1、 _ GENERAL SECRETARIAT INTERNATIONAL TELECOMMUNICATION UNION Subject: Corrigendum 1 (10/2001) Geneva, 26 November 200 1 Recommendation ITU-T G.810 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU ITU-T Recommendation G.810 (08/1996) Defmitions and terminology for synchronization networks In Table II.
2、2 of Appendix II of English version only, in the column of the slope of MDEV(z) corresponding to WFM noise process, replace T-/ by 2-1?2. Union international des tlcommunications Place des Nations 121 1 GEN %E 20 Suisse - Switzerland - Suiza INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICAT
3、ION STANDARDIZATION SECTOR OF ITU G.810 (08/96) SERIES G: TRANSMISSION SYSTEMS AND MEDIA Digital transmission systems - Digital networks - Design objectives for digital networks Definitions and terminology for synchronization networks ITU-T Recommendation G.81 O (Previously CCIlT Recommendation) ITU
4、-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS IN TERNA TIONAL ANALOGUE CARRIER SYSTEM GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER- TRANSMISSION SYSTEMS INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON ME
5、TALLIC LINES GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE WITH METALLIC LINES COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY TRANSMISSION MEDIA CHARACTERISTICS DIGITAL TRANSMISSION SYSTEMS TERM I NAL EQU I PM ENTS DIGITAL NETWORKS SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERC
6、ONNECTION General aspects Design objectives for digital networks Quality and availability targets Network capabilities and functions SDH network characteristics DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G. I OO-G.199 G .200-G. 299 G .300-G . 399 G.400-G.449 G.450-G.499 G.700-G.799 G. 800-G. 899 G.800
7、-G.809 G.81-.819 G.820-G .829 G ,830-G ,839 G. 840-G. 899 G. 900-G ,999 For further details, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION G.810 DEFINITIONS AND TERMINOLOGY FOR SYNCHRONIZATION NETWORKS Summary This Recommendation provides definitions and abbreviations used in t
8、iming and synchronization Recommendations. Source ITU-T Recommendation G.810 was revised by ITU-T Study Group 13 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 27th of August 1996. Keywords Clock Performance, Jitter Performance, SDH, Synchronization network, Wander Per
9、formance. - STD.ITU-T RECMN G.BLO-EFJGL 199b I iib2591 Ob23899 503 W 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 i
10、s 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 Conference (WTSC), which meets every four years, establishes the topics for study
11、 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 procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). In some areas of information technology which fall within
12、 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 both a telecommunication administration and a recognized operating agency. O ITU 1997 All rights reserved.
13、 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. Recommendation G.810 (08/96) li 1 2 3 4 4.1 4.2 4.3 4.4 4.5 4.6 5 6 6.1 6.2 7 7.1 7.2 8 8.1 8.2 9 9.1 9.
14、2 CONTENTS Scope References Abbreviations . Definitions . General definitions . Definitions related to clock equipments Definitions related to synchronization networks . Definitions related to clock modes of operation (applicable to slave clocks) . Definitions related to clock characterization . SDH
15、 specific definitions Description of phase variation components . Impairments caused by phase variation . Types of impairments 6.1.1 Errors 6.1.2 Degradation of digitally encoded analogue information 6.1.3 Slips Control of impairments 6.2.1 Errors 6.2.2 Degradation of digitally encoded analogue sign
16、als 6.2.3 Slips Purpose of phase variation specifications Jitter . Wander . Structure of synchronization networks Synchronization modes Synchronization networks Measurement configurations Synchronized clock measurement configuration . Independent clock measurement configuration . Appendix I . Mathem
17、atical models of timing signals I . 1 Total instantaneous phase model of an ideal timing signal . 1.2 Total instantaneous phase model of actual timing signals . 1.3 Time error model . Recommendation G.810 (08/96) Page 1 1 1 2 2 3 4 5 5 8 8 8 8 8 8 8 9 9 9 9 9 9 10 10 10 10 11 11 11 12 12 12 13 . 111
18、 Page Appendix II - Definitions and properties of frequency and time stability quantities 13 II. 1 Allan deviation (ADEV) 14 11.2 Modified Allan deviation (MDEV) 15 II.3 Time deviation (TDEV) 16 11.4 Root mean square Time Interval Error (TTErms) 18 . . . . . 11.5 Maximum Time Interval Error (MTIE) 1
19、9 iv Recommendation G.810 (08/96) STD-ITU-T RECMN -BIO-ENGL 199b qBb2591 b23902 72b Recommendation G.810 DEFINITIONS AND TERMINOLOGY FOR SYNCHRONIZATION NETWORKS (Melbourne, 1980; revised in 1996) 1 Scope This Recommendation provides definitions and abbreviations used in timing and synchronization R
20、ecommendations. It also provides background information on the need to limit phase variation and the impairments on digital systems. 2 References The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation.
