Gps Site Reference Operation Modes - Motorola MTS LiTE Installation, Configuration And Basic Service Manual

power-up. The four satellites are used to establish a three-dimensional fix (latitude, longitude, and
altitude) for the site called 3D fix mode. This process can take up to 30 minutes, but typically is
completed in less than 5 minutes.
Once the position of the site has been established, the corresponding data is stored in memory and
normal operation resumes.
4.8.1

GPS Site Reference Operation Modes

The ETSI standard allows two modes of operation of adjacent cells: Synchronized and Non-
Synchronized relative to the serving cell. The MTS uses GPS to synchronize to the same time
reference. Both the serving MTS and the adjacent cell need to be synchronized to GPS for an adjacent
cell to be indicated for synchronization.
MTS can be configured through the BTS Service Software for four different operating configurations,
which control the synchronization mode:
Automatic Synchronized Configuration (ASC)
•
This configuration is used to specify that the MTS should operate in synchronized mode relative to
GPS. However, if the GPS reference is lost, the MTS continues to operate in synchronized mode for
a configurable period (free run time – no upper limit). It should be noted that setting this value
greater than the recommended values (4 hours) may mean that the BTS is unable to maintain
synchronization and can result in call failures and erratic network performance. If the GPS reference
is not recovered in this time period, the MTS switches to the non-synchronized mode. If an MTS is
started when no GPS reference is available, it operates in the non-synchronized mode.
Non-synchronized mode will not have optimized hand-over performance. When an MTS operates in
non-synchronized mode, all the adjacent cells will be indicated as non-synchronized with this MTS.
By default the re-synchronization of MTS running non-synchronized is done automatically whenever
there is valid GPS reference signal and the site does not handle traffic. Prolonged operation in non-
synchronized mode will eventually lead to critical alarms and the frequency accuracy of the MTS will
no longer be guaranteed.
To maintain the frequency accuracy, it is necessary that the oscillator within the MTS is periodically
recalibrated. The periodic recalibration happens automatically when a GPS reference is present.
The critical alarms indicate that recalibration is due and should be performed without delay.
• Forced Non-Synchronized Configuration (FNC)
FNC is not recommended for System Release D6.0. In this configuration, the MTS always operates
non-synchronized to GPS. The failure or lack of GPS will not be reported as an alarm. The sets of
events that are reported in ASC and FNC modes are the same, however the events reported in
ASC mode with Minor severity, in FNC mode are reported with lower – Normal severity.
The MTS starts up in non-synchronized mode regardless of the presence of a GPS signal. However
if GPS is present, the site reference is trained accordingly. Prolonged operation in this configuration
without GPS eventually leads to critical alarms and the frequency accuracy of the MTS is no longer
guaranteed. Frequency accuracy is expected to be maintained for 4 to 8 years.
To maintain the frequency accuracy, it is necessary that the oscillator within the MTS is periodically
recalibrated (every 8th year (400 MHz and 260 MHz) or every 4th year (800 MHz and 900 MHz)).
The periodic recalibration happens automatically when a GPS reference is present. If no GPS
reference is present, it is necessary to ship the Site Controller for calibration at a repair center. The
critical alarms indicate that recalibration is due and should be performed without delay.
It is possible to change configuration with BTS Service Software. The new configuration will only be
active after an MTS reset.
• NSC mode
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Chapter 4: Hardware Installation
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