9 GHz, High)
PL (NJ, LOS)
Micro Cell Model
FIGURE 3.47 Microcell path loss summary.
Path Loss Comparison
??“130
??“120
??“110
??“100
??“90
??“80
??“70
??“60
??“50
1000 10000 100000
Distance (meters)
Path Loss (dB)
Free Space
Open Area
Newark
Dhaka #2
San Francisco
Bangkok
NYC
FIGURE 3.48 Macrocell path loss summary.
3.7 SHADOWING DISCUSSION
In this section we will discuss the third mechanism used to characterize the wireless channel, namely
log-normal shadowing. Shadowing occurs when the LOS is obstructed between the BS and MS due
to either large buildings, terrain, and so on. The presence of these obstructions vary the mean of the
received signal that is highly dependent on the environment [91, 126, 127].
The change in the mean received signal can result due to variations in the building height. As we
have seen earlier in the path loss sections, diffraction from the rooftop to ground level contributes to
the path loss. So variations in the building heights will cause random variations in this diffraction loss
to the MS. These variations are also due to different rooftop constructions (triangular versus flat top)
and not to mention the occasional absence of a building (typically found in lots and intersections).
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