ITU-T G 811 1-2017 Timing characteristics of enhanced primary reference clocks (Study Group 15).pdf
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1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.811.1 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2017) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital networks Design objectives for digital networks Timing characteristics of enha
2、nced primary reference clocks Recommendation ITU-T G.811.1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 IN
3、DIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G
4、.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 General aspects G.800G.809 Design objectives for digital networks G.810G.819 Synchronization, quality and availability targets G.820G.829 Network capabilitie
5、s and functions G.830G.839 SDH network characteristics G.840G.849 Management of transport network G.850G.859 SDH radio and satellite systems integration G.860G.869 Optical transport networks G.870G.879 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE
6、GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.
7、811.1 (08/2017) i Recommendation ITU-T G.811.1 Timing characteristics of enhanced primary reference clocks Summary Recommendation ITU-T G.811.1 outlines the requirements for enhanced primary reference clocks (ePRCs) suitable for frequency synchronization. These requirements apply under normal enviro
8、nmental conditions specified for the equipment. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.811.1 2017-08-13 15 11.1002/1000/13301 Keywords ePRC, ePRTC, frequency synchronization. * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field o
9、f your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T G.811.1 (08/2017) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information an
10、d communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. 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 ba
11、sis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Reso
12、lution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration
13、 and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions ar
14、e met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the pos
15、sibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. 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
16、 Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest infor
17、mation and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2017 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.811.1 (08/2017) iii Table of Con
18、tents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Frequency accuracy 2 7 Noise generation . 2 7.1 Wander . 3 7.2 Jitter 4 8 Phase discontinuity . 4 9 Degradation of the p
19、erformance of an ePRC 5 10 Interfaces . 5 Bibliography. 6 Rec. ITU-T G.811.1 (08/2017) 1 Recommendation ITU-T G.811.1 Timing characteristics of enhanced primary reference clocks 1 Scope This Recommendation outlines the requirements for enhanced primary reference clocks (ePRCs) suitable for frequency
20、 synchronization. These requirements apply under normal environmental conditions specified for the equipment. The ePRC provides the reference signal for the timing or synchronization of other clocks within a network or section of a network. In particular, the ePRC in its autonomous form can provide
21、a frequency input to an enhanced primary reference time clock (ePRTC). This Recommendation defines the ePRC output, but it does not apply to the output of a slave clock directly fed by an ePRC. The long-term accuracy of the ePRC should be maintained at 1 part in 1012 or better, with verification to
22、coordinated universal time (UTC). An ePRC may be realized as an autonomous clock, operating independently of other sources. Alternatively, the ePRC may be realized as a non-autonomous clock which is disciplined by UTC-derived precision signals received from a radio or satellite system. In either cas
23、e, the requirements for long-term accuracy and short-term stability, as specified in this Recommendation, apply. Several classes of ePRCs are being considered. This version specifies ePRC class A. Other classes are for further study. The long-term accuracy specified in this Recommendation is adequat
24、e when a single ePRC provides the reference synchronization signal to all other clocks within a network (synchronous mode of operation). In the pseudo-synchronous mode, i.e., not all clocks in the network have timing traceable to the same ePRC, the long-term accuracy is dependent on the number of eP
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