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

Attenuation Due to Roadside Trees: Mobile Case 3-27
3.7.2 Empirical Fading Model (EFM)
This model was derived from measurements made by the Centre for Satellite Engineering
at the University of Surrey, UK. It is based on simultaneous measurements at L, S, and
Ku bands at the higher elevation angles from 60° to 80° [Butt et al., 1993; 1995]. This
model also has a form similar to the ERS model (3-3) and is given by
with
A ( P,
θ , f ) = −M
ln( P)
+ N
(3-24)
M = −0.
029θ
+ 0.
182 f
N = −0.
129θ
+ 1.
483 f +
+
6.
315
21.
374
(3-25)
and where A( P, θ , f ) is the attenuation (in dB) at the percentage P (in %) valid from 1%
to 20%, θ is the elevation angle (in degrees) applicable from 60° to 80°, and the
frequency f (in GHz) may be applied in the range 1.3 GHz to 10.4 GHz. The
multiplying constants on the right hand side of M in (3-25) are the negative of those
presented by Butt et al. [1993, 1995] because M in (3-24) is preceded by a negative sign
to maintain consistency with the EERS model. (Their multiplying coefficient was
positive). Figure 3-25 shows a comparison of the above model distribution at 60°
elevation with those corresponding to the EERS, MERS, and CEFM (to be described
shortly). It is interesting to note that the other three models cluster about one another,
whereas the EFM model deviates considerably from the grouping; especially at
percentages smaller than 5%.