48 System Feature Overview
April 2011 68007024085
2.4.3.2 Services Provided to a Radio User
When the location service is disabled, the radio does not provide any location updates to a
location application server. An icon is displayed on the radio if the location service is enabled. The
absence of this icon indicates that the location service is disabled. The icon shows a full satellite
dish when good GPS signals are detected and an empty satellite dish when the radio is receiving
poor GPS signals.
The radio does not display its current location on its screen. With the exception of pressing the
Emergency button, a radio user cannot trigger a location update to a location application server. In
general, the radio user does not have to take any action in this process; the radio transmits the
location coordinates automatically over the system.
2.4.3.3 Services Provided to a Location Application
For all the services, a third party location application server is required to send an explicit request
to the radio. A radio does not provide unsolicited location update to a location application server.
When the radio turns on and/or selects a properly configured channel (i.e. the previously
mentioned “ARS Parameter”), the radio registers with the presence service. The location
application thus learns that this radio is on the air, and will make an explicit request for location
updates if it is configured to track the location of the radio.
The GPS equipped radios transmit an update of their location coordinates over the radio system in
response to 3 service methods.
• Single Location Update – The location application server wants to know the current
location of a radio user. In this case, the application sends a request for a single location
update.
• Periodic Location Updates – Single location update is used to track the location of a
radio user by a location application server, but is an inefficient use of air interface.
Location tracking allows a location application server to periodically get the location of a
radio user by sending a single location request that contains the time interval between
updates. The radio continues to update its location periodically at the specified time
interval until the request is cancelled by the location application server. The location
tracking application can configure the radio to provide updates as frequently as once
every 10 seconds. The default value is once every 10 minutes. The rate of update is
configurable in increments of 1 second and must be matched with the resource
capabilities of the radio system and the needs of the end-user. This is discussed further
in “System Design Considerations” on page 203.
• On Emergency – A radio will send its location after the user triggers an emergency
alarm or an emergency alarm and call request. The location update is sent only to the
Good Signal Poor Signal
Disabled
no icon
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