User's Guide Part 1

Table Of Contents

Chapter 1: Product description 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 700

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 Trimble Acutime™ GG and Trimble Acutime™ Gold GPS receivers.

In simple networks where all master ODUs are at a single site, the external reference can be

omitted. In this case, one ODU 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 Link Planner User Guide for guidance 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.