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- 1. Direct Broadcast Satellite (DBS) System Presented by: Mohamed Mahmoud Rashad Sally Hossam El-Din
- 2. Outline Overview ofthe DBS DBS delivery technology Components involved in a DBS system DBS operation analysis DBS Link Budget Consumer services and applications Advantages of the DBS service Future directions in DBS technology Conclusion References
- 3. Overview of theDBS DBS Satellite used to deliver TV programs to viewers all over the world. Ex “Nile-Sat” The signals used by broadcast TV satellites are typically digitally compressed. The provider selects programs and broadcasts them to subscribers as a set package. DBS technology enables consumers to receive digitally modulated television signals directly from satellites.
- 4. DBS delivery technology The end user receives data from a high frequency satellite in geosynchronous orbit (GEO).
- 5. WHY GEO?? The high power of transmission from this satellite allows the user’s receiving dish to have very small size. By using video compression and encoding in the transmission, hundreds of channels can be broadcast over the bandwidth available
- 6. Digital DBS-TV DBSsystems use a satellite in geostationary orbit to receive television signals sent up from the Earth's surface, amplify them, and transmit them back down to the surface. The satellite also shifts the signal frequency, so that a signal sent up to the satellite in the 17.3–17.8- GHz uplink band is transmitted back down in the 12.2–12.7-GHz downlink. What about Receiver ??
- 7. Components involved ina DBS system
- 8. Uplink source material"video or audio" are delivered to the up link facility The source Materials are input to audio and video compressors The outputs of the compressors are Packetized Elementary Streams (PES) which are input to the multiplexer A number of separate services are Time Division Multiplexed (TDM) into a single bitstream The Forward Error Correction (FEC) then is applied to the bitstream from the multiplexer The final bitstream (information bits and FEC parity bits) is input to the Quaternary Phase ShiftKeying (QPSK) modulator The bit stream then is converted to the appropriate frequency for that transponder (between 17.3 and 17.8 GHz), amplified, and transmitted to a DBS satellite.
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- 10. Transponder • The transponderfunction consists of converting the uplink frequency to downlink, frequency (it also provides amplification)
- 11. Downlink Tuner :to select the transponder Demodulator : selects which of the four possible subcarrier waveforms was transmitted Forward error correction decode : removes the concatenated FEC DE-multiplexer :extracts the selected service from the overall TDM bit stream Buffer : small storage of DE-multiplexed bytes between DE-multiplexer and decompression engines Decompression engines : DE-compressors for audio and video
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- 14. Consumer services and applications Subscription-based TV Pay per-view (PPV) Public service channel rebroadcasts Digital video recorders (DVR) High-definition television (HDTV) Interactive services
- 15. Advantages of theDBS service More choice More channels per dollar Rural availability Reliable service Digital picture/sound Interactive channel guides
- 16. Future directions inDBS technology Since the early 1990s, there had been significant developments in the area of digital satellite communications. In particular, progress in four important areas of the technology paved the way for a more practical and economically viable launch of the DBS service: Advances in video and audio encoding techniques Advances in modulation and error correction techniques Advances in consumer electronics Advances in satellite platforms
- 17. Conclusion DBS seemsmost appealing to persons who either are disenchanted with cable television or who live in areas that are not served by cable. DBS-TV systems operate with small antennas and low cost receiving systems, and offer a very large number of video and audio channels, making them attractive to customers. A second phase of the technology evolution is making it possible for DBS providers to offer bigger and better services to consumers. There haven’t been any major breakthroughs and much of the basic DBS technology has remained the same.
- 18. References http://encyclopedia2.thefreedictionary.com/Direct+ broadcasting+satellite+systems http://www.maplenet.net/~trowbridge/DBSintro.htm http://ww.museum.tv/eotvsection.php?entrycode=d irectbroadc
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Editor's Notes
- #4 2ndbullet :the provider's broadcast is completely digital, which means it has much better picture and sound quality.which allows multiple programs to be transmitted from a single transponder onboard the satellite. The type of program content delivered by satellite TV could include existing cable services, movies, sports, Pay per View (PPV) and a variety of other services. 3rd bullet:The first digital direct broadcast satellite (DBS) service started in June 1994.Most satellite TV customers get their programming through a DBSprovider. 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 your TV in a form that approximates the competition, cable TV. 4th bullet:Consumers who bought digital satellite receivers are enjoying excellent high-quality pictures and more channel access.
- #5 DBS is a communication link that transmits directly from the transmitter to the user1st bullet:. A geostationary orbitis a circular orbit 35,786 kilometres (22,236 mi) above the Earth's equator and following the direction of the Earth's rotation. A GEO satellite orbits directly above the earth's equator at 0° latitude
- #6 1st bullet:The GEO satellites essentially relay the signal back to earth which can then be picked up by the consumer receiving equipment such as the parabolic shaped mini-dishes and converted back to the original TV programs using Integrated Receiver Decoder (IRD) devices.
- #7 1st bullet:DBS systems use a satellite in geostationary orbit to receive television signals sent up from the Earth's surface, amplify them, and transmit them back down to the surface. The satellite also shifts the signal frequency, so that a signal sent up to the satellite in the 17.3–17.8-GHz uplink band is transmitted back down in the 12.2–12.7-GHz downlink band. 2nd bullet:DBS systems, like all satellite systems operating in the Ku band, are subject to attenuation of their signals by rain. The combination of satellite power and receive-dish antenna size is chosen to enable reception for all but the heaviest rainfall periods of the year.The DBS customer can further reduce this expected outage period by purchasing a slightly larger dish antenna.
