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

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3.7.5 Comparative Summary of Model Limits
Propagation Effects for Vehicular and Personal Mobile Satellite Systems
In Table 3-3 is given a comparative summary of the above competing models and their
domains of validity. The EERS model covers a wider range of percentages than the other
models (1% to 80%) and includes angles as low as 7°. The other models are limited to
20° elevation. It also covers the greatest range of frequencies (e.g., 0.87 to 20 GHz). The
EERS model limitation vis-à-vis the other models is that it does not include elevation
angles greater than 60°. The ITU-R model extends the EERS model from 60° to 90° at
1.6 GHz and 2.6 GHz. The EFM, CEFM, and MERS models include elevation angles up
to 80°.
Table 3-3: Summary of empirical models and their domains of validity.
Model Name
Percentage
Range (%)
Elevation Angle
Range (deg)
Frequency Range
(GHz)
EERS 1-80 7-60 0.87-20
ERS 1-20 20-60 0.87-3
Reference
Goldhirsh and Vogel
[1995a], ITU-R [1997]
Goldhirsh and Vogel
[1992], ITU-R [1994]
ITU-R 1-30 60-90 1.6-2.6 ITU-R [1997]
EFM 1-20 60-80 1.3-10.4 Parks et al. [1993a]
MERS 1-30 20-80 1.5-2.6 Sforza et al. [1993a]
CEFM 1-20 20-80 1.5-2.6 Butt et al. [1995]
3.8 Conclusions and Model Recommendations
The following is recommended:
1. In the elevation angle interval between 20° to 60°, the EERS model should be
executed as outlined in Section 3.3.2 using the step by step approach in Section 3.3.3.
The ITU-R angle extension procedure from 60° to 90° may be used at 1.6 GHz and
2.6 GHz as outlined in Section 3.7.4. The MERS model (Equation (3-21) and Figure
3-24) and the CEFM model (Equation (3-26) and Figure 3-26) show relatively small
differences with the EERS model in the angular range 20° to 60°.
2. For elevation angles between 7° and 20° the EERS model should continue to be
employed in the absence of any direct measurements. The model provides a median
of measured distributions at the smaller angles, but the deviation from the measured
levels may be significantly larger than 5 dB at equal probability levels because of
terrain blockage and multiple canopy tree-shadowing. Where direct measurements
exist, these should be substituted for the model.