Inmarsat is a global two-way satellite communications system that allows data transmission via satellite transmission between fixed and mobile networks anywhere in the world. Inmarsat has been available since 1992 and provides various standardized services that are offered worldwide under the same conditions.
The Inmarsat-A service is for analogvoice communication and data communication by modem. The data transmission rate is 9.6 kbit/s and can be a maximum of 64 kbit/s with special modems.
Inmarsat-Aero is for voice communication, fax communication and data communication from the aircraft and is used for communication with the cockpit. Parabolic anten nas of about 1m diameter are used for this service, which is transmitted for the mobile satellite communication channels in the L-band.
Inmarsat-A is the original analog satellite system with data transmission rates from 9.4 kbit/s to 64 kbit/s. It can be reached via the country codes 00871 to 00874. Inmarsat-A is used in the maritime sector on passenger ships, in coastal and offshore shipping, and on yachts and container ships for communications. On land, its use is useful wherever terrestrial networks are not available. The Inmarsat-A service was discontinued on December 31, 2007.
Inmarsat-B is for digital voice and data communications with transmission rates of 9.6 kbit/s, respectively 64 kbit/s for high-speed data transmission. Digital technology enables better utilization of the available frequency bands. Inmarsat-B uses O- QPSK modulation (O, offset) with Forward Error Correction( FEC) and SCPC technology, Single Channel Per Carrier.
Inmarsat-C is for digital data communication in duplex mode at up to 64 kbit/s. This service is a buffered service. Signals are buffered in the land earth station( LES) before being transmitted into an X.25 network, and are forwarded with a time delay in encrypted or coded form. The message length is limited to a maximum of 32 Kbytes. This service can be coupled with the GPS system and transmit the GPS position data into an Inmarsat-C station. In addition to this service, there is extended group calling( EGC), EGC Network Identity( ENID), multi- addressing, FleetNet as fleet information to specific groups, and polling of position messages. The C service can be used, for example, for traffic control systems, emergency call systems and alarm systems, fleet management and monitoring of technical installations. Inmarsat-C consists of 21 satellites and was introduced in 1991 specifically for communications with ships
Inmarsat-D is a paging service to mobile receivers, such as pagers. This service supports all call classes: from the tone call to the numeric and alphanumeric call to the transparent data transmission. Message transmissionin Inmarsat-D is simplex in broadcast.
Inmarsat-D+ extends the Inmarsat-D service with the possibility of acknowledgement delivery via a return channel
Inmarsat-E is used to transmit signals from sea rescue buoys in the L-band on 1.6 GHz
Inmarsat-M is for digital voice and data transmission at up to 4.8 kbit/s. The service is equivalent to the Inmarsat-A service. Due to the low data transmission rates, the voice quality is worse than that of the A service.
Inmarsat-Phone corresponds to the M service, but is suitable for small terminals using the spot beam. It is aimed equally at the maritime and non-maritime sectors. For example, press agencies also use Inmarsat to connect their globally dispersed correspondence offices with the respective headquarters and quickly deliver press releases. There are worldwide connections to other organizations. Other services are planned or in preparation.