Handbook of Propagation Effects for Vehicular and ... - Courses

5-6
Percentage of Fade Durations > Abscissa
100
9
8
7
6
5
4
3
2
10
9
8
7
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5
1
4
3
2
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
2 4 6 8 2 4 6 8 2 4 6 8
0.01 0.10 1.00 10.00
Fade Duration Distance (m)
Figure 5-3: Best fit lognormal distribution (5-1) of fade duration distances for a 5-dB
threshold. The distribution (1.5 GHz, elevation = 51°) encompasses road types which
exhibit “moderate” and “extreme” shadowing and is plotted against logarithmic scales.
5.4 Fade Duration Measurements in Central Maryland
Goldhirsh and Vogel [1989] have also compiled fade duration statistics from 1.5 GHz
measurements in central Maryland for angles of 30°, 45° and 60° for 5 dB and 10 dB
thresholds. The duration distributions (5 dB threshold) shown in Figure 5-4 exhibit a
slight elevation angle dependence. For example, the 30° fade duration is approximately
twice that for the 60° case. The increased duration distance at the smaller elevation
angles is consistent with the fact that at the lower elevation angles the line-of-sight path is
likely to be shadowed over longer distances for each tree canopy than at the higher
elevation angles.