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Satellite Internet access isInternet access provided throughcommunication satellites; if it can sustainhigh speeds, it is termedsatellite broadband. Modern consumer grade satellite Internet service is typically provided to individual users throughgeostationary satellites that can offer relatively high data speeds,[1] with newer satellites using theKu band to achieve downstream data speeds up to 506 Mbit/s.[2] In addition, newsatellite internet constellations are being developed inlow-earth orbit to enablelow-latency internet access from space.
Following the launch of the first satellite,Sputnik 1, by theSoviet Union in October 1957, the US successfully launched theExplorer 1 satellite in 1958. The first commercial communications satellite wasTelstar 1, built byBell Labs and launched in July 1962.
The idea of ageosynchronous satellite—one that could orbit the Earth above the equator and remain fixed by following the Earth's rotation—was first proposed byHerman Potočnik in 1928 and popularised by thescience fiction authorArthur C. Clarke in a paper inWireless World in 1945.[3] The first satellite to successfully reach geostationary orbit wasSyncom3, built byHughes Aircraft forNASA and launched on August 19, 1963. Succeeding generations of communications satellites featuring larger capacities and improved performance characteristics were adopted for use in television delivery, military applications and telecommunications purposes. Following the invention of theInternet and the World Wide Web, geostationary satellites attracted interest as a potential means of providing Internet access.
A significant enabler of satellite-delivered Internet has been the opening up of theKa band for satellites. In December 1993, Hughes Aircraft Co. filed with theFederal Communications Commission for a license to launch the first Ka-band satellite,Spaceway. In 1995, the FCC issued a call for more Ka-band satellite applications, attracting applications from 15 companies. Among those wereEchoStar,Lockheed Martin,GE-Americom,Motorola and KaStar Satellite, which later becameWildBlue.
Among prominent aspirants in the early-stage satellite Internet sector wasTeledesic, an ambitious and ultimately failed project funded in part byMicrosoft that ended up costing more than $9 billion. Teledesic's idea was to create a satellite Internet constellation of hundreds of low-orbiting satellites in the Ka-band frequency, providing inexpensive Internet access with download speeds of up to 720 Mbit/s. However, the project was abandoned in 2003. Teledesic's failure, coupled with the bankruptcy filings of the satellite communications providersIridium Communications Inc. andGlobalstar, dampened marketplace enthusiasm for satellite Internet development. The first Internet-ready satellite for consumers was launched in September 2003.[4]
In 2004, with the launch ofAnik F2, the firsthigh-throughput satellite, a class of next-generation satellites providing improved capacity and bandwidth became operational. More recently, high throughput satellites such as ViaSat's ViaSat-1 satellite in 2011 and HughesNet's Jupiter in 2012 have achieved further improvements, elevating downstream data rates from 1 to 3 Mbit/s up to 12 to 15 Mbit/s and beyond. Internet access services tied to these satellites are targeted largely to rural residents as an alternative to Internet service via dial-up, ADSL or classicFSSes.[5]
In 2013, the first four satellites of theO3b constellation were launched intomedium Earth orbit (MEO) to provide internet access to the "other three billion" people without stable internet access at that time. Over the next six years, 16 further satellites joined the constellation, now owned and operated bySES.[6]
Since 2014, a rising number of companies announced working on internet access usingsatellite constellations inlow Earth orbit.SpaceX,OneWeb andAmazon all planned to launch more than 1000 satellites each. OneWeb alone raised $1.7 billion by February 2017 for the project,[7] and SpaceX raised over one billion in the first half of 2019 for their service calledStarlink.[8] They expected more than $30 billion in revenue by 2025 from its satellite constellation.[9][10] Starlink, as of February 2024, has 5,402 operational satellites in orbit.[11]
Many planned constellations employlaser communication for inter-satellite links to effectively create a space-basedinternet backbone.[citation needed]
As of 2017, airlines such asDelta andAmerican have been introducing satellite internet as a means of combating limited bandwidth on airplanes and offering passengers usable internet speeds.[12]
In September 2017,SES announced the next generation of O3b satellites and service, namedO3b mPOWER, a constellation of sevenMEO satellites to deliver 10 terabits of capacity globally through 30,000 spot beams for broadband internet services.[13] The number of O3b mPOWER satellites ordered was subsequently increased to 11 and then 13, and on 16 December 2022, the first twoO3b mPOWER satellites were successfully launched, with four more in 2023, and the service began operations alongside the existing O3b constellation in April 2024.[14][15][16] Two further satellites have since joined the constellation, launched in 2024[17][18]
