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A vehicle model represents a 3D model of the vehicle. The vehicle model will move with
the simulated trajectory. The body center of a simulated vehicle will be in the origin pos-
ition of the model, and all trajectory movements defined in the simulation will act on the
body center. The vehicle model should be placed so that its nose points to the north.
The vehicle model will also follow any pitch/roll/yaw movements simulated, i.e. if the
vehicle model rolls by 90 degrees, half of the sky is likely to be blocked by the vehicle itself
(depending on vehicle model used).
The antenna position oftentimes is not in the same location as the vehicle body center pos-
ition. In the simulation, this can be adjusted by configuring the lever arm values (see
"Lever
arm" on page 60 ).
The antenna position can also be specified in the vehicle model file by adding a component
named
RecAnt . In the event that both lever arm, and RecAnt are set, the receiver antenna
position as set in the Vehicle model takes precedence. The vehicle model does not need a
geo-location.
If a satellite is blocked by an object from either environment or vehicle model, i.e. it is not
visible by the receiver antenna, its power will be set to OFF.
GSG can successfully handle vehicle models with up to 130 triangles. Models should be
optimized for a low polygon count. The triangle count is limited to a total of 300 for the
combined environment and vehicle models.
For additional information, see the Orolia Technical Note
Vehicle Modeling
.
Propagation Environment Models
Built-in signal propagation models can be used to simulate multipath propagation in rural,
sub- urban and urban areas. Used propagation models are specified in ITU- R Recom-
mendation M.1225, “
Guidelines for evaluation of radio transmission technologies for
IMT-2000 ” (see Section 2.1.4 Parameters of the wideband models). The document is avail-
able on the ITU website ( http://www.itu.int/rec/R-REC-M.1225/en ).
The ITU model corresponds to a tapped-delay line structure with a fixed number of taps: 3
taps in rural and sub-urban environments and 5 taps in an urban environment.
The first tap (i.e. the direct path) may be either Rice or Rayleigh fading, corresponding to
LOS and NLOS situations, respectively. The other taps are always Rayleigh fading.
The ITU model describes multipath propagation for a single satellite either in a LOS or
NLOS situation. Propagation environment model generates multipath taps for the entire
satellite constellation. Based on the satellite elevation angle, the satellites are divided into
three zones, as illustrated below:
Open Sky, Multipath Zone, Obstruction Zone
3.5 "Select" Menu
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