Study on feasibility of SATCOM for railway communication

Final Report
GEO / S-band
Criterion ID Criterion Evaluation Justification
CRT-TECH-19
The proposed satcom system shall provide high level of
security in the information exchanged.
PC
Table 58: GEO / S-band (S-MIM CS) assessment
The S-MIM standard does not provide specifics mechanisms to prevent intentional
attacks and/or RF interferences, but the spreading in the return link is beneficial
for security.
C.6.1
C.6.1.1
Additional information useful for the assessment
Delay study
Since this solution is based in a GEO satellite, the main part of the transmission delay will be the propagation delay between terminal and satellite and
vice-versa. Therefore, the following approximation is done:
Where,
T tx is the transmission time for a given packet
T rx is the reception time for a given packet
T up is the propagation delay from ground to the overhead satellite
T down is the propagation time from the satellite to the ground
Observe that within this case the formula includes also a ‖T rx ‖ (just like the previous solution including the ANTARES CS). It is due to the fact that the time
spent processing the reception of an asynchronous CDMA burst based on E-SSA cannot be considered a negligible value. An approximation is done at
this point assuming a similar value that ANTARES, where the reception process can take in mean a period of time of 1.5 times de transmission time (i.e.
T rx = 1.5*T tx ).
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
Page 253 of 285