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As of 2024,[update] companies providing home internet service in the United States via satellite includedViaSat, through itsExede brand,EchoStar, through subsidiaryHughesNet,Starlink, andProject Kuiper.[19]
The EU plans to commence theIRIS² project in the 2020s.[20]
As of 2023,[update] China is in the process of developing its own, state-owned,satellite internet constellation, run byChinasat.[21]
India’s main offerings in the space isOneweb andJioSpaceFiber.[22] And is as of 2023, entertaining licenses for Starlink and Project Kuiper.[23]
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Satellite Internet generally relies on three primary components: a satellite – historically ingeostationary orbit (or GEO) but now increasingly inLow Earth orbit (LEO) orMedium Earth orbit MEO)[24] – a number of ground stations known as gateways that relay Internet data to and from the satellite via radio waves (microwave), and further ground stations to serve each subscriber, with a small antenna andtransceiver. Other components of a satellite Internet system include amodem at the user end which links the user's network with the transceiver, and a centralizednetwork operations centre (NOC) for monitoring the entire system. Working in concert with a broadband gateway, the satellite operates aStar network topology where all network communication passes through the network's hub processor, which is at the centre of the star. With this configuration, the number of ground stations that can be connected to the hub is virtually limitless.
Marketed as the centre of the new broadband satellite networks are a new generation of high-powered GEO satellites positioned 35,786 kilometres (22,236 mi) above the equator, operating in Ka-band (18.3–30 GHz) mode.[25] These new purpose-built satellites are designed and optimized for broadband applications, employing many narrow spot beams,[26] which target a much smaller area than the broad beams used by earlier communication satellites. This spot beam technology allows satellites to reuse assigned bandwidth multiple times which can enable them to achieve much higher overall capacity than conventional broad beam satellites. The spot beams can also increase performance and consequential capacity by focusing more power and increased receiver sensitivity into defined concentrated areas. Spot beams are designated as one of two types: subscriber spot beams, which transmit to and from the subscriber-side terminal, and gateway spot beams, which transmit to/from a service provider ground station. Note that moving off the tight footprint of a spotbeam can degrade performance significantly. Also, spotbeams can make the use of other significant new technologies impossible, including 'Carrier inCarrier' modulation.
In conjunction with the satellite's spot-beam technology, abent-pipe architecture has traditionally been employed in the network in which the satellite functions as a bridge in space, connecting two communication points on the ground. The term "bent-pipe" is used to describe the shape of the data path between sending and receiving antennas, with the satellite positioned at the point of the bend.Simply put, the satellite's role in this network arrangement is to relay signals from the end user's terminal to the ISP's gateways, and back again without processing the signal at the satellite. The satellite receives, amplifies, and redirects a carrier on a specific radio frequency through a signal path called a transponder.[27]
Some satellite constellations in LEO such asStarlink and the proposedTelesat constellation will employlaser communication equipment for high-throughput optical inter-satellite links. The interconnected satellites allow for direct routing of user data from satellite to satellite and effectively create a space-basedoptical mesh network that will enable seamless network management and continuity of service.[28]
The satellite has its own set of antennas to receive communication signals from Earth and to transmit signals to their target location. These antennas and transponders are part of the satellite's "payload", which is designed to receive and transmit signals to and from various places on Earth. What enables this transmission and reception in the payload transponders is a repeater subsystem (RF (radio frequency) equipment) used to change frequencies, filter, separate, amplify and group signals before routing them to their destination address on Earth. The satellite's high-gain receiving antenna passes the transmitted data to the transponder which filters, translates and amplifies them, then redirects them to the transmitting antenna on board. The signal is then routed to a specific ground location through a channel known as a carrier. Beside the payload, the other main component of a communications satellite is called the bus, which comprises all equipment required to move the satellite into position, supply power, regulate equipment temperatures, provide health and tracking information, and perform numerous other operational tasks.[27]
