« Satellite TV Communications | Home | Transformational Satellite Communications System (TSAT) »
Satellite Wireless Communications
By Editor | March 13, 2008
Satellite wireless communications are also simply known as satellite communications (which is also abbreviated as satcom). Satellite wireless communications are carried out through artificial satellites positioned in space in different kinds of orbits. There are five different kinds of orbits. These are low (non-polar and polar) Earth (LEO) orbits, medium earth orbits (MEO), highly elliptical orbits (HEO), Molniya orbits and geostationary orbits.
Geostationary communications satellites are said to have been first proposed by the science fiction writer Arthur C. Clarke. Geostationary satellites appear to be in a fixed position to an observer on earth as they revolve around the earth at a constant speed and thus they help in simplifying technology on earth as there is no need to enable the gadget on earth to revolve to track and maintain a link with the satellite. Though geostationary satellites are placed in a high orbit, the cost is balanced by the simpler equipments required on earth.
Global communications satellites form a constellation or a system of interlinked satellites. For geostationary satellites, 4 to 6 satellites are enough to cover the whole surface of the earth. For highly elliptic and medium earth orbit satellite systems, more number of satellites is used. For low earth orbit satellite constellations, about 24 would be required at least. Iridium, the global satellite company has 66 satellites in their constellation. Low earth orbiting (LEO) communications satellites are satellites at about 400 km from earth. Because of the reduced distance, the coverage that such satellites have is only about 1000 km in radius. Molniya satellites are useful for telecommunication near the poles as geostationary satellites revolve around the equator. Molniya satellites are inclined for optimum use at the poles and are primarily used for telephony and TV services over Russia.
Satellite wireless communications is most useful where it is not practical to use fibre optic submarine communication cables (cables laid in seas and oceans for communications across continents) like for use in ships, planes, vehicles, hand held gadgets, TVs and radios.
Satellite wireless communications were initially used primarily for telecommunication between countries and across continents. Telegraphs and telephones relied on satellite wireless communications till the popularity of submarine communication cables. However, satellite wireless communications still serve to connect remote islands, where submarine communication cables have not been laid down, like Saint Helena, Ascension Island and the Pacific islands. Satellite phones (which remain popular) use geostationary satellites or low earth orbit satellites to communicate.
Satellite wireless communications are also used for internet access where wireline broadband or dial-up internet connections are not possible. Ships, planes and vehicles are some of the places where satellite internet connections are used. They also help communication in remote areas like mountains and near the poles. They are also used for are used for satellite television and also for worldwide radio stations. Fixed Service Satellite (FSS) is now being replaced by Direct Broadcast Satellite (DBS) in a lot of countries for satellite television. There are the Orbital Satellite Carrying Amateur Radio (OSCAR) satellites which are meant specifically for amateur radio operators.
Topics: Satellite Communications |
July 16th, 2008 at 11:01 pm
Network 2 Computers :: Share Files, Printers & Internet…
Countries like Canada, Sweden, and South Korea have better, faster Internet connections. People in Japan can download an entire movie in just two minutes, but it can take two hours or more in the United States. Yet, people in Japan pay the same as we d…
July 19th, 2008 at 4:31 am
Countries like Canada, Sweden, and South Korea have better, faster Internet connections. People in Japan can download an entire movie in just two minutes, but it can take two hours or more in the United States. Yet, people in Japan pay the same as we do in the U. S. for their Internet connection. Not only do they have the technology for higher speeds, but a larger percentage of people in those countries have access to high speed connections. The United States has fallen to 16th place behind other…