YachtCom - Mobile Satellite Communication | Satellite Phones | Communications from Space

Satellite facts :-

  • Life times - Satellites have a limited life time, dependent on fuel and orbit.
    • Satellites burn fuel to keep in the correct orbit. Low orbiting satellites are being pulled back toward the earth by gravity and hence have a short life time, 10 years. Higher orbiting geostationary satellites last about 15 years before running out of fuel and drift out into space.
  • Number of calls - The satellite is basically a telephone exchange, it can only handle a limited number of calls.
    • Low orbiting satellites handle between 1700 to 2500 calls per satellite. Higher orbiting satellites can see more of the earth's surface and hence designed to handle a high number of calls, between 5000 to 25000 calls per satellite.
  • Coverage - Depends on technology deployed.
    • Bent pipe technology is the most common due to low cost and small size. This is when all calls are passed to a ground station for processing. On low orbiting satellites, if the satellite cannot see a ground station then it cannot connect calls.
    • Interlink satellite technology uses larger and more expensive satellites. This is when satellite can transfer calls between themselves without going via a ground station.
  • Mobility - You do need an antenna above deck to receive and make calls.
    • The low transmit power from your satellite phone needs to travel a long way. Low orbiting satellites are in the region of 500 miles above your head and move quickly across the sky. Geostationary satellites are some 22000 miles above the equator and you need a clear path between you and the satellite for your signal to reach it.
  • Reliability - In the main good, but like any other mobile phone technology do expect to lose/drop calls.
  • Systems cost - It is very expensive to put satellites up there and maintain them.
    • Satellites are designed to be reliable, you cannot send a man up there to fix them when they go wrong. Launch costs are high and each payload carries between 3 to 6 communication size satellites.

Mobile satellite phone system providers

  • Iridium - Offers global coverage and email. The lifetime of this system is now becoming an issue with end of service by 2014. Replacement system called Iridium Next is in development and should come into service in 2017.
  • Globalstar - Anything but global! Poor global ocean region coverage, email and data service. Second generation satelllites have been launched.
  • Thuraya - European, Middle East and Far East coverage, emails and data services for instant satellite access to the Internet.
  • Inmarsat - A service targeted towards the marine users offering good ocean region coverage and with telephone and data with fast broadband internet access.
    • Inmarsat - C slow but reliable 600 bits per second data only service .
    • Fleet broadband with antenna from 33 to 80 cms and broadband speeds from 150 kbps to 500 kbps. The bigger antenna is used for faster data.
    • Global Xpress operates on a frequency range of 30 GHz and delivers data at rates of up to 50 Mbit/s via a 60cm or one metre dish.


Satellite phone call charges

Telephone call costs range from $0.30 to $2.00 per minute and even more on some systems.
Beware of call costs to your satellite phone from shore, it is usually cheaper to make the call than to receive a call!
Data charges are very expensive. Inmarsat FleetBroadband charge around $12 per Mbit or $12000 per Gbit, which is about 1000 times more than over a 3G/4G moble phone!
Also inter satellite calls between different satellite networks are expensive.

Satellite Data via satellite phone systems. For speech, a narrow bandwidth of only 2400 Hz is required. Some early satellite phone systems (Iridium and Globalstar) were only designed to handle voice communications which uses a very narrow bandwidth.

The narrow band restricts the amount of data which can be sent, data rates range from 2.4 k bits to 9.6 k bits per second depending on the service provider


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