Reference Manual

Synchronization
Description
The timing difference between different carriers within a cell shall be
less than 1/4 bit in the air (920 ns). To fulfil this requirement the
following delays must be compensated for:
•
the distribution delay on the external synchronization bus
•
the transmitter chain delay (delays in transmitter, combiner, feeder
and antenna)
The BSC/OSS operator defines one RBS in the RBS cluster to master
and the others to slave(s). For each slave the OMT operator also
calculates and defines a TF compensation value. The TF compensation
value is forwarded to the slave(s) at TF configuration.
The operator uses the following formula to calculate the TF
compensation value, TF
cv
, for each slave:
TF
cv
= master t
txd
– slave t
txd
–t
esb
t
esb
is the distribution delay on the external synchronization bus between
the master and the slave. There can be different delays for each slave.
Elements that affect this delay are cable length(s), cable type, cabinet
type and the RBS-cluster topology.
t
txd
is the transmitter chain delay (delays in transmitter, combiner, feeder
and antenna). There can be different delays for each RBS.
A positive value on the TF
cv
indicates that the internal timing bus is
delayed relative to the ESB. A negative value indicates that the internal
timing bus is advanced relative to the ESB.
The RBS also adopts the frame number from the ESB and distributes it
on the internal timing bus. The function terminates when TF mode is
changed from Slave.
EN/LZT 720 0008 P2A
2001-11-28
317 (485)
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Preliminary