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

3-16
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
model. We note that the EERS model maintains its median characteristic, although the
variability about the median is large. The low angle distributions are shown to vary
considerably because of the reasons enumerated in Section 3.3.2, with the high
probability fades caused by terrain blockage and multiple trees along the Earth-satellite
path.
Percentage of Distance Fade > Abscissa
100
9
8
7
6
5
4
3
2
10
9
8
7
6
5
1
4
3
2
Extended ERS
0 5 10 15 20 25 30 35 40 45 50 55
Fade (dB)
Figure 3-14: K-band (20 GHz) distributions (elevation = 8°) derived from ACTS
measurements in Alaska. The solid red curve is the EERS model distribution.
3.4.6 K-Band Measurements in Central Maryland
In Figure 3-15 are shown several plots which validate elements of the EERS model. The
solid curve to the left (with circled points) represents the measured distribution derived
from ACTS 20 GHz measurements in March 1994 for Route 108 (traveling south-west)
for the case in which the deciduous trees were without leaves. For this case, the satellite
was on the left and the Earth-satellite path frequently cut the line of roadside trees at or
near orthogonal angles. Shown also (green solid line) is the distribution derived by
applying the foliage adjustment formulation described in the next section. This adjusted
distribution thus represents a predictor of the full foliage case. Also shown is the EERS