Lecture B: Digital Media Broadcasting. ISPACS 2005 Tutorial. C. C. Jay Kuo Department of Electrical Engineering University of Southern California

Transcription

1 Lecture B: Digital Media Broadcasting ISPACS 2005 Tutorial C. C. Jay Kuo Department of Electrical Engineering University of Southern California Outline Digital Audio Broadcasting (DAB) DAB history and current status Technology inside DAB Future develop direction Digital Video Broadcasting (DVB) History of DVB project DVB worldwide DVB-H (DVB-handheld) Comparison of DAB and DVB Conclusion 1

2 Outline Digital Audio Broadcasting (DAB) DAB history and current status Technology inside DAB Future develop direction Digital Video Broadcasting (DVB) History of DVB project DVB worldwide DVB-H (DVB-handheld) Comparison of DAB and DVB Conclusion Analog Audio Broadcast Amplitude Modulation (AM) from 1920s Frequency Modulation (FM) from 1950s 2

3 Digital Audio Broadcast (DAB) Advantages: Higher fidelity Greater noise immunity New services Receive radiotext such as song title & traffic updates Can use radio card to hear DAB with PC DAB History Europe Eureka - 147: Founded in 1987 Aiming to develop and define the digital broadcast system 1992: L and S bands allocated to DAB 1995: WorldDAB forum established 1997: Market introduction of DAB in most European countries 2000: 70~80% population in Europe covered by DAB Evolution of DAB receiver The United States HD Radio TM Technology Only approved DAB standard in U.S 2 nd fast growing industry after mp3 player with an annual growth of 444% in 2003 Available at 3

4 DAB Worldwide Available at DAB Benefit Enhanced sound fidelity Improved delivery and reception Upgraded audio quality Digital FM with current CD quality Digital AM with current FM quality Seamless conversion from analog to nextgeneration digital broadcasting for radio stations Added-value system features Text, graphics and still image transfer 4

5 Overview of DAB System Stations bundle analog and digital audio signals (with textual data, such as artist and song information, weather and traffic, and more) The digital signal layer is compressed The combined analog and digital signals are transmitted. The most common form of interference, multipath distortion, occurs when part of a signal bounces off an object and arrives at the receiver at a different time than the main signal. The signal will be compatible with HD Radio TM or Eureka 147 receivers and analog radios. Generation of a DAB Signal Concept of DAB distribution network Each service coded individually at source level, error protected and time interleaved in the channel coder Services data are multiplexed in Main Service Channel (MSC) Then services data are multiplexed with service information and multiplex control information to form transmission frames Coded Orthogonal Frequency Division Multiplexing (COFDM) shaping the DAB signal Available at 5

6 Reception of a DAB Signal COFDM Reception of DAB signal DAB ensemble is selected in the analogue tuner Digitized output from the tuner is fed into OFDM demodulator and channel decoder to eliminate transmission errors Control information: information in FIC is passed to user interface for service selection and set up the reception service Audio data: further processed in an audio decoder to produce the stereo signals Available at Technique MUSICAM Audio Coding Psychoacoustic Masking Masking Pattern Universal Sub-band Integrated Coding And Multiplexing Low bit-rate: reduced to 1/6 ~ 1/12 of conventional PCM coding Sub-band coding: Enhanced by a psychoacoustic model 32-equally-spaced sub-bands Quantization: quantizing noise matches the masking threshold Sample frequency: 24KHz Standards: MPEG 1 audio layer II MPEG 2 audio layer II Available at 6

