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Mobile Communication Broadcast System Jochen Schiller
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Mobile Communication Broadcast System Jochen Schiller

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  • 1. 6.Broadcast Systems Sonali C. UDIT - M.Sc (IT) 2008-09
  • 2. INTRODUCTION
    • We will focus on unidirectional broadcast.
    • Radio, televisions, distribute information regardless of the need of individual user.
    • 2 way communication technologies, broadcasting information is very cost effective.
    • In future, Television and radio transmissions will be fully digitalize.
    • Along with video and audio transmission multimedia information can be accompany radio and TV programs at low cost compare to individual wireless connection.
  • 3. UNIDIRECTIONAL DISTRIBUTION SYSTEM
    • Asymmetric communication environments
      • Channel characteristic differs in one direction as compare to other direction
    • Symmetric communication environments
      • Channel characteristic is same in both direction
      • E.g.. Same old telephone or GSM (in end-to-end communication).
      • Band width and delay are same not matter who calls
    Cont…
  • 4. UNIDIRECTIONAL DISTRIBUTION SYSTEM
    • Asymmetric communication environments
      • bandwidth limitations of the transmission medium
      • depends on applications, type of information
    • Examples
      • wireless networks with base station and mobile terminals
      • client-server environments (diskless terminal)
      • cable TV with set-top box
      • information services (pager, SMS)
    Cont…
  • 5. UNIDIRECTIONAL DISTRIBUTION SYSTEM
    • Special case: unidirectional distribution systems
    • High bandwidth from server to client (downstream), but no bandwidth vice versa (upstream)
      • problems of unidirectional broadcast systems
      • a sender can optimize transmitted information only for one group of users/terminals
      • functions needed to individualize personal requirements/applications
    Cont…
  • 6. BROADCAST TRANSMISSION sender receiver receiver receiver unidirectional distribution medium A A A A A A A B B B B optimized for expected access pattern of all users individual access pattern of one user 
  • 7. CYCLICAL REPETITION OF DATA
    • Broadcast sender does not know when reviver will listen to message.
    • But in radio and TV, this is not a problem
      • If receiver not listening/tuned in it will not receive data
      • Or. will repeat the information at particular interval of time ( news and weather ) if not received by receiver
  • 8. CYCLICAL REPETITION OF DATA Structuring transmissions – broadcast disks
    • Sender
      • cyclic repetition of data blocks
      • different patterns possible (optimization possible only if the content is known)
    Cont… Every block is transmitted at regular interval of time Average Waiting time is same Favor one or more data block by repeating Distribute blocks more often than others in cyclic pattern Minimize delay if user wants to access Incr probability of receiving repeated locks..if corruped frst time A B C A B C flat disk A A B C A A skewed disk A B A C A B multi-disk
  • 9. CYCLICAL REPETITION OF DATA Structuring transmissions – broadcast disks
    • Receiver
      • use of caching
        • cost-based strategy: what are the costs for a user (waiting time) if a data block has been requested but is currently not cached
        • application and cache have to know content of data blocks and access patterns of user to optimize
    Cont…
  • 10. DAB:DIGITAL AUDIO BROADCASTING
    • Media access
      • COFDM (Coded Orthogonal Frequency Division Multiplex)
      • SFN (Single Frequency Network)
      • 192 to 1536 subcarriers within a 1.5 MHz frequency band
      • VHF and UHF frequencies bands
    • Frequencies
      • first phase: one out of 32 frequency blocks for terrestrial TV channels 5 to 12 (174 - 230 MHz, 5A - 12D)
      • second phase : one out of 9 frequency blocks in the L-band (1452- 1467.5 MHz, LA - LI)
  • 11.
    • MSC (Main Service Channel)
      • carries all user data (audio, multimedia, ...)
      • consists of CIF (Common Interleaved Frames)
      • each CIF 55296 bit, every 24 ms (depends on transmission mode)
      • CIF contains CU (Capacity Units), 64 bit each
    • FIC (Fast Information Channel)
      • carries control information
      • required for interpreting configuration and content of MSC
      • consists of FIB (Fast Information Block)
      • each FIB 256 bit (incl. 16 bit checksum)
    DAB-Transport Mechanism Cont…
  • 12.
