System Feature Overview 55
68007024085 April 2011
For Enhanced Privacy,
If a subscriber is out of range or its battery is dead, it will not send GPS data during its reserved
windows, so the repeater also has a mechanism to free up the windows reserved for that
subscriber. The repeater waits for a certain period of time before releasing the windows and this
time is dependent on the cadence rate of the subscriber’s location request. The table below
summarizes the amount of time the repeater waits before de-allocating windows for a subscriber.
In a subscriber, it is highly recommended to keep the Enhanced GPS Revert channel in the
“Channel Pool” in the CPS. This prevents the user from accessing the Enhanced GPS Revert
channel that may affect GPS reliability. A channel can be configured as an Enhanced GPS Revert
channel by selecting the field “Enhanced GPS” in the channel settings. In order to send responses
to the Enhanced GPS Revert channel, the GPS revert channel setting of the home channel has to
be set to “Enhanced”.
In a multisite system with roaming enabled, all sites are recommended to use the same setting
and window size as an Enhanced GPS Revert channel. This can be configured through the
Enhanced GPS Revert channel of the Home channel.
In a repeater, the CPS allows either one or both slots to be configured as Enhanced GPS. The
window size in the repeater’s Enhanced GPS slot should match the window size in the
subscribers. One slot can be configured for regular Data Revert and the other slot can be
configured for Enhanced GPS Revert. The repeater CPS also allows a user to choose the
maximum percentage of windows that will be used for periodic updates. The possible values are
90%, 75%, 60%, and 45%. The rest of the windows are used for one-time updates and also to
empty out queued data. When a subscriber is participating in a voice call, chances are it may miss
its windows. This will lead to windows getting queued up in the subscriber. When this happens, the
subscriber can make one time requests to ask for additional windows to empty out its queue.
In a situation whereby a system has heavy voice loading, the subscriber may start to miss their
reserved windows quite frequently. Hence, in such a scenario it is advised to run the system at
60% or 45% capacity so the rest of the windows can be used to clear up the queued data. For
more details on system reliability based on voice call loading, refer to Section 4.4.5.6 “Enhanced
GPS Revert – Loading & Reliability”.
In an IP Site Connect system where a revert channel is a wide area channel, only one repeater’s
slot needs to be selected with periodic window reservation (90%, 75%, 60%, and 45%). For all the
other peers, this value should be set to “None”.
Update Rate
Wait Time Before
De-allocation (minutes)
30 seconds 5
1 minute 5
2 minutes 10
4 minutes 20
8 minutes 30
WindowSize LRRPResponseSize 1+()12÷()4+=
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