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Very Small Aperture Terminal (VSAT)

Very Small Aperture Terminal (VSAT) is a small microwave earth station providing two-way communications via satellite. VSAT data rates have risen to 2 Mbps or more and receive rates are approaching 100 Mbps. In VSAT systems VSAT accesses satellites in the geostationary orbit and relays data from terminals in earth to other terminals and hubs, with transmission schemes TDM/TDMA and CDMA (being used to a small extent). The hub also performs network management functions. The alternative to the Hub Network is the Mesh Network, which can allow direct VSAT to VSAT communication. Earlier VSAT systems worked in the C-Band (6/4 GHz), current systems work in the Ku-Band (14/12 GHz). As this band is also becoming congested, systems are now looking to Ka-Band (30/20 GHz). One satellite can cover almost 1/3 of Earth’s surface, offering an extensive reach than any other terrestrial network can achieve.


VSAT is used in electricity industry to provide a SCADA system that interlinks remote substations and SCADA headquarters. For example, Mountain View Electric Association (MVEA) in 1996 deployed 12 VSATs at 11 substations and the operations center, which allows MVEA "to remotely control its substations and monitor customers' meters; it also enables MVEA to operate a direct load-control program that helps minimize its purchased-power costs and, thereby, the prices it must charge customers" [1]. VSAT can also provide location and time synchronization based on a global positioning system (GPS) needed for Phasor Measurement Unit (PMU).


[1] Innovators with EPRI technology - MVEA FIrst Electric Utility to use Lower-Cost Satellite Ground Station, Sep 1996. URL: http://mydocs.epri.com/docs/public/IN-105931.pdf

Key Technology Area: 
Integrated Communications

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