- #8 There are five major components involved in any direct broadcasting satellite system: the programming source, the broadcast center, the satellite, the satellite dish and the receiver.-Programming sources are simply the channels that provide programming for broadcast. The provider doesn't create original programming itself; it pays other companiesfor 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 TV companies work on the same principle.)-The broadcast center is the central hub of the system. At the broadcast center, the TV provider receives signals from various programming sources and beams a broadcast signal to satellites in geosynchronous orbit.-The satellites receive the signals from the broadcast station and rebroadcast them to Earth.-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 TV.
- #15 the DBS industry has successfully created and sustained a consumer subscription based business model. In this type of model, the DBS service provider designs and implements subscription based services to be offered to consumers. The main characteristics of this type of business model are that the service offering has to be compelling and cost effective for the consumer. Some of the most commonly available DBS services and application are discussed below.Subscription-based TVDBS TV providers typically offer tier based subscription services. The vast majority of customers tend to subscribe to the most basic package and perhaps one or two premium packages. Pay per-view (PPV)This type of service allows DBS TV consumers to choose and pay for specific programs as one-off transactions. The chosen program is typically broadcast at the same time to everyone and could include concerts, sports events such as boxing and football matches.Public service channel rebroadcastsMost DBS TV providers offer packages that include the local free-to-air channels. This includes the major public service channels such as BBC.Digital video recorders (DVR)A DVR is essentially a device that allows the recording of video content in a digital format. The content is typically stored on a disk drive but USB memory drives, SD memory cards and various other storage media could also be used. There are two very important aspects of the DBS service that make DVR devices an attractive ancillary application. The first is the Electronic Program Guide (EPG) that provides the consumers with comprehensive program schedules. The second is the availability of program content in a digital format. This allows consumers to select a program from within the EPG and record it directly to the DVR onboard hard disk in a digital format. High-definition television (HDTV)HDTV is rapidly becoming the norm for television viewing. HDTV offers a significantly enhanced viewing experience with notably higher picture quality than standard definition television (SDTV). DBS TV has been one of the earliest adopters of HDTV technology. Support for IP-based home networkingModern DBS receiving and decoding equipment such as set-top boxes provide integrated IP networking capabilities. This typically involves support for an internet connection through a broadband network such as cable or ADSL. The internet connection provides consumers remote DVR scheduling capabilities. Interactive servicesInteractive television (also called iTV) is an increasingly common feature allowing viewers to interact with the television content. The interactivity level of the service varies depending on the delivery platform being used, e.g. cable, or satellite (DBS). At the low end of the interactivity scale, this could involve simple controls, e.g. on/off, volume, browsing channels, etc to more moderate levels of interaction involving features such as movies on demand, etc. highlevel of control can enable the viewer to have some influence over the viewing experience. Some examples of this include, being able to choose the angle to view a football match from or participating in a live program through voting in order to influence the outcome.
- #16 More choiceDBS offers one very important element in the world of paid television service: Competition! Until recently, your only choice was your local cable company, and their monopoly on television service provided no incentive for additions or improvements outside of federal regulation. Today, you have at least two options for satellite television service in lieu of cable, and both are reasonably customizable to your tastes. More channels per dollarThe receiver components which interface the satellite signal to your television also serve as decoders. Therefore, the DBS providers are able to use digital compression techniques to carry up to ten times as many channels on the satellite transponders as would otherwise be possible. As a general rule, you will get many more channels per dollar spent with a satellite service than with cable TV. Rural availabilityFor some people in remote rural areascable is simply not available. Satellite service, on the other hand, is available anywhere in the contiguous 48 states (with more limited availability in Alaska and Hawaii) as long as there is a clear line of sight to the position of the satellite in the sky. Reliable serviceThe cable infrastructure is always at the mercy of accidents resulting in downed lines or severed cables. The only factors that typically affect satellite broadcasts (aside from accidents involving your own dish antenna) are extremely severe weather, or solar interferences during the equinoxes, and these are rare. Digital picture/soundThe analog signals sent over standard cable lines are subject to degradation, interference, and other factors that can result in a less than stellar picture. Satellite signals are digital, and like a compact disc, are not subject to depreciation in picture or sound quality. Satellite TV generally looks and sounds far superior to cable transmissions. Interactive channel guidesSome cable systems include a channel which shows program listings. These usually scroll along at an unbearably slow pace and cannot be advanced to show more than a couple of hours of upcoming shows. Some satellites include highly interactive program guides that can be manually advanced, or can display additional program information, and sometimes can provide one-touch timed VCR recording. Certain programming can also be locked out based upon content ratings.
- #17 Advances in video and audio encoding techniques The development of the MPEG-2 standard for source coding offered significant gains in compression.Advances in modulation and error correction techniques DBS technology provided the basis for the first mass-market application of concatenated coding (FEC).Advances in consumer electronics Rapid improvements in digital circuit design and decreasing cost of consumer electronics equipment.Advances in satellite platformsIncreases in satellite size and weight, higher power generation using more efficient solar technology, support for up to 240W transponders and subsequent increased signal strength.