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

3-28
Percentage of the Time Fade > 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
Model
EERS
MERS
EFM
CEFM
0 2 4 6 8 10 12 14 16 18
Fade Depth (dB)
Figure 3-25: Comparison of various models at 60° elevation with EERS (solid) at
1.5 GHz.
3.7.3 Combined Empirical Fading Model (CEFM)
The Combined EFM (CEFM) model extends the above high elevation angle results with
those contained in the ERS model. It is described by Parks et al. [1993a] and Butt et al.
[1995] and is given as follows:
with
A ( P,
θ , f ) = −M
ln( P)
+ N , (3-26)
M = −0.
002θ
2
+ 0.
15θ
+
N = −0.
33θ
+ 1.
5 f +
27.
2
0.
2
f
+
0.
7
, (3-27)
and where the units are the same as described previously. This formulation may be
applied in the angular range 20° to 80°, over the frequency interval from 1.3 GHz to
3 GHz, and percentage range from 1% to 20%. Here again, the constants in M are the
negative of those presented by Parks et al. [1993a; 1993b] because a negative sign
precedes M in (3-26). The CEFM distributions are shown plotted at L-Band (1.5 GHz) in
Figure 3-26 (dashed curves) and are compared with the EERS model (solid curves) at
30°, 45°, and 60°. Agreement at the three angles is generally within 1 dB.
In order to obtain a handle on the behavior of the distributions at the higher
elevation angles (above 60 ° ), we show plotted the distributions for the MERS and CEFM
models in Figure 3-27 at 70 ° and 80 ° . The MERS model at the higher elevation angles is