„Entwicklung von Mess-und Berechnungsverfahren zur ... - BMU

Seite 9 von 187 des Abschlussberichtes "Entwicklung geeigneter Mess- und Berechnungsverfahren"
(but no traffic) was present during the measurement. This procedure will overestimate the
maximal exposure if the station is in normal operation with traffic. A correct extrapolation is
possible, if the extrapolation is performed on basis of the P-CPICH channel. The CPICH
exposure can be measured only with code selective equipment. This procedure is regarded to
be the most promising for standardised exposure measurements around UMTS stations.
For documentation of the measurements a report has to be drawn up. The report have to be at
least in this form, that the results are clear and easily understood for the customer. For experts
all technical and administrative information has to be provided, that the measurements, the
raw results and the post processing is comprehensible. A uncertainty budget has to be established,
which takes into account equipment based an method based uncertainties. It is argued
that the uncertainty is NOT added to the measurement results.
All results of the here presented investigations are summarised in a proposal for a cellular
base station specific measurement standard.
Calculation methods for the determination of the public exposure due to electromagnetic
fields in the vicinity of cellular base stations can roughly be divided into field-theoretical, rayoptical,
free space based propagation and hybrid methods.
As such software packages contain often more than 10 men years of development work only
commercial software was used for this study concluding all above defined groups.
The cellular radio antenna is that element from the point of a base stations that determines the
distribution of the nuisance. In this context the downtilt angle influences the radiation pattern
in direction of the main loop and the side loops rapidly. It has to be stressed out, that the
downtilt angle represents no fixed but in the context of network optimisation mutable parameter
(more and more remote controlled). As a simulation should result in a long-lasting prediction
and not represent a snap-shot of the nuisance distribution it is reasonable to change the
antenna radiation pattern in that way, that the operating status over all submitted downtilt
angles is considered within one single radiation pattern.
In addition the directional radio pattern is dependent on frequency. As this parameter is often
changed in the context of the frequency-plan it is also reasonable to adjust the radiation
pattern in that way, that this dependency is considered.
Furthermore the installation vicinity of the cellular base station antenna provokes a change of
the radiation pattern. To simplify the modelling of the scenario and therefore neglect the
installation vicinity is also in that way considered as a new radiation pattern is synthesized.
The synthesized antenna radiation pattern represents as a conclusion the dependency of
downtilt angle, frequency and influence of the installation vicinity. In this context its reasonable
to use simulation software that is capable to import such antenna radiation patterns.
To model the three dimensional environment of a cellular base station geographic information
as the outlines of buildings is needed. This information is mainly contained in the landed
property register of the register authority of district towns or independent cities. In addition
the data for this outlines of buildings can be generated out of satellite pictures. A great