User guide

TD 92422GB

18 February 2010 / Ver. E

System Planning

Ascom IP-DECT System

7 Synchronization

7.1 Air Synchronization

This section is a brief description about the air synchronization procedure.

IP-DECT base stations use the DECT air interface to synchronize to each other. The DECT

signals have to be able to travel in the air between the base stations. This means that the

placement of the base stations has to be planned to fullfill this requirement.

For an individual IPBS it is not needed to configure which IPBS to synchronize to. It is

needed to manually select one or several IPBS as synchronization master candidate. The

Pari Master assignes one of these IPBS as an active sync master. The remaining candidates

will act as sync slaves and can be new sync masters in case the active sync master will fail/

break. When using one sync region it is recommended to configure at least two base

stations in the middle of the building as synchronization masters.

All IPBSs in sync slave mode sends its list over received sync candidates to the Pari Master.

The Pari Master informs the IPBS sync slaves which sync candidate it shall synchronize to.

For redundancy, install the base stations so that there are always two alternative sync

routes to a base station.

If both IPBL and IPBS are present in the same system, the IPBS receives its synchronization

over the air from the RFPs, which are connected to the IPBL. In this case the IPBL is the

synch master and all IPBSs in the system must be in slave mode and in sync region 0 to be

able to receive synchronization signal over the air from the RFPs.

If there are many other disturbing DECT systems there can be problems with the

synchronization. For more information, see

Appendix A: Multiple DECT Systems on page

31.

7.2 Considerations for Air Synchronization at a Multiple Building Site

When there is an installation consisting of separated areas for instance two buildings there

are some things to consider. First it has to be determined if there should be both roaming

and handover between the buildings or only roaming.

7.2.1 In systems where handover is required between buildings

If both roaming and handover is to be used between the separated areas, these areas

must have the same Pari Master. It must be sufficient coverage between the areas with

concern for both speech and air synchronization coverage. It might require outdoor

mounting of IPBS and in some cases non-standard antennas.

When there is good coverage between buildings

In case of good coverage between buildings all base stations in the buildings can be

configured to belong to the same synchronization region. It is desirable to have more than

one synchronization path between the Air Sync Master and the area without Air Sync

Master. If creating a bottle neck, major areas may be affected by failure of a single IPBS.

When there is poor coverage between buildings

In figure 4 below there is an example of an installation with three separate buildings

where the synchronization coverage between buildings is not good enough for a stable

synchronization. A solution may be to use separate synchronization regions for the

buildings and have reference synchronization between the regions.