Synchronization
18
Synchronization
The purpose of the "Synchronization" function is to synchronize an
RBS internally. The function is needed to achieve air timeslot
synchronization, according to /GSM:05.10/ and /JTC PCS:7/.
The transition between different states and functions can be seen in the
figure below.
Start up
Free running clock
Establishing
sync state
Hold-over time expired
Sync established
Reference source
is usable
Reference source
is not usable
Synchronized
state
Reference
source
Synchronizing to the
reference source
Supervision of
reference source
Locking to
reference
source
Hold-over
state
Hold-over operation
Supervision of
reference source
01_0277B
Figure 32
Synchronization function states
Short-term stability of the timing is achieved by the RBS itself. The
long-term stability of the RBS will rely on an external or an optional
synchronization reference.
The external synchronization reference is taken from the transport
network interface. The optional synchronization reference is taken from
an optional synchronization function in the RBS.
The two possible sources for synchronization are handled in the same
way by the synchronization function.
The choice of reference source depends on the type of equipment
installed. Units equipped with an optional reference source will always
use this option.
EN/LZT 123 2697
R5A
1998-08-13
125 (306)
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