VSAT (Very Small Aperture Terminal)

VSAT Systems uses a satellite connection as a high-speed digital link between a customers location and the US Internet backbone. The data travels from the satellite equipment at the customers location to the satellite, and then to the teleport for routing to the Internet.

VSAT was originally intended for sporadic store-and-forward data communications but has evolved into real-time internet services. VSAT uses existing satellite broadcasting technology with higher powered components and antennas manufactured with higher precision than conventional satellite television systems. The satellite antenna at the customer's location includes, in addition to the receiver, a relatively high-powered transmitter that sends a signal back to the originating satellite. A very small portion of a transponder is used for each VSAT return path channel. Each VSAT terminal is assigned a frequency for the return path which it shares with other VSAT terminals using a shared transmission scheme such as time division multiple access.

An innovative feature of VSAT is that the technology has evolved to the point that something that previously could only be done with large, high-powered transmitting satellite dishes can now be done with a much smaller and vastly lower-powered antenna at the customer's premises. In addition, several return-path channels can co-exist on a single satellite transponder, and each of these return-path channels is further subdivided using to serve multiple customers.

In the system used by WildBlue, 31 different spot beams are used to serve the continental United States instead of the one beam used by conventional satellites. Thus, the same Ka-band transponders and frequencies are used for different regions throughout the United States, effectively re-using the same bandwidth in different regions.

The return path is transmitted from the customer's receiver in the L-band to a device called a low-noise block upconverter. There it is converted into the much higher frequency satellite transmission frequency, such as Ku-band and Ka-band, and amplified. Finally the signal is emitted to the dish antenna which focuses the signal into a beam that approximately covers the satellite with its beam. Because the transmission cannot be precise in these smaller dishes there is some effort to use frequencies for the uplink that are not used by adjacent satellites otherwise interference can occur to those other satellites.

Another satellite communications innovation, also used by satellite trucks for video transmission, is that only a small portion of a single satellite transponder is used by each VSAT channel. Previously a single transponder was required for a single customer but now several customers can use one transponder for the return path. This is in addition to time-based subdivision.