The Satellite Television
1. Introduction of Satellite Television
As we know, television programs transmitted by communications satellite and used a satellite dish and set-top box to receive is called satellite television. Although we have already had terrestrial television programs and cable television programs, but satellite television still offers a large amount of channels and services covered many areas of the world, mainly focus on the areas that cannot receive terrestrial or cable television signal.
In 1962, the first satellite television signal was transmitted from Europe to the Telstar satellite over North America. In 1963, the first geosynchronous communication satellite Syncom 2 was launched. On April 6, 1965, the first commercial communication satellite Intelsat, also known as Early Bird, was launched into synchronous orbit. In 1967, Soviet Union created the first national network of satellite television Orbita, which relayed and delivered television signal to ground stations by using highly elliptical satellite Molniya based on the same working principle. In 1972, geostationary Anik 1 of Canada was launched as the first domestic North American satellite used to transfer television signal. In 1974, the first experimental educational and Direct Broadcast Satellite ATS-6 was launched. In 1976, geostationary satellite Ekran was launched by Soviet Union to transmit Direct-To-Home television program.
2. Technology of Satellite Television
There are two orbits for satellites transmitting television signals. One is naturally highly elliptical orbit, also called Molniya orbit, with inclination of ±63.4 degrees and orbital period of about 12 hours. The other is geostationary orbit of 37,000 km above the earth's equator.
Satellite television is much similar with other applications provided by satellite, transmitting antenna is the start point and built inside an uplink facility. The size of uplink satellite dishes is very big, almost 9 to 12 meters in diameter. The larger the diameter is, the more accurate pointing and stronger signal at the satellite. Then the uplink dish is looking toward a specific satellite and using a specific frequency range to transmit the uplink signals. Then one of the transponders which has the same frequency range in that specific satellite receives the uplink signals. After that, the signals are retransmitted back to Earth station by the transponder and use a different frequency band for retransmitting. This process is called translation, which use different frequency band to prevent interference with the uplink signals. Nowadays, we mainly use C-band (4GHz-8GHz) or Ku-band (12GHz-18GHz) or both. In addition, the direction from the satellite to the Earth station is called the downlink.
A classical satellite has a maximum value of 32 transponders for Ku-band and a C-band only satellite has a maximum value of 24 transponders. There are more transponders for hybrid satellites. Each transponder has a frequency band between 27MHz and 50MHz. C-band only satellite has to be separated from each other for 2 degrees because of the interference. Ku-band satellite has to be separated from each other for 1 degree. In other words, we can maximum launch 180 geostationary C-band satellites (360 degree/2 degree = 180) and 360 geostationary Ku-band satellites (360 degree/1 degree = 360). Transmission provided by C-band satellite is sensitive to the interference with terrestrial transmission. On the other side, transmission provided by Ku-band satellite is sensitive to rain, since water can absorb microwaves at this frequency.
After transmitting quite long distance, the weak downlink signals are gathered by a receiving dish and reflected to the focal point. Feedhorn is a device built on brackets at the focal point. This device works as a section of flared front end waveguide, which collects signals at or close to the focal point and feed them to a probe, which connects to a low noise block downconverter or LNB. The LNB can implement several functions, like amplifying the weak downlink signals, filtering the frequency band of satellite television signals, transforming the frequency band to a lower frequency range (low frequency band) and etc. The improvement of LNB is one significant research direction these days.
In the early days, C-band satellite television systems used one Low Noise Amplifier, which was connected to the feedhorn at the focal point. Then the increased signal was driven into an indoor receiver by using gas filled hardline coaxial cable, which cost so much and has 50 ohm impedance. Or sometimes, due to other design principles, the increased signal was driven into a downconverter for transforming to an intermediate frequency. Besides, microstrip based converters designed for Amateur Radio frequencies have to changed to the 4 GHz C-band.
Replacing Low Noise Amplifier with an LNB has many advantages. For example, the indoor receiver is connected with the satellite television dish and LNB by using cheaper cable and it is much cheaper for using technology to process low band signal and UHF (UltraHigh Frequency) signal rather than using technology to process C-band signal. Replacing the 50 Ohm impedance cable and N-Connectors with the 75 Ohm impedance cable and F-Connectors makes the original satellite television receivers available to use. However, in fact, modified UHF television tuners downconvert the satellite television channel to a lower intermediate frequency surrounded by 70 MHz (demodulation frequency). According to this shift, evolution of satellite television industry decreases the cost of complete system and increases the production efficiency.
