What does VSAT stand for?
VSAT stands for Very Small Aperture Terminal.
What is VSAT and how does it work?
VSAT is a technology used to define two-way-satellite communications, which transmits and receives data from a relatively small satellite dish on Earth and communicates with an orbiting geostationary satellite 22,300 miles above Earth's Equator.
A VSAT network has three components:
- A central hub (also called a master earth station)
- The satellite
- A virtually unlimited number of VSAT earth stations in various locations across countries or continents or on stabilized antennas on a ship at sea
Depending on bandwidth requirement (data speed and/or communications channels), VSAT systems can be relatively small, using small dish antennas less than 3 meters and generally operate in the Ku-Band and C-Band frequencies. A majority of VSAT antennas range from 75 cm to 2.4 meters in diameter. C-Band requires larger antennas while Ku-Band uses smaller antennas.
Content originates at the hub, which features a very large antenna. The hub controls the network through a Network Management System (NMS) server, which allows a network operator to monitor and control all components of the network. The NMS operator can view, modify and download individual configuration information to the individual VSATs.
Outbound information (from the hub to the VSATs) is sent up to the communications satellite's transponder, which receives it, amplifies it and beams it back to earth for reception by the remote VSATs. The VSATs at the remote locations send information inbound (from the VSATs to the hub) via the same satellite transponder to the hub station.
Since a ship installed with VSAT at sea moves with the water, the antenna needs to be stabilized with reference to the horizon and True North, so that the antenna is constantly pointing at the satellite it uses to transmit and receive signals. It takes about 500ms (half a second) for a signal to travel from the ship, to the satellite, to the earth station and back. This is known as satellite latency and can affect the performance of voice and data communications.
Satellite communications require “line of site” so the antenna must have an unobstructed view of the satellite. Mountains or buildings on land, or structures on the ship can often block the satellite and affect link performance. Satellite antennas must be pointed at the satellite with about 1 degree of accuracy. On moving ships, sophisticated stabilized antennas are used to track the satellite and compensate for the movement of the vessel.
The arrangement where all network communication passes through the network's hub processor is called a "star" configuration, with the hub station at the center of the star. One major advantage of this configuration is that there is virtually no limit on the number of remote VSATs that can be connected the hub.
For satellites to gain a foothold in the delivery of advanced broadband services, seamless interconnectivity with terrestrial networks is imperative. For best results, the network should be designed to use the unique virtue of satellite in geostationary orbit, namely that it can be a shared resource available, as needed, to many users spread over a very large proportion of the Earth's surface. This is the concept of bandwidth-on-demand.
How are VSATs used?
The use of VSAT systems is growing throughout the world as a way of establishing private satellite communications networks and providing high bandwidth needs for critical communications for businesses that have several widely dispersed locations. VSAT networks may transmit voice, data, fax, or video conferencing. While VSAT can be used as a two-way satellite ground station, VSATs are also used for transportable, on-the-move or mobile maritime communications.