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Concept
Mobile-satellite service
Résumé
Mobile-satellite service (MSS, or mobile-satellite radiocommunication service) is – according to Article 1.25 of the International Telecommunication Union's Radio Regulations
– "A radiocommunication service
between mobile earth stations and one or more space stations, or between space stations used by this service; or
between mobile earth stations by means of one or more space stations.
This service may also include feeder links necessary for its operation."
Most commercial voice and some data mobile satellite services are provided by systems operating in the L-band by Iridium, Inmarsat, Globalstar and Thuraya. The L-band spectrum allocated for MSS is between 1.5 and 2.5 GHz, with the upper portion often referred to as the S-band.
Constellations of low earth orbiting (LEO) satellites are used by Iridium (66 satellites) and Globalstar (48 satellites). Inmarsat and Thuraya currently use 4 (i4) and 2 geostationary satellites respectively, their L-band services are similar but not interoperable and most terminals can only use one or the other service, although some data terminals provide a mechanical switch required due to the different polarization schemes used by both systems.
Another MSS service is MSV / MSAT / LightSquared / Ligado with 2 geostationary satellites serving North America.
China has shown an upcoming S-band satellite phone which will use its recently launched Tiantong-1 geostationary satellite.
Additionally to the four active Inmarsat 4 ('I4') satellites, Inmarsat also maintains some legacy L-band services on its previous generation satellites, although they are being gradually phased out and users are invited to upgrade to i4-based services, mostly based on variations of BGAN. Inmarsat also owns and operates a new fleet of three Ka-band satellites, known as the Inmarsat 5 constellation (usually abbreviated to 'I5'), providing high speed mobile satellite data services known as Global Express.
Other MSS systems currently inoperative were Ico / Pendrell, TerreStar and Ellipso.
Source officielle
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