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Satellite Internet services are used in locations where terrestrial Internet access is not available and in locations which move frequently. Internet access via satellite is available worldwide, including vessels at sea and mobile land vehicles. There are three types of satellite Internet service.

One-way multicast satellite Internet systems are used for Internet Protocol (IP) multicast-based data, audio and video distribution. In the U.S., a Federal Communications Commission (FCC) license is required only for the uplink station and no license is required for users. Note that most Internet protocols will not work correctly over one-way access, since they require a return channel. However, Internet content such as web 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.

Similar to one-way terrestrial return, satellite Internet access may include interfaces to the public switched telephone network for squawk box applications. An Internet connection is not required, but many applications include an File Transfer Protocol (FTP) server to queue data for broadcast.

Most one-way multicast 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 queueing, sending, and encapsulating of the data.

One-way terrestrial return satellite Internet systems are used with traditional dial-up access to the Internet, with outbound data traveling through a telephone modem, but downloads sent via satellite at a speed near that of broadband Internet access. In the U.S., an FCC license is required for the uplink station only; no license is required for the users.

Another type of 1-way satellite internet system involves the use of General Packet Radio Service (GPRS) for the back-channel.^[1] By utilizing a connection that is offered in standard GPRS or EDGE, the upload volume is very low and since this service is not per-time charged, but charged by volume uploaded, users are able to surf and download in broadband speeds. Another view of using GPRS as return would be the mobility when the service is provided by a satellite that transmits in the field of 50 to 53 dBW. Using a 33 cm wide satellite dish, a notebook and a normal GPRS equipped GSM phone, users can get mobile satellite broadband.

The transmitting station (also called "teleport", "head end", "uplink facility", or "hub") has two components:

• Internet connection: The ISP's routers connect to proxy servers which can enforce quality of service (QoS) bandwidth limits and guarantees for user traffic. These are then connected to a DVB encapsulator which is then connected to a DVB-S modem. The radio frequency (RF) signal from the DVB-S modem is connected to an up converter which is connected via feed line to the outdoor unit.
• Satellite uplink: The block upconverter (BUC) and optional low-noise block converter (LNB), which may use a waveguide to connect to the optional orthomode transducer (OMT) which is bolted to the feed horn which is connected by metal supports to the satellite dish and mount.

At the remote location (Earth station) the setup consists of:

• Outdoor unit
  • Satellite dish with mount
  • Feedhorn
  • Universal LNB, for Ku band.
  • Feed line
• Indoor unit
  • DVB-S Peripheral Component Interconnect (PCI) card internal to a computer
  • or, DVB external modem where an 8P8C (RJ-45) Ethernet port or a Universal Serial Bus (USB) port connects the modem to the computer

Remote sites require a minimum of programming to provide authentication and set proxy server settings. Filtering is usually provided by the DVB card driver.

Often, non-standard IP stacks are used to address the latency and asymmetry problems of the satellite connection. 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 [[1]] do not need to accept the latency inherent in a satellite connection. For similar reasons, there exist special Virtual 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, and latency is high, as it is for any satellite based Internet. Download speeds can be very fast compared to dial-up:1 Mbit,4 Mbit,16 Mbit packages are generally offered.

The back panel of a satellite modem, with coaxial connections for both incoming and outgoing signals, and an Ethernet port for connection to the internal network.

Remote sites use the proxy server at the earth station (teleport), which is configured to route all outbound traffic to the QoS server, which makes sure no user exceeds their allotted bandwidth or monthly traffic limits. Traffic is then sent to the encapsulator, which puts the IP packets inside of DVB packets. The DVB packets are then sent to the DVB modem and then to the transmitter (BUC).

Two-way satellite Internet service sends data from remote sites via satellite to a hub, which then sends the data to the Internet. The satellite dish at each location must be precisely positioned to avoid interference with other satellites. The oscillators in some radar detectors can cause interference with these systems. Also, each location must use power management to adjust the amount of transmit power to compensate for conditions such as rain fade. There are several types of two way satellite Internet services, including time division multiple access (TDMA) and single channel per carrier (SCPC).

