2. The DTH technology enables us to directly beam the signal to
your TV set through a receiver that is installed in the house.
• In India, direct-to-home (DTH) Broadcasting Service
refers to the distribution of multi channel TV
programmes in Ku Band by using a satellite system by
providing TV signals direct to subscribers' premises. For
DTH connection the broadcasting company provides a
set that comprises the dish and a receiving set. The
company beams an encrypted signal that only the set
installed in your household can receive and enable
viewing.
It is a system of T.V. broadcasting services where T.V.
signal are transmitted directly to the viewer side
stepping the cable operators
3. In DTH system, the service provider branches together signals of
bouquet of channels in a codified or scrambled form to be received by
Ku- band transponder present in Geostationary satellite, from where
these signals can be easily down linked by the viewers-by using dish
antenna.
These signals can be made compatible to T.V. viewing by using a smart
card and decoder, the combination which helps in unscrambling the
codified signals. In general, DTH service is one in which a large number
of channels are digitally compressed, encrypted and beamed from very
high power satellites. The programmes can be directly received at
homes. However, a digital receiver is needed to receive the multiplexed
signals and view them on a TV.
The technology of DTH ensures highest quality of voice, video as it uses
digital form of communication system. The DTH service also provides
various value added services such as internet services, telemedicine,
video conferencing etc. Since in DTH technology, all the encoded
transmission signals are digital.
4. Thus, it provides higher resolution picture quality and better audio than
traditional analog signals. In recent years DTH has become the buzzword
in the satellite broadcasting industry because of immense opportunities
it offers to broadcasters and viewers. However, the main advantages of
DTH transmission are:
1) It facilitates use of small dish antennas which could be easily installed
in individual homes and provides a large number of services within the
same transponder.
2) The broadcaster would be able to introduce a number of new
interactive applications such as internet access, email, VoD. It can be
also used for public service messages.
3) Another benefit of the DTH transmission is that it keeps out
intermediaries like cable operators who could distort the subscription
income.
4) For public broadcaster like Prasar Bharati, free to air DTH
broadcasting has emerged as viable alternative for universal coverage of
population with Television programmes.
5. The government permitted DTH broadcasting in India on
November 2000. The primary reason for the government to have
permitted DTH seems to be its proven capability of serving rural
areas as well as population scattered over vast distances in
remote and hilly areas. The DTH policy is also in place to regulate
the broadcasters and keeping interests of consumer in mind.
The TRAI under unified license Regime has recommended that
DTH can serve as alternative platform for broadband services.
Considering this view, DTH services of Doordarshan has been
launched in 2004.
Apart from India DTH service is operational in US, Europe,
Australia, Japan, South Korea, Thailand and other countries. It is
also estimated that, soon the number of households receiving
DTH will cross 100 million subscriber worldwide. Europe has got
the distinction of having world's most developed DTH market. In
the Asian region its penetration is not to the extent of US and
Europe.
7. ESSENTIAL COMPONENTS
OF DTH SERVICE
Broadcasting
Centre
Satellites
Encoders
Multiplexers
Modulators
DTH receivers
8. ModulatorsIn telecommunication, modulation is the process of varying one or more properties of a
periodic waveform, called the carrier signal, with a modulating signal that typically contains
information to be transmitted.
In telecommunications, modulation is the process of conveying a message signal, for example
a digital bit stream or an analog audio signal, inside another signal that can be physically
transmitted. Modulation of a sine waveform transforms a baseband message signal into a
passband signal.
A modulator is a device that performs modulation. A demodulator (sometimes detector or
demod) is a device that performs demodulation, the inverse of modulation. A modem (from
modulator–demodulator) can perform both operations.
The aim of digital modulation is to transfer a digital bit stream over an analog bandpass
channel, for example over the public switched telephone network (where a bandpass filter
limits the frequency range to 300–3400 Hz), or over a limited radio frequency band.
The aim of analog modulation is to transfer an analog baseband (or lowpass) signal, for
example an audio signal or TV signal, over an analog bandpass channel at a different
frequency, for example over a limited radio frequency band or a cable TV network channel.
Analog and digital modulation facilitate frequency division multiplexing (FDM), where several
low pass information signals are transferred simultaneously over the same shared physical
medium, using separate passband channels (several different carrier frequencies).
9. Broadcasting Centre• The broadcast centre is the main
part of the whole system. It is from
the broadcast station that the
signals are sent to the satellites to
be broadcasted. The broadcast
station receives the signals from
various program channels.
• The satellite receives the signal from
the broadcast centre and
compresses the signals and makes
them suitable for re-transmission to
the ground.
• The DTH providers give dish
receivers for the viewers to receive
the signal from the satellites. There
may be one or multiple satellites
that send the signals at the same
time. The receiver receives the
signal from them and is passed on to
the Set Top Box [STB] receiver in the
viewer’s house.
• The STB receiver changes the signal
in a form suitable for our television
and then passes it on to our TV.
