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

5-4
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
P ( FD > dd,
A > Aq
) = P(
FD > dd | A > Aq
) P(
A > Aq
) , (5-2)
where P(A > Aq) is the is the absolute probability that the fade exceeds the threshold Aq.
Cumulative fade distributions P(A > Aq) are described in Figure 5-2 for road-types whose
degrees of shadowing are classified as “extreme” and “moderate.” These distributions
are described by the “best fit” exponential
P( A > Aq
) = u exp( −vAq
) , (5-3)
where P is the percentage of the distance driven over which the fade Aq (in dB) is
exceeded. The parameters u and v are tabulated in Table 5-1 along with the RMS
deviations of the measured distributions relative to the best fit curves. Also plotted in
Figure 5-2 is the EERS model that shows general agreement with the “moderate”
distribution to within approximately 2 dB over the indicated percentage range.
Percentage of Distance Fade > Abscissa
100
9
8
7
6
5
4
3
2
10
9
8
7
6
5
1
4
3
2
EERS Model
Moderate
Extreme
2 3 4 5 6 7 8 9 10 11 12 13 14 15
Fade Depth (dB)
Figure 5-2: Best fit exponential fade distributions of the form (5-3) derived from
measurements in south-eastern Australia along road types classified as “moderate” and
“extreme.” Measurements were made at L-Band (1.5 GHz) at an elevation of 51°. Also
shown is the EERS model distribution.