Satellite Communication
People need access to enterprise-class, high-speed voice, video and data applications
wherever they happen to be. Satellite connectivity has the power to drive communications
advances across a broad range of industries and geographies.
Whether it’s ship-to-shore maritime communications, Internet access for remote, rural
classrooms, or vital data and communications for petroleum operations, satellite applications
meet a broad range of needs.
Communication satellites are used in fixed or mobile wireless communications to receive and
transmit radio signals from an orbiting satellite to another terrestrial location. There have
been such advances in bandwidth utilization and reliability of communications that satellite
service now provides affordable, always-on, high-speed, quality connectivity.
Global Coverage
Today, satellite communication can deliver a terrestrial-grade experience with voice, video,
and data that can be accessed anywhere in the world. Ubiquitous coverage can be obtained
with a global network of multiple satellites all tying into one central network management
system.
Reliability
Satellite networks are dependable, providing constant connectivity even when terrestrial
networks fail. With satellite networks, enterprises can maintain business continuity with
built-in redundancy and automatic back-up service.
Security
Satellite networks already constitute a private network. By adding encryption technology
satellite can provide a more secure connection than terrestrial networks, making it an ideal
solution for government, military and enterprise VPN (virtual private network) solutions.
Scalability
The modularity of VSAT systems allows for quick time-to-market and fast upgrades. VSAT
remotes can be deployed rapidly and new remote locations are easily added to a network
where limited terrestrial infrastructure exists simply by configuring bandwidth to the site and
having ground equipment installed.
Fast Deployment
Satellite technology is an ideal solution for quick deployment, immune to the challenges
posed by difficult terrain, remote locations, harsh weather, and terrestrial obstacles. In this
rapidly expanding market, satellite allows a service provider to get to market quickly and
efficiently and provide immediate connectivity in disaster and emergency relief scenarios.
Cost Savings
Satellite technology can deliver a communications infrastructure to areas where terrestrial
alternatives are unavailable, unreliable or simply too expensive. Satellite allows service
providers to insure scalability, profitability and maintain low operating expenses, all while
overcoming a lack of existing infrastructure
How Satellite Works
A communications satellite is a satellite located in space for the purposes of
telecommunications. There are three altitude classifications for satellite orbits:
LEO – Low Earth Orbit
LEO satellites orbit from 160-2000km above the earth, take approximately 1.5 hrs for a full
orbit and only cover a portion of the earth’s surface, therefore requiring a network or
constellation of satellites to provide global, continual coverage. Due to the proximity to
Earth, LEO satellites have a lower latency (latency is the time between the moment a packet
is transmitted and the moment it reaches its destination) and require less amplification for
transmission.
MEO – Medium Earth Orbit
MEO satellites are located above LEO and below GEO satellites and typically travel in an
elliptical orbit over the North and South Pole or in an equatorial orbit. These satellites are
traditionally used for GPS navigation systems and are sometimes used by satellite operators
for voice and data communications. MEO satellites require a constellation of satellites to
provide continuous coverage. Tracking antennas are needed to maintain the link as satellites
move in and out of the antenna range.
GEO – Geostationary Orbit
GEO satellites orbit at 35,786 km (22,282 mi) above the equator in the same direction and
speed as the earth rotates on its axis. This makes it appear to the earth station as fixed in the
sky. The majority of commercial communications satellites operate in this orbit; however,
due to the distance from the earth there is a longer latency.
Frequency Bands
There are four radio frequency bands that communication and military satellites operate
within:
C band – uplink 5.925-6.425 GHz; downlink 3.7-4.2 GHz
The C band is primarily used for voice and data communications as well as backhauling.
Because of its weaker power it requires a larger antenna, usually above 1.8m (6ft). However,
due to the lower frequency range, it performs better under adverse weather conditions on the
ground.
X band – uplink 7.9- 8.4 GHz, downlink 7.25 – 7.75 GHz
The X band is used mainly for military communications and Wideband Global SATCOM
(WGS) systems. With relatively few satellites in orbit in this band, there is a wider separation
between adjacent satellites, making it ideal for Comms-on-the Move (COTM) applications.
This band is less susceptible to rain fade than the Ku Band due to the lower frequency range,
resulting in a higher performance level under adverse weather conditions.
Ku band– uplink 14 GHz; downlink 10.9-12.75 GHz
Ku band is used typically for consumer direct-to-home access, distance learning applications,
retail and enterprise connectivity. The antenna sizes, ranging from 0.9m -1.2m (~3ft), are
much smaller than C band because the higher frequency means that higher gain can be
achieved with small antenna sizes than C-band. Networks in this band are more susceptible to
rain fade, especially in tropical areas.
Ka band – uplink 26.5-40GHz; downlink 18-20 GHZ
The Ka band is primarily used for two-way consumer broadband and military networks. Ka
band dishes can be much smaller and typically range from 60cm-1.2m (2' to 4') in diameter.
Transmission power is much greater compared to the C, X or Ku band beams. Due to the
higher frequencies of this band, it can be more vulnerable to signal quality problems caused
by rain fade.
Satellite Architecture
Communications data passes through the satellite using a signal path known as a
”transponder.” Typically satellites have between 24 and 72 transponders. Transponders may
be shared between many customers, in a ”demand access” environment, or segments of
capacity may be dedicated to individual customers, depending on the customer application. A
single transponder is capable of handling up to 155 million bits of information per second.
With this immense capacity, today’s communication satellites are an ideal medium for
transmitting and receiving almost any kind of content, from simple voice or data to the most
complex and bandwidth-intensive video, audio and Internet content.
Diagrammatic Representation of a Satellite
VSAT Network
Network Equipment
A network typically consists of a larger earth station, commonly referred to as a teleport, with
hub equipment at one end and a Very Small Aperture Terminal (VSAT ) antenna with remote
equipment at the other end. The network equipment can be divided into two sets of
equipment connected by a pair of cables: the Outdoor Unit (ODU) and the Indoor Unit (IDU).
Network Equipment
ODU
An ODU is the equipment located outside of a building and includes the satellite antenna or
dish, a low noise block converter (LNB), and a block-up-converter (BUC). The LNB
converter amplifies the received signal and down converts the satellite signal to the L band
(950 MHz to 1550 MHz), while the BUC amplifies the uplink transmission when the antenna
is transmitting.
IDU
The IDU equipment at the teleport usually consists of a rack-mounted hub system and
networking equipment connected to terrestrial networks, like the PSTN or Internet backbone.
There is also a device that converts between satellite and IP protocols for local LAN
applications such as PCs, voice calls and video conferencing. At the remote location, a router
connects to a small VSAT antenna receiving the IP transmission from the hub over the
satellite and converts it into real applications like Internet, VoIP and data.
Network Topologies
Satellite communication supports a number of different network topologies, depending on the
application. At its simplest, satellite can support a simplex (one direction) or duplex (two
directions) link between two Earth Stations. More complex networks can be fashioned to
support ”Star” or ”Mesh” topologies, especially in corporate VSAT applications. In a Star
topology there will be a ”hub” Earth Station, at the center of the network. Content originates
at the hub, which features a large antenna. The hub can control the network through a
Network Management System (NMS), which allows the network operator to monitor and
control all components of the network. Outbound information from the hub is sent up to the
satellite, which receives it, amplifies it and beams it back to earth for reception by the remote
Earth Station(s). The remote locations send information inbound to the hub. In a Mesh
topology, remote Earth Stations can also communicate with each other via the satellite, but
without information being sent through the hub. This is common for international voice and
data traffic via satellite. This is also referred to as a community of Earth Stations. The
following examples show some of the options available to customers for configuring their
satellite networks:
