Huawei Quidway S9300 Configuration Manual page 217

Quidway S9300 Terabit Routing Switch
Configuration Guide - Device Management
Usually, phase synchronization is also called time synchronization; frequency synchronization
is also known as clock synchronization. All of those terms are used in the following sections
and you need to pay attention to the differences between them.
Background
With the evolution towards IP network, devices on the wireless bearer network need to ensure
high-accurate clock synchronization. To achieve clock synchronization between base stations
in an IP RAN, you need to ensure that clock frequencies between base stations are within a
certain precision. Call dropping, otherwise, may occur during handoff. In certain wireless
communications systems, phase synchronization is required in addition to frequency
synchronization.
Table 12-1
Table 12-1 Different requirements for network clock synchronization in wireless
communications
Wireless
Communications
Systems
GSM
WCDMA
TD-SCDMA
CDMA2000
WiMax FDD
WiMax TDD
LTE
The requirement for clock synchronization on different base stations of different standards can
be met through various methods, such as physical clocks (such as the building integrated timing
supply system (BITS) clock, WAN clock, and synchronous Ethernet clock) and recovery clocks
by packets (such as Network Time Protocol and 1588v2 clock). Traditionally, base stations
directly access the global positioning system (GPS) to meet the requirement for time
synchronization. Packet-based time synchronization cannot meet the requirement of base
stations. Time synchronization can reach sub-second precision through the Network Time
Protocol (NTP) and sub-millisecond precision through 1588v1. With the assistance of hardware,
1588v2 can provide the time synchronization of sub-micro second precision. This meets the
requirement of wireless networks for time synchronization.
Compared with GPS, operation and maintenance cost of 1588v2 is lower (do not need to deploy
GPS at each base station). In addition, 1588v2 operates independent of the GPS, which is of
strategic significance.
Issue 03 (2011-12-29)
shows different requirements for network clock synchronization.
Clock Frequency
Accuracy Clock
0.05 ppm
0.05 ppm
0.05 ppm
0.05 ppm
0.05 ppm
0.05 ppm
0.05 ppm
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12 PTP Configuration
Phase Synchronization
Requirement
N/A
N/A
3 us
3 us
NA
1 us
In favor of phase
synchronization
205