Very Small Aperture Terminal (VSAT) Communication Networks
Very Small Aperture Terminal (VSAT) communication networks are a form of satellite communication where business and industry can transmit data, voice and video around the world through a satellite link. Companies such as Walmart use VSATs to process data to and from their stores nationwide (Lawton, 1994). Understanding the basics of what constitutes a VSAT network and how it operates will establish a basis of knowledge to expand on the various applications. Illustrating the commercial and military use of these satellite networks will show how space capabilities can be more advantageous over terrestrial methods of communication. The use of VSAT communication is growing around the world. While few may understand even the basics of how they work, a better understanding of its operations, advantages, disadvantages, and many uses may prove to be beneficial as these space communication technologies unfold.
How VSAT Networks Operate
VSAT networks have very few components, and the system operates independently once it is set up. Each network location uses an antenna and a modem to link to a satellite using radio frequency (RF) bandwidth and various protocols. VSAT networks can be arranged in a mesh topology configuration or a star topology configuration.
A basic VSAT network consists of at least two antennas (usually 1.8 to 2.4 meters in diameter) and two modems placed at two separate distant locations. A modem is an electronic component normally consisting of two parts: a transmit/receive portion and a router portion for signal distribution. J. Reasoner, a VSAT network engineer, described modems stating “the term modem itself describes it’s transmit and receive function: modulate and demodulate, hence the word modem (personal communication, March 15, 2012). When distant communication is desired, an equipment set consisting of an antenna and a modem are set up at each location. One modem will transmit a signal through its respective antennas to a satellite transponder where it converts from an uplink signal to a downlink signal. The downlink signal is then received through the distance end antenna and receiving modem. J. Reasoner also explained the receiving modem will then analyze the signal and route only the desired information to the router (personal communication, March 15, 2012). The modem’s router portion is normally connected to a network or server which distributes the data, voice or video to the individual users.
Signals from the antennas are sent to a geostationary satellite. “VSAT networks use geostationary satellites, which are satellites orbiting in the equatorial plane of the earth at an altitude above the earth surface of 35,786 km” (Maral, 2003, p. 5). Geostationary satellites remain stationary within the earth’s orbit. In other words, they move with the earth’s rotation keeping the satellite over the same point on the earth at...