4.7.4.3
GPS
►
AAVL
The “Autonomous Automatic Vehicle Location” (AAVL) feature adds the ability for GPS-equipped GeminiG3
models to initiate "Here I am" position message transmissions. AAVL allows the system designer to specify the
maximum distance or the time interval between position reports:
If the vehicle moves more than a specified distance since its last report, a new position report will be gen-
erated.
If no report has been sent for a specified amount of time, a new position report will be generated.
AAVL inhibits excessive transmission of reports to prevent network overload.
The “Dynamic Bandwidth Allocation” (DBA) protocol’s “Out Of Band” (OOB) mechanism is used to deliver the-
se “Automatic Vehicle Location” (AVL) reports.
Figure 47 - GPS - AAVL
Item
Description
Report every (*2) meters
MDBR – (Maximum Distance Between Reports)
Distance interval - the vehicle sends a position update each time it has moved this dis-
tance (unless the minimum time interval has not yet elapsed).
The mobile firmware saves the last-transmitted position, and compares it with the current
(latest OOB update) position.
Report every (*10) seconds
This parameter controls the “Maximum Time interval between position Reports”. Thus,
the vehicle will send a position update every time “this interval has elapsed” guarantee-
ing delivery of position reports at least this often. Data traffic and ACKs will generate
additional reports at shorter intervals.
At least (*10) seconds be-
tween reports
At most, the vehicle sends a position update every time this interval, in seconds, has
elapsed.
The main purpose of this parameter is to protect the network from being overloaded by
excessive AVL reporting from one or a few mobiles.
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