Study on feasibility of SATCOM for railway communication

Final Report
Criterion ID
CRT-TECH-15
Related
parameter
Flexibility
Conclusion
It refers to the configurability of the system regarding channelization modes (signal
bandwidth, SF, etc.), set of modcods available (code rates and modulations), etc.
Commercial standards like DVB-S2 and RCS2 are designed to provide high
flexibility. However, constrains from the other system elements (e.g. terminal
constrains, Satcom EIRP and G/T, etc) can limit flexibility and show differences
among these solutions using the same air interface.
CRT-TECH-16
Scalability
It refers to the spectral bandwidth availability for future extensions of the capacity
in term of users or new applications more demanding on data rate. Solutions
operating at higher frequency bands are going to provide more scalability
than these ones operating at lower bands where the spectrum resources are
more limited. In addition, commercial satellites can be more scalable since there
exist more operators offering transponders in the same bandwidth like are the case
of C, Ku and Ka band.
CRT-TECH-17
Types of
terminals
The most restrictive type of terminal in terms of size, weight and power
(SWaP) is the handheld. Only low frequency bands are able to provide all
types of terminals required by the railway domain (including handhelds).
SATCOM systems providing handhelds (e.g. Iridium, Inmarsat...) are not taking
into account the required link availability demanded by safety critical applications,
since they were conceived for commercial voice calls. Solutions enabling
handhelds are providing voice services based on Circuit Switched. High
frequency band solutions do not provide handhelds. In addition, fixed and onboard
terminals are more complex and expensive, since directional and steerable
antennas shall be used.
CRT-TECH-18
Safety
It refers to the robustness of the bearer to non-intentional RF interferences. In
principle, the majority of the solutions are providing several techniques to
counteract the impact of the RF interference or also mitigate the fading, in order
to keep high values of link availability. Example of these techniques are, ACM,
UPC, Diversity techniques, Spreading, Channel Interleavings, etc.
CRT-TECH-19
Security
Commercial SATCOM solutions generally do not provide mechanisms to
prevent intentional attacks and/or counteract intentional RF interferences
(i.e. jammings) at bearer level. However, Inmarsat BGAN provides
authentication and encryption at L2 since this service is used in the aeronautical
domain for air traffic control applications and related ones.
On the other hand, everyday more and more baseband technologies (e.g. iDirect,
Comtech, etc) are including new functionalities at L1/L2 layers of their products
oriented to offer protected waveforms, i.e. TRANSEC/COMSEC (e.g. AES-256 and
FIPS encryption algorithms, etc). However, any of these techniques is still included
in the commercial communication standards.
It is worth noting that most of the security functionalities can be implemented at IP
(L3) or upper layers, which fall out of the scope of this assessment.
Table 30: Horizontal assessment of technical and functional criteria
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
Page 131 of 285