Along with dramatic advances in satellite technology over the past decade, ground equipment has similarly evolved, benefiting from higher levels of integration and increasing processing power, expanding both capacity and performance boundaries.Thegateway—or gateway Earth station—is also referred to as a ground station, teleport or hub. The term is sometimes used to describe just the antenna dish portion, or it can refer to the complete system with all associated components.In short, the gateway receives radio wave signals from the satellite on the last leg of the return or upstream payload, carrying the request originating from the end-user's site. The satellite modem at the gateway location demodulates the incoming signal from the outdoor antenna into IP packets and sends the packets to the local network. Access server/gateways manage traffic transported to/from the Internet. Once the initial request has been processed by the gateway's servers, sent to and returned from the Internet, the requested information is sent back as a forward or downstream payload to the end-user via the satellite, which directs the signal to the subscriber terminal. Each Gateway provides the connection to the Internet backbone for the gateway beam(s) it serves.
The system of gateways comprising the satellite ground system provides all network services for satellite and corresponding terrestrial connectivity. Each gateway provides a multiservice access network for subscriber terminal connections to the Internet.
As the continental United States is north of the equator, all gateway and subscriber dish antenna must have an unobstructed view of the southern sky. Because of the satellite's geostationary orbit, the gateway antenna can stay pointed at a fixed position.
For the customer-provided equipment (i.e. PC and router) to access the broadband satellite network, the customer must have additional physical components installed:
At the far end of the outdoor unit is typically a small (2–3-foot, 60 to 90 cm diameter), reflective dish-type radio antenna. The VSAT antenna must also have an unobstructed view of the sky to allow for properline-of-sight (L-O-S) to the satellite. There are four physical characteristic settings used to ensure that the antenna is configured correctly at the satellite, which are:azimuth, elevation,polarization, andskew. The combination of these settings gives the outdoor unit a L-O-S to the chosen satellite and makes data transmission possible. These parameters are generally set at the time the equipment is installed, along with a beam assignment (Ka-band only); these steps must all be taken prior to the actual activation of service.Transmit and receive components are typically mounted at the focal point of the antenna which receives/sends data from/to the satellite. The main parts are:
The satellitemodem serves as an interface between the outdoor unit and customer-provided equipment (i.e. PC, router) and controls satellite transmission and reception. From the sending device (computer, router, etc.) it receives an inputbitstream and converts or modulates it into radio waves, reversing that order for incoming transmissions, which is calleddemodulation. It provides two types of connectivity:
Consumer grade satellite modems typically employ either theDOCSIS orWiMAX telecommunication standard to communicate with the assigned gateway.
Latency (commonly referred to as "ping time") is the delay between requesting data and the receipt of a response, or in the case of one-way communication, between the actual moment of a signal's broadcast and the time it is received at its destination.
A radio signal takes about 120 milliseconds to reach a geostationary satellite and then 120 milliseconds to reach the ground station, so nearly 1/4 of a second overall. Typically, during perfect conditions, the physics involved in satellite communications account for approximately 550 milliseconds of latency round-trip time.
The longer latency is the primary difference between a standard terrestrial-based network and a geostationary satellite-based network. The round-trip latency of a geostationary satellite communications network can be more than 12 times that of a terrestrial based network.[29][30]
Satellite latency can be detrimental to especially time-sensitive applications such as on-line gaming (although it only seriously affects the likes offirst-person shooters orracing simulators while manyMMOGs can operate well over satellite Internet[31]), but IPTV is typically asimplex operation (one-way transmission) and latency is not a critical factor for video transmission.
