1.DTS
Direct to home technology is a very popular technology. The detailed guidelines for starting the dth services in India were issued by the govt.in 2001 followed by guidelines in 2003.There is a lot of research going on to find out innovative uses of direct to home technology.In this respect seminar report is focused on extended applications of direct to home technology.Direct to home technology can provide internate,e-mail,data casting,e-commerce and interactive multimedia.
2. Introduction
Direct to home technology was first introduced by JAPAN in 1978.Direct to home (DTH) television service, more popularly known as direct broadcast satellite service, is coming to India after a government ordained delay of three years In March 2001, government allowed Ku-band direct to home television broadcasting by issuing a notification and laying down the ground rules for companies wanting to enter DTH in India. There are four serious contenders for DTH services in India: Doordarshan, Star, Zee, and Data Access.Consumers worldwide enjoy digital television from many sources today: terrestrial broadcasts, cable and satellite systems, high-speed Internet connections and a variety of recorded and prerecorded media such as DVDs. It is satellite distribution that provided consumers their first widespread opportunity to enjoy digital television.
2.1 DTH Technology
DTH is short form of Direct-To-Home technology. DTH is defined as the reception of satellite program with a personal dish in an individual home.DTH services were first proposed in
DTH licenses in
DTH does away with the need for the local cable operator and puts the broadcaster directly in touch with the consumer.
2.1.1 What are the concerns over DTH?
In the absence of regulation, DTH operators may hike their fees arbitrarily. They may force consumers to pay for bouquets of channels, instead of individual channels. Also there could be illegal redistribution of DTH feed through multiple distribution units, amounting to evasion of tax.
2.2 CAS
2.2.1 What is CAS?
CAS stands for conditional access system, which is a digital mode of transmitting TV channels trough a set-top box (STB). The transmission signals are encrypted and viewers need to buy a set-top box to receive and decrypt the signal. The STB is required to watch only pay channels, not free-to-air channels, like Doordarshan.
2.2.2 The CAS Bill and what it means
In the new system, Indian broadcasting companies will decide which channels would be 'non-pay' (free-to-air) and which would be 'pay'. The viewer will now be able to select the pay channels he wishes to watch and pay for only these. Each broadcasting channel will determine the rates for buying the channel.
Currently, there is no segregation and subscribers pay a blanket rate for the entire service. There will soon be two levels of segregation. The first will be a broad differential according to lower, middle and upper classes of society across cable households.
The second differential will be amongst pay channels, like premium channels, which will include focused news, entertainment, sports, music channels and niche channels like nature, health and fashion.
2.2.3 When was it first proposed in
The idea of CAS was mooted in 2001, which was followed by a furor over charge hikes by channels and subsequently cable operators. It was decided that it would be first introduced in the four metros. It has been in place in Chennai since September 2003.
According to estimates, only 25 per cent of the people have subscribed the new technology. The rest watch only free-to-air channels. The inhibiting factor is the cost of the STB.
2.2.4 Will CAS be cheaper than cable TV?
Yes, according to a TRAI order, if one opts for all the existing channels then the pay out will be less. For example, the Star bouquet at present comes for Rs 67 for eight channels. Under CAS, if one avails all the eight channels then the pay bill will be Rs 40 plus a 12.2 per cent service tax. The new tariff order will reduce the cable bills in
2.2.5 Advantages of CAS
For viewers:
Under, CAS viewers can watch only what they would like to watch, than what the cable operator has on offer. Subscribers save money they now spend on unnecessary channels. They will get better transmission (because of the use of optic fiber instead of metal cables). The cable operators will no longer have any control over the pricing of channels.
For broadcasters:
It benefits broadcasters as they always had to grapple with the issue of cable operators not declaring the actual number of subscribers, and hence suffering losses. With CAS, they can find out the exact number of subscribers with a cable operator.
For advertisers:
It gives a far more accurate indicator of program popularity with only the actual subscribers of each channel being accounted for.
2.2.6 So why has there been opposition to CAS?
Consumer activists were essentially opposed to the high cost of the STB. If more people subscribe to CAS nationwide, the prices would come down. There were also apprehensions about fees being charged for the bouquet of channels instead of individual channels. The latest ruling from the Telecom Regulatory Authority of India has struck down bouquet-wise pricing.
In simple terms, a person who wants to want only watch Star News, for example, will no longer have to buy the Star bouquet, comprising, Star Movies, Star World, Star One etc.
Activists are also seeking a limit on the duration of advertising on air. Cable operators are opposed to CAS because they become redundant and even if that didn't happen, they can no longer understate the real number of subscribers and cheat the government of entertainment tax.
Service providers are opposed because they have to set up new digital machinery for CAS and may even have to share the price of the STBs, to avert competition from direct-to-home transmission.
There is one alternate option of CAS is DTH. The details of DTH Technology is given below.
