Very-small-aperture terminal

Avery-small-aperture terminal(VSAT)is a two-waysatelliteground stationwith adish antennathat is smaller than 3.8 meters. The majority of VSAT antennas range from 75 cm to 1.2 m.Bit rates,in most cases, range from 4 kbit/s to 16 Mbit/s. VSATs access satellites ingeosynchronous orbitorgeostationary orbitto relay data from small remote Earth stations (terminals) to other terminals (inmeshtopology) or master Earth station "hubs" (instar topology).

A 2.5 mparabolicdishantenna for bidirectionalsatellite Internet access

VSATs are used to transmitnarrowbanddata (e.g.,point-of-saletransactions using credit cards, polling orRFIDdata, orSCADA), orbroadbanddata (for the provision ofsatellite Internet accessto remote locations,VoIPor video). VSATs are also used for transportable, on-the-move (utilisingphased arrayantennas) or mobilemaritimecommunications.

History

The concept of thegeostationary orbitwas originated by Russian theoristKonstantin Tsiolkovsky,who wrote articles onspace travelaround the beginning of the 20th century. In the 1920s,Hermann OberthandHerman Potocnik,also known as Herman Noordung, described an orbit at an altitude of 35,900 kilometres (22,300 miles) whoseperiodexactly matched the Earth's rotational period, making it appear to hover over a fixed point on the Earth'sequator.

Arthur C. Clarke'sOctober 1945Wireless Worldarticle (called "Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?" ) discussed the necessaryorbital characteristicsfor a geostationary orbit and the frequencies and power needed for communication.

Live satellite communication was developed in the 1960s byNASA,which launchedSyncom1–3 satellites.Syncom 3 transmitted live coverage of the1964 OlympicsinJapanto viewers in theUnited StatesandEurope.On April 6, 1965, the first commercial satellite was launched into space,Intelsat I,nicknamed Early Bird.

The first commercial VSATs were C band (6 GHz) receive-only systems by Equatorial Communications usingspread spectrumtechnology. More than 30,000 60 cm antenna systems were sold in the early 1980s. Equatorial later developed a C band (4/6 GHz) two-way system using 1 m x 0.5 m antennas and sold about 10,000 units in 1984–85.

In the early 1980s, LINKABIT (the predecessor to Qualcomm and ViaSat) developed the world's first Ku-band (12–14 GHz) VSAT for Schlumberger to provide network connectivity for oil fielddrillingand exploration units. LINKABIT which had become part of M/A-COM went on to developK_ubandVSATs for enterprise customers such asWalmart,Holiday Inn,Chrysler,andGeneral Motors.These enterprise terminals made up the vast majority of sites for the next 20 years for two-way data or telephony applications. A large VSAT network, with more than 12,000 sites, was deployed bySpacenetand MCI for theU.S. Postal Servicein the 1980s. As of 2015,the largest VSAT Ku-band network containing over 100,000 VSATs was deployed by and is operated byHughes Communicationsforlotteryapplications.

In 2005, WildBlue (now ViaSat) started deploying VSAT networks deploying Ka-band. ViaSat launched the highest capacity satellite ever, ViaSat-1, in 2011 to expand the WildBlue base under its Exede brand. In 2007,Hughes Communicationsstarted deployingK_abandVSAT sites for consumers under its HughesNet brand on the Spaceway 3 satellite and later in 2012 on itsEchoStar XVII/Jupiter 1satellite. By September 2014, Hughes became the first Satellite Internet Provider to surpass one million active terminals.

Configurations

Most VSAT networks are configured in one of thesetopologies:

• Astar topology,using a central uplink site, such as anetwork operations center(NOC), to transport data back and forth to each VSAT via satellite,
• Amesh topology,where each VSAT 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 stemming from it) connected in a multi-star topology with each star (and each terminal in each star) connected to each other in a mesh topology. Others configured in only a single-star topology sometimes will have each terminal connected to each other as well, resulting in each 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.

Future applications

Advances in technology have dramatically improved theprice–performance ratiooffixed satellite service(FSS) over the past five years. New VSAT systems are coming online usingK_abandtechnology 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-speeddata communicationservices, Internet access,satellite news gathering(SNG),Digital Audio Broadcasting(DAB) and others. These systems provide high-quality service because they create efficient communication systems for both residential and business users.

Constituent parts of a VSAT configuration

• 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 satellite mount. As a consequence it is only 500 mW compared with the normal 2W, thus is poorer in rain. Skylogic'sToowaysystem also uses an integrated OMT/BUC/LNB assembly called atransmit and receive integrated assembly(TRIA), which is 3W. For large antennas there are also mechanical struts that prevent them to move due to strong winds, losing the pointing and causing service interruption

Maritime VSAT

A maritime VSAT has features that allow it to be operated on a ship at sea. A ship that is underway is in continuous motion in all axes. The antenna part of a marine VSAT system must be stabilized with respect to the horizon andtrue northas the ship moves beneath it. Motors and sensors are used to keep the antenna pointed accurately at the satellite. This enables it to transmit to and receive from the satellite while minimising losses and interference with adjacent satellites. New technology is emerging that will allow a solid state device (flat panel) to steer an antenna electronically without moving parts.

Technology

Initially, stabilized satellite antennas were used on ships for reception of television signals. One of the first companies to manufacture stabilized VSAT antennas was SeaTel ofConcord,California,which launched its first stabilized antenna in 1978. SeaTel dominates the supply of two-way VSAT stabilised antenna systems to the marine industry with almost 72% of the market in 2007 compared to Orbit's 17.6%.Initially, maritime VSAT was usingsingle channel per carriertechnology, which suited large-volume users like oil drilling rigs andoil platformsand large fleets of ships from one shipowner sailing within one or fewsatellite footprints.This changed when the company iDirect launched its IP-basedtime-division multiple accesstechnology that dynamically allocated bandwidth to each 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.

Market

According to the Maritime VSAT report issued by the Comsys Group, the market for stabilised maritime VSAT services (not including oil and gas rigs) reached more than $400 million in 2007.In 2010,COMSYSreleased its "2nd Maritime VSAT Report", where the market estimate had increased to $590 million in 2009 with predictions for 2010 at $850 million. The estimated size of the market in terms of vessels eligible to get VSAT was in this report set to in excess of 42,000 with just over 34,000 to go. The major companies market share in terms of number of vessels in service were in 2009 (2007 in parentheses) according to these reports: Vizada: 17.6% (26.0%), Ship Equip: 11.0% (10.7%), Cap Rock 2.8% (2.9%), MTN 7.5% (6.4%), Stratos - % (3.6%), KVH 5.4% (- %) Elektrikom 4.9% (3.2%), Intelsat 3.4% (- %), Eutelsat 3.1%, NSSL 3.1%, Radio Holland 3.0%, Telemar 3.0%, DTS 2.6% and others accounted for 32.6% (27.7%). Many of the major providers have branded their maritime VSAT offerings such thatVizadaoffers its service through the Marlink division and the SeaLink and WaveCall products, OmniAccess, through their BroadBEAMproducts and Ship Equip calls its offeringSevsat.

VSAT Maritime Connectivity Service Providers Market Shares Global - Revenues (2018 & 2019):

1. Marlink 23.9%
2. Speedcast 15.0%
3. Inmarsat 11.3%
4. KVH Industries 8.8%
5. Global Eagle 7.6%
6. ITC Global 6.6%
7. RigNet 5.9%
8. NSSLGlobal 5.2%
9. Navarino 4.3%
10. Satcom Global 2.7%

See also

• Satellite modem