digital terrestrial tv

8/8/2019 Digital Terrestrial TV

1/23

As on 08.07.08


2/23

First telecast started in India in Delhi by All India Radio on Sept 15,1959

Doordarshan introduced colour TV in India coinciding with AsianGames in 1982

Terrestrial television broadcasting still remains in the exclusivedomain of only Doordarshan under Prasar Bharati

C&S networks made their appearance in early 1990s

First Direct To Home (DTH) Satellite television service was launchedin October 2003

Over the years, the increase in viewership of cable television andDTH has been at the cost of viewership of terrestrial televisionbroadcasts


3/23

Transmission of airwaves on radio frequenciesusing transmitters, transponders and towersestablished across the territory

Analog ModeTransmission of waves that are continuous in terms of both time andamplitude

Digital ModeTransmission of discontinuous signals using discrete values torepresent information

Makes use of multiplex transmitters to allow reception of multiplechannels on a single frequency range (such as a UHF/ VHF channel)


4/23

Transmission of signals is in Analog mode

Signals are corrupted by noise and interference as theypropagate through terrestrial media

Multipath propagation'Signals reach a TV receiver by both a direct path and a

delayed pathThe delayed path occurs because the signals get reflected

by high rise buildings/trees etc in their path and reach thereceiver slightly delayed

These two combine to produce pictures with ghosts

Transmitter transmits a single TV programme channelthrough a 7/8 MHZ wide RF channel


5/23

Broadcast Uplinking Station

Satellite

Towers

Lowpow

erTransponders

andAmp

lifiers

Terrestrial Antenna

DishAntenna

Set Top Box


6/23

Digital Video/Audio Compression (DVC)Redundant Information of a TV Channel is

compressed (identified and removed) from theincoming digitized signal

Compression reduces the amount ofinformation to be transmitted in a given time,leading to spectrum efficiency

Psycho Visual property of human vision system

also helps prevent human eye from noticingany such loss of resolution in compressedpicture


7/23

Enhanced Services - Broadcaster transmits aseparate data stream carrying someprogramme related information. A viewer ifinterested can run the application

Interactive Services - Involves a continuouscommunication between the service providerand the service consumer.

Internet Services - DTT network can also beused for providing Internet access


8/23

ATSC standard, DVB-T standard, ISDB-Tstandard

DVB-T standard is the most widely deployedaround the world, mainly because of its muchimproved performance in the presence ofMultipath

Doordarshan's DTT service is based on DVB-Tstandard


9/23

Flexible systemWide choice of user selectable transmission

parameters enables a broadcaster to tailor thetransmission system to his requirements

Two layer hierarchical systemTransmitter emits two data streams which may

contain the same programmes or entirely differentprogrammes.

By separate transmission parameters for the twostreams, these two streams can be optimized forreception under different conditions. E.g. forstationery reception and other for mobile reception


10/23


11/23

Forward Error Correction CodingSignals can be protected from impairment caused

by noise/ interference by this techniqueIt enables the receiving system to detect and

correct errors

Tailor-Made ContentProvides a means for broadcasting content tailor -

made and targeted for the local population. This isparticularly important in a country with multiplelanguages, cultures and customs like India


12/23

COFDM (Coded Orthogonal Frequency DivisionMultiplexing)Makes signals highly robust in case of Multipath

reception

Hence, signals can be received not only on fixed rooftop antennas but also by portable indoor/outdoorantenna and also in moving vehicles

Spectrum Efficient TechnologyTransmitter transmits a multiplex of 5or 6 TV channels

through the same RF channelThis increased capacity helps deliver more TV

programmes and several new value added services toviewers


13/23


14/23

Technical issue:Replacement of all analog transmitters by digital ones if

intend to use the current infrastructure of DD

Or set up the complete infrastructure

Licensing Issue:Licenses for Private Terrestrial Television Broadcasting

Service not in place

Licensing likely to be awarded for coverage on national,regional or city level separately

Penetration issue:Public will have to acquire digital TV sets or set-top

boxes to be attached to existing TV sets to receivedigital signals


15/23

DTH gives better quality picture than conventional cableTV because Cable TV in India is analog

Even if the Cable might receive the signal through adigital receiver, the transmission in his cable is still

analog

Analog as we all know is subject to various disturbancesand degradations during transmission on cable

DTH loses out on the fact that it will operate on the Kuband, which has a peculiarity that during heavy rains thesignal just fades away


16/23

Ku-band: Have shorter wavelength signals that tendto get absorbed by rain and snow clouds

DTH service providers charges Rs 3-4 Crores for aGEC channel whereas carriage fee would amount

close to Rs 20 CroresBandwidth requirement:A regular FTA channel would be 3 MHzA GE channel-4.5 MHzAny Sports channel-6Mhz

With compression technology /Mpeg4 formataverage bandwidth per channel is reduced 1-1.2Mhz

Bandwidth increases dramatically for HD quality


17/23

Inflow of private capital in the sector and growth ofterrestrial TV channels

Viewers will get FTA channels without having to pay anysubscription fee which otherwise is required through C&S

Adopt alternative technologies such as MMDS particularlywhere cable and satellite have not penetrated

The right to receive and impart information

More choice for consumers

Possibility of enhanced coverage of local issues, events,

music and cultureComplement the public service broadcaster


18/23

Infrastructure of Doordarshan24 Channels(Parliament-2, National-5, International-1, Regional-11

and State-8)

64 Studio Centers1401 transmitters

Thus in spite of a large number of transmitters,the Studio Centers for producing programmes are

very limited. Private terrestrial televisionbroadcasters would complement the services ofDoordarshan by generating more content


19/23

India chose the DVB-T standard for TerrestrialDigital Broadcasting in July 1999 after 18months of study and testingThe state broadcaster Doordarshan started a

pilot trial in Delhi during 2002 which gotextended to Kolkata, Mumbai and ChennaiStarted experimental transmission of digital TV

in UHF band by installing 1 KW digitaltransmitters in the four metrosEach digital transmitter of Doordarshan carries

five Doordarshan channels


20/23

Hong KongTwo commercial Terrestrial Broadcasters

controlling 4 stations in Chinese and English

JapanMore than 100 Terrestrial Broadcasters (apart

from more than 60 Satellite and CableBroadcasters)

SingaporeDTH is not permitted

Taiwan5 FTA Terrestrial Television stations


21/23

Europe: Most of the European countries have takeninitiatives for the transition of analogue to digital terrestrial

TV broadcastingGermany: Berlin and the surrounding state of Brandenburg

is the Worlds first television broadcasting area to gocompletely digital (switched over exclusively to digital TV

from 4th August 2003 )UK: Sept 1999, govt announced its plans to achieve digital

switchover. The Secretary of State said that digitalswitchover could start as early as 2006 and be completedby 2010 although the precise date would depend on howthe broadcasters, manufacturers and consumers behave.

Presently more than half of UK homes have digital TVJapan: In 1998, the Ministry of Internal Affairs &

Communications (MIC) issued its time frame and plan forfull digitalization of terrestrial by 2011


22/23

Terrestrial mode of transmission of multipleTV channels

Perceived to supplement Cable TV particularlyin remote and inaccessible areas

MMDS transmitter covers a radius between 20and 50 km depending upon the height oftransmitting antenna

MMDS signals are normally being encrypted,to allow the service provider to control and billhis services


23/23

digital terrestrial tv

Documents