3. Types of DTH
3.1 Analog DTH:
In this technology DTH broadcasting process is done in analog way. For this purpose satellite is at 35768 km. high from the earth. The link geometry for homes in the contiguous 48 states typically affords an elevation angle i.e., line-of-sight angle above the horizon of at least 30 . This geometry means that potential obstacles such as trees or adjacent houses are rarely an actual impediment. The link geometry also means that multipath from hills and buildings is not an issue, especially for the microwave frequencies used by DTH systems. Except for the era of big dish DTH, which used a C-band downlink of
4 GHz, all DTH systems in the
The uplink frequencies are in the band 17.3–17.8 GHz and the downlink frequencies are in the band 12.2–12.7 GHz. For Fixed Satellite Service (FSS) systems in the
The most common uplink and downlink bands are 14.0–14.5 GHz and 10.7–11.2 GHz, respectively. In either band the primary link environmental impediment is moisture along the line of sight that is, rain that causes signal fades. This degradation can be sufficiently estimated to establish margins for practical system designs. The DTH systems themselves cause intra-system interference, such as interference of cross-polarized signals at the same frequency, and intersystem interference, such as interference from satellites at neighboring orbital locations received via consumer receive dish side-lobes.
3.2 Digital:
Around 1990, a number of key technologies had made sufficient progress to make all-digital satellite DTH economically practical. These developments provided numerous benefits unavailable with analog solutions as follows:
Smaller consumer dish size
Tuning to dozens of channels without the need to repoint the dish.
More standard-definition(SD) television channels per unit Radio Frequency (RF) bandwidth.
The DTH system designers recognized that they could utilize progress in key areas such as video/audio coding and cost reductions in Very Large Scale Integrated (VLSI) circuit technology, several areas were recognized as fundamental technical system interfaces and constraints, as follows:
Home DTH receiver outputs compatible with home off-air television inputs.
Consumer dish and outdoor electronics power and control via established interfaces.
4. Working
4.1 DVB-S
(Digital Video Broadcasting By Satellite)
4.1.1 DVB-
Many of the formats and transmisson aspects of satellite DVB sevices are standarised by International Standard Organization (ISO) and the International Telecommunication Union (ITU).
The standard developed by the ITU applies to Ku-band satellites operating at 11/12 GHz. It is designed to provide Quasi Error Free (QEF) service at Bit Error Rate (BER) of 10-10 to 10-11.
MPEG Encoder unit can take several v ideo compressed channels. All the data is compressed to produce a single MPEG block of 188 bytes. In DVB-s Time Division Multiplexing (TDM) is taken place.
4.1.2 Data Coding
A Reed Solomon Code (204/188) is applied to data.This coding can correct up to 8 errors.In it ,16 bytes of overhead are added to the 188 bytes from the MPEG Encoder.On the receiver side the Red Solomon decoder can take in coming data.
4.1.3 QPSK Modulation
This single carrier is now Quadrature phase Shift keying modulated.the code rate is dynamically variable.So, when the link is clean,the transmitter may be transmitting at a high code rate.But if the link deteriorates,say, due to rainfall,the transmitter swithes to a higher coder rate .
4.1.4 Satellite Access mode
There are two modes. (1) SCPC (2) MCPC.
SCPC & MCPC transmission differs in data rates & radiated power levels.
4.1.4.1 Data Rates
MCPC transmission have a symbol rate of a 20 to 30 symbols per second.A symbol rate of 27.5MS/s is compatiable with 33 MHz satellite transponder bandwidth and it is most commonly used. A symbol rate of MS/s is compatiable with 36 MHz transponder bandwidth.
4.1.4.2 Power Level
Power level is a measure of signal strength that a satellite transmits to the earth below. The EIRP is the highest at the center of the beam and decreases at angles away from the bore-sight.
4.2 DVB-S Receiver:
Receiver systems are of two types. (1) Individual receiver system (2) Collection receiver system Individual receiver system is referred as DTH system. Collector receiver system is known as satellite master antenna TV system.
In receiver, there is a tuning circuit, which tunes required channel. The signals are demodulated and then decoded by decoder circuit. The data of the signal is decompressed and given to the digital to analog converter. This is required because TV can detect only analog signal and broadcasting process is done in digital format. Thus, the original signal is regenerated in this receiver circuit.
5. Main three components used in DTH Technology.
5.1 DTH Base Station
5.2 DTH Satellite
5.3 Set- top Box with Dish Antena
5.1 DTH Base Station
It is consist of Base Band Processing equipments such as modulators, RF & UP linking and monitoring equipments.
Video or audio signals from different program station are down linking from different satellites in C band.These signals are further QPSK modulated in RF for UP linking system. To compensate the degradation of the signal due to atmospheric effect in UP linking the signals are sent to High Power Amplifier System for required amplification.After amplification to carriers some are combined througe by diplexer to feed horizontol port of the feed & other carriers are separately fed to the vertical port of the feed.
DVB-S contains transmission satellite, multiplexer, video, audio & data signal into QPSK modulating data stream, transmitting rate of 27.5 MS/s.
The Master Control Room is used to continuosly monitor the various broadcast system to ensure that high level of quality maintain.
5.2 DTH Satellite
NSS-6 satellite is been rented for the DD’s DTh Broadcast.It is an Geosynchronous satellite.