7 Technique Transmission Coding and Multiplexing 24 ms Stereo Channel 1 Stereo Chan. 2 Stereo Chan. 3 Stereo Chan. 4 Stereo Chan. 5 Mono Data Fast information channel - Multiplex configuration information - Service information Synchronization Main service channel: - Audio services - Data services Guard interval Service data t S T S Total OFDM symbol Multiplexed DAB frame consists of: Synchronization channel Conveying reference frequency and timing information to synchronize to and decode Fast information channel Containing information to extract and decode individual channel Main service channel Carrying the services data Technique Modulation COFDM Against Multi-path Temporal guard interval (TGI): as long as the delay of the echo signals is less than the guard-interval, there will be a constructive benefit for reception Single frequency network (SFN) of transmitters: efficient use of the scare RF spectrum available Coded Orthogonal Frequency Division Multiplexing Multi-carrier Traditional: digitally modulated carrier with a very high symbol rate Multiple carriers: up to 1536, spacing 1k Hz separation Each carrier independently modulated using differential quadrate phase shift keying (differential QPSK) Multiplexed data distributed amongst all the carriers, spectrum 1.54 M, shown as the COFDM figure 7

8 Technique Transmission DAB transmission mode Mode I: preferable for terrestrial single frequency network of VHF range System Parameters Frame duration (ms) Null symbol duration (us) Guard interval duration (us) Nominal frequency transmitter separations for SFN (km) Nominal frequency range for mobile reception (MHz) Speed/coverage trade-off Useful symbol duration (us) Total symbol duration (us) No. of radiated carriers Transmission Mode I II III IV , ,500 3,000 1,500 No No No Yes 1, Mode II: suitable for local radio application in L band Mode III: appropriate for cable, satellite and complementary terrestrial transmission Mode IV: L-band too but with more transmitter spacing in SFNs Conditional Access (CA) Scrambling / Descrambling Services incomprehensible to unauthorized users Entitlement check Broadcasting the conditions required to access a service Broadcasting encrypted secret codes to descrambling for authorized receivers Entitlement management Distributing entitlement to subscribers 8

9 DAB Future Develop Direction Traffic and travel information Traffic messages Traffic navigation Travel information Text transmission Electronic Newspaper Picture transmission Fax Printout Differential GPS TV Transmission to Mobiles Available at Outline Digital Audio Broadcasting (DAB) DAB history and current status Technology inside DAB Future develop direction Digital Video Broadcasting (DVB) History of DVB project DVB worldwide DVB-H (DVB-handheld) Comparison of DAB and DVB Conclusion 9

10 Analog TV System 4:3 aspect ratio and interlaced scan NTSC in USA and PAL in Europe Luma Sampling Frequency Chroma Sampling Frequency Frame Rate Luma Active Samples/line Chroma Active Samples/line Active Lines/frame Data Rate NTSC 13.5 MHz 6.75 MHz Mb/s PAL 13.5 MHz 6.75 MHz Mb/s Why DTV? Digital TV More programs - Multicast Better picture quality -HDTV New services - Data and itv Two main DTV system standards ATSC (Advanced Television Standards Committee) Terrestrial system is called ATSC or DTV in U.S. DVB (Digital Video Broadcasting) in Europe DVB is almost worldwide-adopted standard 10

11 DVB Worldwide-adopted DTV standard DVB-S/C/T dominate world Basis for most of the alternative standards DVB is based on MPEG-2 for video, audio and data transmission DVB video format Both HDTV and SDTV supported Interlaced and progressive 4:3, 16:9 and 2.21:1 aspect ratio Resolution vary per channel and country Up to 1920x1152 DVB-MHP One standard for Digital / interactive TV and internet access DVB-S SDTV / HDTV DVB-MS DVB-MC DVB-C Interactive STB Interactive PC DVB-T B-ISDN, ASDL, PSTN, GSM DVD DVC 11

12 DVB-MHP (Cont d) DVB-MHP is An open standard for interactive DTV (itv) Extension to existing open standards, DVB, MPEG, JavaTV A platform definition MHP standardizes elements of the home platform A set of Java APIs and HTML document type definition Applications are built in Java or HTML Compatible with current DVB-based solutions Adopted in many countries Germany, Finland, Singapore, S. Korea, Australia and etc. Included in the U.S. OpenCable standard Typical DVB-MHP Applications Electronic Program Guide, Applications synchronized TV content Information Service Interactive Advertising Game 12

