Half-Duplex (& Simplex) - Futurecom PDR8000 Manual

Document 8K088X02 R5.0
PDR8000® Portable Digital Repeater Product Planner
channel, there may be contention by two sources of voice/data for the RF transmit path. For
example, a wireline transmission may be delivered to the PDR8000 via the wireline interface at
the same time a Received CAI transmission is being considered for Local Repeat operation. In
these scenarios, the information chosen by PDR8000 to be passed to the outbound RF path is
governed by a (PTT Priority) configuration parameter (see 6.2.7).
5.3.2 H -D (& S )
ALF UPLEX IMPLEX
A channel configured for Half-Duplex operation is limited to either Transmitting or Receiving
CAI at any given time. On a half-duplex configured channel, if the PDR8000 is receiving
information/voice from both the CAI receiver for delivery to wireline link, and from the wireline
link for delivery over CAI, then the half-duplex nature of this configuration dictates that only one
of these directions is possible at a time. The PDR8000 will determine which direction takes
priority and is allowed per a (PTT Priority) configuration parameter (see 6.2.7).
Some radio systems operate such that the CAI Transmit Frequency is equal to the CAI Receive
Frequency (only one frequency is available/used for both inbound and outbound
communications). This specialized version of half-duplex is referred to as Simplex operation.
In Simplex operation, if more than one user tries to transmit at any time, the RF Signals interfere
with each other. This can result in communications with degraded voice quality, in the worst
case having the communication be unintelligible or not received at all. This is avoided by having
users listen for other activity before they initiate a new transmission, or by enabling certain
options in the subscriber units that prevent initiation of a transmission if another is already in
progress. Customers configure these options in the subscriber units according to their specific
needs. Some customers may wish to avoid contention in all situations (in which case they
program the subscriber unit to block a new transmission attempt while a received signal exists).
Other customers may want to allow the conflict, which gives the second talker some chance of
being heard in a situation deemed critical by the user. The PDR8000 is also configurable as to
whether it should allow a wireline-sourced transmission to occur when other activity is being
received on the CAI. This PDR8000 behavior is governed by a (PTT Priority) configuration
parameter (see 6.2.7).
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