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

3-30
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
3.7.4 ITU-R Fade Model at Elevation Angles above 60°
The ITU-R has recommended that for elevation angles greater than 60°, the ERS model
be linearly interpolated with the fade values listed in Table 3-2 (at 80°) and plotted in
Figure 3-28 for the frequencies of 1.6 GHz or 2.6 GHz at the indicated percentages [ITU-
R, 1994]. The tabulated values in the right two columns of Table 3-2 were derived from
measurements described by Smith et al. [1993]. We have extended this methodology
below to apply to the formulation (3-1) employing the following steps:
1. Apply equation (3-1) at the frequency of 1.6 GHz and 2.6 GHz at an elevation angle
of 60° (values in the second and third columns).
2. Linearly interpolate between the fade calculated for an angle of 60° and the fade for
an elevation angle of 80° provided in Table 3-2 (second and fourth columns) at
1.6 GHz.
3. Linearly interpolate between the value calculated for an angle of 60° and the fade
values for an elevation angle of 80° provided in Table 3-2 at 2.6 GHz (third and fifth
columns) only for percentages of 15% and smaller.
4. Linearly interpolate between the values in the fourth and fifth columns in Table 3-2
and a value of zero at 90° to arrive at fade levels at elevation angles between 80 ° and
90 ° .
The above methodology is self-consistent at 1.5 GHz for percentages between 1% and
30% in that the 60° elevation fade values derived from the EERS model are larger than
the respective tabulated 80° fade values at the same percentages. On the other hand, this
is not the case at 2.6 GHz for percentages of 20% and larger (see columns three and five
of Table 3-2 showing values with *). It is therefore suggested that at 2.6 GHz the above
methodology be used at percentages of 15% and smaller as stated in Step 3 above. In
Figure 3-29 is shown plotted the L-Band (1.5 GHz) fade exceeded versus elevation angle
showing linear interpolation of fades between angles 60° and 90°.
Table 3-2: Fades exceeded at elevations of 60° and 80°.
Percentage, P
EERS Fade (dB) at
Elevation = 60°
Fade (dB) at
Elevation = 80°
f = 1.6 GHz f = 2.6 GHz f = 1.6 GHz f = 2.6 GHz
1 8.2 11.0 4.1 9.0
5 4.8 6.5 2.0 5.2
10 3.4 4.5 1.5 3.8
15 2.6 3.4 1.4 3.2
20 1.9 2.6* 1.3 2.8*
30 1.4 1.8* 1.2 2.5*