VSAT Technology

By | April 2, 2012

Typically a VSAT station consist of 2 major equipment – ODU(Outdoor Unit) which is consist of an antenna – feed horn – rft (buc – lnb) and pedestal (antenna mounting) and IDU (modem).
When a remote VSAT transmits data, first the modem will convert digital signal become a radio frequency signal, then it will convert to designated RF Band then Amplify using BUC. At reverse, when receive data the RF Signal receive using feed horn n pre amplify using LNB then convert to low frekuensi RF (IF) and decode using modem.
in Point 2 Point Topology, 2 Earth VSAT Station will communicate each other trough a transponder in satellite, one channel (carrier) frequency used to transmit and one channel (carrier) frequency used to receive. this topology used to call SCPC (Single Channel Per Carrier), one channel for receive and one channel to transmit.

in advance configuration commonly used today is VSAT IP, itu consist of one sentral earth station called HUB VSAT and many remotes site. this kind of topology called VSAT Star Topology, one as central and many remotes connected to the central. usually, for central earth station (HUB VSAT) it’s consist of a big antenna, a high power RFT (BUC/HPA – LNB/LNA), modem and several devices to organize and controlling all remotes connected. in the remotes side, it’s just like common vsat remote, it’s consist of small antenna, feed horn, RFT (BUC – LNB) and a modem.

in VSAT IP, the transmit channel from HUB to Remotes called Outbound (Outroute/Forward Channel) and from Remotes to HUB called Inbound (Inroute/Return Channel). almost all VSAT IP Technology, using FDMA access scheme in Outroute frequency (because of this, the outbound can be use as broadcast channel to all remotes. and from this access scheme the satellite TV broadcast can deliver the tv channel to all it’s subscriber) and MF TDMA access scheme in Inroute Technology.
what is int Outbound / Forward Channel / Outroute Technology? FDMA (Frequency Division Multiple Access) is a typical access to transmit a signal/carrier using frequency modulation access scheme. the technology in Outroute nowadays using DVB S2 ( Digital Video Broadcasting S2) modulation technic from QPSK (Quad Phase Shift Keying), 8PSK, 16 APSK and 32APSK with LDPC (LowDensityParityCheck) from 1/2 – 9/10.
and what is in Inbound / Return ChannelĀ  / Inroute Technology? MF TDMA (MultiFrequency Time Division Multiple Access) is a typical access to transmit the signal divide by a time shift periode in one carrier for a multiple access and can combine using multiple frequency. typically, nowadays the technology behind Inroute using Modulation QPSK – 8PSK with TurboCode Coding (or maybe LDPC also) with forward error correction from 1/2 – 4/5 (for TC) and til 9/10 (for LDPC).
to be continued….

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