Site Reference Operation Modes - Motorola DIMETRA MTS 2 Installation, Configuration And Basic Service Manual

Site Reference Operation Modes

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. For an adjacent cell to be indicated to be synchronized requires that both the
serving MTS and the adjacent cell are synchronized to GPS.
MTS can be configured through the BTS Service Software for two different operating
configurations, which control the synchronization mode:
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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 above may
mean the BTS is unable to maintain synchronisation 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 operating in
non-synchronized mode, all the adjacent cells will be indicated as non-synchronized with
the 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
will always operate 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 (UHF) or every 4th year (800 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
This mode can be configured (for example, through TESS) for compatibility
reasons but will be treated as ASC.
Chapter 4: Hardware Installation
6802800U74-N September 2009