It has transponders, receiving and transmitting antennas.It has frequency band of 11 to 18GHz. So size of the antenna’s dish is small.The transmitted signal of Ku band from broadcasting center is received by dish.For this we have to set the dish of transmission antenna towards the position of the satellite in space. This is UP linking, and it’s frequency is 13.75 to 14.50 GHz.
The reflector receives signal from the base station & reflects it towards the sub reflector. The sub reflector sends signal to the satellites transponder. It converts up linking frequency into down linking frequency of 10.95 to 12.75 GHz. Now the microwave of less frequencye sent to the sub-reflector of the satellite which is near from the transponders by the transmitting antenna.These sub-reflector reflect the signal towards the main reflector dish. This dish transmits the signal towards the earth. It is Down Linking. So, we can get program by DTH in around 50,000 square kilometer area on the earth.
5.3 Set top Box with Dish Antenna
5.3.1 Dish Antenna
The DTH broadcasting is in Ku band so the receiving dish antenna is capable of receiving of Ku band signals.The size of dish is around 0.6 meters.If the broadcasting of Ku band is better than average frequency than size of dish required is 0.45 meters.
This dish is placed in such direction that it is in front of the satellite. The dish is not an antenna but it is a parabolic reflector,which collect the Down link microwave of DTH satellite and send to feed horn,infront of it which is the real receiver.
5.3.2 Set top Box
A Set-top Box is basically convert digital signals to analog signals (MPEG 2-DVB) for analog TV.It decodes the data which has been encoded by a broadcasting center.It decompresses the compressed data.The broadcasting center places some sign in place of repeated data in digital data of up linking signal.So the size of the signal decrease.So we can trasmit the more data in small bandwidth and speedy.We can watch different channels by tunning different frequency on set-top box.
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6. Comparison
6.1 DTH versus cable TV
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.
DTH can also reach the remotest of areas since it does away with the intermediate step of a cable operator and the cables that come from the cable operator to your house.
DTH offers better quality picture than cable TV. This is because cable TV in
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. DTH will not be able to be an alternative to cable if the initial investment is more than that for cable. DTH requires initial investment for both a dish antenna and a TV-top box.
With cable TV, the waiting period can be long and have to pay more to get facilities of movies on demand and lots of other channels. on the other hand, A satellite TV system involves minimal waiting periods.
Setting-up a satellite TV system is easy and affordable. After installment of the receiver and satellite dish you'll instantly get high quality satellite TV signals directly from the broadcaster. On the other hand, digital cable is relayed from sub-station to sub-station. This diminishes the picture quality and sound quality, making it inferior to a satellite TV system. For the clearest reception, ensure your satellite dish has been installed and mounted with a clear view of the southern sky in a place where it won't be damaged by high winds.
A satellite TV system offers local and community broadcasts for an additional charge. These features come free with cable TV package. A satellite TV system cannot receive them in case.
In mosoon rain disturb down linking signals.
We can not watch local TV channels.
7. DTH In World
Cable competition is increased in
Subscriber illegally using US made dishes and receiving
US
The main factors affecting consumer choice between cable and DBS are programming choices, cost, and signal quality. In major markets, DBS offers a few local channels but cable still has the advantage. As in the
The general view has been that Europe could take up to five years to catch up with the
Europe is served among others by the Eutelsat 5 satellite Hotbird network to provide more than 530 Television channels and 400 digital radio channels to approximately 24 million homes in Europe, North Africa and the
Europe has developed the ability to do satellite television differently from the
Cable television has been in the
The
In
Sub-Saharan
It is difficult to predict the future for television in
The challenges, however, facing the African DTH market can be identified by a lack of funds, technological discrepancies or government intervention.
Broadcasting in
8. DTH In
The most significant event in the cable sector was the passage of the Cable Television Ordinance Law in January 1995. This ordinance requires the registration of cable operators and mandated technical standards that required most operators to upgrade their systems in addition to issues regarding content.
The challenge for cable exists in the rural areas where installation and application are extremely cost prohibitive, and nearly three quarters of
The Indian scenario is potentially exciting with a series of decisions taken by the Government to regulate the Indian DTH scene. But the initial excitement in Nov. 2000 has largely been transformed by a realistic look at the guidelines for DTH service in
The key features of the guidelines are:
* The total foreign investment cannot exceed 49 per cent.
* No broadcast or cable company can own more than 20 per cent.
* The applicant company will have to pay an entry fee of Rs 100 million, pay 10 per cent annual revenue and execute a bank guarantee of RS 400 million for the duration of the 10 years license.
* Violation of license conditions can include revocation of license and / or penalty of up to RS 500 million.
* The licensee will have to set up an Indian earth station in 12 months and provide access to various content providers on a non-discriminatory basis.
* The set top boxes required to receive the encrypted signals will have to be open standard boxes.
* The DTH license cannot be used for other modes of communication including voice fax, data Internet unless specific licenses for these value added services have been obtained from the competent authority.
9. Conclusion:
• The audio & video quality of DTH technology is vary high compared with cable TV.
• People, living in remote area, can also watch TV by this technology.
• We can watch program as we wish.
• Atmosphere can affect the broadcasting process in this technology.
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