At the end, television signals were demodulated and converted to the appropriate form (video, audio and data) by the satellite receiver. In some design, the satellite receiver is able to decrypt or unscramble, which is known as Integrated Receiver/Decoder (IRD). Besides, we need specific type of cable to connect the satellite receiver to the LNB, like low loss type RG-6, quad shield RG-6 or RG-11 and so on. (NB. RG-59 is not allowed.)
3. Direct Broadcast Satellite (DBS)
Direct Broadcast Satellite (DBS) is mainly focus on the satellite television broadcasting for home reception. In most cases, DBS television program is available as same as the program available to cable television subscribers. The different thing is DBS subscribers can receive the television programs directly from the telecommunications satellites, which are powerful and launched in the geosynchronous orbit (22,000 miles above the Earth), rather than receiving programs from terrestrial cable systems. In the other hand, DBS suppliers put multiple kinds of services or channels together and sell them to potential DBS subscribers for monthly payment.
There are three main differences between DBS and Television Receive Only (TVRO), technology, programming and cost. Almost four million families in the United States use TVRO and they have to pay approximately $1,800 for a satellite dish (including installation fee), of which the diameter is between 7 to 10 feet. TVRO users can receive 75 unscrambled programs but also have to pay monthly for a collection of scrambled programs. TVRO programs are transmitted by using C-band (3GHz-6GHz) and a maximum power of 10 watts.
However, the diameter of DBS dish is less or equal to 18 inches and cost about $700. Although DBS and TVRO provide similar program collections, but DBS subscribers cannot receive the completely same unscrambled programs that TVRO can receive. DBS programs are transmitted by using Ku-band (11GHz-15GHz) and a minimum power of 120 watts. In other words, Ku-band can provide much stronger satellite television signal because of the high power. Therefore, compared with the size of receiver dish for C-band reception, a much smaller receiver dish is required.
In 1975, it was the first time that Home Box Office (HBO) used one satellite to transmit program to local cable television systems. It was also the beginning of DBS. A large number of people from rural areas who cannot receive cable television programs, installed TVRO dishes outside their houses and received all the programs radiated from satellites. After that, TVRO suppliers stopped providing free service for their subscribers. Therefore, in 1985, HBO and other similar organizations started to encrypt the television signals, and then TVRO subscribers had to pay extra fee for receiving such type of television programs.
In 1980, it was the first time that Satellite Television Corporation (STV) raised an idea of true DBS service to the Federal Communications Commission (FCC) in the United States. After that, STV's idea was accepted by FCC and other companies started to focus on DBS services as well. At the end, 13 companies sent their ideas to the FCC and eight of them were accepted. Unfortunately, when time went to the early 1990s, it was estimated that more than a billion dollars were required to build up a DBS service. That was the main reason why a lot of DBS projects were delayed or canceled at the same time. In addition, DBS companies doubted whether program suppliers can apply their services into DBS, because in the past time they always provided services to cable systems. However, the Cable Television Consumer Protection and Competition Act of 1992 handled this problem by enforcing cable program suppliers to sell their services to DBS operators.
FCC allows DBS companies to provide their services by distribution of satellite transmitter and DBS orbital slot. Satellites are allowed to launch DBS services by using 8 orbital slots, which are 175, 166, 157, 148, 119, 110, 101 and 61.5 degrees west longitude.
In July 1991, the first generation of DBS service, known as Primestar, was launch by collaboration of cable television system owners. In 1995, Primestar can provide 67 program channels to almost 70,000 families by using 45 watt transmitters, which was built on the Satcom K1 satellite of America. As a result, DBS subscribers had to spend money on both sides: one is the monthly fee of $25-$35 for the Primestar service, the other is the installation fee of $100-$200 for receiving hardware which is owned by Primestar.
On December 17, 1993, the DBS-1 satellite was launched into orbit, which meant the second generation of DBS service put into use. There were 32 transmitters carried by the DBS-1, which was created by Hughes Space and Communications Group. Ten of them were belong to United States Satellite Broadcasting (USSB), and rest of them were belong to DirecTV. Although Primestar, DirecTV and USSB use the same frequency band, the Ku-band to transmit television signals, a much smaller receiving dish was available to DirecTV and USSB subscribers because of the higher power of DBS-1 satellite.
