Beijing Huahuan Electronics Co., Ltd
antenna is needed because the attenuation introduced by the coax cable requires as
good reception as possible. Still the very weak satellite signal limits the cable to
just a few dozen meters, and thick coax cable and an intermediate active amplifier
is usually required for longer reach, aggravating the installation task. This
distance limitation also complicates the equipment room site selection.
2.2.
1PPS+ToD Scenario
In many applications, PTP is not used or supported. Many pre-PTP devices
requiring time and frequency synchronization have 1PPS and ToD inputs for
timing reference. Such devices include basestations, smallcells, telprotection
equipment in power networks. Even in PTP networks, many IEEE-1588V2
compliant network nodes such as Ethernet switches, routers, PTN transmission
equipnent, have their own 1PPS+ToD inputs for timing reference, and then act as
GM in the domain. In such applications, the GeckoSynco does not run PTP
protocol, but output 1PPS+ToD signal to those nodes.
Let’s again take the example of the enterprise smallcell network depicted in
Figure 2-1. The Ethernet LAN switch here is a PTP boundery clock that has a
1PPS+ToD input as its timing reference, and act as the T-GM in the domain. The
role of the GeckoSynco in the diagram is no longer a PTP GM, but provides
timing reference gained from GPS satellite through its 1PPS+ToD output. Though
not much different from the previous example in terms of equipment used,
installation simplicity, as well as performance, it does have an added benifit: a
much longer distance buget between the GeckoSynco and the equipment room
without resort to optical fibers. This is because the 1PPS+ToD cable can be 10
times longer than the 100 meters limit of Ethernet. When distance budgt exceeds
100 meters, this configuration may be considered. The 1PPS+ToD cable is
usually also made with CAT5 cable just like the Ethernet cable, but the plug used
6 HX.PTP-GM02 IEEE-1588 Grandmaster Clock V1.0
Summary of Contents for HX.PTP-GM02
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