Cambium Networks PTP 820S, Техническое описание

Страница: 128 / 208

Chapter 4: Feature Description Synchronization
Available Synchronization Interfaces
Frequency signals can be taken by the system from a number of different interfaces (one reference
at a time). The reference frequency may also be conveyed to external equipment through different
interfaces.
Table 22 Synchronization Interface Options
Available interfaces as frequency
input (reference sync source) Available interfaces as frequency
output
•
Radio carrier
•
GE Ethernet interfaces
•
Radio carrier
•
GE Ethernet interfaces
It is possible to configure up to eight synchronization sources in the system. At any given moment,
only one of these sources is active; the clock is taken from the active source onto all other
appropriately configured interfaces
Synchronous Ethernet (SyncE)
SyncE is standardized in ITU-T G.8261 and G.8262, and refers to a method whereby the frequency
is delivered on the physical layer.
SyncE PRC Pipe Regenerator Mode
In SyncE PRC pipe regenerator mode, frequency is transported between two GbE interfaces
through the radio link.
PRC pipe regenerator mode makes use of the fact that the system is acting as a simple link (so no
distribution mechanism is necessary) in order to achieve the following:
•
Improved frequency distribution performance, with PRC quality.
•
Simplified configuration
In PRC pipe regenerator mode, frequency is taken from the incoming GbE Ethernet signal, and
used as a reference for the radio frame. On the receiver side, the radio frame frequency is used as
the reference signal for the outgoing Ethernet PHY.
Frequency distribution behaves in a different way for optical and electrical GbE interfaces, because
of the way these interfaces are implemented:
•
For optical interfaces, separate and independent frequencies are transported in each direction.
•
For electrical interfaces, each PHY must act either as clock master or as clock slave in its own
link. For this reason, frequency can only be distributed in one direction, determined by the
user.
Page 4-96