In order to share the market, DirecTV cooperated with USSB to sell the receiving system, which was available to both DBS services. The receiving system contained several components, such as dish antenna, decoder unit and remote control, which were known as the Digital Satellite System (DSS). In 1995, it cost $700 for basic DSS unit not including installation fee. If DBS subscribers install DSS unit by themselves, it will cost $70; if DBS subscribers choose dealer assistance to install for them, it will cost $200. There were more than 400,000 DSS units sold out until March 1995.
However, there are several serious problems brought by DBS to subscribers. As we know, the receiving dish should exactly face toward the transmitting satellite and stand in alignment, which is defined as the line-of-sight (LOS). But unfortunately, heavy winds can easily move the position of receiving dish and thunderstorms can interrupt DBS signal reception. Besides, the local over-the-air channels cannot provide DBS television programs. Although DBS still has all these problems, they cannot stop people choosing DBS services, especially people who lose hope for cable television or people who come from rural areas and cannot receive cable television.
4. Commercial DBS Services
In 1989, Sky Television plc, also known as BSkyB nowadays after combined with five-channel network of British Satellite Broadcasting, was introduced into market as the first commercial DBS service. After that, Sky TV started to provide a four-channel free-to-air analogue service by using the Astra 1A satellite, which covered the United Kingdom and Republic of Ireland. And then, in 1991, Sky transferred into conditional access, which subscribers had to pay extra money for program reception. In 1998, Sky Digital, a digital service was provided, and in 2001, television programs which used analogue transmission were disappeared. However, in the UK or Ireland, people have no idea about the term DBS, so they call the products which can support Sky's service as "minidish" and "digibox" excluding Sky's hardware. Besides, BSkyB has to obey News Corporation.
As mentioned in the third sub topic, in 1991, it was the first time that PrimeStar transmitted an analog service to North America. Later, in 1994, DirecTV allowed PrimeStar to join in, and was belong to GM Hughes Electronics, a branch of General Motors. No matter what happen, the introduction of DirecTV became the best known consumer electronics among Americans. However, in 1994, PrimeStar moved its direction into digital system, but finally it failed to compete with DirecTV, because DirecTV only used a smaller size transmitting antenna to relay more television programs. As a result, in 1999, PrimeStar was purchased by DirecTV and all its subscribers were replaced by installing DirecTV equipments. In 2003, after a long time of processing, Hughes Electronics was separated from General Motors. After that, News Corporation owned more than 50% stocks of a new company, which was known as The DIRECTV Group. However, DIRECTV which News Corporation focused on was purchased by Liberty Media Corporation in 2008.
In addition, started from 1996, Dish Network of EchoStar was launched into market of United States and made the same benefits as DirecTV. So EchoStar can compete with DirecTV very easily. Besides, AlphaStar and Astro also started their business at that time but only the latter one was succeed and used the DBS system. Also, in the same year, Sky Angel was provided by Dominion Video Satellite Inc, which delivered the DBS service mainly focused on the religion and household market. At the very beginning, Sky Angel had only six TV and radio channels, but nowadays it grows up to 36 channels and provides family entertainment, 24-hour news and some religious programs. Actually, in 1981, Dominion followed by its parent company Video Satellite Systems Inc and got the second place in the first nine companies, which use FCC to achieve a high power DBS license. In addition, Dominion was the key survivor for DBS beginners since forward-thinking. Because Sky Angel has an agreement with Echostar, which can use all the same equipments like Dish Network, e.g., transmitting equipment, reception facilities and communication satellites. So by regarding Sky Angel as an independent and separate DBS service, the channels from Dish Network are also available for Sky Angel subscribers. Although EchoStar tried its best to purchase DirecTV in 2003, but American government rejected this proposal because of monopolization reason.
5. Free DBS Services
It seems that Germany is the most important country which focuses on the free-to-air DBS service, also called FTA. This service provides broadcasting programs through 40 analogue channels and 100 digital channels by using the SES Astra 1, which comes to the position at 19.2E longitude. Although these programs are not introduced into market as a DBS service, but almost 12 million families are receiving them, and also, any subscriber of German commercial DBS who uses Sky Deutschland can receive them as well.