13 New Business Opportunities DVB - History 1991 European Launching Group (ELG) Milestone: Memorandum of Understanding (MoU) Game rule for digital TV broadcasting 1993 Digital Video Broadcasting Project (DVB) Satellite (DVB-S) and cable (DVB-C) delivered the first round of digital TV services, later terrestrial (DVB-T) 1997 Everything in Europe on track, promotion around the world 2000 release of DVB-MHP (Multimedia Home Platform) specification 2001 DVB-2.0 new DVB commercial and technique strategy 2004 DVB-H (handheld) formally adopted by ETSI wireless industry announced to support DVB-H 13

14 DVB Worldwide DVB-S DVB-T DVB-C DVB-MHP Vision of DMB (or DVB-H) Bring Digital TV to Your Cell Phone 80s~90s Now Future Telephone belongs to An office An individual A household TV belongs to An living room A caravan A personal smart phone 14

15 What is DVB-H H? Newest specification of DVB project Evolved from DVB-T Technology to deliver live digital TV on cell phones Live broadcast, digital TV Digital real-time TV Local and national wide channels High-quality 25~30 frames/sec Open standard Ensure rapid market growth Driving Force of DVB-H There are 3 main problems when DVB-T goes to mobile Power consumption Performance in wireless environments Lower SNR in mobile channels Doppler effect due to mobility Impulse interface (burst data arrival) Antenna design for medium to large SFN (Single Frequency Network) Solution: DVB-H!!! 15

16 Competitive Solutions in Bringing Digital TV to Handheld Systems Region Video Codec Audio Frequency (MHz) Bit rate (M bps) Modulation Optimized power reduction for handset ISDB-T Japan MPEG-2 MPEG-2 (AAC) 6 23 OFDM (13 seg/ch) Mobile use 1 seg. only DVB-H US/Europe/Asia H.264 MPEG-2 (BC) 8 31 COFDM Time slicing DMB Korea H.264 MPEG-4 (BASC) COFDM None Technologies Incorporated in DVB-H Applications Wireless processors Wireless processors integrated communications processor 16

17 Comparison of DVB-H H & DVB-T T Systems New to DVB-H Existing in DVB-T DVB-H: How It Works Possible transmission mode for U.S. Europe and Asian Satellite to digital TV tower, terrestrial broadcast to handset North America market timing Today, nationwide spectrum available Now Crown Castle Network trial in Pittsburgh Mid 2005 networking testing of prototype phones 2006 trial phones launch 2007 volume phones launch Being offered in Korea Satellite sends to handset directly Europe market timing Current trials in Europe Mid 2005 network testing of prototype phones 2006 trial phones launch Early 2007 volume phones launching 17

18 Sharing DVB-T T Networks Sharing by multiplex Sharing by hierarchy Dedicated DVB-H H Networks 18

19 DVB-H H Challenges and Solutions Challenges Battery life Solutions Time-slicing for power saving Mobility with high data rate Single antenna reception Impulse noise tolerance MPE-FEC for robustness and mobility 4K mode for network flexibility Seamless handover Coverage Overview of DVB-H H Technical Features Time slicing Mandatory for power saving MPE-FEC Optionally used in DVB-T physical network Robustness can be adjusted according to the requirements Code rate 1/2~7/8 recommendation 1/2 or 2/3 19

20 DVB-H H Features (1): 4K mode 4K mode with 3409 active carriers Compromise between High-speed small-area SFN capability of 2K DVB-T and Lower-speed but larger-area SFN of 8K DVB-T Better immunity to ignition interface Achieved by enhanced in-depth interleaving in the 2K and 4K modes BER after Viterbi SNR (db) DVB-H outline DVB-H H Features (2): Time Slicing Burst data are received at a time (so called IP carousel ) Transmitter is on all the time, receiver switches off Mandatory Pro: receiver could be inactive Receiver sleep over 90% power saving Power saving (%) Burst size Synchronization time Delta-t jitter Burst bit rate (Mbps) 2Mb 250ms 10ms DVB-H outline 20

