1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.785 (1 1 /96) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital transmission systems - Terminal equipments - Principal characteristics of multiplexing equipment for the sy nch r
2、o nous d ig i ta I h era rc h y Characteristics of a flexible multiplexer in a synchronous digital hierarchy environment ITU-T Recommendation G.785 (Previously CCITT Recommendation) STD-ITU-T RECMN G-785-ENGL L99b 48b257L Db36802 bL5 U ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, D
3、IGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS INTERNATIONAL ANALOGUE CARRIER SYSTEM TRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE WITH METALLIC LIN
4、ES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TRANSMISSION SYSTEMS TERMINAL EQUIPMENTS GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION General Coding of analogue signals by pulse c
5、ode modulation 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
6、 multiplication equipment Operations, administration and maintenance features of transmission equipment Princi al characteristics digita P hierarchy Other terminal equipment General aspects Design objectives for digital networks Quality and availability targets Network capabilities and functions SDH
7、 network characteristics General Parameters for optical fibre cable systems Digital sections at hierarchical bit rates based on a bit rate of 2048 kbitls Digital line transmission systems on cable at non-hierarchical bit rates Digital line systems provided by FDM transmission bearers Digital line sy
8、stems Digital section and digital transmission systems for customer access to ISDN Optical fibre submarine cable systems Optical line systems for local and access networks DIGITAL NETWORKS DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.100-G.199 G.200-G.299 G. 300-G. 399 G .400-G .449 G.450-G.499 G.700-
9、G.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 G. 760-G .769 G.770-G.779 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 G.950-G.959 G. 960-G.969 G.9
10、70-G.979 G.980-G.999 For further details, please refer to ITU-T List of Recommendations STD-ITU-T RECMN G.785-ENGL L77b D LiBb257L Ob3b803 551 D ITU-T RECOMMENDATION G.785 CHARACTERISTICS OF A FLEXIBLE MULTIPLEXER IN A SYNCHRONOUS DIGITAL HIERARCHY ENVIRONMENT Summary This Recommendation covers func
11、tional requirements for a flexible multiplexer intended to be installed in a synchronous digital hierarchy environment. The flexible multiplexer provides time-division multiplexing and demultiplexing functions of signals supporting a variety of user services. This Recommendation should be used in co
12、njunction with Recommendations G.783 and G.797 as only additional requirements are presented to describe the functions of the equipment. Source ITU-T Recommendation G.785 was prepared by ITU-T Study Group 15 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of Novembe
13、r 1996. FOREWORD ITU (International Telecornmunication Union) is the United Nations Specialized Agency in 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 qu
14、estions 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 Groups which, in their turn, produce Reco
15、mmendations 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 on a collaborative basis with IS0 an
16、d 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 The ITU draws attention to the possibility that the practice or implementation of this Recom
17、mendation may involve the 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
18、 approval of this Recommendation, the ITU hadhad 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 strongly urged to cons
19、ult the TSB patent database. O ITU 1997 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 G.785 (11196) . STD-ITU-T
20、RECMN G.785-ENGL L97b 9 48h2571 Ob3b805 324 CONTENTS Page 1 General characteristics 1.1 Definitions 1.2 Abbreviations . 1.3 Application of the equipment . 1.3.1 Network configurations . 1.3.2 Services . 1.4 Size . 1.5 Modularity 1.6 Timing signal 2 Functions 2.1 Mapping 2.2 Signal processing 2.3 Con
21、centration function for switched services 2.4 Management . 3 3.1 Functional representation . 3.2 Definition of functional blocks . 3.2.1 Common blocks . 3.2.2 Functional blocks defined in Recommendation G.797 . 3.2.3 Functional blocks defined in Recommendation G.782 . Definition of reference points
