Satellite communication
Satellite communication is bidirectional telecommunication between two ground stations via a satellite . Similar to cellular radio, it runs from a transmitter to the receiver and back, with the diameter of the transmitting / receiving antennas currently between around 75 cm and up to 32 meters.
Services such as satellite broadcasting (television and radio) or military and espionage communication also run via satellites. But satellite communication is primarily understood to mean individual communication via communication satellites .
For control tasks , each satellite also communicates with a control station on the ground.
Technology and areas of application
With mobile satellite communication, a connection to a mostly geostationary communications satellite is established via a satellite telephone .
The advantage of satellite communication over terrestrial networks is that it can simultaneously use the connection from, for example, the Canary Islands to the Chinese border under a single satellite footprint and thus reach geographically widely distributed network nodes and users of voice, data and video. On the other hand, the connection prices are higher than for terrestrial mobile radio systems or the fixed network . The antennas must also be aligned with the satellite, which is possible wherever there is a theoretical line of sight to the satellite.
A corresponding mobile satellite telephone is accommodated in a housing the size of a somewhat larger normal mobile phone or a laptop . It not only enables phone calls, but all other types of data transmission such as fax , e-mail or the Internet .
Stationary satellite systems are almost mobile today and are called VSAT (Very Small Aperture Terminals) . The advantage of the stationary 75 cm VSATs, for example, lies in the very high transmission bandwidth of several Mbit / s, which enables very fast Internet access from almost any point on earth and at moderate prices.
providers
There are currently several commercial operators of satellite communication networks :
- The Orbcomm network consists of 30 satellites in low orbit and 13 earth stations distributed around the world and is the cheapest satellite communication system for small amounts of data.
- The Iridium network has 66 satellites and is the most widely used mobile - cellphone-like - satellite communication network in the world.
- Thuraya covers140 countrieswith three satellites and 2/3 of the earth's population. Reception is possible in Europe , North, East and Central Africa , Asia , the Middle East , Oceania and Australia.
- Globalstar works with 40 satellites at an altitude of 1230 km, while parts of Africa , Asia , Oceania and the world's oceansremainunsupervised.
- Inmarsat operates eleven active satellites in geostationary orbit and offers various services worldwide (with the exception of the polar regions).
- Satlynx , a global operator of satellite communications networks for broadband Internet, intranet and connections with leased line characteristics. See also SES Managed Services . A SES Global Services company with subsidiaries ASTRA (Europe), SES AMERICOM (North America) and New Skies Satellites (Africa, South America, the Middle East and parts of Asia). Directly or through strategic partnerships with the satellite operators AsiaSat, SES SIRIUS, QuetzSat, Ciel and Star One, over 95% of the world's population can be reached through satellite broadcasts from a single source and can communicate without terrestrial connections.
- atrexx , one of the leading providers of two-way internet satellites with several hundred VSAT systems in Europe, Africa, Asia, Latin America and the Middle East. In addition to classic Internet access, atrexx also plans, implements and delivers complex satellite connections for Voice over IP (VoIP) and wireless access ( WiMAX ) or virtual private networks (VPN). Other focal points are company networks via satellite at home and abroad.
- MEDIA-BROADCAST GmbH , worldwide service provision by geostationary satellites. The Teleport Usingen (near Frankfurt) serves as a gatewayto provide access to a large number of satellites, whereby an almost global coverage for iLink satellite connections can be provided.
- ND SatCom , a leading global provider of satellite-based broadband VSAT systems, network solutions for television and radio broadcasting, government and military communications, and ground stations.
Other options
But there are also several amateur radio satellites that offer the possibilities for amateur radio services to communicate. Both data transmission and voice transmission are possible. During various space missions, for example the ISS, astronauts with an amateur radio license could be reached on board their spaceship.
History of the Satellite Phones
As early as the late 1970s , satellites were used for communication over long distances. However, the transmitting and receiving systems of these systems were stationary. The International Maritime Satellite Organization ( Inmarsat ) provided a system for mobile devices from 1982 onwards, which was mainly used in maritime shipping . The first devices for mobile land use were available from 1989 .
In the late 1980s, Canada was the first country to take advantage of satellite telephones to supply large, sparsely populated areas with telecommunications, without having to provide complex, ground-based infrastructure . At the same time, a comparable system was started in the USA. The satellites used were in geostationary positions ( GEO ).
From 1985 Motorola developed the Iridium communication system , whose satellites orbit the earth from pole to pole.
By shifting the geostationary position of the satellites to lower orbits (MEO, LEO - see also orbit description ), the distance between the satellite and the end device could be significantly reduced and the necessary transmission power in the end device could be reduced. Only this generation of devices was able to measure its weight and size with the mobile phones that have now become established .
