This document discusses various applications of satellite communication including satellite telephony, satellite television, satellite radio, VSAT networks, and national satellite systems. Satellite telephony networks employ GEO and LEO satellites to provide two-way voice services using circuit switching. Satellite television can be delivered directly to homes via small dishes or indirectly through cable networks using GEO satellites. VSAT networks are used for data broadcasting, point-to-point voice services, and one-way video using small terminals connected via GEO satellites. National satellite systems like INSAT in India provide domestic telecom, television, and weather monitoring services.

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Satellite telephony networks employ point-
to-point duplex satellite links enabling
simultaneous communication in both the
directions
Single GEO satellites or a constellation of
LEO, MEO and GEO satellites are used for
providing telephony services.
Telephone satellite links generally employ
circuit-switched systems offering a constant
bit rate services
Some of the major satellite systems
offering voice services are Intelsat,
Eutelsat, Inmarsat, Globalstar, Iridium,
ICO, Ellipso and Odyssey systems.
Satellite Telephony

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1.The user lifts the receiver when he or she wants to make a call. This
sends a request to the local Earth station, which in turn sends a service
request to the master station.
2. If the master station is able to provide the satellite capacity, it sends a
confirmation signal to the local Earth station, resulting in a dial tone in
the telephone instrument.
3. The user then dials the destination number, which is transferred to the
control station, which determines the destination Earth station and
signals it that a connection needs to be established.
4. The destination Earth station then signals the called party of the
incoming call by ringing that telephone instrument.
Local ES
Master ES
Dest ES
Control
station
Satellite Telephony

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5. The satellite capacity is allocated to the connection and the
telephone link is established once the called party lifts the handset.
6. Once the conversation is over, the calling party hangs up the
receiver, hence indicating to the local Earth station to terminate the
call.
Satellite Telephony

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Point-to-Point Trunk Telephone Networks
Trunk telephony services come under the domain of fixed satellite
services (FSS), mainly utilizing C and Ku bands.
Generally, GEO satellites are utilized for providing these services.
Intelast, Europestar, Eutelsat, PamAmSat are examples of some of
the satellites used for the purpose.

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Mobile Satellite Telephony
One of the important services provided by mobile satellite services (MSS) is the interactive voice
communication to mobile users.
MSS satellites launched in the periods 1980–1990 and 1990–1998 were GEO satellites, categorized as
Generation-I and Generation-II satellites respectively,
Third generation mobile satellites, comprising constellations of LEO, MEO, HEO and GEO satellites,
provide voice and multimedia services to mobile and hand-held terminals.
The third generation mobile satellite services have entered the realm of personal communications and
are also referred to as global mobile personal communication services (GMPCS)
GMPCS is a personal communication system providing transnational, regional or global two-way
voice, fax, messaging, data and broadband multimedia services from a constellation of satellites
accessible with small and easily transportable terminals

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There are several different types of GMPCS systems:
GEO systems
small LEO systems
big LEO systems
MEO systems
HEO systems and
broadband GMPCS systems.

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Satellite Television
Satellites can provide TV programmes either directly to
the users (direct-to-home television)
or
indirectly with the help of cable networks or terrestrial
broadcasting networks, where the satellite feeds the
signal to a central operator who in turn transmits the
programmes to the users either using cable networks or
through terrestrial broadcasting
Satellite television employs GEO satellites acting as
point-to-multipoint repeaters receiving a certain telecast
from the transmission broadcasting center and
retransmitting the same after frequency translation to the
cable TV operators, home dishes, etc., lying within the
footprint of the satellite.

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A typical satellite TV network, like any other satellite network,
can be divided into two sections:
the uplink section
the downlink section.
The uplink section comprises three main components:
the programming source,
the broadcasting center,
the main broadcasting satellite

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The programming source comprises
TV channel networks,
cable TV programmers, etc.,
that provide various TV programming signals, like
TV channels,
sports coverage,
news coverage
or local recorded TV programmes,
to the broadcasting centre either through terrestrial means,
like using the line-of-sight microwave communication
and
the fiber optic cable, or using satellites referred to as back-
haul satellites.

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The satellite downlink comprises the main broadcasting satellite
and the TV receiving network.
Satellite–Cable Television
Direct-to-Home Satellite Television

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cable TV refers to the use of coaxial and fiber optic cables to
connect each house through a point-to-multipoint distribution
network to the head end distribution station. Cable TV,
originally referred to as CATV (community antenna television)
Satellite–Cable Television
The head end in this case consists of various receive-only Earth
stations with the capability of receiving telecast from two to six
satellites.
These Earth stations either have multiple receiving antennas or,
a single dish antenna with multiple feeds, with each feed so
aligned as to receive telecast from a different satellite.

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Satellite–Cable Television
The transmission from the satellite is either in the analogue format
(mainly in the C band) or in the digital format (mainly in the Ku
band).
This processed digital or analogue information is then transmitted
over a typical cable distribution network to a large number of
houses known as subscribers, who pay a monthly fee for the service.
The cable operators scramble their programmes to prevent
unauthorized viewing.
The receiving end then consists of a set top box to descramble and
retrieve the original signal.
The cable TV operators also transmit the videotaped recorded
programmes from other sources in addition to showing
programmes received from the satellites.

