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.
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
- 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
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 500ms).
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)
