multiplexing equipment Characteristics of frame structures carrying channels at various bit rates in 8448 kbit/s interface . Interface at 8448 kbit/s carrying 64 kbit/s channels . 6.1.1 Frame structure 6.1.2 Use of 64 kbit/s channel time slot
27、s 6.1.3 Description of the CRC procedure in 64 kbit/s channel time slot 99 Interface at 8448 kbit/s carrying other channels than 64 kbit/s 6.1.4 Signalling Annex A . Examples of CRC implementations using shift registers A . 1 CRC-6 procedure for interface at 1544 kbit/s (see 2.1.3.1.2) . A.2 CRC-5 p
28、rocedure for interface at 63 12 kbit/s (see 2.2.3.2) A.3 CRC-4 procedure for interface at 2048 kbit/s (see 2.3.3.5) Annex B . Alphabetical list of abbreviations used in this Recommendation . Page 28 28 28 28 28 28 29 29 29 29 29 30 31 31 31 32 32 32 32 33 34 35 35 35 36 36 37 iv Recommendation G.704
29、 (10/98) STD. ITU-T RECMN G.704-ENGL L998 Recommendation G.704 SYNCHRONOUS FRAME STRUCTUlZES USED AT 1544,6312, 2048,8448 AND 44 736 kbith HIERARCHICAL LEVELS (Malaga-Torremolinos, I984; amended at Melbourne, 1988; revised in 1990, 1995 and 1998) 1 Scope - network nodes, in particular, synchronous d
30、igital multiplex equipment and digital exchanges - PCM multiplexing equipment. This Recommendation gives functional characteristics of interfaces associated with: in IDNs for telephony and ISDNs; and Clause 2 deals with basic frame structures, including details of frame length, kame alignment signal
31、s, Cyclic Redundancy Check (CRC) procedures and other basic information. Clauses 3 to 6 contain more specific information about how certain channels at 64 kbit/s and at other bit rates are accommodated within the basic frame structures described in clause 2. Electrical characteristics for these inte
32、rfaces are defined in Recommendation G.703. NOTE 1 -This Recommendation does not necessarily apply to those cases where the signals that cross the interfaces are devoted to non-switched connections, such as those for the transport of encoded wideband signals (e.g. broadcast TV signals or multiplexed
33、 sound-program signals which need not be individually routed via the ISDN). See also Annex A/G.702. NOTE 2 - The frame structures recommended in this Recommendation do not apply to certain maintenance signals, such as the all Is signals transmitted during fault conditions or other signals transmitte
34、d during out-of-service conditions. NOTE 3 - Frame structures associated with digital multiplexing equipments using justification are covered in each corresponding equipment Recommendation. NOTE 4 - lnclusion of channel structures at bit rates other than 64 kbit/s is a matter for further study. Reco
35、mmendations G.761 and G.763 dealing with the characteristics of PCM/ADPCM transcoding equipment contain information about channel structures at 32 kbit/s. The more general use of those particular structures is a subject of further study. 2 Basic frame structures 2.1 Basic frame structure at 1544 kbi
36、t/s 2.1.1 Frame length 193 bits, numbered 1 to 193. The frame repetition rate is 8000 Hz. 2.1.2 F-bit The first bit of a frame is designated an F-bit, and is used for such purposes as frame alignment, performance monitoring and providing a data link. 2.1.3 Allocation of F-bit Two alternative methods
37、 as given in Tables 1 and 3 for allocation of F-bits are recommended. Recommendation G.704 (10/98) 1 2.1.3.1 Method 1: 24-frame multiframe Allocation of the F-bit to the multiframe alignment signal, the CRC check bits and the data li the last check bit (e,) is the least significant bit of the remain
38、der. Each multifi-ame contains the CRC-6 check bits generated for the preceding CMB. At the receiver, the received CMB, with each F-bit having first been replaced by a binary 1, is acted upon by the multiplicatioddivision process described above. The resulting remainder is compared on a bit-by-bit b
39、asis, with the CRC-6 check bits contained in the subsequently received multiframe. The compared check bits will be identical in the absence of transmission errors. 2.1.3.1.3 4 kbith data link Beginning with fi-ame 1 of the multiframe (see Table l), the first bit of every other frame is part of the 4
40、 kbit/s data link. This data link provides a communication path between primary hierarchical level terminals. In prioritized order the data link will contain priority operations messages, other maintenance or operations messages, periodic terminal performance reports, or an idle data link sequence.
41、a Both categories of operations messages are transmitted in the form of 16-bit sequences of the form 11 11 11 110P,P2PP4PP60, where the particular message is coded by the six bits P, through P, permitting up to 64 distinct messages. Designated sequences and their functional uses are listed in Table
42、2. Use of sequences not shown in the table is for further study. a Periodic terminal performance reports are formatted using the unnumbered, unacknowledged frame option of Q.92l/LAPD, as described in 2.1.3.1.3.3. Transmission of any of the assigned 16-bit sequences terminates any processing of a (lo
43、wer priority) performance report that might be in progress, as seven or more consecutive ones are recognized in Recommendation Q.92 1 as an abort command. o The idle data link sequence is a continuous repetition of the pattern O1 11 11 10. o The transmission of Loss of Frame Alignment (LFA) - also c
44、alled Remote Alarm Indication (RAI) - and idle data link sequence in m-bits is mandatory. The other use of m-bits is optional, but when a function other than mandatory functions is used, the specification described here should be applied to guarantee the interworking of terminals. Recommendation G.7
45、04 (10/98) 3 STD=ITU-T RECMN Ga704-ENGL L998 m 48b259L Ob5639L L82 m NOTE - Some functions, such as PM, are mandatory in some national standard. Table 2/G.704 - Assigned operations data link messages Priority Messages Function Codeword LFA (also called RAI) 1111111100000000 Loopback Retention 111111
46、1101010100 Other Operation Messages Category Function Codeword Loopbacks: Customer Installation Type A Operate Customer Installation Type A Release Customer Installation Type B Operate Customer Installation Type C Operate Payload Operate Payload Release Network Type A Operate Universal Release Prote
47、ction switching: Operate Line 1 Operate Line 2 Operate Line 3 Operate Line 4 Operate Line 5 Operate Line 6 Operate Line 7 Operate Line 8 Operate Line 9 Operate Line 10 Operate Line 1 1 Operate Line 12 Operate Line 13 Operate Line 14 Operate Line 15 Operate Line 16 Operate Line 17 Operate Line 18 Ope
48、rate Line 19 Operate Line 20 Operate Line 2 1 Operate Line 22 Operate Line 23 Operate Line 24 Operate Line 25 Operate Line 26 Operate Line 27 Acknowledge protection switching actic , Release protection switch 1111111101110000 1111111100011100 1111111100000100 1111111101110100 1111111100101000 111111
49、1101001100 1111111101001000 11111111 00100100 1111111101000010 1111111100100010 11111111 01100010 1111111100010010 1111111101010010 1111111100110010 1111111101110010 1111111100001010 11111111 01001010 11111111 00101010 1111111101101010 1111111100011010 1111111101011010 11111111 00111010 1111111101111010 1111111100000110 1111111101000110 1111111100100110 1111111101100110 1111111100010110 1111111101010110 1111111100110110 1111111101110110 1111111100001110 1111111101001110 1111111100101110 1111111101101110 ln 111111110001100
