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DIGITAL TERRESTRIAL TRANSMISSIO N EMERGING TECHNOLOGIES

DIGITAL TERRESTRIAL TRANSMISSIO N EMERGING TECHNOLOGIES. GOPALAKRISHNAN. K N ASSISTANT ENGINEER DOORDARSHAN KENDRA TRIVANDRUM. DD reach to public - Current sceneri o. Terrestrial mode - Predominantly Analog Satellite mode (DTH) - Fully digital Cable TV- Both analog and digital.

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DIGITAL TERRESTRIAL TRANSMISSIO N EMERGING TECHNOLOGIES

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  1. DIGITAL TERRESTRIALTRANSMISSION EMERGING TECHNOLOGIES GOPALAKRISHNAN. K N ASSISTANT ENGINEER DOORDARSHAN KENDRA TRIVANDRUM

  2. DD reach to public-Current scenerio • Terrestrial mode - Predominantly Analog • Satellite mode (DTH) - Fully digital • Cable TV- Both analog and digital.

  3. Analog Transmission Technique • Base band signal is analog, 5MHz ccvs • Modulation technique is VSB • Video is Amplitude Modulated and Sound is Frequency Modulated

  4. VSB Technique • Full USB, carrier and part of LSB transmitted. • Total channel B/W is 7 MHz

  5. SINGLE CHANNEL ONLY • NOISY RECEPTION • NOT EFFICIENT IN TERMS OF POWER AND B/W • DATA PROTECTION BY SCRAMBLING NOT POSSIBLE • FRINGE AREA / SHADOW AREAS DUE TO GEOGRAPHICAL LOCATIONS • SIGNALs Subject to MULTIPLE REFLECTIONS-Hence GHOST RECEPTION

  6. ADVANTAGES: • DUE TO VARIOUS MULTIPLEXING TECHNIQUES, & EFFICIENT CODING TECHNIQUES, EFFECTIVE B/W CONSERVATION IS POSSIBLE. • MULTIPLE SIGNALS IN A SINGLE CARRIER, HENCE MULTIPLE CHANNEL RECEPTION. • DUE TO EFFICENT CODING TECHNIQUES, POWER SAVING & ALSO NOISE FREE, ERROR FREE RECEPTION POSSIBLE.

  7. NEED FOR TERRESTRIAL TRANSMISSION • DD being India's National Broadcaster should have a reliable standby mode of transmission to maintain uninterrupted transmission for public. • The risk of catastrophic satellite failures. This fact is of paramount importance during wartime • Satellite (DTH) suffers from rain fading • DTT is highly efficient in terms of spectrum utilization • Moblile/ Handheld Reception will make TV more popular.

  8. ENABLING TECHNOLOGIES • Source digitisation (Rec 601 digital studio). • Compression technology (MPEG) • Data multiplexing (MPEG) • Transmission Technology (Modulation)

  9. ATSC- ADVANCED TELEVISION SYSTEM COMMITTEE (USA) uses 8VSB • DVB- DIGITAL VIDEO BROADCASTING (EUROPE) • DiBEG- DIGITAL BROADCASTING EXPERTS GROUP (JAPAN) INDIA HAS ADOPTED FOR DVB – DIGITAL VIDEO BROADCASTING.

  10. DVB Overview • The Digital Video Broadcasting (DVB) Project is an industry-led consortium of around 200 broadcasters, manufacturers, network operators, software developers, regulatory bodies and others committed to designing open interoperable standards for the global delivery of digital media and broadcast services. • The DVB project was announced in sept. 1993 and became operational by 1995. • DVB–S, DVB-C and DVB-T are different sub stds of DVB.

  11. DIFFERENT VIDEO RESOLUTIONS • STANDARD DEFINITION 720x576 • HIGH DEFENITION 1280x720 • FULL HD 1920x1080 • UHD/4K 3840x2160

  12. DIGITISATION OF SD VIDEO SIGNAL

  13. Color sub-sampling

  14. Color sub-sampling

  15. Color sub-sampling

  16. COMPRESSION IS THE KEY FOR SUCCESS • SDI VIDEO BIT RATE 270 Mbps FOR SD • HD DIGITAL VIDEO BIT RATE 1.485 Gbps • AVAILABLE CHANNEL B/W IS 7/8 MHz

  17. SPECTRAL REDUNDANCY • SPATIAL REDUNDANCY. • TEMPORAL REDUNDANCY. • ENTROPY REDUNDANCY. • PSYCHO VISUAL REDUNDANCY.

  18. COMPRESSION TYPES • LOSSLESS COMPRESSION ( FULLY –REVERSIBLE) • LOSSY COMPRESSION ( REMOVING IRRELEVENT INFORMATION- IRREVERSIBLE) • 270 Mbps signal can be compressed to about 3Mbps without much noticible loss of quality using MPEG 2 • DISCRETE COSINE TRANSFORM IS THE KEY ALGORITHM FOR COMPRESSION.

  19. TRANSPORT STREAM • The data streams of different programs, multiplexed and combined to form a complete data stream so that they can be transmitted via satellite, cable or terrestrial transmission links is called an “MPEG-2 transport stream” (TS for short). • The base band signal for DVB is MPEG 2 TS

  20. MPEG-2 transport stream (Simplified) Header Header Payload Payload Sync Ctrl.bits Ctrl. bits PID Payload 47Hex Payload Packet header 184 bytes 4 bytes MPEG-2 packet size 188 bytes

  21. CHALLENGES IN TERRESTRIAL MODE • •Real life terrestrial delivery is complex. • •Received signal is a dynamic combination of signals arriving at varying delays. • •Resulting channel spectrum is far less than ideal

  22. HOW TO OVERCOME THE CHALLENGES • Transmitted Data spread over large number of closely spaced frequency sub- bands. • Data protected before transmission • Interleaving helps to recover lost data

  23. COFDM • Coded - Inner / Outer coding • Orthogonal - No interference among carriers • FDM - Frequency Divison Multiplexing

  24. COFDM - Orthogonal Carriers Frequency

  25. No inter carrier interference (ICI) • Carrier spacing = 1/T • Efficiently produced by IFFT FREQUENCY Orthogonality (Fqcy Domain)

  26. OFDM (Simple Analogy) Data Loss Due To Frequency Selective Fading Is Minimized In Multi Carrier System Further protection can be ensured by deviding the same type of load across different carriers

  27. Data carrier • 1 bit / symbol BPSK • 2 bits / symbol QPSK • 4 bits / symbol 16-QAM • 6 bits / symbol 64-QAM • 8 bits / symbol 256-QAM Symbols/Modulation

  28. DVB T2- 2nd Generation DTT • DVB-T2 is the world’s most advanced digital terrestrial television (DTT) system • Offers more robustness, flexibility and at least 50% more efficiency than any other DTT system • It supports SD, HD, UHD, mobile TV, or any combination thereof.

  29. Comparison Of DT T Techniques

  30. Advantage with PLPs • Possibilty to reach different kinds of receivers with different levels of robustness within the same RF channel

  31. Mobile Reception • The commercial focus on DVB-T2 is primarily on SD and HDTV , but DVB-T2 is also designed to work well in mobile/handheld devices. • DVB-T2-Lite is a new feature added to DVB-T2, intended for reception in mobile devices. • Reduced data rates and pixel size • Makes use of FEF in DVB T2 • DVB NGH is also based on DVB T2

  32. THANK YOU

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