YD/T 2375-2019 English PDF (YDT2375-2019)

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YD/T 2375-2019: Technical requirements for high accuracy time synchronization
YD/T 2375-2019
COMMUNICATION INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 33.040.20
M33
Replacing YD/T 2375-2011
Technical requirements for high accuracy time
synchronization
ISSUED ON: NOVEMBER 11, 2019
IMPLEMENTED ON: JANUARY 01, 2020
Issued by: Ministry of Industry and Information Technology of PRC
Table of Contents
Foreword ... 4 
1 Scope ... 6 
2 Normative references ... 6 
3 Abbreviations ... 7 
4 Time synchronization requirements and precision grade division ... 8 
4.1 Classification of time synchronization precision ... 8 
4.2 Requirements for high-precision time synchronization ... 10 
5 Requirements for high-precision time synchronization networking ... 10 
5.1 Hierarchical structure of high-precision time synchronization network ... 10 
5.2 Composition and basic functions of time synchronization device ... 11 
5.3 Principles of time synchronization networking ... 11 
6 Requirements for high-precision time synchronization performance indicators ... 15 
6.1 Overview ... 15 
6.2 Allocation of performance indicators of time synchronization network when satellite
timing is available ... 16 
6.3 Allocation of performance indicators of time synchronization network when satellite
timing service is unavailable ... 17 
7 High-precision time synchronization transmission technology ... 18 
7.1 High-precision time synchronization technology ... 18 
7.2 Inter-office transmission technology ... 19 
7.3 Intra-office distribution technology ... 19 
8 Requirements for high-precision time synchronization interface ... 19 
8.1 Overview ... 20 
8.2 PTP time interface requirements ... 20 
8.3 1PPS+ToD time interface ... 22 
9 Reliability requirements of high-precision time synchronization network ... 27 
9.1 Reliability requirements for time sources ... 27 
9.2 Requirements for time synchronization device and time link settings ... 27 
9.3 Redundant configuration requirements of time synchronization device ... 28 
9.4 Selection requirements for time reference source ... 28 
10 Basic requirements for high-precision time synchronization related device ... 31 
10.1 High-precision time synchronization device ... 31 
10.2 Basic requirements for time synchronization of bearer device ... 33 
10.3 Basic Requirements for time synchronization of synchronized devices ... 35 
Appendix A (Informative) IRIG/DCLS time coding ... 37 
Appendix B (Informative) Setting location and quantity of time synchronization device
... 41 
Appendix C (Informative) Engineering feasibility requirements ... 42 
Appendix D (Informative) Estimation of time distribution of time source part in case of
satellite timing failure ... 44 
Appendix E (Informative) Key factors affecting inter-office transmission accuracy . 45 
Appendix F (Informative) 1588V2 protocol and BMC algorithm ... 48 
Technical requirements for high accuracy time
synchronization
1 Scope
This standard specifies the networking requirements for high-precision time
synchronization, the performance index requirements for high-precision time
synchronization, the reliability requirements for high-precision time synchronization
networks, the basic requirements for equipment related to high-precision time
synchronization.
This standard applies to high-precision time synchronization networks, based on ground
transmission using PTP technology.
2 Normative references
The following documents are essential to the application of this document. For the dated
documents, only the versions with the dates indicated are applicable to this document;
for the undated documents, only the latest version (including all the amendments) is
applicable to this standard.
YD/T 900-1997 Technical requirement for SDH equipment - Clock
YD/T 1012-1999 Node clock set of digital synchronization network and its timing
feature
YD/T 1479-2006 Technical requirements and testing methods of primary reference
clock equipment
YD/T 2879-2015 (OAM) technical requirements based on the synchronous network
operation management and maintenance of a packet network
ITU-T G.8262 Timing characteristics of synchronous Ethernet equipment slave
clock
ITU-T G.8275.1 Precision time protocol telecom profile for phase/time
synchronization with full timing support from the network
IEEE 1588-2008 Standard for a precision clock synchronization protocol for
networked measurement and control systems
3GPP TR 25.836 Node B synchronization of time division duplex (TDD)
Figure 1 -- Hierarchical structure of time synchronization network
5.2 Composition and basic functions of time synchronization device
The level-1 time synchronization device shall be composed of two cesium clocks and
two satellite timing receivers, etc., which can be traced to a higher-level domestic time-
keeping reference (for example, the National Time Service Center), through a dedicated
comparison method.
The level-2 time synchronization device shall be equipped with at least rubidium clocks.
The device consists of two rubidium clocks and two satellite timing receivers. It shall
support the traceability of time to the level-1 time synchronization device, through
ground means; support the punctuality function of ground frequency signals. It shall be
able to be reliably traced to China's frequency synchronization network.
The level-3 time synchronization device shall be equipped with at least a high-stable
crystal oscillator. The device consists of two high-stable crystal oscillators and at least
one satellite timing receiver. It shall support time traceability to the level-2 time
synchronization device or the level-1 time synchronization device, through ground
means; support the punctuality function of ground frequency signals. It shall be able to
be reliably traced to China's frequency synchronization network.
See Appendix B, for the location and quantity of time synchronization devices, at all
levels.
5.3 Principles of time synchronization networking
5.3.1 General principles of time synchronization networking
Under normal circumstances, the time synchronization device shall prefer the signal of
the satellite timing receiver. When the satellite signal is unavailable, the low-level time
synchronization device shall trace to the high-level time synchronization device,
through the ground time link. In the case where both the satellite signal and the ground
time link are unavailable, the low-level time synchronization device shall be able to use
the signal from the frequency synchronization network, to keep time. If conditions
permit, the time synchronization network shall be traced to the national time-frequency
standard system.
When building a time synchronization network, according to the actual network
conditions, flexible networking structures (for example, level-2 or level-3 networking)
and setting methods (for example, a level-3 time synchronization device with a
rubidium clock) can be used.
5.3.2 Relationship between time synchronization network and frequency
the best network element of frequency time keeping as the reference. See 8.3.4, for the
specific mapping mechanism of scheme 1 and scheme 2. See 9.4.2, for the source
selection processing mechanism.
5.3.3 Principles of reference source setting
5.3.3.1 The principle of setting the timing reference of the level-1 time
synchronization
The principle of setting the timing reference of level-1 time synchronization is as
follows:
a) Under normal circums...