About VSAT - Satellite Basics
VSAT means Very
Small Aperture Terminal, VSAT is a technology used to define a
two-way-satellite communications. VSAT system use small dish antennas
that varies from 75 cm to 2.4 meters in diameter. VSAT terminal access
satellites in orbit, to transfer data from one earth station to other
or to access the internet (two way satellite internet). The VSAT
network is managed by the HUB (mater earth station).
VSAT system are
commonly used to transmit narrowband data for applications such a
telemetry (SCADA), Point-of-Sale transactions such as credit cards,
Internet Access, Voice-Over-IP, Bank transactions between head
quarters and branches and any IP application.
Satellites provide
today's businesses with a flexible, universal, reliable and quickly
deployable means to address a wide range of communications needs. Use
this guide to find out why and how companies from a variety of
industries use satellite-based solutions to advance their businesses.
2.
How Satellite
Communications Work?
a.
What is a Communications
satellite and How it Work?
b. What are
the Different Kinds of Orbits?
*
What are the
different kinds of orbits
*
Medium Earth Orbit (MEO): 8,000-20,000 km above the earth
*
Low
Earth Orbit (LEO): 500-2,000 km above the earth
c. GEO vs. MEO vs. LEO
d. Satellite Architecture
e. Orbital Location and
Footprint
f. Frequency Bands and
Beams
g. What is Installed on
the Ground?
h. Network Topologies
3.
Key Factors in Considering a Satellite
Solution
Every satellite network is unique and the right
choice depends on three
key factors:
Benefits of Satellite
Communications
(top)
A. How do Satellites Deliver Vital
Communications Around the World?
Because of their
universal and multi-point nature, satellite-based solutions can
provide a flexible and cost-effective answer to support:
In every case, VAT
Caribbean solutions provide for the delivery of vital information,
news, sports and entertainment to every corner of the globe, no matter
how remote.
B:
What are the Key Benefits of Satellites?
(top)
Satellite
communications have distinct benefits over terrestrial alternatives:
-
UNIVERSAL: Satellite
communications are available virtually everywhere.
A small constellation of satellites can cover the Earth's entire
surface. And even the reach of a single satellite is far more
extensive than what any terrestrial network can achieve.
-
VERSATILE: Satellites
can support all of today's communications needs - transactional and
multimedia applications, video, voice, cellular networks,
entertainment and breaking news.
-
Bring broadband to
the last mile of residences and businesses.
-
Overcome regulatory
issues that make alternative carriers dependent on incumbents.
-
Deliver a
communications infrastructure to areas where terrestrial
alternatives are unavailable, unreliable or simply too expensive.
-
RELIABLE: Satellite
is a proven medium for supporting a company's communications needs.
Whereas terrestrial IP networks are often a mix of different
networks and topologies, with different level of congestion and
latency. Satellite networks are extremely predictable allowing
constant and uniform quality of service to hundreds of locations,
regardless of geography.
-
SEAMLESS: Satellite's
inherent strength as a broadcast medium makes it ideal for the
simultaneous distribution of bandwidth-intensive information to
hundreds or thousands of locations.
-
FAST: Unlike most
terrestrial alternatives, satellite networks can be rolled out
quickly and inexpensively to hundreds or thousands of locations,
connecting cities or remote locations across a large landmass, where
copper or fiber is cost prohibitive. Since satellite networks can be
set up quickly, companies can be fast-to-market with new services.
-
EXPANDABLE: Satellite
networks are easily scalable, allowing users to expand their
communications networks and their available bandwidth easily. In
coordination with local vendors, expanding a network on the ground
requires the ordering of new terminal components and the
commissioning of increased bandwidth at each site.
-
FLEXIBLE: Satellites
can be easily integrated to complement, augment or extend any
communications network, helping overcome geographical barriers,
terrestrial network limitations and other constraining
infrastructure issues.
2.
How Satellite
Communications Work
(top)
A. What is a communications
satellite and how does it work?
A communications
satellite is a radio relay station in orbit above the earth that
receives, amplifies, and redirects analog and digital signals carried
on a specific radio frequency.
In addition to communications
satellites, there are other types of satellites:
-
Weather satellites:
These satellites provide meteorologists with scientific data to
predict weather conditions and are equipped with advanced
instruments
-
Earth observation
satellites: These satellites allow scientists to gather valuable
data about the earth's ecosystem
-
Navigation
satellites: Using GPS technology these satellites are able to
provide a person's exact location on Earth to within a few meters
B.
What are the
different kinds of orbits?
(top)
An orbit is the path
that a satellite follows as it revolves around Earth. In terms of
commercial satellites, there are three main categories of orbits:
Geosynchronous Orbit (GEO):
35,786 km above the earth
-
Orbiting at the
height of 22,282 miles above the equator (35,786 km), the satellite
travels in the same direction and at the same speed as the Earth's
rotation on its axis, taking 24 hours to complete a full trip around
the globe. Thus, as long as a satellite is positioned over the
equator in an assigned orbital location, it will appear to be
"stationary" with respect to a specific location on the Earth.
