VSAT

2.5 méter 2 arah pikeun *satellite Internet access* ]]

**VSAT** (dina basa Inggris, mangrupa singgetan ti *Very Small Aperture Terminal*)  , nyaéta hiji satelit stasiun bumi dua arah atawa anteneu VSAT maritim stabil kalayan anteneu parabola anu leuwih leutik ti 3 méter. Lolobana diameter anteneu VSAT nyaéta ti 75&nbsp;cm nepi ka 1.2 m. *C-band* merlukeun anteneu anu leuwih badag, samentara *Ku-band* ngagunakeun anteneu anu leuwih leutik. Gancangna data biasana antara ti 56 kbit / detik nepi ka 4 Mbit / detik. VSAT ngaksés satelit di *orbit geosynchronous* pikeun ngariléy data ti stasiun bumi leutik *remote* (terminal) ka terminal lain (dina *mesh* *topology*) atawa puseur stasiun bumi badag *"Hubs"* (dina *topologi star*).

VSAT anu pang mindeng dipaké pikeun ngirimkeun data *narrowband* transaksi (titik panjualan  kawas kartu kiridit, *polling data* atawa RFID atawa SCADA), atawa data *broadband* (pikeun penyediaan aksés internet satelit pikeun lokasi nyengceling, VoIP atawa vidio). VSAT ogé bisa dipaké sacara pundah-pindah, *on-the-move* (ngagunakeun anteneu *phased array)* atawa komunikasi maritim usik.

## Sajarah
Konsép orbit geostationér asalna ti Konstantin Tsiolkovsky saurang ahli téori Rusia, anu nulis artikel ngeunaan lalampahan rohang jomantara kira-kira mimiti abad Ka-20. Taun 1920, Hermann Oberth sarta Herman Potocnik, dipikawanoh ogé minangka Herman Noordung, ngécéskeun hiji orbit dina luhurna 35.900 kilométer hiji période anu cocog jeung période rotasi Bumi, ku kituna satelit katingali ngalayang di luhur tetep dina ekuator Bumi. .

Arthur C. Clarke ilubiung dina pamahaman Satelit ngaliwatan hiji artikel anu dipedar di  *Wireless World* bulan Oktober 1945 anu dijudulan *"Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?"*. Dina artikel ieu, Clarke henteu ngan nangtukeun   karakteristik orbit anu diperlukeun pikeun orbit géostasionér, tapi ogé ngabahas frékuensi sarta daya anu diperlukeun pikeun komunikasi.

Komunikasi Satelit dimekarkeun dina taun genep puluhan ku NASA, ngaranna *Syncom 1-3*. Manéhna mancarkeun liputan langsung    Olimpiade 1964 di Jepang pikeun pemirsa di AS sarta Eropa. Sanggeus ti éta, dina tanggal 6 April 1965 satelit komérsial kahiji diapungkeun ka jomantara, *Intelsat I*, katelahna *Early Bird*.

VSAT Komérsial kahiji nyaéta *C band*  (6&nbsp;GHz) sistem ngan ukur narima ku *Equatorial Communications* ngagunakeun téknologi *spread spectrum*. Leuwih ti 30,000 sistim anténeu 60&nbsp;cm anu dijual dina awal taun 1980an. Saterusna *Equatorial*  ngamekarkeun sitsim 2 arah *C band*  (4/6&nbsp;GHz) ngagunakeun anténeu 1 m x 0.5 m  sarta geus ngajual kira-kira 10.000 unit taun 1984-85.
Taun 1985, *Schlumberger Oilfield Research* jeung *Hughes Aerospace* ngamekarkeun *Ku band* (12–14&nbsp;GHz) kahiji di dunya  VSAT   nyadiakeun konektivitas raramat portabel pikeun pengeboran lapangan minyak sarta unit éksplorasi. VSAT *Ku Band* lolobana lokasi ayeuna dipakéna  pikeun data atawa aplikasi telepon. Raramat VSAT pangbadagna (leuwih ti 12.000 lokasi) dipaké ku *Spacenet* sarta *MCI* pikeun *US Postal Service*.

## Konfigurasi
Most VSAT networks are configured in one of these topologies:
* A star topology, using a central uplink site, such as a network operations center (NOC), to transport data back and forth to éach VSAT terminal via satellite,
* A mesh topology, where éach VSAT terminal relays data via satellite to another terminal by acting as a hub, minimizing the need for a centralized uplink site,
* A combination of both star and mesh topologies. Some VSAT networks are configured by having several centralized uplink sites (and VSAT terminals stemming from it) connected in a multi-star topology with éach star (and éach terminal in éach star) connected to éach other in a mesh topology. Others configured in only a single star topology sometimes will have éach terminal connected to éach other as well, resulting in éach terminal acting as a central hub. These configurations are utilized to minimize the overall cost of the network, and to alleviate the amount of data that has to be relayed through a central uplink site (or sites) of a star or multi-star network.

## Aplikasi Mangsa ka Hareup
Advances in technology have dramatically improved the price/performance equation of FSS (Fixed Service Satellite) over the past five yéars. New VSAT systems are coming online using  technology that promise higher data rates for lower costs.

FSS systems currently in orbit have a huge capacity with a relatively low price structure. FSS systems provide various applications for subscribers, including: telephony, fax, television, high speed data communication services, Internet access, Satellite News Gathering (SNG), Digital Audio Broadcasting (DAB) and others. These systems are applicable for providing various high-quality services because they créate efficient communication systems, both for residential and business users.

## Bagéan-bagéan Tina Konfigurasi Hiji VSAT
* Antenna
* Block upconverter (BUC)
* Low-noise block downconverter (LNB)
* Orthomode transducer (OMT)
* Interfacility link cable (IFL)
* Indoor unit (IDU)

All the outdoor parts on the dish are collectively called the ODU (Outdoor Unit), i.e. OMT to split signal between BUC and LNB. The IDU is effectively a Modem, usually with ethernet port and 2 x F-connectors for the coax to BUC (Transmit) and from LNB (Receive). The Astra2Connect has an all-in-one OMT/BUC/LNA that looks like a QUAD LNB in shape and size which mounts on a regular TV sat mount. As a consequence it is only 500&nbsp;mW compared with the normal 2W, thus is poorer in rain. Skylogic's Tooway system also uses an integrated OMT/BUC/LNB assembly named TRIA (Transmit/Receive Integrated Assembly) which is 3W.

## VSAT Maritim 
Maritime VSAT is the use of satellite communication through a VSAT terminal on a ship at séa. Since a ship at séa moves with the water, the antenna needs to be stabilized with reference to the horizon and True North. The antenna is constantly pointing at the satellite it uses to transmit and receive signals.

### Téhnolohi 
Initially the use of VSAT antennas at séa was for transmission of television signals. One of the first companies to manufacture stabilized VSAT antennas was SeaTel  of Concord, California which launched their first stabilized antenna in 1978. Séa Tel dominates the supply of two-way VSAT stabilised antenna systems to the marine market with almost 72 percent of the market in 2007 compared with Orbit’s 17.6 per cent.
Initially maritime VSAT was using Single Channel Per Carrier - SCPC technology - which suited large volume users like oil drilling rigs and oil platforms and large fleets of ships from one shipowner sailing within one or few satellite footprints.
This changed when the company iDirect launched its IP-based Time Division Multiple Access (TDMA) technology that dynamically allocated bandwidth to éach ship for shared bandwidth, lowering the entry level cost for getting maritime VSAT installed, which turned out to be of key importance to small-to mid-sized fleets, and thus to the market acceptance of VSAT.

### Pasar
According to the Maritime VSAT report  products and Ship Equip  calls its offering Sevsat.

## Palatihan
modérn VSAT systems are a prime example of convergence, and hence require skills from both the RF and IP domains.  VSAT specific training includes:

* ITC Global VSAT Career Certifications
* Global VSAT Forum VSAT Installer Certification 

## Référénsi
## Tumbu Kaluar
*About VSAT - Satellite Basics Guide
*All about Maritime VSAT  
*Enterprise VSAT Networking
*VSAT Solutions 
*The Role of Satellite Comms in Remote Area Mining Operations 
*Tool to point VSAT antennas