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.
The amount of time for which service is lost is reduced by increasing the size of the dish so as to gather more of the satellite signal on the downlink and producing a more intense transmission on the uplink.
Modern consumer-grade dish antennas tend to be fairly small, which reduces the rain margin or increases the required satellite downlink power and cost.
Large commercial dishes 3.7m to 13m diameter are used to achieve large rain margins and also to reduce the cost per bit by requiring far less power from the satellite.
Modern download DVB-S2 carriers, with RCS feedback, are intended to allow the modulation method to be dynamically altered, in response to rain problems at a receive site. This allows the bit rates to be increased substantially during normal clear sky conditions, thus reducing overall costs per bit.
The signal delay can be as much as 500 milliseconds to 900 milliseconds, which makes this service unusable for applications requiring real-time user input, such as online games or remote surgery. This delay can be very unpleasant with interactive applications, such as VoIP, videoconferencing, or other person to person communication. The functionality of live interactive access to a distant computer can also be subject to the problems caused by high latency. These problems are more than tolerable for just basic email access and web browsing and in most cases are barely noticeable.
There is no simple way to get around this problem. The delay is primarily due to the speed of light being 299,792.458 km/second (186,262.397 miles per second) in a vacuum. Even if all other signaling delays could be eliminated it still takes the electromagnetic wave 233 milliseconds to travel from ground to the satellite and back to the ground, a total of 70,000 km (44,000 miles) to travel from the source to the destination. 140,000 km (88,000 miles) for a round trip (user to ISP, and then back to user).Factoring in normal delays from other network sources gives a typical connection latency of 500–700 ms. This is far worse latency than even most dial-up modem users' experience, at typically only 150–200 ms total latency.
A proposed alternative to the geostationary relay is a special solar-powered ultralight airplane, which would fly along a circular path above a fixed ground location, operating under autonomous computer control at a height of approximately 65,000 feet. Onboard batteries would charge from solar panels covering the wings during the daylight hours, and would provide power to the plane during the night. Ground-based satellite dishes would relay signals off the plane, resulting in a greatly reduced roundtrip signal latency of only 0.12 milliseconds.
Typically a completely clear line of sight between the dish and the satellite is required for the system to work. 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, the penetration through vegetation increases, but most satellite communications operate above 2 GHz making them sensitive to even minor obstructions such as the leaves of a tree. A dish installation in the winter must factor in plant foliage growth that will appear in the spring and summer.
Two-way satellite Internet service involves both sending and receiving data from the remote VSAT site via satellite to a hub teleport, which then sends relays data via the terrestrial Internet. The satellite dish at each location must be precisely pointed to avoid interference with other satellites. 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 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.
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 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 terminal dish has a 500mW 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 cumbersome and very expensive. The technology for ASTRA2Connect was delivered by a Belgian company called Newtec.
Home users tend to make use of 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 Mbytes allowances, the company may slow down their access, deprioritise their traffic or charge for the excess bandwidth used. For consumer satellite internet, the allowance can range from 500MB to 17GB 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 4000 end users. Note the average bit rate per end user PC is only about 10 - 20kbit/s. This is adequate for most people but will definitely not be suitable people wanting to do large scale file transfers, video or music, of talk for long periods using VoIP phones.
The uplink direction for shared user customers is normally TDMA, which involves transmitting occasional short packet bursts, for example when the mouse is clicked.
Business users tend to opt for dedicated bandwidth services where any congestion is under their local control.
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 - 2.4m dia) 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.
Using such a modem is extremely expensive—bandwidth costs between $5 and $7 per megabyte. The modems themselves are also expensive, usually costing between $1000 and $4000.
Another type of 1-way satellite internet system involves the use of General Packet Radio Service (GPRS) for the back-channel. 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.
At the remote location (Earth station) the setup consists of:
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 500ms). Download speeds can be very fast compared to dial-up.
In space, Internet access is also achieved through satellite-based connection.
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 for displaying ads (for the purpose of maximizing the number of ad views seen by the affiliate marketing company's server).