Base Station Synchronisation - Gigaset N870 IP PRO Installation, Configuration And Operation

Base stations

Base station synchronisation

Synchronisation and the logical structuring of the base stations in clusters are prerequisites for
the functioning of the multicell system, intercell handover, and (over)load balancing. Overload
balancing means that a handset can roam to a free base, when current base is fully loaded and
cannot accept further handset connections.
Base stations can be synchronised "over the air", meaning that they are synchronised via DECT.
If the DECT connection between specific base stations seems to be not reliable enough, synchro-
nisation can also take place via LAN. To carry out the synchronisation you will need the plan of
the clusters with the synchronisation level for each base station.
Synchronisation always refers to a cluster. In case you set up several clusters that are
not synchronised with one another, there will be no possibility of a handover or
(over)load balancing between them.
Synchronisation for handover between base stations in clusters managed by
different DECT managers can be configured via DECT manager administration
( page 34).
For detailed information on DECT network planning, please refer to the "N870 IP PRO - Site Plan-
ning and Measurement Guide".
A base station shows its synchronisation status with an LED (
Synchronisation planning
Base stations that combine to form a DECT wireless network must synchronise with one another
to ensure a smooth transition of the handsets from cell to cell (handover). No handover and no
(overload) balancing is possible between cells that are not synchronised. In the event of loss of
synchronisation, the base station stops accepting calls once all ongoing calls that were being
conducted on the asynchronous base station have ended and then it re-synchronises the asyn-
chronous base station.
The synchronisation within a cluster takes place in a master/slave procedure. This means that
one base station (sync master) defines the synchronisation cycle for one or more additional base
stations (sync slaves).
The synchronisation needs some kind of 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 synchroni-
sation (sync level 1). DECT signal providing reference timer synchronisation is relayed along
a chain of multiple base stations, until it finally synchronises 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.
42
page 34).