Study on feasibility of SATCOM for railway communication

Final Report
their physical layer to the so demanding railway channel or their interface with new elements because
of the multi-technology. For instance, the physical channel could require the addition of special
techniques in order to counteract main impairments due to the railway channel (such as the fast
fadings caused by catenaries and power arches or the Doppler effect due to the high speed). And
regarding multi-technology, if for example the IMS (IP Multimedia Subsystem) is used to control data
flow policies and their QoS (Quality of Service) regardless of the transport network, specific signalling
with the elements involved in the IMS platform should be implemented.
3) On what geographical part of the European railway network could a satcom solution be used
successfully?
The complete set of SATCOM solutions assessed provides coverage to the pan-European region,
since solutions not compliant with this requirement have been discarded in advance (such as the O3b
solution).
However, depending on the final SATCOM solution selected, not all the areas will be covered with the
same quality, due mainly to the satellite elevation angle. In this sense, if the SATCOM solution is
based on a geostationary (GEO) constellation, northern European areas will have lower satellite
elevation angles than southern parts of Europe. It means that northern countries will have a degraded
service regarding southern ones.
On the contrary, solutions using Low or Medium Earth Orbits (i.e. LEO or MEO) do not have this
constraint, since satellites are continuously in movement and one new satellite appears when the
current being used has reduced its elevation angle to the minimum required by design.
Other important aspect to be considered when talking about geography is the distribution of users,
since for a SATCOM solution is not only relevant the total number of users to be served, but also how
they are located. This is because, SATCOM, unlike terrestrial systems, do not require a specific
deployment per each new line. This positive aspect of SATCOM solutions implies that the same
system deployed and operative have to absorb new users when new lines are created or implemented
with ERTMS. A clear example is a system with more than one satellite (such as LEO or MEO
constellations), where the total capacity of the system is the capacity of a satellite multiplied by the
number of satellites. But if all users are located in an area covered by only one satellite at one specific
time interval, the system could not be able to absorb the total demand even though the complete
system had enough capacity for that number of users (if they were located uniformly along the area
covered by the system). Therefore, studies and simulations about traffic demand and its distribution
are required in order to avoid service disruptions.
4) What are the conditions to create and implement suitable solutions?
In order to successfully deploy a SATCOM solution as part of the multi-technology railway
architecture, several aspects have to be considered, such as the regulatory framework, railway
certifications, the use of communication standards, geographical constraints and some other technical
implications as a result of introducing SATCOM technologies into the railway field and in a multitechnology
architecture. It is even of relevance to consider the SATCOM market interest to offer
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
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