International Mobile Satellite Organization

Inmarsat plc is an international telecommunications company founded in 1979, originally as an intergovernmental organization. It operates a fleet of eleven (as of 2005) geosynchronous telecommunications satellites. The company is publicly traded on the London Stock Exchange (LSE: ISAT) as of June 2005. It is a constituent of the FTSE 250 Index.

Inmarsat provides telephony and data services to users world-wide, via special digital radios called "terminals". An Inmarsat terminal contacts the satellite and communicates to a ground station through the satellite. It provides reliable communications services to a range of governments, aid agencies, media outlets and businesses needing to communicate in remote regions or where there is no reliable terrestrial network.

Services include traditional voice calls, low-level data tracking systems, and high-speed data services as well as distress and safety services. The most recent of these provides GPRS-type services at up to 492 kbit/s via the BGAN IP satellite modem the size of a notebook computer. Other services provide mobile ISDN services used by the media for live reporting on world events via videophone.

Historically expensive, calls via Inmarsat have now dropped to a level where they are comparable, and in many cases favorable, to international roaming costs, or hotel phone calls.

Newer services using IP technology feature an always-on capability where the users are simply charged for the amount of data they send and receive rather than the length of time they are online. Voice call charges are the same wherever in the world the service is used.

The satellites are digital transponders that receive digital signals, reform the pulses, and then retransmit them to ground stations. The ground stations perform billing and act as gateways to the public switched telephone network and Internet.

Inmarsat's most recent series of satellites were launched in June and November 2005. These were the largest commercial telecomunications satellites ever launched. Each satellite is equipped with a global beam, 19 regional spot beams, and 228 narrow spot beams.

Coverage

There are 3 types of coverage related to each Inmarsat satellite.

Global beam coverage. Each satellite is equipped with a single global beam that covers up to one-third of the Earth's surface, apart from the poles. In general, global beam coverage extends from latitudes of −78 to +78 degrees regardless of longitude.

Wide spot beam coverage. It relates to the overlap of the wide spot beams (a set of narrower beams creating a coverage pattern). Wide spot beam coverage is optimised for covering most areas of interest to Inmarsat's customers and is thus somewhat limited in comparison to global beam coverage. This coverage was introduced with the I-3 satellites. Each I-4 satellite provides 19 wide spot beams.

Narrow spot beam coverage. It relates to the overlap of the narrow spot beams (a set of very narrow beams creating a coverage pattern). Narrow spot beam coverage is designed to form the backbone of Inmarsat's future broadband services, including the Broadband Global Area Network (BGAN). This coverage is introduced with the I-4 satellites. Each I-4 satellite provides 228 narrow spot beams.

Satellites

At the present most of the Inmarsat satellites handling the normal traffic are of the I-3 (3d) generation but transition to the I-4 generation is on the way (starting with IOR).

Inmarsat-4 satellites

Inmarsat-4F1 / Coverage: IOR / 63 degrees East longitude / Launched with Atlas on 11 March 2005.
Inmarsat-4 F2 / Coverage: AOR-West / 53 degrees West Longitude / Launched 8 November 2005 14:07 GMT.

Inmarsat-3 satellites

Inmarsat-3F1 / Coverage: IOR / 64 degrees East longitude / Launched with Atlas Centaur IIA on 3 April 1996.
Inmarsat-3F2 / Coverage: AOR-E / 15 degrees West longitude / Launched with Proton D-1-E on 6 September 1996.
Inmarsat-3F3 / Coverage: POR / 179 degrees East longitude / Launched with Atlas Centaur IIA on 17 December 1996.
Inmarsat-3F4 / Coverage: AOR-W / 141 degrees West longitude / Launched with Ariane 4 (V97) on 3 June 1997.
Inmarsat-3F5 / Spare (IOR-W) / 25 degrees East longitude / Launched with Ariane 4 (V105) on 4 February 1998.

Inmarsat-2 satellites

Inmarsat-2F1
Inmarsat-2F2
Inmarsat-2F3
Inmarsat-2F4

Country codes

The telephone country codes for calling Inmarsat destinations are:

870 SNAC (Single Network Access Code)
871 Atlantic Ocean Region – East (AOR-E)
872 Pacific Ocean Region (POR)
873 Indian Ocean Region (IOR)
874 Atlantic Ocean Region – West (AOR-W)

The 870 SNAC number is actually a locator service so that you don't have to know to which satellite the destination Inmarsat terminal is logged in. SNAC however doesn't support calls to Inmarsat-A terminals.

The other four country codes correspond to the areas which Inmarsat satellites cover (normally one satellite per area). These areas are commonly called "Ocean Regions".

