User's Guide Part 1

Chapter 1: Product description Wireless operation
Wireless operation
This section describes how the PTP 700 wireless link is operated, including modulation modes,
power control and security.
Time division duplexing
TDD cycle
PTP 700 links operate using Time Division Duplexing (TDD). They use a TDD cycle in which the
ODUs alternately transmit and receive TDD bursts. The TDD cycle is illustrated in Figure 2. The
steps in the cycle are as follows:
1
The TDD m
aster transmits a burst to the TDD slave.
2
A delay occurs as
the master-slave burst propagates over the link.
3
The s
lave receives the burst from the master.
4
T
he slave processes the master-slave burst.
5
The slave transmits a burst to the
master.
6
A delay occurs as the
slave-master burst propagates over the link.
7
The m
aster receives the burst from the slave.
8
The m
aster transmits the next burst to the slave.
The frame duration must be long enough to allow the master to receive the complete burst in 7
before starting to transmit in 8.
TDD frame parameters
The TDD burst duration varies depending on the following:
• Channel bandwidth
• Link range
• Link optimization mode
• Link symmetry
• Offered traffic loading.
The TDD frame duration varies depending on the following:
• TDD burst duration master-slave.
• TDD burst duration slave-master.
• Link range.
The propagation delay in Step 2 is necessarily equal to the propagation delay in Step 6, and is
determined solely by the link range. There may be added delays between rx and tx on the
master and slave to minimize interference, as set up by the link planner or installer.
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