A SEMINAR REPORT ON DTH(DIRECT TO HOME TELIVISION)

ABSTRACT
DTH is a new technology and it has matured to its full potential in other parts of the world. There are many application has been found everyday for exploitation of benefits of DTH.
The word ‘DTH’ is synonymous with transmission of digital video channel to home subscriber’s using a small dish antenna. The DTH utilizes a technology which enables a home to receive high speed internet broadband access data communication, voice over internet protocol (IP) telephony and much more using an open standard Digital Video Broadcasting (DVB) technology. The video channels are received with a suitable set top box. Capable of demodulating Motion Picture Engineering Group (MPEG-2) standard videos. It is for the return channel required for other services such as voice over internet protocol and broadband access data communications, that a return channel is also required for the home terminal. The return channel via the satellite is called RCS and is an open standard.
Hardware compatible with DVB-RCS technology are readily available in the market in both Ku-band and C-band. DVB-RCS is an international open standard for multimedia satellite network where the return data rates in access of 2 Mbps are possible using low cost user terminals. The forward ink is usually at 40 Mbps. Today, most satellite TV customers in developed television markets get their programming through a direct broadcast satellite (DBS) provider, such as DISH TV or DTH platform. The provider selects programs and broadcasts them to subscribers as a set package. Basically, the provider’s goal is to bring dozens or even hundreds of channels to the customer’s television in a form that approximates the competition from Cable TV. Unlike earlier programming, the provider’s broadcast is completely digital, which means it has high picture and stereo sound quality. Early satellite television was broadcast in C-band - radio in the 3.4-gigahertz (GHz) to 7-GHz frequency range. Digital broadcast satellite transmits programming in the Ku frequency range (10GHz to 14 GHz). There are five major components involved in a direct to home (DTH) satellite

INTRODUCTION

DTH stands for Direct-To-Home television. DTH is defined as the reception of satellite programmes with a personal dish in an individual home. DTH does away with the need for the local cable operator and puts the broadcaster directly in touch with the consumer. Only cable operators can receive satellite programmes and they then distribute them to individual homes.

A DTH network consists of a broadcasting centre, satellites, encoders, multiplexers, modulators, and DTH receivers.

A DTH service provider has to lease Ku-band transponders from the satellite. The encoder converts the audio, video and data signals into the digital format and the multiplexer mixes these signals. At the user end, there will be a small dish antenna and the set-top boxes to decode and view numerous channels on the user’s end, receiving dishes can be as small as 45cm in diameter.

DTH is an encrypted transmission that travels to the consumer directly through a satellite. DTH transmission is received directly by the consumer at his end through the small dish antenna. A set top box, unlike the regular cable connection, decodes the encrypted transmission.

Fig: DTH

HISTORY OF DTH
"Less than three decades later, or approximately the period of one generation of mankind, more than 30 million homes in the world are equipped with their own satellite dishes. The early Intelsat ,ATS, and Molniya satellites were capable of relaying one (or atmost, two) simultaneous TV programs; each satellite of the current generation easily can deliver as many as 200 program channels to dish antennas less than one-thirtieth of the size required for reception of the original "Our World" telecast.

Well before the turn of the century, virtually any location in Asia or the Pacific will have direct access to hundreds of channels of TV, high-speed Internet links, and thousands of radio program channels. It is not an exaggeration to suggest that satellites are redesigning the very fabric of life by creating full-time universal access to “our world”.

All of this technology creates virtually unlimited opportunities form new business enterprise and personal development. You are holding in your hand a key that will unlock for you, your family, and your business the "secrets" of the 21st century "Information Revolution." There has never been a point in the history of the world when so much opportunity has presented itself to mankind. Use what you learn here wisely and your life will forever be changed.

HISTORY OF DTH IN INDIA
DTH services were first proposed in India in 1996. But they did not pass approval because there were concerns over national security and a cultural invasion. In 1997, the government even imposed a ban when the Rupert Murdoch-owned Indian Sky Broadcasting (ISkyB) was about to launch its DTH services in India.
Finally in 2000, DTH was allowed. The new policy requires all operators to set up earth stations in India within 12 months of getting a license. DTH licenses in India will cost $2.14 million and will be valid for 10 years. The companies offering DTH service will have to have an Indian chief and foreign equity has been capped at 49 per cent. There is no limit on the number of companies that can apply for the DTH license.

OVERVIEW OF DTH SYSTEMS

Direct to Home are nothing but the Direct Broadcast Satellite Television and Radio Systems. Geostationary satellites play an important role for DTH systems. In general, DTH service is the one in which a large number of channels are digitally compressed, encrypted and beamed from very high power Geostationary satellites. The programs can be directly received at homes. Also, DTH transmission eliminates local cable operator completely, since an individual user is directly connected to the service providers.