22、. 3.3.1 Common reference points . 3.3.2 Reference points defined in Recommendation G.797 . 3.3.3 Functional representation of the equipment and definition of reference points . 3.3 Reference points defined in Recommendation G.783 . 4 Tributary interfaces . 5 Aggregate interfaces . 5.1 SDH STM-1 inte
23、rface . 5.2 VC- 12 integrated baseband line interface . 6 Synchronization interface at 2048 kHz 7 Local control interface 8 Power interfaces . 9 Defect or failure conditions and consequent actions for the tributary interfaces . Recommendation G.785 (11/96) 2 2 6 6 6 6 7 7 7 7 7 7 7 9 9 9 10 11 11 11
24、 11 12 12 12 12 12 12 13 13 . 111 9.1 9.2 10 10.1 10.2 11 11.1 11.2 12 13 13.1 13.2 13.3 13.4 13.5 13.6 14 Defect or failure conditions for a VC- 12 integrated baseband line tributary interface . Consequent actions for a VC-12 integrated baseband line tributary interface . Defect or failure conditio
25、ns and consequent actions for the aggregate interfaces Defect or failure conditions 1 O . 1 . 1 STM- 1 interface 1 O . 1.2 Consequent actions . 1 0.2.1 STM- 1 interface 10.2.2 VC- 12 Integrated baseband line interface . Defect or failure conditions and consequent actions for the core of the equipmen
26、t . Defect or failure conditions Consequent actions . Performance monitoring . Performance ofthe equipment Jitter Transfer delay . Slips Service availability . Error performance . Bit sequence independence . VC- 12 Integrated baseband line interface . Management . Page 13 13 13 13 13 13 14 14 14 14
27、14 14 14 15 15 15 15 15 16 16 16 iv Recommendation G.785 (1 1/96) Introduction This Recommendation gives the characteristics of a flexible multiplex equipment intended to be installed in a synchronous digital hierarchy environment. This Recommendation provides additional requirements to those presen
28、ted in Recommendations G.797 and G.783 and necessary to describe the functions of the equipment. The flexible multiplex equipment is able to handle a variety of services with transparency for service provider, allowing enhanced management capabilities and to be used in the access network. The manage
29、ment of the equipment is in line with general principles of the Telecommunications Management Network (TMN). Recommendation G.785 (11/96) V Recommendation G.785 CHARACTERISTICS OF A FLEXIBLE MULTIPLEXER IN A SYNCHRONOUS DIGITAL HIERARCHY ENVIRONMENT (Geneva, 1996) 1 General characteristics 1.1 Defin
30、itions This Recommendation defines the following terms. Refer also to 1.2 for additional functional description. 1.1.1 flexible access system (FA): A flexible access system is a means of providing a wide range of telecommunication services to customers in a flexible manner. These services may be del
31、ivered at the customer premises or from a public network location. On the network side, connections are established to the appropriate service networks. The flexible access system is managed by the TMN. 1.1.2 flexible multiplexer (FM): A device that provides time-division multiplexing and demultiple
32、xing of signals supporting a variety of user services. In addition, the device provides enhanced management capabilities. The flexible multiplexer is part of flexible access system. 1.1.3 flexible access termination (FAT): The flexible access termination is used in conjunction with the flexible mult
33、iplexer to constitute a flexible access system. 1.1.4 monoservice 2048 kbit/s G.704 frame: A digital signal with structure according to 2.3/G.704 and clause UG.704 comprising constituent 64 kbit/s or n x 64 kbit/s signals and any related signalling corresponding to only one particular service networ
34、k. 1.1.5 multiservice 2048 kbit/s G.704 frame: A digital signal with structure according to 2.3/G.704 comprising constituent 64 kbit/s or n x 64 kbit/s signals and any related signalling corresponding to various service networks. 1.1.6 embedded operation channel (EOC): An embedded operation channel
35、is a physical channel of the managed network used for management communication purposes, specifically to exchange information between Network Element (NE) functions and Operations System (OS) or Mediation Device (MD) functions. It may be carried over different physical bearers. 1.2 Abbreviations Thi
