Prediction
of the Mobile Radio Channel for Satellite Transmitters
|
|
Transmitters
in ProMan must not be terrestrial. Also satellite transmitters can be
considered. Geostationary satellites are defined by their height (e.g.
36,000 km) and their longitude. All LEOs and navigation satellites are
described either by the Two Line Element method or for the GPS
satellites by the data provided in the Almanac. Antenna
gains for the satellite transmitters are considered in the path loss
predictions.
The
satellite radio transmission to the mobile terminal is strongly
affected by the variation of the received signal power because of the
presence of fading phenomena (slow fading due to obstacles and fast
fading due to multipath propagation). Multipath propagation arises from
signal reflection and diffraction on obstacles. In satellite
communications, the received signal is usually the superposition of two
components: a main path and a summation of time-delayed scattered
paths. The occurence of these fading phenomena can be predicted with
ProMan by using specific wave propagation models depending on the
environment.
|
___
|
|
|
|
Wave
Propagation Model for Wide Areas
|
|
For
wide areas (corresponding to thousands of km^2) the empirical
prediction model according to DLR is used. This model provides
realistic and representative characterisations of the land mobile
satellite (LMS) radio channel based on the evaluation of measurement
data without taking into account a specific transmitter-receiver
configuration. The prediction of the channel impulse response depends
on the elevation of the satellite and the land usage (clutter) at the
receiver location.
The
following clutter types are supported:
-
urban
-
sub-urban
-
rural
-
open
|
|
Satellite LOS
Prediction based on clutter map
|
|
The
wideband channel model uses three submodels describing the different
parts of the impulse response depending on the echo delay: direct path,
near echos and far echos. The impulse response of the satellite
wideband channel is then superposed by a sum of all echos.
ProMan
needs topographical and clutter databases to work with
the DLR model.
|
|
|
Wave
Propagation Model for Urban Areas
|
|
The
mobile radio channel in urban environments is characterized by
multipath propagation. Dominant propagation mechanisms in these
scenarios are reflection, diffraction and shadowing by discrete
obstacles. With an ray optical approach it is possible to consider
these effects in a wave propagation model. The urban ray-optical
propagation model (IRT) included in ProMan is used for the prediction of
ProMan
needs building (and
optionally topographical)
databases to work with the ray-optical prediction model (IRT).
|
|
Satellite received
power in Munich
|
|
|
Modelling
of the Satellite to Indoor Channel
|
|
The
satellite to indoor propagation channel is becoming of significant
importance (especially in L and S bands) as future satellite mobile
communication, broadcast and navigation systems (as e.g. S-DMB and
Galileo) are aiming at optimum performance in all kind of environments,
i.e. even in indoor scenarios. The indoor scenarios are of special
relevance for the attractiveness of new MSS services in order to
provide ubiquitous coverage over all environments.
Of course also the penetration into buildings can be computed with
ProMan. To see the influence of the walls (and their materials) inside
the building and the neighboring buildings, the ray-optical propagation
models are used for the prediction of
As
basis for the computation ProMan needs an indoor database (including the
outdoor walls of the neighboring buildings) which will be used as input
for the ray-optical prediction model.
|
|
|
Examples
|
|
Here
are some sample predicitons presented. Please click on the pictures to
enlarge them.
|
|
Predicted channel profile for satellite
transmitter
|
Predicted channel profile (relative delays)
for
hybrid terrestrial & satellite network
in an urban scenario
|
|
