Study on feasibility of SATCOM for railway communication

Final Report
Table 8: Satellite constellation main types and features
Other constellation type not mentioned in the above table is HEO (Highly Elliptical Orbit). This specific
satellite constellation is ideal for fixed and mobile applications within high latitudes of Northern and
Southern Hemisphere including both Polar Regions. The only problem is that the user terminal needs
reliable antenna tracking systems and numerous Gateway Earth Stations (GES). The essential
employment possibility of this orbit is to be in hybrid constellation with GEO or Medium Earth Orbit
(MEO) satellite systems to provide worldwide coverage.
SATELLITE BEAMS
All satellites generate beams, which focuses microwaves signals onto the specified portions of the
earth‘s surface to most effectively use the limited power of their transponders. These focused signals
create unique beam patterns called ―footprints.‖ The most typical footprints types are:
Global beam footprint,
Mobile (or regional) beam footprint or
Spot beams
Satellites do not always support perfectly spherical coverage areas. Therefore, shaped spot beams let
the operator concentrate coverage and power where required. In addition, movable antennas also let
the satellite operator provide more support (traffic) to a region on demand.
An example of typical SATCOM architecture is shown in the next figure:
Forward Link
Return Link
Terrestrial Link
SATELLITE SYSTEM
SPACE
SEGMENT
Traffic
Control
Centre
GROUND
SEGMENT
USER
SEGMENT
Train
Stations
WAN
GES/NCC
GAP FILLERS
RBCs
Figure 11: Satcom baseline system architecture (railway oriented)
Above figure identifies the main components of each one of the segments (i.e. user, ground and
space) and their relationships through the satellite communication payload.
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
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