36、s subclause contains the abbreviations which are not defined in the core text of the Recommendation. AIS Alarm Indication Signal CRC Cyclic Redundancy Check DC Direct Current DCC Data Communication Channel DCE Data Circuit-terminating Equipment Recommendation G.785 (11/96) 1 EOC ES FA FAT FM HOA IS0
37、 MD MF MTBF MTTR NE os PPm Q QAF Sa SDH SES STM-1 TS TSO TS16 TTF u1 vc-12 Embedded Operation Channel Errored Second Flexible Access system Flexible Access Termination Flexible Multiplexer Higher Order Assembler International Organization for Standardization Mediation Device Mediation Function Mean
38、Time Between Failure Mean Time To Repair Network Element Operations System part per million The NE interface to the TMN Q Adaptation Function A spare bit in time slot O of the 2048 kbit/s G.704 frame Synchronous Digital Hierarchy Severely Errored Second Synchronous Transport Module-1 Time Slot Time
39、slot O of a 2048 kbit/s G.704 frame Time Slot 16 of a 2048 kbit/s G.704 frame Transport Terminal Function Unit Interval Virtual Container- 12 1.3 Application of the equipment 1.3.1 Network configurations The recommended network configurations are given in Figures 1 and 2. Figures 3, 4 and 5 give the
40、 possible distribution of functions in a flexible access system. 2 Recommendation G.785 (11/96) - I I I I _t_ Tributary . Optional duplication _fi Aggregate including EOC 2048 kbit/s access to service network Service 1 SDH SDH Flexible Multiplexer C Flexible (FAT) n x 2048 kbit/s . t! . Access . Ser
41、vice 2 Termination (FM1 Service n a) Functional view t t t t SDH STM-I FM SDH n x 2048 kbis - multiplexer EOC Service 1 Service 2 Service n T152093-96 Transport of n VC-i 2 b) Access structure Figure UG.785 - Flexible access system, application of monoservice 2048 kbit/s frames In the network config
42、uration given in Figure 1, the Flexible Access Termination (FAT) is serving as the SDH multiplexer of type 1.2 described in Recommendation G.782. Recommendation G.785 (1 1/96) 3 - - STD-ITU-T RECMN G-785-ENGL 177b D 48b257L Ob3b8IL b2 m - I Tributaries SDH Multiplexer SDH n x 2048 kbit/s Flexible Fl
43、exible +Q . 7 . .-+ Tributary . Optional duplication _$ Aggregate including EOC 2048 kbitls access to service network Access Termination (FAT) a) Functional view . SDH multiplexer SDH t - c- SDH multiplexer multiplexer FM Service 1 Service 2 Service n Service 2 FAT - Service n _. b) c) an internal o
44、scillator with an accuracy of frequency of L4.6 ppm according to NOTE 1 -The internal oscillator should not be used as a primary timing source when the flexible multiplexer is connected to the synchronous network. one of a number of external timing source(s) at 2048 kHz; one of a number STM-1 signal
45、; Recommendation G.8 13 on timing characteristics of SDH Equipment slave Clocks (SECS). 6 Recommendation G.785 (1196) NOTE 2 -The provision of the timing signal to an output of synchronization interface for the purpose of synchronizing other equipment or to control the internai timing signal is an o
46、ptional function. On failure condition on the active synchronization signal, it shall be possible to programme a fall- back strategy up to three steps, preferably from case a) to case b) and then to case c) as the last possibility. Complementary information is given in clause 14 corresponding to the
47、 management aspects of the equipment. 2 Functions 2.1 Mapping The mapping function comprises a two-step process. The first relates to the allocation of time slot(s) in any 2048 kbit/s G.704 framed aggregate signal to any tributary signal. This mapping function is based on Recommendation G.704. The s
48、econd relates to the association of the 2048 kbit/s G.704 framed signals to a given VC-12. This two-step process is completed by multiplexing the VC-12 into a STM- 1. This is based on Recommendation G.707. 2.2 Signal processing The signal processing covers functions such as analogue to digital conve
49、rsion, rate adaptation, handling of signalling information and control signals. 2.3 When implemented, this function should apply the principles provided in Recommendation G.965. The corresponding requirements are for further study. Concentration function for switched services 2.4 Management The management includes control functions and provision of maintenance information. The management functions of the flexible multiplexer are presented in clause 14. 3 Functional representation of the equipment and definition of reference points 3.1 Functional represen
