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ME60 V800R010C10SPC500 Feature Description - System Management 01

This is ME60 V800R010C10SPC500 Feature Description - System Management
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Overview of 1588v2and G.8275.1

Overview of 1588v2and G.8275.1

Definition

  • Synchronization

    This is the process of ensuring that the frequency offset or time difference between devices is kept within a reasonable range. In a modern communications network, most telecommunications services require network clock synchronization in order to function properly. Network clock synchronization includes time synchronization and frequency synchronization.

    • Time synchronization

      Time synchronization, also called phase synchronization, means that both the frequency of and the time between signals remain constant. In this case, the time offset between signals is always 0.

    • Frequency synchronization

      Frequency synchronization, also called clock synchronization, refers to a constant frequency offset or phase offset. In this case, signals are transmitted at a constant average rate during any given time period so that all the devices on the network can work at the same rate.

    Figure 14-1 Schematic diagram of time synchronization and frequency synchronization

    Figure 14-1 shows the differences between time synchronization and frequency synchronization. If Watch A and Watch B always have the same time, they are in time synchronization. If Watch A and Watch B have different time, but the time offset remains constant, for example, 6 hours, they are in frequency synchronization.

  • IEEE 1588

    IEEE 1588 is defined by the Institute of Electrical and Electronics Engineers (IEEE) as Precision Clock Synchronization Protocol (PTP) for networked measurement and control systems. It is called the Precision Time Protocol (PTP) for short.

    IEEE 1588v1, released in 2002, applies to industrial automation and tests and measurements fields. With the development of IP networks and the popularization of 3G networks, the demand for time synchronization on telecommunications networks has increased. To satisfy this need, IEEE drafted IEEE 1588v2 based on IEEE 1588v1 in June 2006, revised IEEE 1588v2 in 2007, and released IEEE 1588v2 at the end of 2008.

    Targeted at telecommunications industry applications, IEEE 1588v2 improves on IEEE 1588v1 in the following aspects:
    • Encapsulation of Layer 2 and Layer 3 packets has been added.
    • The transmission rate of Sync messages is increased.
    • A transparent clock (TC) model has been developed.
    • Hardware timestamp processing has been defined.
    • Time-length-value (TLV) extension is used to enhance protocol features and functions.

    1588v2 is a time synchronization protocol which allows for highly accurate time synchronization between devices. It is also used to implement frequency synchronization between devices.

  • ITU-T G.8275.1

    ITU-T G.8275.1 defines the precision time protocol telecom profile for phase/time synchronization with full timing support from the network.

    G.8275.1 defines three types of clocks, including T-GM, T-BC and T-TSC. A Bearer Network Device is configured as the T-BC.

Purpose

Data communications networks do not require time or frequency synchronization and, therefore, ME devices on such networks do not need to support time or frequency synchronization. On IP radio access networks (RANs), time or frequency needs to be synchronized among base transceiver stations (BTSs). Therefore, ME devices on IP RANs are required to support time or frequency synchronization.

Frequency synchronization between BTSs on an IP RAN requires that frequencies between BTSs be synchronized to a certain level of accuracy; otherwise, calls may be dropped during mobile handoffs. Some wireless standards require both frequency and time synchronization. Table 14-1 shows the requirements of wireless standards for time synchronization and frequency accuracy.

Table 14-1 Requirements of wireless standards for time synchronization and frequency accuracy
Wireless Standards Requirement for Frequency Accuracy Requirement for Time Synchronization
GSM 0.05 ppm NA
WCDMA 0.05 ppm NA
TD-SCDMA 0.05 ppm 3us
CDMA2000 0.05 ppm 3us
WiMax FDD 0.05 ppm NA
WiMax TDD 0.05 ppm 1us
LTE 0.05 ppm In favor of time synchronization

Different BTSs have different requirements for frequency synchronization. These requirements can be satisfied through physical clock synchronization (including external clock input, WAN clock input, and synchronous Ethernet clock input) and packet-based clock recovery.

Traditional packet-based clock recovery cannot meet the time synchronization requirement of BTSs. For example, NTP-based time synchronization is only accurate to within one second and 1588v1-based time synchronization is only accurate to within one millisecond. To meet time synchronization requirements, BTSs need to be connected directly to a global positioning system (GPS). This solution, however, has some disadvantages such as GPS installation and maintenance costs are high and communications may be vulnerable to security breaches because a GPS uses satellites from different countries.

1588v2, with hardware assistance, provides time synchronization accuracy to within one micro second to meet the time synchronization requirements of wireless networks. Thus, in comparison with a GPS, 1588v2 deployment is less costly and operates independently of GPS, making 1588v2 strategically significant.

In addition, operators are paying more attention to the operation and maintenance of networks, requiring ME devices to provide network quality analysis (NQA) to support high-precision delay measurement at the 100 us level. Consequently, high-precision time synchronization between measuring devices and measured devices is required. 1588v2 meets this requirement.

1588v2 packets are of the highest priority by default to avoid packet loss and keep clock precision.

Benefits

This feature brings the following benefits to operators:

  • Construction and maintenance costs for time synchronization on wireless networks are reduced.

  • Time synchronization and frequency synchronization on wireless networks are independent of GPS, providing a higher level of strategic security.

  • High-accuracy NQA-based unidirectional delay measurement is supported.

  • Y.1731 and IPFPM are supported.

Concepts of G.8275.1

ITU-T G.8275.1 defines the precision time protocol telecom profile for phase/time synchronization with full timing support from the network. G.8275.1 is defined as a time synchronization protocol.

A physical network can be logically divided into multiple clock domains. Each clock domain has its own independent synchronous time, with which clocks in the same domain synchronize.

A node on a time synchronization network is called a clock. G.8275.1 defines three types of clocks:
  • A Telecom grandmaster (T-GM) can only be the master clock that provides time synchronization.

  • A Telecom-boundary clock (T-BC) has more than one G.8275.1 interface. One interface of the T-BC synchronizes time signals with an upstream clock, and the other interfaces distribute the time signals to downstream clocks.

  • A Telecom time slave clock (T-TSC) can only be the slave clock that synchronizes the time information of the upstream device.

NOTE:

The ME60 can function as the T-BC only.

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Updated: 2019-01-04

Document ID: EDOC1100059466

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