Networks

Inmarsat has gradually developed a series of networks providing certain sets of services (most networks support multiple services). Some of these networks are:

Inmarsat-A: provides voice services, telex services, medium speed fax/data services and, optionaly, high speed data services at 56 or 64 kbit/s. This is the only analog network of Inmarsat and is scheduled for phase-out by 31 December 2007. The rest of the Networks are digital and no phase-out date is currently available. The Inmarsat-A service on IOR has been moved to a backup satellite at 109 degrees East longitude due to the use of the new Inmarsat-4 satellite for the primary IOR coverage. The Inmarsat-A service on AOR-West has been moved to a backup satellite at 98 degrees West longitude due to the use of the new Inmarsat-4 satellite for the primary AOR-West coverage.

Inmarsat-Aero: provides voice/fax/data services for aircraft. Three levels of terminals, Aero-L (Low Gain Antenna) primarily for packet data including ACARS and ADS, Aero-H (High Gain Antenna) for medium quality voice and fax/data at up to 9600 bit/s, and Aero-I (Intermediate Gain Antenna) for low quality voice and fax/data at up to 2400 bit/s. Note, there are also aircraft rated versions of Std-C and mini-M/M4. The Swift-64 system is the M4 (64 kbit/s per channel) terminal for aircraft.

Inmarsat-B: provides voice services, telex services, medium speed fax/data services at 9.6 kbit/s and high speed data services at 56, 64 or 128 kbit/s. There is also a 'leased' mode for Inmarsat-B available on the spare Inmarsat satellites.

Inmarsat-C: effectively this is a "satellite telex" terminal with store-and-forward, polling etc capabilities. Certain models of Inmarsat-C terminals are also approved for usage in the GMDSS system, equipped with GPS.

Inmarsat-M: provides voice services at 4.8 kbit/s and medium speed fax/data services at 2.4 kbit/s. It paved the way towards Inmarsat-Mini-M.

Inmarsat-Mini-M: provides voice services at 4.8 kbit/s and medium speed fax/data services at 2.4 kbit/s. Uses Inmarsat's zonal ray technology

Inmarsat-M4: provides a selection of low speed services like voice at 4.8 kbit/s, fax & data at 2.4 kbit/s, ISDN like services at 64 kbit/s (called Mobile ISDN) and shared-channel IP packet-switched data services at 64 kbit/s (called Mobile Packet Data Service MPDS, formerly Inmarsat Packet Data Service – IPDS). This network is also known as GAN (Global Area Network).

Inmarsat-Fleet: actually a family of networks that includes the Inmarsat-Fleet77, Inmarsat-Fleet55 and Inmarsat-Fleet33 members. Much like the Inmarsat-M4, it provides a selection of low speed services like voice at 4.8 kbit/s, fax/data at 2.4 kbit/s, medium speed services like fax/data at 9.6 kbit/s, ISDN like services at 64 kbit/s (called Mobile ISDN) and shared-channel IP packet-switched data services at 64 kbit/s (called Mobile Packet Data Service MPDS). However, not all these services are available with all members of the family. The latest service to be supported is Mobile ISDN at 128 kbit/s on Inmarsat-Fleet77 terminals.

Inmarsat-D/D+: Inmarsat's version of a pager, although much larger than terrestrial versions. Some units are equipped with GPS. The original Inmarsat-D terminals were one-way (to mobile) pagers. The newer Inmarsat-D+ terminals are the equivalent of a two-way pager. The main use of this technology nowadays is in tracking trucks and buoys and SCADA applications. Inmarsat D+ is the only GPS tracking service available via Inmarsat. Competing systems such as from Skybitz only operate on the MSAT geostationary satellite over [North America].

Inmarsat-E: A global maritime distress alerting service using small emergency position indicating beacons that automatically send message to maritime Rescue Coordination Centres. This service is schedule to end in 2006. Inmarsat is offering users a replacement 406 MHz EPIRB.

Inmarsat-RBGAN: RBGAN (Regional BGAN) offers a shared-channel IP packet-switched service of up to 144 kbit/s based on MPDS technology. Coverage is limited to parts of Europe, Asia, Africa & Australia. The new Inmarsat-4 satellite for the Indian Ocean Region (IOR) has taken over RBGAN service from the Thuraya satellite. The new Inmarsat-4 satellite for AOR-West now provides service to South America and the Western edges of Europe and Africa, however no service is offered to North or Central America. Inmarsat have announced the closure of the RBGAN service on December 31, 2008.

Inmarsat-BGAN: Broadband Global Area Network (BGAN) benefits from the new I-4 satellites to offer a shared-channel IP packet-switched service of up to 492 kbit/s (uplink and downlink speeds may differ and depend on terminal model) and a streaming-IP service from 32 up to 256 kbit/s (services depend on terminal model). Certain terminals also offer circuit-switched Mobile ISDN services at 64 kbit/s and even low speed (4.8 kbit/s) voice etc services. BGAN service is available on the IOR satellite and AOR-West satellite, with POR service planned for 2007.

External links

Official site