User's Guide Part 1

User Guide: PTP 600 Series Wireless operation
phn-0896_009v003
Feb 2010
UNDER DEVELOPMENT
1-27
Performance considerations when enabling TDD
synchronization
In certain configurations, the TDD frame can adapt to allocate more of the frame to a
particular link direction. This is called adaptive TDD. It works by the PTP 600
automatically and independently adjusting the Burst Duration in each link direction as
the level of offered traffic in each direction changes. This was discussed in more detail
in Link symmetry on
page 1-21 . As TDD synchronization requires TDD frames to be
constantly aligned in time, a varying TDD frame is not an option when TDD
synchronization is enabled. Only the symmetric mode is available when TDD
synchronization is enabled.
When TDD synchronization is enabled, the capacity of an “ideal” link is generally a few
percent lower than the case where TDD synchronization is disabled. The term “ideal”
is important as this is the capacity assuming that there is no interference. The benefit
of eliminating half of the network interference mechanisms generally outweighs this
small reduction in capacity. The exact reduction can be examined using Link Planner.
UltraSync
PTP 600 application software supports the synchronization method based on the
MemoryLink UltraSync GPS receiver. An additional control in the web-based
management interface allows a user to configure the ODU for operation with
UltraSync or for PTP-SYNC. If the installation is converted from UltraSync to PTP-
SYNC, the UltraSync unit must be disconnected.
PTP-SYNC
TDD synchronization using PTP-SYNC is an improved method for synchronizing TDD
transmission in a network of PTP 600 links. This method is based on the PTP-SYNC
hardware platform connected in-line between the PIDU and the master ODU. Figure
1-14 shows
a single PTP-SYNC within a system. In this example, the chosen system
configuration requires an LPU between the GPS receiver module and the PTP-SYNC.