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Mobile Satellite
Commuications
Mobile satellite communications is now well established and
works on your yacht just like a terrestrial mobile phone. Most systems allow
phone calls and send emails and there are now satellite systems offering fast
mobile packet data service (MPDS) and broadband global area network (BGAN)
offering speeds between 65 kbps to 498 kbps which allow for fast satellite
Internet access. Although with mobile satellite communications you can make telephone calls from your yacht, do consider that you may not be able to talk to other vessels or rescue services on the high seas. Therefore mobile satellite communications should not be considered as a replacement for conventional marine VHF or SSB communications.
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.
- Iridium - Offers good global coverage and email at 2.4kbit per second. The lifetime of this system is now becoming an issue with end of service by 2014.
- Globalstar - Anything but global! Poor global ocean region coverage, email and data at 9.6kbits per second.
- ICO - Offering good ocean region coverage and high speed 140kbit per second packet switched Internet access.
- Thuraya - European, Middle East and Far East coverage, emails at 9.6kbit per second and a high speed 144 kbps data services for instant satellite access to the Internet.
- Inmarsat Good
ocean region coverage. Reliable but expensive call and mobile unit cost.
However, there are no monthly contract charges, it is a 'pay-as-you-go' type
services.
- Inmarsat - B require large antenna.
- Inmarsat - C slow but reliable 600 bits per second data only service.
- Inmarsat -M / mini M small antenna size good coverage but not all parts of the world covered.
- Fleet 33 is ideal for yachts as it comes with a small antenna which is just 35 cms by 35 cms. Fleet 33 offers telephone, fax, data and Mobile Packet Data Service (MPDS) with downstream speed of 64 kbps and an upstream speed of 28 kbps.
- Fleet 55 is for medium size vessels and comes with an antenna with is 55 cms by 55 cms. Fleet 55 offers telephone, fax, data and Mobile Packet Data Service (MPDS) with downstream speed of 128 kbps and an upstream speed of 64 kbps.
- Fleet 77 is for large size vessels, the antenna size is 80 cms by 80 cms. Fleet 77 offers telephone, fax, data , ISDN and Mobile Packet Data Service (MPDS) with downstream speed of 128 kbps and an upstream speed of 128 kbps.
Telephone call cost range from $0.30 to $2.00 per minute and even more on some systems. Beware of call costs to your satellite phone and transfer call costs from your GSM mobile phone to your satellite 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. Basically satellite phone only system were not designed to handle data communication.
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. High speed mobile packet data services (MDPS) and broadband global area network (BGAN) services offer fast data to and from your boat but do not come cheap and you have to pay for all the data you receive and send.
Satellite communications is the most expensive form of communication on the planet.
For low cost communications, do consider terrestrial SSB and SSB email
Click here for an overview of satellite systems from Surrey University.
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