-
A single
geostationary satellite can view approximately one third of the
Earth's surface. If three satellites are placed at the proper
longitude, the height of this orbit allows almost all of the Earth's
surface to be covered by the satellites.
Medium Earth Orbit (MEO): 8,000-20,000 km above the earth
(top)
-
These orbits are
primarily reserved for communications satellites that cover the
North and South Pole
-
Unlike the circular
orbit of the geostationary satellites, MEO's are placed in an
elliptical (oval-shaped) orbit
Low
Earth Orbit (LEO): 500-2,000 km above the earth
(top)
-
These orbits are much
closer to the Earth, requiring satellites to travel at a very high
speed in order to avoid being pulled out of orbit by Earth's gravity
-
At LEO, a satellite
can circle the Earth in approximately one and a half hours.
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c.
GEO vs. MEO vs. LEO
Most communications satellites in use
today for commercial purposes are placed in the geostationary orbit,
because of the following advantages:
-
One satellite can
cover almost 1/3 of Earth's surface, offering a reach far more
extensive than what any terrestrial network can achieve.
-
Communications
require the use of fixed antennas. Since geosynchronous satellites
remain stationary over the same orbital location, users can point
their satellite dishes in the right direction, without costly
tracking activities, making communications reliable and secure.
-
GEO satellites are
proven, reliable and secure - with a lifespan of 10-15 years
For a more comprehensive understanding of
satellite advantages, see benefits of satellite.
d.
Satellite Architecture (top)
Communications data
passes through a satellite using a signal path known as a transponder.
Typically satellites have between 24 and 72 transponders. 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
e.
Orbital Location and
Footprint
(top)
The location of a
geostationary satellite is referred to as its orbital location.,
International satellites, are normally measured in terms of
longitudinal degrees East (° E) from the Prime Meridian of 0¼ (for
example, Intelsat satellite 805 is currently located at 304.5° E).
The geographic area of
the Earth's surface over which a satellite can transmit to, or receive
from, is called the satellite's "footprint." The footprint can be
tailored to include beams with different frequencies and power levels.
f.
Frequency Bands and Beams
(top)
Satellites transmit
information within radio frequency bands. The frequency bands most
used by satellite communications companies are called C-band and the
higher Ku-band. Over the next several years, the use of a higher
frequency band known as Ka-band is expected to increase. Modern
satellites are designed to focus on different ranges of frequency
bands and different power levels at particular geographic areas. These
focus areas are called beams.
Common beam types:
- Global: covering almost 1/3 of
Earth's surface
- Hemi: covering almost 1/6 of Earth's
surface
- Zone: covering a large landmass area
- Spot: covering a specific geographic
area
All communications with
a geostationary satellite require using an earth station or antenna.
Earth Stations may be either fixed (installed at a specific location)
or mobile for uses such as Satellite News Gathering (SNG) or maritime
applications. Antennas range in size, from large telecommunications
carrier dishes of 4.5 to 15 meters in diameter, to VSAT antennas which
can be as small as under one meter, designed to support services such
as Direct to Home TV (DTH) and rural telephony.
The antenna, itself,
will generally be connected to equipment indoors called an indoor unit
(IDU), which then connects either to the actual communications devices
being used, to a Local Area Network (LAN), or to additional
terrestrial network infrastructure.
Depending on the
application, satellites can be used with different ground network
designs or network topologies. At its simplest, satellite can support
one-direction or two-direction links between two earth stations
(called respectively simplex transmission and duplex transmission).
More complex communications needs can also be addressed with more
sophisticated network topologies, such as star and mesh.
The following examples
show some of the options available to customers for configuring their
satellite networks:
VSAT Simplex
Transmission
(top)
Applications for simplex services
include broadcast transmissions such as:
- TV and video services
- Radio services
Applications for duplex services
include:
- Voice Telephony transport
- Data and IP transport (especially in
asymmetric configurations)
- Corporate networks
- TV and Broadcast program
contribution and distribution
VSAT Point-to-Multipoint
Transmission
(top)
(May be simplex or duplex, symmetric or
asymmetric).
Applications for point-to-multipoint
services include:
- Corporate networks, including VSAT
services and business television
- Video and broadcast distribution,
including Direct-to-Home Internet services
VSAT
Mobile Antenna Service
(top)
Applications for mobile antenna
services include:
- Satellite News Gathering
- Special Event Backhaul and
Broadcasting
- Maritime services
Applications for Star Networks include:
- Corporate Networks
- Distance Learning
Applications for Mesh Networks include:
- National and International Telephony
and Data networks
- Rural Telephony
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