User's Guide Part 1

Wireless operation Chapter 1 Product description

phn-0896_009v003

1-26

UNDER DEVELOPMENT

Feb 2010

This type of interference may be eliminated if the TDD frames of the two links are

synchronized such that ODUs which share a mast are configured to always transmit

together and always receive together. An ODU will never be transmitting when an

ODU sharing the same mast is receiving. Similarly, the paired ODUs installed at the

remote ends from the common mast will also transmit together and receive together

but in the opposite half (or opposite phase) of the TDD cycle. Synchronization can be

extended beyond the single mast case where the TDD frames of all links in a network

can be synchronized. The benefit is that interference between any pair of units in the

network will be eliminated if they are configured to transmit in the same half of the

TDD frame, that is, with the same phase. In summary, TDD synchronization eliminates

half of the network interference mechanisms.

Network timing reference

For links to be synchronized, they must have access to a common network timing

reference. This is achieved by connecting each Master PTP 600 to a synchronization

unit. One synchronization unit is required for each Master. Two alternative

synchronization units are available:

• MemoryLink UltraSync GPS receiver: This unit contains a GPS receiver which

produces the common network timing reference. For more information, refer to

UltraSync on

page 1-27.

• PTP-SYNC: This option is the preferred solution. For simple networks centred on

a single common mast, the common network timing reference may be derived

from one of the PTP 600 ODUs installed at the common mast. The timing signal is

then daisy chained to the other collocated ODUs. For larger distributed

networks, sites which consist of one or more Master PTP 600 units will require a

single GPS receiver. For more information, refer to PTP-SYNC on

page 1-27.

Configuring the TDD frame

The Master PTP 600 automatically configures the TDD frame by optimizing parameters

such as the Frame Duration and Burst Duration (see Time division duplex

ynchronization on page 1-25). When

TDD synchronization is enabled, this is no longer

the case and it is up to the user to configure the frame parameters appropriately. This

should be done with the aid of LINKPlanner. Please refer to the

Link Planner User

Guide

for guidance on configuring TDD synchronization.