In UK, free DBS services are provided through 160 digital channels, which contain some BBC and ITV channels based on the regional variations. Then these services are broadcasted by using the SES Astra 1 when it comes to the position at 28.2E. Subscribers can use any receiver which supports DVB technology for program reception. Sky Digital EPG holds the majority of these channels and the number of channels which belong to Freesat EPG is increasing as well. Besides, both of them add several FTA HDTV channels to the original channels.
Doordarshan, which is the national broadcaster in Indian, launches a free-to-air DBS service called DD Direct Plus. Regarding as an essential technology, it supports the whole country's terrestrial transmission network. Besides, there are plenty of French channels providing free-to-air DBS services. Although at the very beginning they were introduced like the feedback of digital terrestrial television service, but nowadays they have already become the core technology in the DTT network. In addition, more than 80 FTA digital channels offered by Galaxy 19 are being used in North America, like Canada, USA and Mexico. Most of these channels provide ethnic or religious programs. There are other satellites which support FTA digital channels as well, for example, AMC-4, AMC-6, Galaxy 18, Satmex 5 and so on. Among all these satellites, GloryStar (a company name) provides FTA religious broadcasting programs by using Galaxy 19 and AMC-4.
6. Satellite Television in UK
In order to separate from signal reception for non-consumer use, in UK, three different types of DBS services are launched into market, which is called DTH (Direct-to-Home) as well.
First one is Sky TV. It is one of the services provided by British Sky Broadcasting, which is known as the most significant DBS service supplier. Compared with other suppliers, Sky TV can provide the maximum number of channels. Since September 2008, service fee costs from 18 pounds to 47 pounds one month and installation fee costs from 0 pound to 150 pounds based on which kind of set-top-box (STB) the subscriber will choose. Furthermore, pay-per-view services are available as well, such as movies, sport events and personalized channels. In the market, Sky+ and Sky+HD are sold by Sky TV, and Sky+HD means that it can support High Definition Television as well. However, video on demand service does not include in Sky TV.
Second one is Freesat from Sky. It is a free DBS service provided by British Sky Broadcasting. Subscribers have to install all the equipments like program receiver, antenna dish, viewing card and access equipment which connect with all free-to-air channels and free-to-view channels in the UK. The Sky TV subscribers can stop the service they are using right now, and change to the free-to-view viewing card, which can provide Freesat from Sky service. However, High Definition Television and video on demand are not included in Freesat from Sky.
The third one is Freesat, which is launched into market as a free satellite service by both BBC and ITV. Compared with Freesat from Sky, it is not necessary for Freesat to have a viewing card. Besides, Freesat is the first one in UK which supports High Definition Television without any subscription. Actually, video on demand is not included in Freesat service, as well as broadcasting program through some specific free channels encrypted by BSkyB, for example, Channel 4 HD, Fiver and so on.
Sky TV, Freesat from Sky and Freesat provide television programs by using Eurobird 1 satellite of Eutelsat when it comes to the position at 28.5E longitude, and using SES Astra satellite when it comes to the position at 28.2E longitude. Because both satellites are launched in the geostationary orbit, so it means that they are above the equator of the Earth, which are nearly 35,786 km higher than the sea level.
In this technical paper, first of all, a brief view of satellite television and technology used in satellite television are introduced. After that, a detailed description of Direct Broadcast Satellite (DBS) is represented, followed by two main conceptions as commercial DBS services and free DBS services. At the end of this paper, it mainly focuses on three DBS services launched in UK, Sky TV, Freesat from Sky and Freesat. As a result, this paper tries to give a fully description in each area about Direct Broadcast satellite television systems.
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(2) Direct-broadcast satellite, From Wikipedia, the free encyclopedia, For the Japanese communication satellite, see Broadcasting Satellite (Japanese). Website: http://en.wikipedia.org/wiki/Direct-broadcast_satellite
(3) Television in the United Kingdom, From Wikipedia, the free encyclopedia, "United Kingdom television" redirects here. For the digital cable and satellite television network, see UKTV. Website: http://en.wikipedia.org/wiki/Television_in_the_United_Kingdom
(4) DIRECT BROADCAST SATELLITE, Satellite Delivery Technology Website: http://www.museum.tv/eotvsection.php?entrycode=directbroadc