18 System Feature Overview
April 2011 68007024085
participating in the call (i.e. destination of the call is not of their interest) move to the new
Rest Channel.
If the current Rest Channel is the last idle channel (i.e. all the other available channels are
in use), the current Rest Channel remains as the Rest Channel. The call starts on the
channel and non-participating radios stay on the channel. In this condition, non-
participating radios indicate that the channel is busy via its yellow LED. If all channels are
busy and a radio user initiates a call, then the radio generates a distinct tone to indicate
that the system is busy. As soon as a channel becomes free in the Capacity Plus system,
the non-participating radios are informed, and move to the free channel.
At the end of the call (i.e. after the call hang time), the repeater also broadcasts the status
of all other available channels. This triggers any radio on the channel to move to the
current Rest Channel or to a channel where a Group Call of interest is active.
The Capacity Plus system has no central controller to manage the Rest Channel. The
Rest Channel is managed collectively by all the trunked repeaters. A trunked repeater
periodically informs the status of its channels to other trunked repeaters whenever the
status of its channels change. When a new Rest Channel is selected, the selecting
repeater informs all the other repeaters. The new Rest Channel is selected based on the
following conditions:
• At the start of a call, the repeater of the current Rest Channel selects the new Rest
Channel.
• On detection of interference or before starting CWID (i.e. BSI) transmission, the
repeater of the current Rest Channel selects the new Rest Channel.
• On detection of no Rest Channel (in the event of a failure of the current Rest Channel
repeater or the backend network), the repeater with the lowest ID selects the new
Rest Channel.
• When a call ends on a system, if a call is in progress on the current Rest Channel,
then the repeater of the current Rest Channel selects the new Rest Channel.
The Capacity Plus system does not require an exclusive control channel. The Rest
Channel changes on every call; in case of an interference or if the repeater becomes
unavailable due to failure. This results in the following advantages:
• Non-exclusive channels make it easier to satisfy regulator frequency coordination
(where exclusive use of channels is not possible).
• Capacity Plus does not use “request and grant” mechanism to allocate channels and
does not require any central controller to trunk the channels.
• The dynamic Rest Channel mechanism makes Capacity Plus very suitable for an
environment where channels are shared by multiple radio systems.
• The dynamic Rest Channel mechanism also improves the reliability of the Capacity
Plus system. In the event of a repeater failure, the other available repeaters
automatically reconfigure themselves and continue to work as the Capacity Plus
system.
The Capacity Plus system configuration of MOTOTRBO does not require any new
hardware apart from backend network devices such as routers. If a customer has multiple
MOTOTRBO systems working in digital repeater mode at the same site and wants to
convert to a Capacity Plus system, then the repeaters and radios should be updated with
the new software, and the repeaters need to be connected to an IPv4-based backend
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