The effects of this delay may be mitigated using data compression, TCP-acceleration, and HTTP pre-fetching.[32]
Ageostationary orbit (or geostationary Earth orbit/GEO) is a geosynchronous orbit directly above the Earth's equator (0° latitude), with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero (i.e. a "circular orbit"). An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers. Launchers often place communications satellites and weather satellites in geostationary orbits, so that the satellite antennas that communicate with them do not have to move to track them, but can point permanently at the position in the sky where the satellites stay. Due to the constant 0° latitude and circularity of geostationary orbits, satellites in GEO differ in location by longitude only.
Compared to ground-based communication, all geostationary satellite communications experience higher latency due to the signal having to travel35,786 km (22,236 mi) to a satellite in geostationary orbit and back to Earth again. Even at thespeed of light (about 300,000 km/s or 186,000 miles per second), this delay can appear significant. If all other signaling delays could be eliminated, it still takes a radio signal about 250 milliseconds (ms), or about a quarter of a second, to travel to the satellite and back to the ground.[33] The absolute minimum total amount of delay varies, due to the satellite staying in one place in the sky, while ground-based users can be directly below (with a roundtrip latency of 239.6 ms), or far to the side of the planet near the horizon (with a roundtrip latency of 279.0 ms).[34]
For an Internet packet, that delay is doubled before a reply is received. That is the theoretical minimum. Factoring in other normal delays from network sources gives a typical one-way connection latency of 500 to 700 ms from the user to the ISP, or about 1,000 to 1,400 ms latency for the total round-trip time (RTT) back to the user. This is more than most dial-up users experience at typically 150–200 ms total latency, and much higher than the typical 15 to 40 ms latency experienced by users of other high-speed Internet services, such ascable orVDSL.[35]
For geostationary satellites, there is no way to eliminate latency, but the problem can be somewhat mitigated in Internet communications withTCP acceleration features that shorten the apparent round trip time (RTT) per packet by splitting ("spoofing") the feedback loop between the sender and the receiver. Certain acceleration features are often present in recent technology developments embedded in satellite Internet equipment.
Latency also impacts the initiation of secure Internet connections such asSSL which require the exchange of numerous pieces of data between web server and web client. Although these pieces of data are small, the multiple round trips involved in the handshake produce long delays compared to other forms of Internet connectivity, as documented by Stephen T. Cobb in a 2011 report published by the Rural Mobile and Broadband Alliance.[36] This annoyance extends to entering and editing data using some Software as a Service orSaaS applications as well as in other forms of online work.
Functions, like live interactive access to a distant computer—such asvirtual private networks, can be affected by the high latency. Many TCP protocols were not designed to work in high-latency environments.
Medium Earth orbit (MEO) and low Earth orbit (LEO) satellite constellations do not have such long delays, as the satellites are closer to the ground. For example:
Unlike geostationary satellites, LEO and MEO satellites do not stay in a fixed position in the sky and from a lower altitude they can "see" a smaller area of theEarth, and so continuous widespread access requires a constellation of many satellites (low-Earth orbits needing more satellites than medium-Earth orbits) with complex constellation management to switch data transfer between satellites and keep the connection to a customer, and tracking by the ground stations.[24][41]
MEO satellites require higher power transmissions than LEO to achieve the same signal strength at the ground station but their higher altitude also provides less orbital overcrowding, and their slower orbit speed reduces bothDoppler shift and the size and complexity of the constellation required.[42][43]
Tracking of the moving satellites is usually undertaken in one of three ways, using:
In May 2022,Kazakhstani mobile network operator,Kcell, and satellite owner and operator,SES used SES'sO3b MEO satellite constellation to demonstrate that MEO satellites could be used to provide high-speed mobile internet to remote regions of Kazakhstan for reliable video calling, conferencing and streaming, and web browsing, with a latency five times lower than on the existing platform based ongeostationary orbit satellites.[44][45]
A proposed alternative to relay satellites is a special-purposehigh altitude platform stations aircraft, which would fly along a circular path above a fixed ground location, operating under autonomous computer control at a height of approximately 20,000 meters.
