Study on feasibility of SATCOM for railway communication

Final Report
C.8 SATCOM SOLUTION 8: GEO / X-BAND
GEO / X-band
Criterion ID Criterion Evaluation Justification
CRT-TECH-1
The “link availability” of the proposed satcom system shall be
High.
NC
High link availability required for safety critical applications is very difficult to obtain
in GEO / X-band satcom solutions, taking into account that this frequency band is
higher than S and C bands. In this case, elements required to achieve the high link
availability will suppose impossible elements to deploy, such as BUC power or
antenna size.
CRT-TECH-2 The “reliability” of the proposed satcom system shall be High. C (High)
For future "opened" solutions in X-band, it can be assumed that both space and
ground segments can be designed with redundancy in order to achieve the
required reliability.
CRT-TECH-3
The end-to-end error ratio of the proposed satcom system
shall be Low.
Note: Since this criterion only considers the satellite system,
the error ratio shall be measured after the last satellite
communication
C
This GEO/X-band solution relies on DVB-S2X/RCS2 standards, which provides
mechanisms to guarantee high level of service continuity defining, among others,
FEC codes and ARQ mechanisms. Therefore, this solution is able to provide a low
end-to-end error ratio.
CRT-TECH-4a
Transfer delay for the proposed satellite system shall be Low.
Note: It refers to the end-to-end (one-way) delay due to the
satellite channel. Therefore, it shall be measured from satellite
transmitter to satellite receiver.
4a: Single-hop required
C (Low)
A GEO satcom solution minimum transfer delay is limited by the distance between
terminal and satellite, which is around 250 ms.
The X-band assuming DVB-S2/DVB-RCS2+M communication standards can
assure a minimum data rate to a satcom system capable to make the data
transmission (quasi) negligible in front of the 250 ms due to the GEO satellite.
CRT-TECH-4b 4b: Double-hop required NC
The double hop transfer delay for a GEO solution is not compliant with railway
requirements with independence of the frequency band used, since only
considering the propagation delay to a GEO satellite is around 500 ms.
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
Page 260 of 285