VSAT Considerations

VSAT installations are associated with higher initial start-up costs due to more-costly equipment and complexity.

MSS antennas are generally a smaller alternative, therefore quicker to install.

Some trading areas/routes still do not have acceptable VSAT coverage in C-, Ku- or Ka-band. Often, VSAT services will be backed up with MSS to allow fall back to the MSS system during VSAT down time.
Detailed knowledge of VSAT technology is still limited by some of the potential adopters and the process of measuring the value-proposition of introducing maritime VSAT is complex.

This is exactly why www.maritimevsat.com was created. Ship managers can often find it difficult to quantify their comparable savings following a move to VSAT. Some less obvious incremental savings can sometimes be missed.

Latency is defined as the amount of delay, measured in milliseconds, that occurs during data transmission. Latency is unavoidable in any Internet connection but it can be minimised by using a better managed network.There are four main factors that affect latency:

1. The Speed of Light It takes the signal a certain period of time to get to the satellite and back, also according to which type of satellite. The speed of light is 300,000 km per second The distance to GEO satellites from Earth is approximately 36,000 km. The distance to MEO satellites from Earth is approximately 10,000 km.

2. Processing The processing of signals going through modems, routers, PBX and other devices onboard and onshore causes delay, approximately 6-8 mS (milliseconds).

3. Terrestrials Once the data or voice signals have been terminated on the Land Earth Station, many customers have the data transferred directly to their Head Quarters. This means further transport of the signals on the terrestrial network which causes further delay, approximately 20-100 mS each direction depending on geographical location of the Teleport and HQ.

4. TCP/IP Normally data and voice are transferred over IP. Using a protocol like TCP/IP can cause further delays due to the limitation of packets that can be transferred simultaneously additional to the packet exchange acknowledgement. Using a real time protocol like UDP can improve the latency impact.

Because of the low frequency range, Ku-band services are more exposed to rain fade. However, outages are increasingly rare. However, new Ka-band services are most susceptible to rain-fade, which is why in general they come bundled with MSS for back-up. Twice a year, there are brief periods (lasting a few minutes) where the Sun moves directly in line with the satellite. The Sun, being a very powerful source of radio signals, temporarily jams the satellite signal.

These outages can be predicted very precisely and last only a short time. (Most users can tolerate scheduled outages, it is those unscheduled outages that cause the most problems.)

Another possibility is that of snow building up in a dish, but proper system design (e.g. installation of covers, heaters, and occasional vigilance) can prevent such issues.

Fortunately, failure of the Satellite itself is extremely rare. Satellites are some of the most reliable pieces of equipment made – and they are loaded with redundant systems.

Even in the event of a failure, it is practical to restore service simply by pointing the antenna at a different satellite.

Satellite is a line-of-sight service. Any blockage of the view between the satellite and the antenna will affect the quality of communications.

Blockage (Mast, stack, antennas, etc.) should be avoided if at all possible. A dual antenna solution can negate most blockage issues.


VSAT Strenghts
Choosing a VSAT Provider