Mobile-satellite service

Mobile-satellite service (short: MSS ;also: mobile-satellite radiocommunication service) is – according to Article 1.25 of the International Telecommunication Union´s (ITU) Radio Regulations (RR) – defined as «A radiocommunication service

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 con 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.

As of mid 2016 Iridium has experienced in-orbit failures which cannot be corrected with in-orbit spare satellites, thus only 64 of the 66 satellites required for seamless global coverage are in operation. As a result, service interruptions can be observed, especially around the equatorial region where the satellite footprints are most spread out and there is least overlap.

Additionally to the 4 active 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.

Other MSS systems currently inoperative were Ico / Pendrell, TerreStar and Ellipso.

Several governments also operate and use MSS systems, although most make extensive use of the Iridium and Inmarsat systems. Mexico is currently developing an S-band system based on its own geostationary satellites and the United Staes uses MUOS and other systems. The US Government also runs its own gateway in Hawaii for direct access to the Iridium constellation under a contract lasting at least until 2018.

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Wikipedia