System Feature Overview 9
68007024085 April 2011
NOTE: When used in direct mode without a repeater, two-slot TDMA systems on a 12.5 kHz
channel do not deliver 6.25 kHz equivalent efficiency. This is because the repeater is
necessary to synchronize the time slots to enable independent parties to share them.
Thus, on a direct or talkaround channel, when one radio begins transmitting, the whole
12.5 kHz channel is effectively busy, even though the transmitting radio is using only one
time slot. The alternate time slot is unavailable for another, independent voice call.
However, the alternate time slot can potentially be utilized as a signaling path. The ETSI
DMR Tier 2 standard refers to this capability as Reverse Channel signaling, and it is
envisioned to be used to deliver important future benefits to professional users, such as
priority call control, remote-control of the transmitting radio, and Emergency Call pre-
emption. This future capacity for reverse channel signaling is a unique capability of TDMA
technology and, if supported by your system, may be deployed in both repeater and direct/
talkaround configurations. At this time, the MOTOTRBO system does NOT support
Reverse Channel signaling.
2.1.2.5 Two-Slot TDMA System Planning Considerations
System Planning considerations associated with the increased capacity and the flexibility of the
MOTOTRBO two-slot TDMA architecture include:
• Capacity planning:
• How many voice and data users do you have?
• What usage profiles are anticipated?
• How many channels and repeaters are needed?
These questions are addressed in more detail in “System Design Considerations” on page 203.
• Fleetmapping:
• How to map users, voice services and data services such as messaging or location
tracking to channels.
Voice and data service capabilities are described in more detail in this module and in “System
Components and Topologies” on page 137. Fleetmapping considerations are addressed in more
detail in “System Design Considerations” on page 203, in the MOTOTRBO Systems Training, and
within the MOTOTRBO radio CPS.
• Migration Planning:
• How to migrate existing channels to digital channels?
• What updates to licensing requirements may be needed?
These questions are addressed in mode detail in Section 4 “System Design Considerations” on
page 203.
2.1.3 Digital Audio Quality and Coverage Performance
This section describes how digital audio drives coverage performance. It also sets expectations for
how digital audio behaves and sounds from the end-user’s perspective.
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