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Satellite–Cable Television
Satellite–Local Broadcast TV Network
Here the satellite distributes programming to local
terrestrial broadcasting stations instead of distributing it to
the cable head end stations
The broadcasting stations use powerful antennas to transmit
the received signals to various users within the line-of-sight
(50–150 km) using UHF and VHF microwave bands
The users receive these TV signals using directional
antennas like yagi antennas, reflector antennas or dipole
antennas

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Satellite–Cable Television
Direct-to-Home Satellite Television
Direct-to-home (DTH) satellite television refers to the direct
reception of satellite TV programmes by the end users from the
satellite through their own receiving antennas
DTH services can be broadly classified into two types, namely the
television receive-only (TVRO) and the direct broadcasting
satellite (DBS) services, depending upon the frequency band
utilized and the size of the receiving antennas.
TVRO systems operate in the C band whereas the DBS systems
operate in the Ku band

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Satellite–Cable Television
Television Receive-Only (TVRO) Services Direct Broadcasting Satellite (DBS) Services
TVRO systems employ large dishes (6 to 18 feet across)
placed in the user’s premises for the reception of analogue
signals from the satellite operating in the C band
Generally, each C band transponder provides one analogue
TV channel, and hence a satellite with 16 such
transponders will be able to support only 16 TV channels.
These systems are made user friendly by using
microprocessor control, allowing the viewer to select the
desired channel with a remote control unit.
The antenna then moves automatically using electronic
control methods to point to the desired satellite.
TVROs are based on open standard equipment and provide
the largest variety of TV programs, including cable TV
programs, foreign stations, free programming channels and
live unedited feeds between broadcasting stations like news,
sports, etc
The DBS service uses high powered Ku band satellites that
send digitally compressed television and audio signals to
relatively small (45–60 cm across) fixed satellite dishes
DBS satellites transmit signals to Earth in the BSS segment
of the Ku band (between 12.2 and 12.7 GHz), making use of
MPEG-2 (Moving Picture Experts Group) digital
compression techniques
The channel capacity per transponder is five to twelve
channels depending upon the data rate and the compression
parameters, and hence they can provide about 200 channels
from one satellite.

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Satellite–Cable Television
There are no free channels available on DBS systems. DBS
systems are easy to install and are cheaper as compared to
TVRO systems.
Some of the DBS service providers include DirecTV,
Echostar, PrimeStar of the USA, TataSky and DishTV of
India and Star Choice of Canada.
The FCC has allocated eight orbital slots at 61.5, 101, 110,
148, 157, 166 and 175 west longitude GEO locations for
DBS systems
TVRO systems have better picture quality than DBS or
digital cable systems, which tend to use larger amounts of
digital signal compression.

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Block schematic for the outdoor unit (ODU)
Direct-to-Home Satellite Television
Block schematic for the indoor unit (IDU)

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A satellite providing high fidelity audio broadcast services to the broadcast radio stations is referred to as a
satellite radio and is a major revolution in the field of radio systems.
Sound quality is excellent in this case due to a wide audio bandwidth of 5–15 kHz and low noise
provided over the satellite link.
Satellite radio like the satellite TV employ GEO satellites and the network arrangement for the satellite radio is
more or less identical to that used for TV broadcasting.
Using point-to-multipoint connectivity, the audio signals from various music channels, news and sports centres
are transmitted by the satellite to a conventional AM or FM radio station.
The signal is then de-multiplexed and the local commercials and other information is added here in the same way
as in a TV network and then sent to the users using terrestrial broadcasting topology.
The satellite can also transmit the signal directly to the user’s radio sets.
Some of the major providers of satellite radio services include Sirius and XM Radio of the USA.
Satellite Radio

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http://www.radio.garden

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VSATs (Very Small Aperture Terminals)
are used for providing one-way or two-way data broadcasting services, point-to-point voice services and
one-way video broadcasting services.
VSAT networks are ideal for centralized networks with a central host and a number of geographically
dispersed terminals
Typical examples are small and medium businesses with a central office, banking institutions with
branches all over the country, reservation and airline ticketing systems,
VSATs suffer from a major problem of delay between transmission and reception of data (around 250
ms) due to the use of GEO satellites.

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most VSAT systems operate in the Ku band
with the antenna diameter of the Earth
stations being as small as 1 to 2 m.
VSAT networks can transmit at a rate of
64–1024 kbps (64 kbps per remote terminal)
in the outbound direction and
64–256 kbps (1.2 to 16 kbps per remote
terminal) in the inbound direction.
VSAT networks generally support data, video
and voice services in the outbound direction
and
only data and voice services in the inbound
direction

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VSAT Network Topologies
bidirectional star networks
Unidirectional star networks
Mesh networks

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National Satellite Systems
National satellite systems, also referred to as domestic satellite systems, provide services to a
particular country
INSAT (Indian National Satellite)
Owned by the Indian Department of Space, named the Indian Space Research Organization (ISRO),
INSAT is one of the largest domestic communication satellite networks in the world, providing services
in the areas of
telecommunications,
television broadcasting,
mobile satellite services and
meteorology including disaster warning
INSAT is a joint venture of the
Department of Space (DOS),
Department of Telecommunications (DOT),
Indian Meteorological Department (IMD),
All India Radio (AIR) and
Doordarshan.

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