Two-way systems can be simple VSAT terminals with a 60-100cm dish and output power of only a few watts intended for consumers and small business or larger systems which provide more bandwidth. Such systems are frequently marketed as "satellite broadband" and costs two to three times as much per month as land-based systems such as ADSL. The modems required for this service are often proprietary, but ones made by companies such as Gilat Satellite Networks are can be compatible with several different providers. They are also notoriously expensive, costing in the range of $600 to $2000 USD.

A line of sight between the dish and the satellite is required for the system to work and most providers will oblige the customer to pay for a member of the provider's staff to install the system and correctly align the dish. Thus making these type of systems generally unsuitable for use on moving vehicles or other frequently moved installations, however some dishes are fitted to an automatic pan and tilt mechanism which will automatically align the dish - but these are cumbersome and very expensive.

Downstream speeds range from 256kbit to 4mbits and above, with speeds between 512kb/s and 2mbits being the most common. Upstream speeds above 1mbit are technically possible but rarely seen with "ordinary" VSAT-style satellite internet. Most usually the upstream bandwidth is 128kbit, or 256kbit for the slightly more expensive packages.

Satellite internet providers usually impose very restrictive monthly bandwidth allowances. When a user exceeds this the company will slow down their access significantly, deprioritise their traffic or bill them for the excess bandwidth used. For consumer satellite internet this is usually only a few gigabytes per month.

Each remote location may also 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 for file transfers.

In 2006 the European Commission sponsored the UNIC project which aims at developing 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. The UNIC architecture employs DVB-S2 standard for downlink and DVB-RCS standard for uplink.

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 as Ethernet, Universal serial bus. Some also have an integrated Bluetooth transceiver and double as a satellite phone. The modems also tend to have their own batteries so they can be connected to a laptop without draining its battery. The most common such system is INMARSAT's BGAN - these terminals are about the size of a briefcase and have near-symmetric connection speeds of around 350-500kbits. Smaller modems exist like those offered by Thuraya but only connect at 144kbps in a smaller coverage area.

Using such a modem is extremely expensive - bandwidth costs between $5 and $7 per megabyte. The modems themselves are not cheap either, usually costing between $1000 and $4000

For many years now Satellite phones have been able to connect to the internet. Bandwidth varies from about 2400bps for Iridium and ACeS based phones to 15kbps upstream and 60kbps downstream for Thuraya handsets. Globalstar also provides internet access at 9600bps - like Iridium and ACeS a dial-up connection is required and is billed per minute, however both Globalstar and Iridium are planning to launch new satellites offering always-on data services at higher speeds. With Thuraya phones the 9600bps dial-up connection is also possible, the 60kbps service is always-on and the user is billed for data transferred (about $5 per megabyte). The phones can be connected to a laptop or other computer using a USB or RS-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, ssh and using other low-bandwidth protocols. Since satellite phones tend to have omnidrectional antennae no alignment is required as long as there is a line of sight between the phone and the satellite.

This article or section may contain original research or unverified claims. Please improve the article by adding references. See the talk page for details. (December 2007)

One solution is to use satellites in much lower orbit very close to the Earth, to shorten the travel distance. Such orbital paths are no longer geostationary, and so would require a large number of satellites in orbit so that at least one is visible in the sky at all times. Communication dishes could no longer be fixed, and would either need some way to track the satellites as they move across the sky, or to work in an omnidirectional manner without causing interference for anything else.

A theoretical alternative to satellites that is being explored is the use of ultra-light solar powered airplane (see the NASA Pathfinder) that could fly in a continuous, circling path perhaps 70,000 feet (20 km) high or an airship (see Stratellite). These would act as flying satellites, providing high-speed service to customers below the aircraft. Since the roundtrip signal distance would only be 30 miles (50 km), the latency caused by the speed of light is an almost insignificant 0.1 ms under the craft, and 2 ms at the edge of the covered area, at a 300 km (200 miles) distance. Such service via aircraft is still in the experimental stages as of 2006.

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.^[2]

• Back-channel and return channel
• HughesNet (formerly DIRECWAY)
• Ts_2
• IP over DVB
• Satellite dish
• StarBand
• Very small aperture terminal
• WildBlue
• Voice over IP
• Virtual private network
• List of device bandwidths
• Teledesic
• UNIC - UNIversal satellite home Connection