VSAT

A Very Small Aperture Terminal (VSAT) is a two way fixed satellite ground station or a marine stabilised antenna with a dish diameter of less than 3m. Most fixed VSAT antennas are typically 90-110cm and stabilised marine antennas are 1.0m. The antennas access geo-stationary satellites that are positioned 36,000 kms above the equator. At this orbit the satellites rotate at the same speed as the earth allowing a permanent link to be established.

VSAT services tend to provide direct access to the Internet using IP data connectivity with speeds starting at 64Kbps up to 5Mbps+. Networks can be designed in various different ways so that bandwidth resources can be used efficiently such as Mesh or Star topology where you may link various remote sites/vessels back to each other or a central location.

There are a wide variety of services available using different parts of the radio spectrum including C-band, Ku-band and Ka-band which all offer different capabilities and characteristics such as global coverage, good all weather performance and higher speeds.

The satellite links are offered in a variety of ways differentiated by being either Contended and Non-Contended access or SCPC (Single Channel per Carrier). In short, “Contended” means that you will share the satellite bandwidth with a group of other users within the same satellite footprint. As a result your actual throughput speeds will vary as other users start and stop sending data. “Non-Contended” or SCPC simply means that you purchase the bandwidth you require and it is yours to use alone. Due to multiple users sharing the same bandwidth resource, the costs for “Contended” services are significantly cheaper than “Non-Contended" or SCPC based services and the users benefit from having access to the full resource when others are not online. The middle ground is to have a Contended service with CIR (Committed Information Rate), which means that there is a guaranteed portion to the satellite link but the service can burst up to the maximum when the bandwidth is available.

Services are typically charged for on a monthly basis and usually commit the user to a contract period of 1 to 2 years. True VSAT services are two way, providing a direct link or high speed IP based Internet connection with additional value added services like VoIP, VPN access and port blocking facilities available.

The majority of VSAT services available provide an IP backbone giving the user options like VoIP (Voice-over-IP) which can significantly reduce the cost of satellite phone calls. Services can be set-up so that the remote office / vessel has a number of terrestrial telephone numbers assigned to it. When dialled the terrestrial call is routed to the Land Earth Station where the call is transferred to a VoIP circuit over the satellite to the vessel. At this point it is converted back to a standard analog connection and typically routed via the PABX, just like other satellite communication.

VSAT services can also be used to provide back-up connectivity for businesses that need fail over redundancy, which come online as soon as the primary ADSL or Fibre connection is lost. With most communications outages caused by contractor damage, vandalism or copper cable theft, flooding or terrorist activity, which are all unfortunately on the increase a satellite continuity solution provides a truly independent Internet connection that can keep your business operational and protected.