For example, the United StatesDefense Advanced Research Projects AgencyVulture project envisaged an ultralight aircraft capable of station-keeping over a fixed area for a period of up to five years, and able to provide both continuous surveillance to ground assets as well as to service extremely low-latency communications networks.[46] This project was cancelled in 2012 before it became operational.[citation needed]
Onboard batteries would charge during daylight hours through solar panels covering the wings and would provide power to the plane during night. Ground-based satellite internet dishes would relay signals to and from the aircraft, resulting in a greatly reduced round-trip signal latency of only 0.25 milliseconds. The planes could potentially run for long periods without refueling. Several such schemes involving various types of aircraft have been proposed in the past.
Satellite communications are affected by moisture and various forms of precipitation (such as rain or snow) in the signal path between end users or ground stations and the satellite being utilized. This interference with the signal is known asrain fade. The effects are less pronounced on the lower frequency 'L' and 'C' bands but can become quite severe on the higher frequency 'Ku' and 'Ka' band. For satellite Internet services in tropical areas with heavy rain, use of the C band (4/6 GHz) with a circular polarisation satellite is popular.[47] Satellite communications on the Ka band (19/29 GHz) can use special techniques such as largerain margins,adaptive uplink power control andreduced bit rates during precipitation.
Rain margins are the extra communication link requirements needed to account for signal degradations due to moisture and precipitation, and are of acute importance on all systems operating at frequencies over 10 GHz.[48]
The amount of time during which service is lost can be reduced by increasing the size of thesatellite communication dish so as to gather more of the satellite signal on the downlink and also to provide a stronger signal on the uplink. In other words, increasing antenna gain through the use of a larger parabolic reflector is one way of increasing the overall channel gain and, consequently, the signal-to-noise (S/N) ratio, which allows for greater signal loss due to rain fade without the S/N ratio dropping below its minimum threshold for successful communication.
Modern consumer-grade dish antennas tend to be fairly small, which reduces the rain margin or increases the required satellite downlink power and cost. However, it is often more economical to build a more expensive satellite and smaller, less expensive consumer antennas than to increase the consumer antenna size to reduce the satellite cost.
Large commercial dishes of 3.7 m to 13 m diameter can be used to achieve increased rain margins and also to reduce the cost per bit by allowing for more efficient modulation codes. Alternately, larger aperture antennae can require less power from the satellite to achieve acceptable performance. Satellites typically usephotovoltaic solar power, so there is no expense for the energy itself, but a more powerful satellite will require larger, more powerful solar panels and electronics, often including a larger transmitting antenna. The larger satellite components not only increase materials costs but also increase the weight of the satellite, and in general, the cost to launch a satellite into an orbit is directly proportional to its weight. (In addition, since satellite launch vehicles [i.e. rockets] have specific payload size limits, making parts of the satellite larger may require either more complex folding mechanisms for parts of the satellite like solar panels and high-gain antennas, or upgrading to a more expensive launch vehicle that can handle a larger payload.)
Modulated carriers can be dynamically altered in response to rain problems or other link impairments using a process called adaptive coding and modulation, or "ACM". ACM allows the bit rates to be increased substantially during normal clear sky conditions, increasing the number of bits per Hz transmitted, and thus reducing overall cost per bit. Adaptive coding requires some sort of a return or feedback channel which can be via any available means, satellite or terrestrial.
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Two objects are said to be within line of sight if a straight line between the objects can be connected without any interference, such as a mountain. An object beyond the horizon is below the line of sight and, therefore, can be difficult to communicate with.
Typically a completely clear line of sight between the dish and the satellite is required for the system to work optimally. In addition to the signal being susceptible to absorption and scattering by moisture, the signal is similarly impacted by the presence of trees and other vegetation in the path of the signal. As the radio frequency decreases, to below 900 MHz, penetration through vegetation increases, but most satellite communications operate above 2 GHz making them sensitive to even minor obstructions such as tree foliage. A dish installation in the winter must factor in plant foliage growth that will appear in the spring and summer.
