Reference Manual

Synchronization
Cold start Transmission network or other
RBS as source
5 minutes
Optional frequency source 10 minutes
For both network and optional
RBS is synchronized
and Reset command
received on ABIS
Transmission network, Optional
frequency source or other RBS as
source
10 seconds
RBS is synchronized
and Start command
after Function
Change is received
Transmission network, Optional
frequency source or other RBS as
source
30 seconds
Warm start Transmission network, Optional
frequency source or other RBS as
source
90 s when there
is not jitter in
the synch.
source
31.4 Selection of the Reference Source
Purpose
The purpose is to increase the system’s air time; that is to say, the
possibility to use different synchronization sources decreases the
possibility for system failure caused by lack of a synchronization source.
Precondition and Initiation
The PCM reference must be marked available in order to be considered
for selection. The function is initiated by one of the following events:
• Start-up of RBS
•
"Hold-over expired time" is reached (see Hold-over Operation)
•
Synchronization reference source is re-established in Hold-over
state
• At TF (Timing Function) configuration
• When locking to the reference source is terminated without
successful locking
Description
The function decides which reference source is to be used for
synchronization; that is to say, PCM interface, optional reference or
other RBS. The choice depends on the type of equipment installed and
parameters received at TF configuration according to the table below.
Units equipped with an optional reference source will always use this
option as default. By a command over A-bis it is possible to change
between the optional reference source (if installed) and the PCM
interface.
250 (421)
EN/LZT 720 0008 R1A
2001-06-26
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