User guide

TD 92422GB
18 February 2010 / Ver. E
System Planning
Ascom IP-DECT System
31
Appendix A: Multiple DECT Systems
This section describes issues and recommendations about installations of multiple DECT
systems and how the interference between them affect the available capacity in the radio
environment.
To enable the best possible performance it is important to know that there are base station
planning issues that must be considered. The issues are not of high concern for planning
and commissioning in a normal home or office environment, however when there is a mix
of multiple resedential and/or enterprise DECT systems it should be understood that the
shared radio capacity available will be decreased in relation to the number of systems that
are installed within the same coverage area.
This section will give an overview explanation to the technical issues concerning
installation of multiple DECT systems in one area.
A.1 DECT
The DECT standard provides 12 slots on 10 carriers in each direction, see figure 15 on
page 31. A carrier uses 2 MHz each and the TDMA frame is 10 ms, these providing 120
available channels in each direction.
Figure 15. System with three on-going traffic or data calls.
A.2 Continuous Base Station Broadcast (Dummy Bearer)
A base station (or repeater) continuously transmits one or two, depending on
implementation, so called dummy bearer when idle (i.e. when no calls or data are
transmitted to or from the base station). The reason for continuously transmitting the