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Even if there is a direct line of sight between the transmitting and receiving antenna, reflections from objects near the path of the signal can decrease apparent signal power through phase cancellations. Whether and how much signal is lost from a reflection is determined by the location of the object in theFresnel zone of the antennas.
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Home or consumer grade two-way satellite Internet service involves both sending and receiving data from a remotevery-small-aperture terminal (VSAT) via satellite to a hubtelecommunications port (teleport), which then relays data via the terrestrial Internet. The satellite dish at each location must be precisely pointed to avoid interference with other satellites. At each VSAT site the uplink frequency, bit rate and power must be accurately set, under control of the service provider hub.
There are several types of two-way satellite Internet services, includingtime-division multiple access (TDMA) andsingle channel per carrier (SCPC). Two-way systems can be simpleVSAT terminals with a 60–100 cm dish and output power of only a few watts intended for consumers and small business or larger systems that provide more bandwidth. Such systems are frequently marketed as "satellite broadband" and can cost two to three times as much per month as land-based systems such asADSL. Themodems required for this service are often proprietary, but some are compatible with several different providers. They are also expensive, costing in the range of US$600 to $2000.
The two-way "iLNB" used on theSES Broadband terminal dish has a transmitter and single-polarity receive LNB, both operating in theKu band. Pricing for SES Broadband modems range from €299 to €350. These types of system are generally unsuitable for use on moving vehicles, although some dishes may be fitted to an automatic pan and tilt mechanism to continuously re-align the dish—but these are more expensive. The technology for SES Broadband was delivered by a Belgian company called Newtec.
Consumer satellite Internet customers range from individual home users with one PC to large remote business sites with several hundred PCs.
Home users tend to use shared satellite capacity to reduce the cost, while still allowing high peak bit rates when congestion is absent. There are usually restrictive time-based bandwidth allowances so that each user gets their fair share, according to their payment. When a user exceeds their allowance, the company may slow down their access, deprioritise their traffic or charge for the excess bandwidth used. For consumer satellite Internet, the allowance can typically range from 200 MB per day to 25 GB per month.[49][50][51] A shared download carrier may have a bit rate of 1 to 40 Mbit/s and be shared by up to 100 to 4,000 end users.
The uplink direction for shared user customers is normallytime-division multiple access (TDMA), which involves transmitting occasional short packet bursts in between other users (similar to how a cellular phone shares a cell tower).
Each remote location may also be equipped with a telephone modem; the connections for this are as with a conventional dial-up ISP. Two-way satellite systems may sometimes use the modem channel in both directions for data where latency is more important than bandwidth, reserving the satellite channel for download data where bandwidth is more important than latency, such as forfile transfers.
In 2006, theEuropean Commission sponsored theUNIC Project which aimed to develop an end-to-end scientific test bed for the distribution of new broadband interactive TV-centric services delivered over low-cost two-way satellite to actual end-users in the home.[52] The UNIC architecture employsDVB-S2 standard for downlink andDVB-RCS standard for uplink.
Normal VSAT dishes (1.2 to 2.4 m diameter) are widely used for VoIP phone services. A voice call is sent by means of packets via the satellite and Internet. Using coding and compression techniques the bit rate needed per call is only 10.8 kbit/s each way.
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These usually come in the shape of a self-contained flat rectangular box that needs to be pointed in the general direction of the satellite—unlike VSAT the alignment need not be very precise and the modems have built in signal strength meters to help the user align the device properly. The modems have commonly used connectors such asEthernet orUniversal Serial Bus (USB). Some also have an integratedBluetooth transceiver and double as a satellite phone. The modems also tend to have their own batteries so they can be connected to alaptop without draining its battery. The most common such system isINMARSAT'sBGAN—these terminals are about the size of abriefcase and have near-symmetric connection speeds of around 350 to 500 kbit/s. Smaller modems exist like those offered byThuraya but only connect at 444 kbit/s in a limited coverage area.
