VSAT stands for Very Small Aperture Terminal. It was developed to make access to the satellite more affordable and without any intermediate distribution hierarchy. Most VSAT systems operate in Ku band with antenna diameter of only 1 to 2 meters and transmitting power of 1 to 2 watts. Possible implementation approaches are: One-way, Split two-way and two-way. One-way VSAT configuration is shown in Fig. In this case, there is a master station and there can be many narrow-banding groups within a large broadcasting area of the satellite. This configuration is used in Broadcast Satellite Service (BSS). Other applications of one-way VSAT system are the Satellite Television Distribution system and Direct to Home (DTH) service as shown in Fig. 5.10.14, which has become very popular in recent times.
One-way satellite configurations
Satellite Television distribution system
In case of two-way configuration, there are two possible topologies: star and mesh. In the first case, all the traffic is routed through the master control station as shown in Fig(a). On the other hand, each VSAT has the capability to communicate directly with any other VSAT stations in the second case, as shown in Fig(b). In case of split two-way system, VSAT does not require uplink transmit capability, which significantly reduces cost.
(a) Two-way VSAT configuration with star topology, (b) Two-way VSAT configuration with mesh topology
