Page 271 - Integrated Wireless Propagation Models

M i c r o c e I P r e d i c t i o n M o d e I s 249
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FIGURE 4.5.5.1.1 Typical propagation situations n urban areas (top view).

picocell environment. In these environments, the signal propagation is occurs
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mainly within street canyons, as shown in Fig. 4.5.5. . 1 . Four situations are consid­
ered for the base-to-mobile links:
1 . BS 1 propagates over the rooftop to MS1 .
2. BS 1 propagates passing rows of buildings to MS •
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3. BS propagates passing only one row of buildings to MS •
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4. BS propagates to MS • from diffracted waves.
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For mobile-to-mobile links, both ends of the link are below rooftop level, and the
models relating to BS may be used.
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4.5.5.2 LOS Condition
Under the LOS condition, the model can be applied to two types of LOS paths: the
paths BS 1 to MS and BS to MS , shown in Fig. 4.5.5 . 1 . 1 .
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The basic transmission loss from the signal propagation in the UHF range can be
characterized by two slopes and a single breakpoint.45 An approximate lower bound is
given by

(4.5.5.2.1)
for d > Rb p

where Rb is the breakpoint distance and is given by
p

R b p _ - - 4hbhm (4.5.5.2.2)
).._ -