11. An artificial satellite is a man made object placed into orbit around the
Earth for the purpose of scientific research, weather reports, or
military reconnaissance. Scientific satellites are set into orbit to
observe the space environment, the Earth, the Sun, stars and extra
galactic objects. These satellites have retrieved a huge amount of
information helpful to scientific research. Weather satellites are used
every day for meteorological forecasts and in shipping. Also military
satellites play a important role in today's modern military. Satellites
are extremely important today. All artificial satellites have certain
features in common. They all include radar systems, sensors like
optical devices in observation satellites and receivers and transmitters
in communication satellites. Solar cells are used to generate power for
the satellites and in some cases ,nuclear power is used. All satellites
need altitude-control equipment to keep the satellite in the desired
orbit.
12. Encoders• The Digital Encoder is a combinational circuit that generates a specific
code at its outputs such as binary or BCD in response to one or more
active inputs. There are two main types of digital encoder. The Binary
Encoder and the Priority Encoder.
• We have seen that the Binary Encoder converts one of 2n inputs into an
n-bit output. Then a binary encoder has fewer output bits than the input
code. Binary encoders are useful for compressing data and can be
constructed from simple AND or OR gates. One of the main
disadvantages of a standard binary encoder is that it would produce an
error at its outputs if more than one input were active at the same time.
To overcome this problem priority encoders were developed.
• The Priority Encoder is another type of combinational circuit similar to a
binary encoder, except that it generates an output code based on the
highest prioritised input. Priority encoders are used extensively in digital
and computer systems as microprocessor interrupt controllers where
they detect the highest priority input.
• In the next tutorial about combinational logic devices, we will look at
complementary function of the encoder.
13. Multiplexers
• a multiplexer (or mux) is a device that selects one of
several analog or digital input signals and forwards the
selected input into a single line. A multiplexer of 2n
inputs has n select lines, which are used to select which
input line to send to the output. Multiplexers are
mainly used to increase the amount of data that can be
sent over the network within a certain amount of time
and bandwidth. A multiplexer is also called a data
selector.
• An electronic multiplexer makes it possible for several
signals to share one device or resource, for example
one A/D converter or one communication line, instead
of having one device per input signal.
15. Ku Band
• The Ku band is the 12–18 GHz portion of the electromagnetic spectrum in the
microwave range of frequencies. This symbol refers to "K-under" (originally
German: Kurz-unter)—in other words, the band directly below the K-band. In
radar applications, it ranges from 12-18 GHz according to the formal definition of
radar frequency band nomenclature in IEEE Standard 521-2002.
• Ku band is primarily used for satellite communications, most notably for fixed and
broadcast services, and for specific applications such as NASA's Tracking Data
Relay Satellite used for both space shuttle and International Space Station (ISS)
communications. Ku band satellites are also used for backhauls and particularly
for satellite from remote locations back to a television network's studio for
editing and broadcasting. The band is split into multiple segments that vary by
geographical region by the International Telecommunication Union(ITU). NBC
was the first television network to uplink a majority of its affiliate feeds via Ku
band in 1983.
• Some frequencies in this radio band are used for vehicle speed detection by law
enforcement, especially in Europe.
17. MAIN FEATURES AND
TECHNOLOGY OF EDUSAT
The need for simple cost effective but more powerful satellite remote
terminals calls for very powerful transponders on the satellite and the
large number of wide band channels indicates the need to move to the
higher frequency bands such as the Ku band. Thus Edusat is a satellite
constellation which carries five Ku band transponders providing spot
beams, one Ku band transponder providing a national beam and six
extended C band transponders providing national coverage beams.
Following are some of the major parameters of EDUSAT (GSAT-3)
transponders ,2007 A total of 6 FSS C-band transponders, which will
operate in upper Ext. C-band. A total of 6 FSS Ku-band transponders and
A Beacon operating in Ku-Band. The coverage contours on earth’s surface
are, Indian Coverage of C-band (ICC) Beam will be over Indian
geographical Boundary. Ku-band National beam will be over Indian
mainland region.
22. ROT Installation Procedure
While going for the receiving center installation
we need to follow certain criteria's,
mentioned as follows;
1) Material Check List.
(Consumable, Non Consumable & tools).
2) Line Of Sight for receiving antenna.
3) Antenna pointing.
4) IDU and ODU connectivity.
23. Material Check List.
(Consumable, Non
Consumable & tools).
• Here this section we will discuss about the
materials & equipments required at the
receiving center; broadly classified as:
1) Consumables.
2) Tools.
24. Consumables.
• Consumables are those items which are a part
of ROT systems and need to be installed i=on
site.
• Dish Antenna with stand & LNB
31. CONCLUSION
• DTH has made the hope of the people of rural
area to come true.
• DTH service in India is in its initial stage.
• We are enriching the education system with
help of DTH service.
• In near future, launch of DTH internet service
is expected in India.
• It provides the wide thinking of ruler people
which helps to develop the culture of society.
