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A
PPENDIX
A: M
ULTIPLE
DECT
SYSTEM
5.3
Single vs. Multiple Base Station System
In this section we differentiate single (residential) and multiple (enter-
prise) base station systems. The reason is that it should be understood
that they work in similar way but that they are designed to be used for
different purposes.
Residential base stations are designed to be installed in homes and
small offices with a natural distance between each cell. Multiple base
station systems are on the other hand designed to be used and installed
in traffic intense areas which also means that they can be installed very
close to each other.
Residential base station systems are not synchronized. There is no need
for this since the density of users and/or calls are normally low in the
coverage area where these systems are supposed to be used.
Multiple base station systems have an internal intra-system synchroni-
zation, which means that all base stations are transmitting at the same
time, as well as, listening at the same synchronized time. This means
that multiple base station systems know, in contrast to residential base
stations, which slots that are free to be used and not. This enables a very
high call capacity, robustness and possibility to make intra-system hand
overs (i.e. possibility to move from one base to another with an ongoing
seamless voice conversation).
5.4 Radio
Interference
A DECT system is as described earlier, designed to work, also in busy
and/or hostile radio environments. This also applies to interference from
other DECT systems operating in the same frequency range. If interfer-
ence is found on the traffic channel, that a base station or portable
device is listening to, it will communicate to the other part (portable
device or base station) that a switch of slot or a hand over must be made.
Any interference will of course disturb and the actual package sent will
be discarded, but it will not be noticeable to the user in the speech since
the packets are very small (10 milliseconds). If it is data traffic, the sent
package will be discarded and a retransmission will be made. This
means that due to the excellent dynamic channel selection and alloca-
tion in DECT, no user will notice any disturbances in the conversation.
Interferences exist everywhere, unless the system is installed in an
isolated laboratory environment. It may be due to other DECT systems
running in the same coverage area or it may be by reflections in the own
radio environment, for example due to metal plates or walls in the area.
All DECT systems are robust to this, to a certain extent. However when
many un synchronized systems are used in environments with a high