21 DVB-H H Features (3): MPE-FEC Multi Protocol Encapsulation Forward Error Correction Multiplexer level error correction scheme Additional Reed-Solomon coding for IP datagrams RS data delivered in special FEC section (virtual interleaving) Reuses time slicing buffer (2 Mbit) 7~8 db benefit with impulse noise 21~58 Hz benefit with Doppler frequency PER PER Interference level (db) Doppler (Hz) DVB-H outline DVB-H H Receiver Overview Existing in DVB-T New in DVB-H 21

22 COFDM Channel Decoder Critical points: Channel estimation/correction Memory technology Three DVB-H H Terminal Modes Set top boxes and HDTV Normal MPEG-2 reception for compatibility concern DVB-H time slice terminal Time slicing support Power saving Full DVB-H terminal Support both time slicing and MPE-FEC Power saving and good performance 22

23 Commercial Products (1): TI Solution Hollywood chipset Complement video processing Support DVB-H and ISDB-T Real-time transmission Media: air interface, not the cellular network Highly-integrated single chip Incorporate 3 function modules into one chip OMAP Extensively used in current US, Europe and Korea handsets Commercial Products (2): DiBcom DVB-H H Chip DiBcom DIB 7000H 1 st DVB-H chip, offering good solution to DVB-H reception Possible to be integrated into mobile devices as a plug and play feature 0.13 um, P < 20 mw MPE-FEC hardware acceleration Time slicing with embedded micro-controller 23

24 Commercial Products (3): Other DVB-H H Solutions Nokia 7700 (w/o 4K, MPE-FEC & w TS) FPGA based (w 4K) Siemens: March 9, 2005 Sony SES and Motorola SPS FPGA based (w 4K, MPE-FEC and TS) Panasonic Integrated receiver (w/o 4K, w MPE-FEC & TS in PC) Samsung First CDMA DVB-H phone in 2005 Conclusion: Impact of DVB-H Consumers New attractive services Media & broadcasters Re-use of popular content via new distribution platform Broadcast network operators Additional core business opportunity Mobile operators Provision of interactive service and potential new roles in digital broadcast business Equipment vendors New products and features 24

25 Outline Digital Audio Broadcasting (DAB) History and current status of DAB Technology inside DAB Future develop direction Digital Video Broadcasting (DVB) History of DVB project DVB worldwide DVB-H (DVB-handheld) Comparison of DAB and DVB Conclusion Technical Comparison of DAB and DVB-H System DAB Bandwidth 1.5 MHz FFT size 256, 512, 1k and 2k Timing slicing No Timing interleaving Yes Unequal error protection (UEP) Yes Multi protocol encapsulation forward error correction (MPE-FEC) No Demodulation DQPSK (less complexity) Receiver power consumption 400 mw DVB 5~8 MHz 2k, 4k and 8k Yes No No Yes, working within one time slice only 16QAM/QPSK 400 mw 25

26 Transmitter Power Comparison Sensitivity comparison of GSM, DVB-H and DAB Frequency range (MHz) Modulation GSM D-Net (900) E-Net(1800) GMSK DVB-H VHF (174 ~230) UHF (470 ~ 838) 16QAM / QPSK DAB VHF (174 ~230) L-band (1452 ~1477) DQPSK Thermal noise (dbm/hz) Bandwidth (dbhz) Noise figure (db) System requirements (db) C/N or E c /N o 8 15~22 15 Sensitivity (dbm) ~ Delta (db) ~ Outline Digital Audio Broadcasting (DAB) DAB history and current status Technology inside DAB Future develop direction Digital Video Broadcasting (DVB) History of DVB project DVB worldwide DVB-H (DVB-handheld) Comparison of DAB and DVB Conclusion 26

27 Conclusion DAB DAB fits better for mobile application with bit rate less than 300 k bps Little efforts made to enhance DAB for broadband services Conditional access and copyright issues are crucial DVB DVB-H offers higher rates at the expense of larger transmission power consumption and lower flexibility DVB-H can be simply deployed by using the current DVB-T infrastructure Antenna design and power concern are critical issues for DVB-H 27