Satellite Phones - Phone home in ditial quality
Satellite phones, also known as satphones are mobile phones that communicate directly with orbiting communications satellites. The mobile equipment is also known as terminal or earth station. The coverage may include the entire Earth or only specific regions depending on the architecture of a particular system. A satellite phone handset is usually has a large and retractable antenna and its size and weight is comparable to that of late 1980s or early 1990s mobile phones. They are popular on expeditions into remote areas where cellular phone service is unavailable. Fixed installations like aboard a ship have large, rugged, rack mounted electronics, and manageable microwave antenna on the mast that automatically tracks the overhead satellites.
Some disadvantages in using satellite phones is that the phone is bigger than usual, it takes a bit longer to connect than normal, poor speech quality like the phone sounded as if it was underwater, dropped calls, the handsets are very expensive, and the call costs are also expensive. But the call was far from the sea; instead it’s thousands of miles direct from a handset up to a satellite and into a home a thousand miles away. Its history is very unhappy; a satellite phone company has filed for bankruptcy protection. Many prospective customers were no longer interested due to the increase of cellular coverage and better reception. Some cellular phone companies are making a dual phone that can be used as a cellular phone or a satellite phone and it is inexpensive. The market for satellite phones is the people who are in remote areas and do not have access to phone lines. The call costs of this type of phone are cheaper compared to a satellite phone.
When using a satellite phone the call is placed via satellite to one or more gateways. The gateway routes the call to the existing phone network such as the Public Land Mobile Network (PLMN) network. The Public Land Mobile Network routes the call to the intended receiver and the call is completed. The duration of the call, service used, and service area are reported to the service provider for billing. In making a call via satellite versus a cellular, the call is placed and its signal is handled by a passing satellite, then the satellite relays the call to a gateway in its path. The gateway converts the signal to work with the local PTSN and passes on the call. The call might pass through several gateways and PTSNs before locating the receiving phone depending on the distance between the callers. To connect to another gateway that knows where the receiving phone is located the PTSN uses the calls routing information. The gateway which is located closest to the receiving phone converts the signal to a certain format and up links it to a satellite. The satellite relays the phones power in a registration message to the gateway that’s why the gateway knows that the receiving phone is in the area. The gateway's visitor location register (VLR) stores this information. The call linkage is complete when the call is relayed to the receiving satellite phones.