Operation and Configuration Guide 3.14
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5.4.3 Geographical Regions Policy Overview
The
Geographic Region Policy
increments a link's score to make it the preferable
WAN link for a defined geographic bounding region. Up to three regions can be
defined per link. This policy is often used when the quality and/or cost of coverage
for a particular area is known ahead of time and selection of the best WAN link
can be decided in advance (i.e. when configuring the WAN link).
For example, if the cellular coverage for different Mobile Network Operators is
known to be good in certain areas, then regions for those areas can be defined on
the respective links and scores applied accordingly.
Similarly, if there is a WiFi connection available (e.g. within and around a depot),
then a region for the depot could be defined for the WiFi WAN link with a very high
score to ensure that the WiFi WAN link is used when the vehicle is in or near the
yard.
As a basic example, consider the following in which there are two regions, where
part of each overlaps the other. The coverage in Region 1 is known to best for
Mobile Network Operator 1 (C1), and the coverage in Region 2 is known to be
best for Mobile Network Operator 2 (C2).
To provide the best coverage and prevent unnecessary switchovers throughout
the vehicle's journey, the following policy settings were defined for two cellular
WAN links and the following settings were specified:
The overall score for a cellular link is then calculated as follows:
Overall score = Priority Score + Score for current region
For example, when a vehicle is in Region 1, C1's score is 1200+300=1500 and
C2's score is 1100+100=1200.
In the case of overlapping regions, each link's score is calculated by including the
link's score for all regions which are part of the overlap.
For example, when a vehicle is in an overlapping region comprised of Region 1
and Region 2, C1's score is 1200+300+0=1500 and C2's score is
1100+100+300=1500.
Table 5-2: Example of Geographical Region Policy Settings
Dynamic Priority
Policy
Geographic Region
Policy
Cellular Link 1 (C1)
Priority (Base) Score:
1200
Region 1 Score: 300
Region 2 Score: 0
Cellular Link 2 (C2)
Priority (Base) Score:
1100
Region 1 Score: 100
Region 2 Score: 300