1. Direct Broadcast Satellite(DBS) SystemPresented by:Mohamed Mahmoud RashadSally Hossam El-Din

2. Outline Overview of the 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 the DBS 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 users 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 DBS systems use a satellite in geostationary orbit to receive television signals sent up from the Earths 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 17.317.8- GHz uplink band is transmitted back down in the 12.212.7-GHz downlink. What about Receiver ?? 7. Components involved in a DBSsystem 8. Uplink source material "video or audio" are deliveredto the up link facility The source Materials are input to audio and video compressorsThe outputs of the compressors are PacketizedElementary Streams (PES) which are input to themultiplexerA number of separate services are TimeDivision Multiplexed (TDM) into a single bitstream The Forward Error Correction (FEC) then is applied to the bitstream from the multiplexerThe final bitstream (information bits and FEC parity bits) is input to the Quaternary PhaseShiftKeying (QPSK) modulatorThe bit stream then is converted to theappropriate frequency for that transponder(between 17.3 and 17.8 GHz), amplified, andtransmitted to a DBS satellite. 9. DBS operation analysisUplink 10. Transponder The transponder function consists ofconverting the uplink frequency todownlink, frequency (it also providesamplification) 11. Downlink Tuner : to select the transponder Demodulator : selects which of the four possiblesubcarrier waveforms was transmitted Forward error correction decode : removes theconcatenated FEC DE-multiplexer :extracts the selected service fromthe overall TDM bit stream Buffer : small storage of DE-multiplexed bytesbetween DE-multiplexer and decompressionengines Decompression engines : DE-compressors foraudio and video 12. DBS operation analysisDownLink 13. DBS Link Budget 14. Consumer services andapplications Subscription-based TV Pay per-view (PPV) Public service channel rebroadcasts Digital video recorders (DVR) High-definition television (HDTV) Interactive services 15. Advantages of the DBS service More choice More channels per dollar Rural availability Reliable service Digital picture/sound Interactive channel guides 16. Future directions in DBS technology Since the early 1990s, there had been significantdevelopments in the area of digital satellitecommunications. In particular, progress in fourimportant areas of the technology paved the way for amore practical and economically viable launch of theDBS service: Advances in video and audio encoding techniques Advances in modulation and error correctiontechniques Advances in consumer electronics Advances in satellite platforms 17. Conclusion DBS seems most 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 havent 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=directbroadc 19. Thank you