Study on feasibility of SATCOM for railway communication

Final Report
Inmarsat 5 (Global Xpress)
Criterion ID Criterion Evaluation Justification
CRT-TECH-17
CRT-TECH-18
CRT-TECH-19
The proposed satcom system shall allow the use of the
following types of terminals: “On-board (mobile)”, “Handheld”
and “Fixed”.
The proposed satcom system shall provide high level of safety
in the information exchanged.
The proposed satcom system shall provide high level of
security in the information exchanged.
C.11.1 Additional information useful for the assessment
C.11.1.1 Delay study
PC
C (High)
NC
Table 63: Inmarsat 5 assessment
High frequency bands such as Ka do not make possible the use of handhelds.
In addition, fixed and on-board terminals shall use directive antennas, making
them more complex (and expensive) than low frequency band terminals.
Global Xpress is based on DVB-S2/RCS2 standards, which can provide
techniques for safety purposes, such as diversity, enhanced FECs, fast signal
acquisition… Therefore, GX can make use of these mechanisms to provide the
level of safety required.
Commercial standards such as DVB-D2/RCS2 are not implementing specific
functionalities to counteract intentional interferences effects on the L1 and L2.
Taking into account the high data rates achievable by GX and the GEO constellation, the main part of the transmission delay will be the propagation
delay between terminal and satellite and vice-versa. In fact it is an example very similar to the one performed for the GEO / Ku-band satcom solution.
Therefore, and following the same approximation:
Where,
T tx is the transmission time for a given packet
T up is the propagation delay from ground to the overhead satellite
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
Page 281 of 285