VSAT 101

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 that transmit and receive data from a relatively small satellite dish on Earth and communicate 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 antennae on ships at sea

Depending on bandwidth requirement (data speed and/or communications channels), VSAT systems can be relatively small, using small dish antennae less than 3 meters in diameter, and generally operate in the Ku-band and C-band frequencies. The majority of VSAT antennae range from 75 cm to 2.4 meters in diameter. C-band requires larger antennae, while Ku-band uses smaller antennae.

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 at sea installed with VSAT 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 satellite latency can affect the performance of voice and data communications.

Satellite communications require a line of sight, so the antenna must have an unobstructed view of the satellite. Mountains, buildings or structures on a ship can often block the satellite and affect link performance. Satellite antennae must be pointed at the satellite with about 1 degree of accuracy. On moving ships, sophisticated stabilized antennae are used to track the satellite and compensate for the movement of the vessel.

The arrangement by which 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 nature of a 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 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, it is also used for transportable, on-the-move or mobile maritime communications.   

Space Segment:  The satellites' transponders receive signals from the earth, amplify them, and then retransmit the signals back to earth. Leveraging leased space segment on over forty satellites around the globe to provide these connections, MTNGS is able to choose satellites based on the coverage requirements and technical fit that best meets the specific customer needs.

Hubs: The hub, or master earth station, which includes an antenna typically larger than 4.5 meters in diameter, controls the operation of the network. Several hubs operated on the same site are referred to as a teleport. MTNGS's network includes global teleports, strategically located to provide optimum coverage.

The remote site equipment is used to connect the client's local area and telephone networks to other networks over satellite (e.g. corporate Internet). The outdoor equipment including the antenna and the transmission gear is referred to as the VSAT terminal.

MTNGS deploys different antenna types based on whether customers' operations are on land or at sea or require fixed or transportable configurations. The indoor equipment includes the network gateway (i.e. satellite, modem, Ethernet, switch, and router) that provides the interface for the connection of phones, fax machines and computers.