Installation manual

IP DECT Installation Page 22
15-601085 Issue 04f (11 June 2009)IP Office
2.1 Base Station Synchronization
To allow call handover when a caller moves from the coverage area of one base station to another, the base stations
need to exchange synchronization signals. They do this using wireless signalling between the base stations. This therefore
requires the base station coverage areas to overlap.
For one IP base station to synchronize to another IP Base Station, the signal strength cannot drop below –70 dBm. You
must consider this requirement during the site survey.
Within the IP DECT configuration, all base stations in the same physical area with overlapping coverage are configured
with the same 'cluster' number. During system start-up, these base stations exchange synchronization signals with others
in the same cluster until all base stations are synchronized.
If a base station loses the synchronization signal it will not accept new calls until it is able to synchronize again. If the
unsynchronized base station already has active calls, it will delay up to a maximum of 3 minutes before it tries to
synchronize again.
An IP DECT installation is more reliable if each base station can receive the synchronization signals from more than one
other base station in the same cluster. Clusters without multiple synchronization paths can cause problems if a single
base station loses the synchronization signal from its neighbour or needs to be switched off or restarted during
maintenance.
Unreliable Installation
With this layout, the loss of synchronization
signal causes the loss of the base station.
None of the base stations have backup
redundant signalling to other base stations.
Potentially this may cause loss of
synchronization within the whole cluster.
Reliable Installation
With this layout, each base station has
multiple synchronization signal paths to
other base stations in the cluster. The
interruption of any signal path does not
cause loss of synchronization within the
cluster.
Sometimes IP Base Stations do not or cannot be synchronized, for example if they are in different buildings. These base
stations should be configured into separate clusters. This is reasonable so long as users are aware that handover of calls
will not be possible when they move between areas covered by different clusters.