P31003C1020M1000276A9, 01/2018
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OpenScape Cordless IP V2, Administrator Documentation
Base stations
Base station synchronisation
The synchronisation needs a some kind synchronisation hierarchy with the following criteria:
1 There must be one single and common root source for the synchronisation in the hierarchy (sync level 1).
2 With synchronisation over LAN there are just two levels needed (LAN-Master and LAN-Slave).
3 DECT synchronisation usually needs more than two levels and just one hop, because most base stations won't
be able to receive the DECT signal from the root source of the synchronisation (sync level 1). DECT signal pro-
viding reference timer synchronisation is relayed along a chain of multiple base stations, until it finally synchro-
nises the last base station in a sync chain.
4 The number of hops along any branch of DECT synchronisation tree should be minimised, because any hop
can introduce jitter in the synchronisation timer and could so lower the quality of the synchronisation.
DECT-based synchronisation
To relay DECT synchronisation signals from base station A to base station B, base station B must be able to
receive signals from base station A in a sufficient signal quality.
A base station can synchronise with each base station on a higher sync level. The sync level concept allows base
stations to automatically select the best suitable base station to receive synchronisation signal from. Simultane-
ously, it guarantees a strictly limited number of hops a long any branch in the synchronisation tree and to prevent
circles between automatically optimised synchronisation chains.
During configuration, assign one level in the synchronisation hierarchy (sync level) to each base station. Sync level
1 is the highest level; this is the level of the sync master and appears only once in each cluster. A base station
always synchronises itself with a base station that has a better sync level. If it sees several base stations with a
better sync level, it synchronises itself with the base station that provides the best signal quality. If it does not see
any base station with a higher sync level, it cannot synchronise.
LAN-based synchronisation
If the DECT connection between base stations seems to be not reliable enough to permanently guarantee a stable
DECT over the air synchronization, e.g., because they are separated by iron doors or a firewall, you can determine
that synchronisation should take place via LAN. In this case the base station with the higher sync level will act as
LAN master, the base station with the lower sync level is a LAN slave. One base station must be explicitly be
defined as LAN master. Currently, it must be on DECT sync level 1.
Advantages of LAN synchronisation compared with DECT synchronisation:
• Higher flexibility in the arrangement of the base stations as no synchronisation chains need to be formed.
• Fewer base stations required as the overlapping area of the base stations is smaller. The overlapping area for
handset handover can be smaller, because neighboured base stations do not need to receive each other in
stable error free quality, but they must still be able to detect each other for the process of dynamic channel
selection.
• Configuration of the system is simplified as all base stations can be synchronised on one synchronization
master.
DECT manager and base stations must be connected to the same Ethernet or virtual
LAN sharing a common broadcast domain.