At $5 to $7 per megabyte on average, portable satellite internet is typically more expensive than other modes of Internet access, with modems usually costing between $1,000 and $5,000.[53] Due to this, it is most often used on vehicles without access to other modes of Internet access, such as seafaring vessels.[citation needed]
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For many years[when?]satellite phones have been able to connect to the Internet. Bandwidth varies from about 2400bit/s forIridium network satellites andACeS based phones to 15 kbit/supstream and 60 kbit/sdownstream forThuraya handsets. Globalstar also provides Internet access at 9.6 kbit/s; like Iridium and ACeS adial-up connection is required and is billed per minute, however bothGlobalstar and Iridium are planning to launch new satellites offering always-on data services at higher rates. With Thuraya phones the 9.6 kbit/s dial-up connection is also possible, the 60 kbit/s service is always-on and the user is billed for data transferred (about $5 permegabyte). The phones can be connected to a laptop or other computer using a USB orRS-232 interface. Due to the low bandwidths involved it is extremely slow to browse the web with such a connection, but useful for sending email,Secure Shell data and using other low-bandwidth protocols. Since satellite phones tend to haveomnidirectional antennas no alignment is required as long as there is a line of sight between the phone and the satellite.
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One-way terrestrial return satellite Internet systems are used with conventionaldial-up Internet access, with outbound (upstream) data traveling through a telephonemodem, butdownstream data sent via satellite at a higher rate. In the U.S., an FCC license is required for the uplink station only; no license is required for the users.
Another type of one-way satellite Internet system usesGeneral Packet Radio Service (GPRS) for the back-channel.[54] Using standard GPRS orEnhanced Data Rates for GSM Evolution (EDGE), costs are reduced for higher effective rates if the upload volume is very low, and also because this service is not per-time charged, but charged by volume uploaded. GPRS as return improves mobility when the service is provided by a satellite that transmits in the field of 100 to 200 kW.[citation needed] Using a 33 cm wide satellite dish, a notebook and a normal GPRS equippedGSM phone, users can get mobile satellite broadband.
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The transmitting station has two components, consisting of a high-speed Internet connection to serve many customers at once, and the satellite uplink to broadcast requested data to the customers. The ISP's routers connect to proxy servers which can enforce quality of service (QoS) bandwidth limits and guarantees for each customer's traffic.
Often, nonstandardIP stacks are used to address thelatency and asymmetry problems of the satellite connection. As with one-way receive systems, data sent over the satellite link is generally also encrypted, as otherwise it would be accessible to anyone with a satellite receiver.
Many IP-over-satellite implementations use paired proxy servers at both endpoints so that certain communications between clients and servers[55] need not to accept the latency inherent in a satellite connection. For similar reasons, there exist specialVirtual private network (VPN) implementations designed for use over satellite links because standard VPN software cannot handle the long packet travel times.
Upload speeds are limited by the user's dial-up modem, while download speeds can be very fast compared to dial-up, using the modem only as the control channel for packet acknowledgement.
Latency is still high, although lower than full two-way geostationary satellite Internet, since only half of the data path is via satellite, the other half being via the terrestrial channel.
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One-way broadcast satellite Internet systems are used forInternet Protocol (IP)broadcast-based data, audio and video distribution. In the United States, aFederal Communications Commission (FCC) license is required only for the uplink station, not for its users. Note that most Internet protocols will not work correctly over one-way access, since they require a return channel. However, Internet content such asweb pages can still be distributed over a one-way system by "pushing" them out to local storage at end user sites, though full interactivity is not possible. This is much like TV or radio content which offers little user interface.
The broadcast mechanism may include compression and error correction to help ensure the one-way broadcast is properly received. The data may also be rebroadcast periodically, so that receivers that did not previously succeed will have additional chances to try downloading again.
The data may also be encrypted so that while anyone can receive the data, only certain destinations are able to actually decode and use the broadcast data. Authorized users only need to have possession of either a shortdecryption key or an automaticrolling code device that uses its own highly accurate independent timing mechanism to decrypt the data.