An individual user has a small dish usually 45 to 60cm in diameter and Low Noise Block Converter (LNBC) pointed towards satellite. At home digital receiver i.e. Set top box is connected to TV which receives digitally multiplexed channels from LNBC and gives RF output for TV.

The satellite transmission is usually in Ku-Band. The digital channels are first multiplexed and then QPSK modulated before transmission. The small dish along with LNBC receives the signals and LNBC converts these Ku band signals to Intermediate Frequency based on the local IF which is typically 10.7GHz. Now, the set top box receives the down-converted satellite signals and performs the demodulation and de-multiplexing and finally D to A conversion before making signal competent to TV.

The DTH receivers available in the Market are affordable and the use of such systems is nowadays increasing dramatically in urban as well as ruler areas.

DD DIRECT
DD Direct is launched by Doordarshan. It operates from NSS-6Satellite and gives 33 free to air channels and 13 radio channels. The transmission covers most of the India. The cost of the Dish, LNBC and Set top box is around Rs. 2500/-. With this setup only free to air channels are visible.

DISH TV Dish TV is launched by Essel Group. The Dish TV has different set top box with Smart card facility to decode paid channels. The cost of the unit is around Rs. 4000/-. So user can watch paid as well as free channels and radio programs. The user has to pay monthly rental for paid channels. The entire 'Zee Network' channels are available on Dish TV. Dish TV Transmission is also from NSS-6Satellite.

NSS 6
NSS 6, Ku-band satellite with Ka band uplink capabilities, will provide fully interactive access to high speed internet and other multimedia communications. Additionally, it will provide direct to home broadcasting services a well as the full compliment of traditional enterprise telecommunications services across the large coverage area stretching from the eastern Mediterranean and southern Africa to Australia, Japan and Korea. Access Cable Operators (ACOs) or your local cable guy who actually lays the wires to your house. The local cable operators or the ACOs then allegedly underreport the number of subscribers they have bagged because they have to pay the MSOs something like Rs 30-45 per household.

Showing a lesser number of households benefits ACOs. With no way to actually cross check, the MSOs and the broadcasters lose a lot. Broadcasters do not earn much in subscription fees and are mostly dependent on advertisement revenue to cover their costs, which is not sustainable and does not offer high growth in revenues for broadcasters.

The way out of this is to use a set-top box so that it will be clear how many households are actually using cable or going for DTH where broadcasters directly connect to consumers and can actually grow revenues with a growth in the subscriber base.

Specifications of NSS-6 Satellite
Location: 95 degree East
No. of Ku-Band Transponders (36MHz wide): 60
Saturated EIRP: 44-55 dBW.
Ku Band Uplink: 13.75 to 14.5 GHz
Ku Band Down links: 10.95 to 11.2 GHz 11.45 to 11.70 GHz 12.50 to 12.75 GHz
Modulation Type: QPSK
Symbol Rate: 27.5 Mb/s. Downlink for DD Direct: 12815,12534,12898 GHz.
Look Angles for GMRT:
Azimuth= 130.51 degree from North.
Altitude= 57.26 degree
THE COMPONENTS

Programming sources are simply the channels that provide programming for broadcast. The provider doesn't create original programming itself; it pays other companies (HBO, for example, or ESPN) for the right to broadcast their content via satellite. In this way, the provider is kind of like a broker between you and the actual programming sources. (Cable television companies work on the same principle.)

The broadcast center is the central hub of the system. At the broadcast center, the television provider receives signals from various programming sources and beams a broadcast signal to satellites in geostationary orbit.

The satellites receive the signals from the broadcast station and rebroadcast them to the ground.

The viewer's dish picks up the signal from the satellite (or multiple satellites in the same part of the sky) and passes it on to the receiver in the viewer's house.

The receiver processes the signal and passes it on to a standard television.

COMPARISION OF DTH AND CABLE TV

The way DTH reaches a consumer's home is different from the way cable TV does. In DTH, TV channels would be transmitted from the satellite to a small dish antenna mounted on the window or rooftop of the subscriber's home. So the broadcaster directly connects to the user. The middlemen like local cable operators are not there in the picture.

DTH can also reach the remotest of areas since it does away with the intermediate step of a cable operator and the wires (cables)that come from the cable operator to your house. As we explained above, in DTH signals directly come from the satellite to your DTH dish. Also, with DTH, a user can scan nearly 700 channels!

For multiple connections in the same premises one can use the same connection. However every television set will need to have individual STB. Also, DTH is a national service and the STBs enable a viewer to change the service providers without changing the STB, even if one moves from one city to another.

