Satellite Phones

A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites. Depending on the architecture of a particular system, coverage may include the entire Earth, or only specific regions.

The mobile equipment, also known as a terminal, varies widely. Early satellite phone handsets had a size and weight comparable to that of a late 1980s or early 1990s mobile phone, but usually with a large retractable antenna. More recent satellite phones are similar in size to a regular mobile phone while some prototype satellite phones have no distinguishable difference from an ordinary smartphones. Satphones are popular on expeditions into remote areas where terrestrial cellular service is unavailable. A fixed installation, such as used shipboard, may include large, rugged, rack-mounted electronics, and a steerable microwave antenna on the mast that automatically tracks the overhead satellites. Satellite phones have notoriously poor reception indoors, though it may be possible to get a consistent signal near a window or in the top floor of a building if the roof is sufficiently thin. The phones have connectors for external antennas that are often installed in vehicles and buildings. Some systems also allow for the use of repeaters, much like terrestrial mobile phone systems.

Satellite phones are usually issued with numbers in a special country calling code. For example, Inmarsat satellite phones are issued with codes +870 through +874, while Iridium satellite phones are issued with codes +881 6 and +881 7. Some satellite phones are issued with ordinary phone numbers, such as Globalstar satellite phones issued with U.S. telephone numbers.

In some countries ruled by oppressive regimes such as Burma and Bangladesh possession of a satellite phone can be illegal as their signals will usually bypass local telecoms systems hindering censorship and wiretapping

LEO telephones utilizes LEO (low Earth orbit) satellite technology. The advantages include providing worldwide wireless coverage with no gaps. LEO satellites orbit the earth at high speed, low altitude orbits with an orbital time of 70–90 minutes, an altitude of 640 to 1120 kilometres (400 to 700 miles), and provide coverage cells. Since the satellites are not geosynchronous, they must fly complete orbits and thus further guarantee complete coverage over every area by at least one satellite at all times.

Two such systems, both based in the United States started up in the late 1990s but soon went into bankruptcy after they failed to gain the number of subscribers required to fund the large satellite launch costs. They are now operated by new owners who bought the assets for a fraction of their original cost and are now both planning to launch replacement constellations supporting higher bandwidth. Data speeds for current networks are between 2200 bit/s and 9600 bit/s using a satellite handset.

* Globalstar - A network covering most of the world's landmass using 44 active satellites however many areas are left without coverage due to the fact that a satellite must be in range of an earth station. Satellites fly in an inclined orbit of 52 degrees and therefore polar regions are not covered either. The network went into limited commercial service at the end of 1999.

* Iridium - A network operating 66 satellites in a polar orbit that claims coverage everywhere on the earth's surface. Commercial service started in November 1998 and went into bankruptcy soon after. Notably radio cross-links are used between satellites in order to relay data to the nearest satellite with a connection to an earth station.

Globalstar offers high quality, low-cost satellite voice and data services to commercial and recreational users from virtually anywhere in more than 120 countries around the world.

Globalstar, which was established in 1991 and began commercial service in late 1999, currently offers service from virtually anywhere across over 120 countries, as well as from most territorial waters and several mid-ocean regions. Signals from a Globalstar phone or modem are received by the company's constellation of Low Earth Orbiting (LEO) satellites and relayed to ground-based gateways, which then pass the call on to the terrestrial telephone network.

As a result, Globalstar is able to provide a variety of telephone services to users who live, work, and travel in areas far beyond the reach of cellular networks. In addition to normal voice communications, these services* include:

These services are supported by a growing range of products and accessories designed to make Globalstar service productive and easy-to-use in almost any situation or environment, including aviation and maritime applications. The company's data modem products can also be used for asset tracking and environmental telemetry applications.

Looking ahead, Globalstar intends to continue expanding its operations to provide service in the few remaining land areas not covered today, as well as across mid-ocean regions. Products and accessories will also continue to be developed and upgraded to make the service even more useful.

Globalstar phones look and act like mobile or fixed phones with which you're familiar. The difference is that they can operate virtually anywhere, carrying your call / data over an exceptionally clear, secure Code Division Multiple Access (CDMA) satellite signal.

Globalstar Satellite Constellation

Like "bent-pipes", or mirrors in the sky, the Globalstar constellation of 40 Low Earth Orbiting (LEO) satellites picks up signals from over 80% of the Earth's surface, everywhere outside the extreme polar regions and some mid-ocean regions. Several satellites pick up a call, and this "path diversity" assures that the call does not get dropped even if a phone moves out of sight of one of the satellites.

As soon as a second satellite picks up the signal and is able to contact the same terrestrial gateway, it begins to simultaneously transmit. If buildings or terrain block your phone signal, this "soft-handoff" prevents call interruption. The second satellite now maintains transmission of the original signal to the terrestrial "gateway".

Additional advantages of using Low Earth Orbiting (LEO) satellites within the Globalstar system include no perceptible voice delay and lighter / smaller all-in-one phones.

Gateways process calls, then distribute them to existing fixed and cellular local networks. Terrestrial gateways are an important part of Globalstar's strategy to keep key technology and equipment easily accessible and to integrate our services as closely as possible with existing local telephony networks. This makes the Globalstar system and its services simple to manage, expand and improve.

