Study on feasibility of SATCOM for railway communication

Final Report
GEO / L-band + ANTARES CS (IRIS FOC)
Criterion ID Criterion Evaluation Justification
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)
This solution is based on a pure random multiple access scheme providing low
data rate in the return link. This low data rate makes the transmission time (Tx) not
negligible in front of the delay due to the use of a GEO satellite (of around 250
ms).
In addition, the reception process of asynchronous bursts sent requires an
iterative processing that is usually greater than the transmission time (it can be
estimated as a 1.5 times the Tx [RD-23]).
All these issues make the transfer delay in this system near the 500 ms.
CRT-TECH-4b 4b: Double-hop required NC
CRT-TECH-5
Delay jitter of the proposed satcom system shall be Low.
Note: Since this criterion refers to the one-way satellite channel
jitter, it shall be measured from satellite transmitter to satellite
receiver.
C (Low)
Taking into account that a single-hop is close the 500 ms., the double-hop will be
close 1 second.
There exist mechanisms to compensate the delay time variations between packets
at IP level. Therefore, it is assumed that IP-based satcom solutions are capable to
comply with a Low delay jitter requirement.
In this case (GEO satcom solution), and considering that the lower the orbit the
lower the jitter, this criterion is market as a "C (Low)".
CRT-TECH-6
Network registration delay for the proposed satcom system
shall be Normal (with similar values of current GSM-R system).
C
The registration process of the GEO/L-band based on ANTARES CS system can
be designed in order to assure a "normal" value. In fact, and taking into account
the pure random access method on return link, the network registration could be
considered quick.
CRT-TECH-7
The call establishment delay for the proposed satcom system
shall be Low.
Note: as a first reference, GSM-R establishment delays can be
considered.
C (High)
ANTARES does not require a call establishment since it is based on a pure
random access multiple access. It means that voice data packets are sent when
they are available without asking for resources.
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
Page 240 of 285