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

5-8
Percentage of Fade Durations > Abscissa
100
9
8
7
6
5
4
3
2
10
9
8
7
6
5
1
4
3
2
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
Elevation Angle
40°
60°
80°
2 4 6 8 2 4 6 8
0.01 0.10 1.00
Fade Duration Distance (m)
Figure 5-5: Fade duration distributions at 1.3 GHz derived from measurements of Sforza
and Buonomo [1993] in North Yorkshire, U.K. for a “wooded” environment.
5.6 Summary of Fade Duration Results
In Figure 5-6 are shown the above described duration distributions given in Figure 5-3
through Figure 5-5. In Table 5-3 are summarized the 50% and 10% probability values of
the durations for the various curves. It is noted in Figure 5-6 that the Central Maryland
fade durations at 30°, 45° and 60° are in close proximity to the ITU-R model results
derived from the Australian database at 51°. The roadside tree conditions for these
databases were, in general, similar. On the other hand, the duration results from England
give significantly smaller fade durations. These results suggest that the canopy
dimensions, tree heights and foliage densities were also significantly different. The
median and 10% time durations may be determined by dividing the values in Table 5-3
by the appropriate vehicle speed. For example, the ITU-R model gives median and ten
percentile time durations of 8.8 ms and 41.6 ms, respectively, assuming a vehicle speed
of 25 m/s (approximately 55 miles/h).