Spectracom GSG-5 series, User Manual With Scpi Manual

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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 available 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 con
stellation. Based on the satellite elevation angle, the satellites are divided into three zones, as
illustrated below:
Open Sky, Multipath Zone, Obstruction Zone
Figure 3-17:
ITU multipath propagation model
Satellites above the Open Sky limit are not affected by multipath propagation.
Satellites in the Multipath Zone (elevation angle between Obstruction Limit and Open Sky Limit)
are considered LOS signals, but affected by multipath propagation. The ITU model for LOS situ
ation is used for these satellites.
For satellites in the Obstruction Zone (elevation angle below Obstruction Limit), the direct signal
path may be obstructed, e.g., by a building. This is modelled by giving a probability for an
NLOS situation. With the given probability, the simulator classifies satellites as NLOS and takes
the ITU model for the NLOS situation into use. The NLOS situation changes only when a satellite
leaves the Obstruction Zone.
Note that, in addition to the two elevation limits mentioned above, the Elevation mask setting
applies to the simulation as normally.
3.5 "Select" Menu
CHAPTER
3
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User Manual GSG-5/6 Series Rev. 26
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