Similar to one-way terrestrial return, satellite Internet access may include interfaces to thepublic switched telephone network for squawk box applications. An Internet connection is not required, but many applications include aFile Transfer Protocol (FTP) server to queue data for broadcast.
Most one-way broadcast applications require custom programming at the remote sites. The software at the remote site must filter, store, present a selection interface to and display the data. The software at the transmitting station must provide access control, priority queuing, sending, and encapsulating of the data.
Emerging commercial services in this area include:
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In its report released in February, 2013, the Federal Communications Commission noted significant advances in satellite Internet performance. The FCC's Measuring Broadband America report also ranked the major ISPs by how close they came to delivering on advertised speeds. In this category, satellite Internet topped the list, with 90% of subscribers seeing speeds at 140% or better than what was advertised.[56]
Much of the slowdown associated with satellite Internet is that for each request, many roundtrips must be completed before any useful data can be received by the requester.[a] Special IP stacks and proxies can also reducelatency through lessening the number of roundtrips, or simplifying and reducing the length of protocol headers. Optimization technologies includeTCP acceleration,HTTP pre-fetching andDNS caching among many others. See theSpace Communications Protocol Specifications standard (SCPS), developed by NASA and adopted widely by commercial and military equipment and software providers in the market space.
TheWINDS satellite was launched on February 23, 2008. The WINDS satellite is used to provide broadband Internet services to Japan and locations across the Asia-Pacific region. The satellite to provides a maximum speed of 155 Mbit/s down and 6 Mbit/s up to residences with a 45 cm aperture antenna and a 1.2 Gbit/s connection to businesses with a 5-meter antenna.[57] It has reached the end of its design life expectancy.
SkyTerra-1 was launched in mid-November 2010, providing North America, whileHylas-1 was launched in November 2010, targeting Europe.[58]
On December 26, 2010, Eutelsat'sKA-SAT was launched. It covers the European continent with 80 spot beams—focused signals that cover an area a few hundred kilometers across Europe and the Mediterranean. Spot beams allow for frequencies to be effectively reused in multiple regions without interference. The result is increased capacity. Each of the spot beams has an overall capacity of 900 Mbit/s and the entire satellite will has a capacity of 70 Gbit/s.[58]
ViaSat-1 was launched Oct. 19, 2011 from Baikonur, Kazakhstan, offering 140 Gbit/s of total throughput capacity, through theExede Internet service. Passengers aboardJetBlue Airways can use this service since 2015.[59] The service has also been expanded toUnited Airlines,American Airlines,Scandinavian Airlines,Virgin America andQantas.[60][61][62]
TheEchoStar XVII satellite was launched July 5, 2012 by Arianespace and was placed in its permanent geosynchronous orbital slot of 107.1° West longitude, servicingHughesNet. This Ka-band satellite has over 100 Gbit/s of throughput capacity.[63]
In 2015 and 2016, the Australian Government launched twoSky Muster geostationary satellites to provide internet to regional Australians and residents of External Territories, such asNorfolk Island andChristmas Island.[64]
In 2006[65] and 2015,[66] the Argentinian companyARSAT launched theARSAT-1 andARSAT-2 satellites, respectively. Providing internet and TV access to remote locations in its country of origin.
Since 2013, theO3b satellite constellation (inMedium Earth Orbit at an altitude of 8,063 km) claims an end-to-end round-trip latency of 140 ms for data services. Since 2024, the next generationO3b mPOWER constellation has been operating alongside in MEO, offering tens of Mbps to multiple Gbps per service with a latency of about 150 ms[67]
As of September 2024[update], 6,426Starlink satellites are orbiting Earth. As of September 2024, Starlink has over 4 million subscribers.[68][69][70] There are 648Oneweb has satellites in low Earth orbit.[71]
Satellite communications are used for data transmission,remote instrument diagnostics, for physical satellite andoceanographic measurements from the sea surface (e.g.sea surface temperature andsea surface height[72]) to theocean floor, and forseismological analyses.[73]
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