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This
empirical model is a combination of the models from J.
Walfisch and F. Ikegami. It was further developed by the
COST 231 project. It is now called Empirical
COST-Walfisch-Ikegami Model.
The model considers the buildings in the vertical plane
between the transmitter and the receiver. The accuracy
of this empirical model is quite high because in urban
environments especially the propagation over the
rooftops (multiple diffractions) is the most dominant
part. If the scanario is analyzed individually for each
receiver pixel (parameters of building data are
determined depending on the actual buildings between Tx
and Rx) the accuracy is high - only wave guiding effects
due to multiple reflections are not considered.
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Propagation situation with COST 231 Walfisch
Ikegami. Click
here
to enlarge the figure.
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The main
parameters of the model are:
-
Frequency
f (800...2000 MHz)
-
Height of
the transmitter hTX (4...50 m)
-
Height of
the receiver hRX (1...3 m)
-
Distance
d between transmitter and receiver (20...5000 m)
Parameters
depending on the buildings in the vertical plane between
transmitter and receiver:
-
Mean
value of building heights hROOF
-
Mean
value of widths of streets w
-
Mean
value of building separation b
The
orientation of the road with respect to the Tx-Rx line
is not considered in the WinProp implementation, because
the orientation of the road cannot be determined for all
pixels (e.g. in courtyards, on crossings,...) .
In WinProp, the above mentioned building-.dependant
parameters are determined for each receiver location
individually based on the actual buildings between Tx
and Rx. If the parameters (mean building height, mean
street width, ...) are determined only once for the
whole database, all prediction pixels assume the same
scenario (which leads to reduced accuracy). |
