Motorola PTP 600 series User Manual page 76

Wireless operation
Timing references for use with PTP-SYNC
PTP-SYNC requires an external timing reference in all but the simplest networks. Up
to ten PTP-SYNCs can be connected in a chain to share the timing signal from one
timing reference. In the majority of applications, one reference is required for each
site that contains PTP 600 master ODUs.
The timing reference can be from any timing system that provides a 1 Hz signal,
accurately synchronized in frequency and phase with a network-wide master timing
reference. GPS timing receivers are a very practical way of obtaining a suitable
reference. The PTP-SYNC is compatible with the following GPS timing receivers:
•
Trimble Acutime™ Gold GPS receiver
In simple networks where all master ODUs are at a single site, the external reference
can be omitted. In this case, one PTP 600 unit acts as a reference for other collocated
units.
Configuring the TDD frame
In synchronized operation, frame duration and burst duration must be configured
directly in the web-based management interface. Frame duration must be identical
across all links in a synchronized network.
The PTP Link Planner provides a capability for computing suitable frame parameters
in a synchronized network. Please refer to the
on configuring TDD synchronization.
Link symmetry is always 1:1 in synchronized networks.
Link capacity in synchronized networks
The TDD frame duration is extended in synchronized networks to allow for the
propagation delay of the longest link in the network and to incorporate additional
guard periods. These guard periods protect against delayed interference from distant
units in the same network.
The longer frame duration results in slightly lower link capacity than for an equivalent
non-synchronized link with the same channel bandwidth and modulation mode.
However, TDD synchronization also reduces interference, and this may allow operation
in higher modulation modes. The benefit of operating in a higher modulation mode
normally outweighs the penalty of the slightly longer TDD frame.
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Chapter 1 Product description
Link Planner User Guide
phn-0896_012v000
for guidance
Jul 2010