Study on feasibility of SATCOM for railway communication

Final Report
Conversational services
(video and audio)
Data (telemetry, C2,
Telnet, etc)
Fax BER < 10 -6
PLR < 1-3% (BER < 10 -3 )
Error-free (PLR < 0,1%, BER < 10 -8 )
Table 44: Examples of QoS requirements for tolerance to information losses
CRITERION TRACEABILITY
FRMCS URS v2.0
UNISIG SUBSET-93 v2.3.0 (6.3.3.6; 6.3.6.5)
ITU-T Recommendation G.1010: ―End-user multimedia QoS categories‖
CRT-TECH-4 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.
RATIONALE
URS document [AD-01] defines several grades of ―latency‖ according to the different applications
described. The strictest one is ―Low‖, which means ―immediate‖.
For a satcom system the transfer delay will depend on the constellation type and bandwidth (data
rate), and due to the distance from remote terminals to satellites this delay is usually greater than
in terrestrial systems.
Following values (the most stringent part derived from GSM-R [RD-15]) are considered for the
characterization of a Satcom system:
Low
Medium
High
CRITERION TRACEABILITY
Transfer delay < 0.5 s
2s < Transfer delay > 0.5 s
Transfer delay > 2 s
Table 45: Transfer delay values
FRMCS URS v2.0
UNISIG SUBSET-93 v2.3.0 (6.3.4.3): ―The end-to-end transfer delay of a user data block of 30
bytes shall be ≤0.5s (99%).‖
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.
RATIONALE
Since some of the railway critical applications are voice services, delay jitter of the satellite system
for railways shall be small because excessive jitter makes speech choppy and difficult to
understand.
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
Page 188 of 285