21、 All Recommendations 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 references listed below. A list of the currently valid ITU-T Recommendations is regularly publis
22、hed. ITU-T Recommendation G.707 (1 996), Network node interface for the Synchronous Digital Hierarchy (SDH). CClTT Recommendation G.811 (1988), Timing requirements at the outputs of primary rejirence clocks suitable for plesiochronous operation of international digital links. CCITT Recommendation G.
23、8 12 (1988), Timing requirements at the outputs of slave clocks suitable for plesiochronous operation of international digital links. l“-T Recommendation G.8 13 (1996), Timing characteristics for SDH equipment slave clocks (SEC). CClTT Recommendation G.822 (1 988), Controlled slip rate objectives on
24、 an international digital connection. ITU-T Recommendation G.823 (1993), The control of jitter and wander within digital networks which are based on the 2048 kbith hierarchy. KU-T Recommendation G.824 (1993), The control of jitter and wander within digital networks which are based on the I544 kbit/s
25、 hierarchy. ITU-T Recommendation G.825 (1993), The control of jitter and wander within digital networks which are based on the Synchronous Digital Hierarchy (SOH). Abbreviations For the purposes of timing and synchronization Recommendations, the following abbreviations ADEV Allan Deviation AIS Alarm
26、 Indication Signal AP Access Point CUT Clock Under Test FFM Flicker Frequency Modulation FPM Flicker Phase Modulation apply: Recommendation G.810 (08/96) 1 MC MDEV MRTIE MST MTIE NE PDH PRC PSTN RWFM SASE sc SDH SE SEC SETS STM ssu TDEV TIE TTErms TVAR u1 UIP-P UTC WFM WPM Master Clock Modified Alla
27、n Deviation Maximum Relative Time Interval Error Multiplex Section Terminal Maximum Time Interval Error Network Element Plesiochronous Digital Hierarchy Primary Reference Clock miblic Switched Telephone Network Random Walk Frequency Modulation Stand Alone Synchronization Equipment Slave Clock Synchr
28、onous Digital Hierarchy Synchronization Element SDH Equipment Clock SDH Equipment Timing Source Synchronous Transport Module Synchronization Supply Unit Time Deviation Time Interval Error root mean square Time Interval Error Time Variance Unit Interval Unit Interval peak-to-peak Coordinated Universa
29、l Time White Frequency Modulation White Phase Modulation 4 Definitions For the purposes of timing and synchronization Recommendations, the following definitions apply. 4.1 General definitions 4.1.1 digital signal and sampling clock derived from it. 4.1.2 both ends of the link. 4.1.3 from its ideal f
30、requency. 4.1.4 time and/or frequency to all elements in a network. alignment jitter: The short-term variations between the optimum sampling instants of a bilateral: A synchronization link where the corrective action to maintain locking is active at frequency departure: An underlying offset in the l
31、ong-term frequency of a timing signal network synchronization: A generic concept that depicts the way of distributing a common 2 Recommendation G.810 (08/96) 4.1.5 single ended synchronization: A method of synchronizing a specified synchronization node with respect to another synchronization node, i
32、n which synchronization information at the specified node is derived from the phase difference between the local clock and the incoming digital signal from the other node. 4.1.6 synchronization chain: An active interconnection of synchronization nodes and links. 4.1.7 synchronization reference chain
33、: A specific synchronization chain to form the basis for simulations of jitter and wander in the synchronization network. 4.1.8 slip: The repetition or deletion of a block of bits in a synchronous or plesiochronous bit stream due to a discrepancy in the read and write rates at a buffer. 4.1.9 standa
34、rd frequency: A frequency with a known relationship to a frequency standard. 4.1.10 time: Time is used to specify an instant (time of the day) or as a measure of time interval. NOTE - The words time or timing, when used to describe synchronization networks, usually refer to the frequency signals use
35、d for synchronization or measurement. 4.1.11 time scale: A system of unambiguous ordering of events. NOTE - This could be a succession of equal time intervals, with accurate references of the limits of these time intervals, which follow each other without any interruption since a well-defined origin