DTH offers better quality picture than cable TV. This is because a cable TV in India is analog. Despite digital transmission and reception, the cable transmission is still analog . DTH offers stereophonic sound effects. It can also reach remote areas where terrestrial transmission and cable TV have failed to penetrate. Apart from enhanced picture quality, DTH has also allows for interactive TV services such as movie-on-demand, internet access, video conferencing and e-mail. But the thing that DTH has going for it is that the powerful broadcasting like Star, Zee, etc are pushing for it.

In DTH, payments will be made directly by the subscriber to the satellite company offering the service. A big problem that broadcasters face in India is the issue of under reporting of subscribers by cable operators.

Consider the cable operators pyramid. Right at the top is the broadcaster. Next comes the Multi Service Cable Operator (MSOs) like Siti cable, In Cable, etc. Below them are the Access Cable Operators (ACOs) or your local cable guy who actually lays the wires to your house. The local cable operators or the ACOs then allegedly under-report the number of subscribers they have bagged because they have to pay the MSOs something like Rs 30-45 per household. Showing a lesser number of households benefits ACOs. With no way to actually cross check, the MSOs and the broadcasters lose a lot. Broadcasters do not earn much in subscription fees and are mostly dependent on advertisement revenue to cover their costs, which is not sustainable and does not offer high growth in revenues for broadcasters. The way out of this is to use a set-top box so that it will be clear how many households are actually using cable or going for DTH where broadcasters directly connect to consumers and can actually grow revenues with a growth in the subscriber base. Today, broadcasters believe that the market is ripe for DTH. The prices of the dish and the set-top box have come down significantly. Overall investments required in putting up a DTH infrastructure has dropped and customers are also reaping the benefits of more attractive tariffs. The major thing that DTH operators are betting on is that the service is coming at a time when the government is pushing for CAS (conditional access system), which will make cable television more expensive, narrowing the tariff gap between DTH and cable.

SET TOP BOX
The typical block diagram of the set top box is as shown in the following figure

As per the diagram, the set top box accepts the entire downconverted band and separates out the individual transponder frequency. Then signals are first converted to fixed IF and then QPSK demodulated. The bandwidth of QPSK signals is 27.5 MHz as the bit rate is 27.5Mb/s. It is observed that 11 digitalchannelsare multiplexed in 27.5 MHz bandwidth. The powersupply forLNB,polarization selection signals as wellas LO setting signalsare send by the set top box itself by using the same cable between the LNB and set top box.

After the QPSK demodulation, the digital bit stream obtained contains several multiplexed channels as well as error control bits. The bit stream is processed to correct and detect errors, de-interleaved, and decrypted. A digital demultiplexer then extracts the bits for wanted channel, and sends them to MPEG decoder, and finally generates analog Audio and Video signals with
DtoA converters to drive TV set. The paid channels are encrypted, and a smart card having the correct key for decryption is required to view the paid channels. The key is provided by the paying monthly rent by the user.

CONCLUSION

DTH projects in India are just a beginning and we are taking the advantage of DTH revolution. Direct to home connects urban, rural and remote areas of the country and provides desire information communication, education and entertainment at the click of a button.

* Broadband noise will have negligible effect on GMRT Observations, as the minimum separation distance is 90meters with the assumption that there is no DTH system in 100meter circle from any of the GMRT antennas. Care must be taken for arm antennas.

* Narrow band noise can cause RFI, in spectral line observations below 400MHz, if located at about 2 km from a GMRT antenna.

FUTURE SCOPE

* It is useful to be able to control LNB without set top box so as to understand the exact spectrum at LNB o/p. Effort is to be put to make the circuit on page 18 (or some other approach) work.

* Effect of Narrow band noise on GMRT must be studied in detail. Towards this, a DTH Receiver needs to be installed on an evaluation basis at the GMRT Guest housel Recreation Room and test observations in spectral line mode performed with different "poorly made" coaxial cables to link the LNB and STB. Careful check for lines seen in nearby antennas like C3, C4, and C9 etc in 235 and 325 MHz bands would help in getting a clearer picture regarding the severity of the problems in a controlled manner.

* Finally, to restrict possible RFI, one can design a Hair Pin Filter with provision of passing DC and 22 KHz tone which can be added between the LNB and set top box. This will only allow the required satellite signals and attenuate noise in the GMRT band. Depending on the result of above, we may have to plan a strategy of adding such units BEFORE THE STB at installations in nearby villages.

* We may find that a simpler solution might be to buy a good quality double shielded cable, assemble connectors professionally and supply to the nearby villages, if the tests as in above does show interference to operation of GMRT.