VSAT – Brief Introduction

VSAT – Brief Introduction

Nowadays Satellite is used for communication and VSAT is a well-established technology used for voice, data, and videoconferencing communication. VSAT stands for Very Small Aperture Terminal. Previously before some years ago VSAT station is named as earth station.

Present VSAT networks use Geostationary satellites, which are satellites orbiting in the equatorial plane of the earth at an altitude above 35786 km away from the earth’s surface. The satellite moves on its circular orbit in the same direction of earth rotation with the equal speed of earth rotation, thus satellite appears from any station on the ground as a fixed relay in the sky.

For VSAT communication there are mainly two parts at earth station and they are

1) HUB (Network Management System)

2) Remote Stations used for VSAT communication.

There are several services of VSAT can be used but as I previously mentioned VSAT can be used for – Data Transfer or Broadcast (viz. News Broadcast, Computer data transfer, etc.), Interactive Data (Bank Transactions, Electronic funds transfer, etc.), Voice communication (OPX, E&M, etc.), SCADA, Video Transmission, Video Conferencing, etc.

Data Transmission

Standard VSAT products offer data transmission facilities. Rates offered to the user range typically from 50 b/s to 1.2 Mb/s and above which further depend on bandwidth and technology used. Typically VSAT used with RS232, RS422, V.35, X.21, HSSI, and so on standards for data communication.

Voice transmission

Voice transmission in VSAT uses a low bit rate voice encoder (vocoder). Typically information rate ranges from 4.8 kb/s to 9.6 kb/s. For VSAT system voice communication prone to suffer delay associated with voice circuitry.

Video Transmission

VSATs are used for Video transmission using present Video standards like PAL, NTSC, SECAM with additional equipment.

VSAT can be used with C-Band, Extended C-Band, Ku-Band as per the requirement of service and technology. There are pros and cons to these technologies also.

The equipment inside the room is considered as IDU and are network terminals, routers, hubs, servers, Modems, exchanges, etc. Where as equipment outside to room is considered as ODU and are Radio Transceivers, Antenna, tracking motors, etc.

ODU and IDU are interconnected for VSAT communication. Please note equipment configuration for it may differ but it needs to interconnect with proper manner.