Iridium satellite phone company profile

Based in Bethesda, Maryland, U.S.A., Iridium Satellite LLC, a privately held company, is the only provider of truly global satellite voice and data communications solutions with complete coverage of the entire Earth including oceans, airways and even Polar Regions. Iridium delivers reliable, secure, real-time, mission-critical communications services to and from areas where landlines and terrestrial-based wireless services are either unavailable or unreliable.

Iridium's constellation consists of 66 low-earth orbiting (LEO), cross-linked satellites operating as a fully meshed network and supported by multiple in-orbit spares. It is the largest commercial satellite constellation in the world.

The Iridium service is ideally suited for industries such as maritime, aviation, government/military, emergency/humanitarian services, mining, forestry, oil and gas, heavy equipment, transportation and utilities. For example, tens of thousands of aircraft are currently equipped with Iridium-based systems and nearly half of the traffic on the Iridium network comes from international waters. Iridium provides service to subscribers from the U.S. Department of Defense (DoD), as well as other civil and government agencies around the world. The company also designs, builds and sells its products, solutions and services through a worldwide network of more than 150 partners.

Iridium manages several operations centers including those in Tempe, Arizona and Leesburg, Virginia, U.S.A. In addition, through its own gateway in Hawaii, the U.S. DoD relies on Iridium for global communications capabilities.

The company supplies both voice and data connections. Voice services are provided via dedicated handsets, or through a variety of installed communications systems onboard ships, aircraft and land-based vehicles. Increasingly incorporated into hundreds of applications, Iridium's 9601 short burst data (SBD) transceiver provides packet data connections to every corner of the Earth, transferring location information, weather reports, email, or any other data requiring a reliable, global, two-way connection. At a current annual growth rate of 137 percent, Iridium's most rapidly expanding business segment is the machine-to-machine sector, in which the Iridium constellation provides mobile data links for asset tracking and other monitoring applications.

Iridium is a profitable company and has been since 2004. Business is growing at an impressive rate with the constant acquisition of new customers and partners both domestically and abroad in some of the furthest reaches of the planet. These individuals recognize the value of a system that is global, secure and guaranteed to work.

Iridium is also planning for the future sustainability of its constellation, making major investments in network enhancements and launching the Iridium NEXT initiative, its next generation satellite constellation, which will be fully operational by 2016.

The 9505A is the ideal communications option for people who work in or travel to remote locations. Take it with you on your next trip.

Handheld satellite phone that works anywhere in the world. Larger than a typical mobile phone, but still small enough to carry in a backpack. Very simple to use. Uses a familiar GSM dialing sequence. For outdoor use only.

How it Works

The Iridium system is a satellite-based, wireless personal communications network providing a robust suite of voice and data features all over the globe. It is comprised of three principal components -- the satellite network, the ground network and the Iridium subscriber products, including phones and data modems.

The design of the Iridium network allows voice and data messages to be routed anywhere in the world. Voice and data calls are relayed from one satellite to another until they reach the satellite above the Iridium handset or terminal and the signal is relayed back to Earth. When an Iridium customer places a call from a handset or terminal, it connects to whatever satellite happens to be overhead, and is relayed among satellites around the globe to whatever satellite is above the appropriate Earth gateway, which downlinks the call and transfers it to the global public voice network or Internet so that it reaches the recipient.

The satellites are in a near-polar orbit at an altitude of 485 miles (780 km). The 66 active satellites fly in formation in six orbital planes, evenly spaced around the planet, each with 11 satellites equally spaced apart from each other in that orbital plane.

A single satellite completely circles the Earth once every 100 minutes, traveling at a rate of 16,832 miles per hour, and traveling from horizon to horizon across the sky in about ten minutes. As a satellite moves out of reach, the call is seamlessly handed over to the next satellite coming into view.

Since Iridium is a LEO satellite system, voice delays are typically unnoticeable. Other mobile satellite systems use Geostationary Earth Orbits (GEOs), which, by comparison, are about 22,300 miles above the equator. As a result, latency can be quite high, causing speakers to have to wait for each other to finish. GEOs are also largely ineffective in more northern or southern latitudes. The curvature of the Earth disrupts message transmission when attempted at the edge of a GEO satellite's footprint.

Each Iridium satellite is cross-linked to four other satellites - two satellites in the same orbital plane and two in an adjacent plane. These links create a dynamic network in space - calls are routed among Iridium satellites without touching the ground, creating a highly secure and reliable connection. Cross-links make Iridium particularly impervious to natural disasters - such as hurricanes, tsunamis and earthquakes - that can damage ground-based wireless towers since cross-links are space-based.

The Iridium ground network is comprised of the system control segment and telephony gateways used to connect into the terrestrial telephone system. With centralized management of the Iridium network, the system control segment supplies global operational support and control services for the satellite constellation, delivers satellite tracking data to the gateways, and controls the termination of Iridium messaging services.

The system control segment consists of three primary components -- four telemetry tracking and command/control (TTAC) stations, the operational support network, and the satellite network operation center (SNOC). Ku-Band feeder links and cross-links throughout the satellite constellation supply the connections among the system control segment, the satellites and the gateways.

Gateways are the ground-based antennas and electronics that provide voice and data services, messaging, prepaid and postpaid billing services, as well as other customer services. The gateways are responsible for the support and management of mobile subscribers and the interconnection of the Iridium network to the terrestrial phone system. Gateways also provide management functions for their own network elements and links.