User's Manual

The redundancy options can be combined with each other.
3.5.1 Redundant main control channel (MCCH)
By redundant main control channels (MCCH) the operation of a base station is guaran-
teed even if the carrier with the MCCH drops out or should be disturbed.
If the carrier that provided the main control channel last drops out, an alternative carrier
will take on this task. The MCCH is thus transferred. This will maximally be repeated as
often as the number of carriers that are available at the base station. In this case, the
replacement carriers for the MCCH keep on sending on their original frequency, not on
the frequency of the failed carrier. This frequency change is useful especially when inter-
fering carriers affect the MCCH frequency that was being used up to that point.
Irrespective of the number of carriers, each radio cell has only one MCCH, via which the
mobile stations receive information, e.g. on adjacent radio cells. As a rule, the first
channel of the first carrier of a base station is used as the MCCH, the three remaining
channels of that carrier and all the channels of all the other carriers are used as voice
channels or the Packet Data service. Redundant MCCH are enabled by default and apply
to all the base stations with more than one carrier.
3.5.2
Transceiver redundancy
To increase the system stability of carriers or to ensure the Base Station Function (BSF),
as many as two redundant transceivers can be used in one base station. If one trans-
ceiver fails, these spare transceivers ensure the radio coverage with the frequency of the
failed transceiver. Transceiver redundancy is mostly used in cases, in which only a few
frequencies are available.
3.5.3
Controller redundancy
The controller required for operating a base station can be designed redundantly. In this
case, two BSCUs (Base Station Controller Units) are used, whereby one BSCU is in
operation and the other is kept ready for operation (standby). In case of a failure of the
active BSCU or its ethernet connection, the standby BSCU is automatically switched to
active and takes over its function. This ensures continued operation of the base station.
3.5.4
Fallback operation
The radio coverage of base stations is also ensured if the base station loses the connec-
tion to an IP Node (IPN) with Switching Controller Function (SCF). In this case, the base
station changes to fallback operation. In fallback operation, the base station in its radio
cell still maintains the Base Station Function (BSF). Even in fallback operation, authenti-
cation and authorization validation are ensured since the corresponding subscriber data
are stored in the base station.
Product description
Redundancy options> Fallback operation
DIB-R5 advanced
61Operation Manual 90DIBR5advancedOM02 - 1.0