36、. A time scale allows to date any event. For example, calendars are time scales. A frequency signal is not a time scale (every period is not marked and dated). For this reason “UTC frequency“ must be used instead of “UTC“. 4.1.12 (timing) jitter: The short-term variations of the significant instants
37、 of a timing signal from their ideal positions in time (where short-term implies that these variations are of frequency greater than or equal to 10 Hzj. 4.1.13 unilateral: A synchronization link where the corrective action to maintain locking is only active at one end of the link. 4.1.14 UTC: The ti
38、me scale, maintained by the Bureau International des Poids et Mesures (BIPM) and the International Earth Rotation Service (ERS), which forms the basis of a coordinated dissemination of standard frequencies and time signal. NOTE - The reference frequency for network synchronization is the frequency w
39、hich generates the UTC time scale. It is therefore preferable to use the words “UTC frequency“ instead of “UTC“. 4.1.15 wander: The long-term variations of the significant instants of a digital signal from their ideal position in time (where long-term implies that these variations are of frequency l
40、ess than 10 Hzj. NOTE - For the purposes of this Recommendation and related Recommendations, this definition does not include wander caused by frequency offsets and drifts. 4.2 4.2.1 Definitions related to clock equipments clock: An equipment that provides a timing signal. NOTE - The word “clockt ge
41、nerally means, when used for synchronization networks, the generator of the frequencies which will be used to synchronize the network. 4.2.2 4.2.3 other generators. 4.2.4 frequency standard: A generator, the output of which is used as a frequency reference. master clock: A generator which generates
42、an accurate frequency signal for the control of node clock: A clock distributing synchronization to one or more synchronized equipment. Recommendation G.810 (08/96) 3 4.2.5 frequency signal compliant with Recommendation G.8 1 1. 4.2.6 received from a higher quality clock. 4.2.7 logical SSU function,
43、 which incorporates its own management function. 4.2.8 processing and distribution, having the frequency characteristics given in Recommendation G.8 12. primary reference clock (PRC): A reference frequency standard that provides a reference slave clock: A clock whose timing output is phase-locked to
44、 a reference timing signal stand alone synchronization equipment (SASE): The stand alone implementation of the synchronization supply unit (SSU): A logical function for frequency reference selection, 4.3 4.3.1 4.3.2 local node: A synchronous network node which interfaces directly with customer equip
45、ment. 4.3.3 standard which is disseminated to all other clocks which are slaved to the master clock. 4.3.4 other. Definitions related to synchronization networks asynchronous mode: A mode where clocks are intended to operate in free running mode. master slave mode: A mode where a designated master c
46、lock is used as a frequency mutually synchronized mode: A mode where all clocks exert a degree of control on each 4.3.5 plesiochronous mode: A mode where the essential characteristic of time scales or signals such that their corresponding significant instants occur at nominally the same rate, any va
47、riation in rate being constrained within specified limits. 4.3.6 pseudo-synchronous mode: A mode where all clocks have a long-term frequency accuracy compliant with a primary reference clock as specified in Recommendation G.8 11 under normal operating conditions. Not all clocks in the network will h
48、ave timing traceable to the same PRC. 4.3.7 synchronization element: A clock providing timing services to connected network elements. This would include clocks conforming to Recommendations G.8 1 1, G.8 12 and G.813. 4.3.8 synchronization link: A link between two synchronization nodes over which syn
49、chronization is transmitted. 4.3.9 synchronous network: A network where all clocks have the same long-term accuracy under normal operating conditions. 4.3.10 synchronization network: A network to provide reference timing signals. In general, the structure of a synchronization network comprises synchronization network nodes connected by synchronization links. 4.3.11 synchronization network node: A group of equipment in a single physical location which is directly timed by a node clock. NOTE - A physical location may contain more than one synchroniz
