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How do satellite phones work?

– Satellite phone or telephone are type of mobile phones that work based on their connection to the satellites that orbit the earth rather than connecting to the cell sites situated on the surface of the earth.
– In short, these phones are called as satphones.
– The functionality and services provided by these phones are somewhat similar to those provided by the terrestrial mobile phones such as the low – bandwidth internet access, short messaging service or voice services etc.
– These services are supported by a number of systems.
– It depends up on the architecture of the system whether the entire Earth is covered or only a specific part of it.
– A wide variation is seen in the terminal i.e., the mobile equipment.
– The satellite phones that were used earlier were of the size of mobile phones of 1990s and they had a large antenna with retractable feature.
– The satellite phones that we have today are of the size of the regular cell phones that we use today while there are some phones that are exactly same like our usual smart phones.
– Satellite phones are mostly used in the remote areas where no terrestrial cellular service is available.
– A fixed installation might be used for example on a ship.
– It may constitute of rugged, large, rack – mounted electronics and moving antenna for automatic tracking of the satellites moving overhead. VoIP over 2 – way satellite broadband service might be used in smaller installations.
– Examples for such services include VSAT or BGAN.
– They are within the financial reach of the owners or the leisure vessels.
– Satellite phones using the internet services are characterized by their poor reception capabilities.
– However, receiving a consistent signal is possible if you sit near the window or if the ceiling is quite thin.
– These phones come with connectors which are used for connecting them to the external antennas that are installed outside the buildings or on vehicles.
– Just like the terrestrial mobile phone systems, some of the satellite phone systems also provide the facility of repeaters.
– Some of the satellite phones are known to make use of the satellites that lie in the geostationary orbit.
– These satellites are bound to remain at a fixed position in sky.
– Such systems are capable of maintaining continuous global coverage with at most 4 satellites that lie in the near area.
– This helps in cutting down the launching costs.
– The satellite is situated at a certain altitude and therefore while making a phone call the users experience a noticeable delay.
– The bandwidth offered by these systems is quite high than what is presented by the LEO (low Earth orbit) systems.
– The use of the geostationary satellites is limited by the latitude ranging from 70 degrees north to 70 degrees in south.
– This is because of the low look angles that increase the risk of interference from various sources in the bands of same frequencies.
– Geostationary satellites have one more disadvantage which is that the line of sight might be broken because of the obstructions such as forest and hills.
– By the networks of the satellite phones, the voice traffic is encrypted for the prevention of the eavesdropping.
– However, the satellite phones are not fit to be used for the applications that demand high security.
– A one – way paging channel is provided by some of the satphone networks for alerting the users of a call.
– The cost of a satellite phone is higher than that of the terrestrial phones.
– Usually the price of these phones varies with the performance of the network.

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