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PMP 450 Planning Guide
Wireless operation
This section describes how the PMP 450 wireless link is operated, including modulation modes, power control and
security.
Time division duplexing
The system uses Time Division Duplexing (TDD) – one channel alternately transmits and receives rather than using
one channel for transmitting and a second channel for receiving. To accomplish TDD, the AP must provide sync to
its SMs. Furthermore, collocated APs must be synced together – an unsynchronized AP that transmits during the
receive cycle of a collocated AP can prevent a second AP from being able to decode the signals from its SMs. In
addition, across a geographical area, APs that can “hear” each other benefit from using a common sync to further
reduce self-interference within the network.
Modules use TDD on a common frequency to divide frames for uplink (orange) and downlink (green) usage, as
shown in the figure below.
For more information on synchronization configuration options, see section
Planning for co-location and using the
on page
Figure 15 TDD Frame Division
OFDM and channel bandwidth
The PMP 450 Series transmits using Orthogonal Frequency Division Multiplexing (OFDM). The channel
bandwidth of the OFDM signal may be configured to 5 MHz (2.4 GHz, 3.5GHz, 3.6 GHz and 5.8 GHz only), 10
MHz or 20 MHz.
Time
pmp-0047 (March 2014)
1-37
Summary of Contents for PMP 450
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