Page 348 - Integrated Wireless Propagation Models

326 C h a p t e r F i v e

Rx
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L w 3
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L w 2
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...
L w 1
Tx

i
FIGURE 5.5.1.1 Building n put for COST 231 mode . l
is the loss per floor. Some recommended values are L = 1 . 9 dB (900 MHz), 3.4 dB
w
(1800 MHz) for light walls, 6.9 dB (1800 MHz) for heavy walls, L = 14.8 dB (900 MHz),
1
18.3 dB (1800 MHz), and b = 0.46. L is empirical derived constant and can be adjusted for
c
each different environment.
The COST 231 model is the most sophisticated empirical model. All walls intersect­
ing the direct ray between transmitter and receiver are considered and for each wall,
individual material properties are taken into account, as shown in Fig. 5.5. . 1 .
1
o
The predictions f COST 231 models are often too pessimistic. Therefore, an exten­
sion was added to modify the model: with an increasing number of penetrated walls,
the individual attenuations (due to the material properties) of the walls are decreased.
With this modification, the COST 231 model achieves good results with very fast com­
putation times.

(
5.5.2 IT - R 1238 E mpirical)
U
The ITU-R 1238 is an empirical model that is used for indoor path-loss prediction47
assuming that the base station and portable are located inside the same building. The
indoor base station to mobile/portable radio path loss can be estimated with either site­
general or site-specific models. The models described in this section are considered to
be site general, as they require little path or site information. The model accounts for the
loss through multiple floors to allow frequency reuse between floors. The model also
can estimate the loss for transmission through walls and over and through obstacles
within a single floor of a building.
The basic model has the following linear form:

L total = 20 log10 f + N log10 d + L (n) - 28 dB (5.5.2.1)
1
where N = distance power loss coefficient,
f= frequency (MHz),
d = separation distance (m) between the base station and portable,
L = floor penetration loss factor (dB), and
1
n = number of floors between base and portable.