Study on feasibility of SATCOM for railway communication
SRAIL-FNR-010-IND%20-%20FinalReport_v1.1_20170216
SRAIL-FNR-010-IND%20-%20FinalReport_v1.1_20170216
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Final Report<br />
northern part <strong>of</strong> Europe would have low satellite elevati<strong>on</strong> angles that would make this soluti<strong>on</strong><br />
unfeasible 17 .<br />
- Off-axis. An important factor to keep in mind when designing a mobile <strong>SATCOM</strong> soluti<strong>on</strong> (i.e. with<br />
low pr<strong>of</strong>ile antennas) if the <strong>of</strong>f-axis compliance, which refers to the power density radiated in any<br />
directi<strong>on</strong> from a certain angle (usually from 2.5º). This parameter refers directly to the antenna<br />
design, and the maximum <strong>of</strong>f-axis value is regulated by ITU. To fulfil with such regulati<strong>on</strong>s<br />
adequate measures shall be implemented in order to be homologated by the satellite operator.<br />
Most <strong>of</strong> times, it is fixed by spreading the signal using more robust modcod (lower modulati<strong>on</strong><br />
and/or coding rate) or using a spreading sequence to reduce the power spectral density.<br />
- Vertical handovers (in a multi-technology envir<strong>on</strong>ment) 18 . FRMCS (Future Railway Mobile<br />
Communicati<strong>on</strong>s System) will c<strong>on</strong>sist <strong>of</strong> several communicati<strong>on</strong>s systems, just like NGN (Next<br />
Generati<strong>on</strong> Networks) trends show. One <strong>of</strong> these systems could be a <strong>SATCOM</strong> soluti<strong>on</strong>, used<br />
especially <strong>for</strong> some c<strong>on</strong>crete scenarios or as a backup or complementary system (<strong>for</strong> example).<br />
But regardless <strong>of</strong> whether <strong>SATCOM</strong> is used or not, the capacity to per<strong>for</strong>m vertical handovers (i.e.<br />
handovers between communicati<strong>on</strong>s systems) is required in the FRMCS in order to switch to other<br />
communicati<strong>on</strong> technology when necessary. A smart router could be in charge <strong>of</strong> per<strong>for</strong>ming<br />
these handovers, since it is an intelligent element capable to m<strong>on</strong>itor all the networks enabled and<br />
per<strong>for</strong>m the switch am<strong>on</strong>g them when required.<br />
- Railway certificati<strong>on</strong> <strong>for</strong> <strong>SATCOM</strong> equipments. Since all <strong>on</strong>-board <strong>railway</strong> equipment shall be<br />
certified according to <strong>railway</strong> standards and rules established, <strong>SATCOM</strong> equipment shall also be<br />
certified according to <strong>railway</strong>s normative (e.g. EN50155, etc).<br />
17<br />
HEO c<strong>on</strong>stellati<strong>on</strong>s can become in a good soluti<strong>on</strong> <strong>for</strong> these more northern areas (i.e. near polar area) as <strong>for</strong> example Molnya and<br />
Tundra.<br />
18<br />
Despite vertical handovers have been c<strong>on</strong>sidered in multi-technology criteria, they have not been evaluated because it applies to<br />
final architecture design and operati<strong>on</strong>al c<strong>on</strong>diti<strong>on</strong>s.<br />
Doc.Nº: SRAIL-FNR-010-IND<br />
Edit./Rev.: 1/1<br />
Date: 16/02/2017<br />
Page 169 <strong>of</strong> 285
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