Two-way satellite Internet service involves both sending and receiving data from a remote very-small-aperture terminal (VSAT), a two-way satellite ground station or a stabilized maritime VSAT antenna with a dish antenna that is smaller than three meters; via satellite to a hub telecommunications port (teleport), a satellite ground station with multiple parabolic antennas (i.e., an antenna farm) that functions as a hub connecting a satellite or geocentric orbital network with a terrestrial telecommunications network. It will then relay data via the terrestrial Internet.
The satellite dish at each location must be precisely pointed to avoid interference with other satellites. The two way satellite market can be divided into those systems that support professional applications, such as banking, retail, etc., and those built to provide home or small business users with access. The key difference between these systems can be seen in their ability to support advanced quality of service controls. While systems for professional such as those from VT iDirect (“iDirect”), a Herndon, Virginia based company that develops satellite-based IP communications technology, will allow the operator to define and meet strict service level agreements (”SLA”), a part of a service contract where the level of service is formally defined--those used for consumer access provide a ‘best effort’ service level.
Some providers oblige the customer to pay for a member of the provider’s staff to install the system and correctly align the dish--although the European ASTRA2Connect system (now “SES Broadband”), a two-way satellite broadband Internet service available across Europe, which launched in March 2007, and uses the Astra series of geostationary satellites, encourages user-installation and provides detailed instructions for this. Many customers in the Middle East and Africa are also encouraged to self installs. At each VSAT site, the uplink frequency bit rate and power must be accurately set, under control of the service provider hub, example connection Magellano Internet Satellitare KaSat.
These are the several types of two-way satellite Internet access, including: time division multiple access (TDMA), a channel access method for shared medium networks; and single channel per carrier (SCPC), referring to using a single signal at a given frequency and bandwidth.
Two-way systems can be simple VSAT terminals with a 60-100 cm 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 can cost two to three times as much per month as land-based systems such as ADSL (“Asymmetric Digital Subscriber Line”), a type of digital subscriber line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voice band modem can provide.
The satellite modems, or modems used to establish data transfers using a communications satellite as a relay, required for this service are often proprietary, but some are compatible with several different providers. They are also expensive, consisting in the range of US $ 600 to US $ 2000.
The portable satellite Internet modem usually comes 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 to help the user align the device properly.
The modems have commonly used connectors such as Ethernet, a family of computer networking technologies for local area networks (LANs), or Universal Serial Bus (USB), an industry standard developed in the mid-1990s that defines the cables, connectors and communications protocols used in a bus for connection, communication and power supply between computers and electronic devices. Some also has an integrated Bluetooth transceiver, a wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from 2400-2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security, and double as a satellite phone. The modems also tend to have their own batteries so they can be connected to a laptop computer (a personal computer for mobile use) without draining its battery.
The most common in such system is INMARSAT plc’s (a British satellite telecommunications company, offering global, mobile services) BGAN (“Broadband Global Area Network”), a global Satellite Internet Network with telephony using portable terminals--these terminals are about the size of a briefcase, a narrow box-shaped bag or case used mainly for carrying papers and other documents and equipped with a handle, and have near-symmetric connection speeds of around 350-500 kbit/s. Smaller modems exist like those offered by Thuraya (from the Arabic name Thurayya meaning Star), an international mobile satellite services provider that delivers communications solutions in more than 140 countries across Europe, the Middle East, north central and East Africa, Asia and Australia, but only connect at 444 kbit/s in a limited coverage areas.
Using such a modem is extremely expensive--bandwidth costs between $5 and $7 per megabyte (abbreviated as “Mbyte” or “MB”--a multiple of the unit byte for digital information storage or transmission with three different values depending on context: 1 048 576 bytes (220) generally for computer memory; and one million bytes (106, see prefix mega-) generally for computer storage). The modern themselves are also expensive, usually costing between $1,000 and $5,000.
See: Two-way satellite-only communication: Bandwidth
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