Information on Satellite Internet access
Satellite Internet access
is Internet access provided through satellites. The service can be provided to users world-wide through low Earth orbit (LEO) satellites. Geostationary satellites can offer higher data speeds, but their signals can not reach some polar regions of the world. Different types of satellite systems have a wide range of different features and technical limitations, which can greatly affect their usefulness and performance in specific applications.
Two-way satellite-only communication
Two-way satellite Internet service involves both sending and receiving data from a remote very-small-aperture terminal (VSAT) via satellite to a hub telecommunications 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. 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 professionals such as those from iDirect will allow the operator to define and meet strict service level agreements - 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 dishâ€”although the European ASTRA2Connect system encourages user-installation and provides detailed instructions for this. Many customers in the Middle East and Africa are also encouraged to do 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
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 - 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. The modems 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 the ASTRA2Connect.
The two-way "iLNB" used on the ASTRA2Connect terminal dish has a transmitter and single-polarity receive LNB, both operating in the Ku band. Pricing for Astra2Connect 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 ASTRA2Connect was delivered by a Belgian company called Newtec.
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 17,000 MB per month. 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 normally time 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 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.
Normal VSAT dishes (1.2 - 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.
Portable satellite Internet
Portable satellite modem
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 or Universal Serial Bus (USB). 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 - 500 kbit/s. Smaller modems exist like those offered by Thuraya but only connect at 444 kbit/s in a limited coverage area.
Using such a modem is extremely expensiveâ€”bandwidth costs between $5 and $7 per megabyte. The modems themselves are also expensive, usually costing between $1,000 and $5,000.
Internet via satellite phone
For many years satellite phones have been able to connect to the internet. Bandwidth varies from about 2400 bit/s for Iridium network satellites and ACeS based phones to 15 kbit/s upstream and 60 kbit/s downstream for Thuraya handsets. Globalstar also provides internet access at 9600 bit/s - 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 rates. With Thuraya phones the 9,600 bit/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 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, Secure Shell data and using other low-bandwidth protocols. Since satellite phones tend to have omnidirectional antennas no alignment is required as long as there is a line of sight between the phone and the satellite.
One-way receive, with terrestrial transmit
One-way terrestrial return satellite Internet systems are used with conventional dial-up Internet access, with outbound (upstream) data traveling through a telephone modem, but downstream 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 1-way satellite Internet system uses General Packet Radio Service (GPRS) for the back-channel. Using standard GPRS or Enhanced Data Rates for GSM Evolution (EDGE), if the upload volume is very low and since this service is not per-time charged, but charged by volume uploaded, costs are reduced for higher effective rates. GPRS as return improves mobility when the service is provided by a satellite that transmits in the field of 50 - 53 dBW. Using a 33 cm wide satellite dish, a notebook and a normal GPRS equipped GSM phone, users can get mobile satellite broadband.
System hardware components
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 modulator. The radio frequency (RF) signal from the DVB-S modulator 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
- 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
System software components
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 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 (minimum of 240 ms one-way, resulting in a minimum round-trip time of almost 500 ms). Download speeds can be very fast compared to dial-up.
Theory of operation
Remote sites use proxy server or(and) Virtual private network servers 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)
One-way broadcast, receive only
One-way broadcast satellite Internet systems are used for Internet Protocol (IP) broadcast-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.
System hardware components
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 a File Transfer Protocol (FTP) server to queue data for broadcast.
System software components
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.
Reducing satellite latency
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. Special IP stacks and proxies can also reduce latency through lessening the number of roundtrips, or simplifying and reducing the length of protocol headers. These types of technologies are generally referred to as TCP acceleration, HTTP pre-fetching and DNS caching.
Elimination of advertising
While also effective for terrestrial communications, the use of ad-blocking software such as Adblock for Firefox is exceptionally beneficial for satellite Internet, as most Internet advertising websites use cache busting in order to render the browser and ISP's cache useless, by displaying advertisements (for the purpose of maximizing the number of ad views seen by the affiliate marketing company's server).
A satellite nicknamed Kizuna, means "ties between people", also known formally as the WINDS satellite was launched on February 23, 2008. The WINDS satellite will be used to provide broadband Internet services to Japan and locations across the Asia-Pacific region. It is equipped with a multi-beam antenna that can obtain two-way communication with the ground at speeds of 1.2 Gigabit/s for businesses (with a 15 ft diameter antenna) and 155 Megabyte/s (with 4 ft ground antenna). This satellite also contains a sort of switchboard device that allows it to route messages by itself. This is a notable departure from past satellites that required assistance from ground based facilities.
SkyTerra-1 was launched in mid-November 2010 and will provide service across North America while Hylas-1 was launched at the end of November 2010 and will target Europe.
On December 26, 2010, Eutelsat's KA-SAT was successfully launched by an ILS Proton Breeze M vehicle at the BaÃ¯konour Cosmodrome Kazakhstan. The last satellite was due in service in mid 2011. 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 will have an overall capacity of 900 Mbit/s and the entire satellite will have a capacity of 70 Gbit/s.