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With the development of 3G/LTE, wireless networks have higher and higher requirements for time synchronization performance. GPS satellite systems have problems such as difficult installation and site selection, difficult maintenance, difficult feeder cable laying, high security risks, and high costs. Therefore, high-precision The ground time synchronization scheme has become a big demand.
The 1588v2 international standard launched by IEEE at the end of 2008 became the best solution. In the same year, various equipment manufacturers started the research and development of 1588v2 technology. After nearly two years of development, the 1588v2 synchronization technology has gradually matured.
Basic concepts of synchronization
Definition and classification of synchronization
Synchronization means that two or more signals maintain a certain specific relationship in frequency or phase, that is, the phase difference or frequency difference of two or more signals at the corresponding effective instant is maintained within the agreed allowable Within range. Synchronization can be divided into:
*- Clock synchronization (frequency synchronization)
Same frequency / frequency locked; different phase / fixed phase difference; different time / inconsistent UTC time
*- Time synchronization (phase synchronization)
Same frequency / frequency locked; same phase / no phase difference; same time / same UTC time
Synchronization requirements of wireless networks
The current time synchronization solution in wireless systems—GPS
Problems with GPS time synchronization solutions
*- Difficulty in construction
GPS antenna has special requirements for the installation environment, and the GPS antenna feeder is thicker at long distances
*- High failure rate, no failure backup protection
GPS failure rate is about 10% per year; each base station is equipped with only 1 star card, no failure protection
*- Poor maintainability
GPS failure requires on-site hardw***e replacement; remote maintenance is not possible
*- There are safety risks
GPS may be turned off under w*** conditions, causing the entire network to be paralyzed
Due to the above problems, Huawei proposed a 1588V2 high-precision time solution to replace GPS equipment in wireless systems
Why do you need 1588?
Whether it is TOP or Ethernet physical layer synchronization, they can only achieve frequency synchronization, but they cannot achieve time synchronization.
What is 1588?
IEEE 1588 is a precision clock synchronization protocol standard for network measurement and control systems. It adopts the PTP (precision clock synchronization) protocol with an accuracy of microseconds. The purpose of this standard is to accurately synchronize the decentralized and independent clocks in the measurement and control system.
What is 1588V2?
The full name of IEEE 1588v2 is: the precision clock synchronization protocol standard for network measurement and control systems
IEEE P1588 TM D2.2
Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems
The IEEE 1588 protocol is designed to accurately synchronize the real-time clock of each node in distributed network communication. The basic idea is to synchronize the internal clock of the network device (client) with the master clock of the master computer through hardw***e and softw***e;
IEEE 1588v2 overview
*- IEEE 1588V2 is a precision clock synchronization protocol standard for network measurement and control systems. It adopts the PTP (precision clock synchronization) protocol, which can achieve sub-microsecond accuracy and achieve frequency synchronization and time (phase) synchronization.
*- The key technical points of the IEEE 1588V2 protocol can be divided into three: BMC (best master clock) algorithm, master-slave synchronization principle, and transparent clock TC model.
*- 1588V2 uses a handshake method to complete frequency and time synchronization with precise time stamps.
Basic concepts of IEEE 1588v2-network model
The basic concept of IEEE 1588v2-port status
IEEE 1588v2 key technical points-master-slave synchronization principle
Key Technical Points of IEEE 1588v2-Other Points
Key Technical Points of IEEE 1588v2-Fiber Asymmetry
IEEE 1588v2 technical summary
*- The BMC algorithm of the 1588V2 protocol needs to ensure that the distance between the receiving and transmitting fibers between the master and slave sites is the same to accurately restore the time. However, there are often inconsistencies between the receiving and transmitting in the existing network, such as fiber patching, fusion, etc., resulting in receiving and transmitting fibers The length is not consistent, this phenomenon is called fiber asymmetry.
*- The 1588V2 protocol itself cannot solve the problem of fiber asymmetry, which is a problem in the industry, but Huawei's OTN's SFIU+ST2 solution perfectly solves this problem.
That's all for today, you are welcome to leave a message and exchange in the comment area. Thank you!
