Study on feasibility of SATCOM for railway communication

Final Report
Handovers
Given that the MEO architecture implies satellites movement from the Earth point of
view, and the railway scenario implies mobile terminals, too, the number of possible
types of handover to take into account increases:
- Beam handover (intra-satellite HO)
- In a multi-beam satellite network, beam handover occurs when the
terminal moves from a beam area to another. Beam handover can
be used, for example, for load balancing or service quality purposes.
- Beam handover is essentially a transponder change and typically
entails both forward and return links.
- Satellite handover (Inter-satellite HO)
- In a satellite constellation where there are more than one satellite
providing coverage, satellite handovers occur when a terminal
moves from a current beam to another one that belongs to a
different satellite. A satellite handover always entails a beam
handover.
- GES handover
- A satellite constellation may include more than one ground station
(GES), even when using ISL. And in this case, when a beam
handover occurs, the new beam could be associated with a different
ground station than the current one. Therefore, a GES handover
need also to be considered.
- In the same way that previous situations, a GES handover always
entails a beam handover.
- Intersystem handover (vertical handover)
- Considering that a whole communication architecture does not
consist only of a satellite system, but also by a terrestrial system (as
it occurs in the architectures presented in this document), a vertical
handover between systems shall also be considered.
Table 16: MEO architecture main design aspects to be considered
6.2.5 O3b (MEO Ka-band)
6.2.5.1 System Overview
Currently there is a MEO/Ka-band system providing broadband service. It is the O3b system, which
despite it is not able to provide service to the whole European area, it is analysed within this study in
order to analyse key features and performances of a system with these characteristics. Subsequently,
conclusions will be derived to a similar solution providing coverage to the whole European area.
6.2.5.2 System architecture
The O3b system offers broadband services with a MEO constellation of 12 satellites in Ka-band. Since
the O3b constellation has been design to use only one Equatorial orbit 8000 km above the sea level, it
provides continuous service to all parts of the Earth within 45 degrees of the Equator (see Figure 22).
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
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