    • Two transport modes are defined for MSC
    • Stream mode
      • transparent data transmission with a fixed bit rate
    • Packet mode
      • transfer addressable packets
      • Use to convey MSC data within a sub channel
    • Program association data (PAD)
      • Program info, control info, still pictures etc
    DAB-Transport Mechanism Cont…
  • 13. DAB- Transmission frame Cont… synchronization channel SC main service channel FIC MSC null symbol phase reference symbol data symbol data symbol data symbol . . . . . . symbol T u frame duration T F guard interval T d L 0 0 1 2 L-1 1 L fast information channel FIC DAB Frame structure
  • 14. DAB- Sender Cont… Trans- mitter Trans- mission Multi- plexer MSC Multi- plexer ODFM Packet Mux Channel Coder Audio Encoder Channel Coder DAB Signal Service Information FIC Multiplex Information Data Services Audio Services Radio Frequency FIC: Fast Information Channel MSC: Main Service Channel OFDM: Orthogonal Frequency Division Multiplexing 1.5 MHz f carriers
  • 15. DAB- Receiver Cont… Packet Demux Audio Decoder Channel Decoder Independent Data Service Audio Service Controller Tuner ODFM Demodulator User Interface FIC Control Bus (partial) MSC
  • 16. MULTI-MEDIA OBEJCT TRANSFER PROTOCOL
    • Problem
      • Broad range of different receiver capacity
        • audio-only devices with single/multiple line text display, additional color graphic display, PC adapters etc.
      • different types of receivers should at least be able to recognize all kinds of program associated and program independent data and process some of it.
    • Solution
      • common standard for data transmission: MOT
      • important for MOT is the support of data formats used in other multimedia systems
      • DAB can therefore transmit HTML documents from the WWW with very little additional effort
    • MOT formats
      • MHEG, Java, JPEG, ASCII, MPEG, HTML, HTTP, BMP, GIF, ...
  • 17. MOT Structure
    • Header core
      • 7 byte
      • size of header and body, content type
      • Depending on the header information, receiver may decide if its enough resources to decode
    • Header extension
      • handling information, e.g., repetition distance, segmentation, priority
      • information supports caching mechanisms
    • Body
      • arbitrary data can be transferred in variable body as describe in header field.
    header core header extension body 7 byte
  • 18. DIGITAL VIDEO BROADCASTING
    • 1991 foundation of the ELG (European Launching Group) goal: development of digital television in Europe
    • 1993 renaming into DVB (Digital Video Broadcasting)
    • goal: introduction of digital television based on
      • satellite transmission
      • cable network technology
      • later also terrestrial transmission
  • 19. DIGITAL VIDEO BROADCASTING SDTV EDTV HDTV Multimedia PC B-ISDN, ADSL,etc. DVD, etc. Terrestrial Receiver Cable Multipoint Distribution System Satellites DVB Digital Video Broadcasting Integrated Receiver-Decoder DVB-S DVB-C DVB-T
  • 20. DVB Container
    • Uses Container to transmit data
    • Containers are basically MPEG-2 frames-do not restrict type of info.
    • DVB Service Information specifies the content of a container
      • NIT (Network Information Table): lists the services of a provider, contains additional information for set-top boxes
      • SDT (Service Description Table): list of names and parameters for each service within a MPEG multiplex channel
      • EIT (Event Information Table): status information about the current transmission, additional information for set-top boxes
      • TDT (Time and Date Table): Update information for set-top boxes
  • 21. multimedia data broadcasting MPEG-2/DVB container single channel high definition television MPEG-2/DVB container HDTV multiple channels standard definition MPEG-2/DVB container SDTV multiple channels enhanced definition MPEG-2/DVB container EDTV
  • 22. Example- High Speed internet Access
    • Apart from data and multimedia broadcasting we can use DVB for Internet access
    DVB-S adapter PC Internet TCP/IP leased line service provider information provider satellite provider satellite receiver DVB/MPEG2 multiplex simultaneous to digital TV
  • 23. Convergence of broadcasting and mobile comm.
    • Definition of interaction channels
      • Interacting/controlling broadcast via GSM, UMTS, DECT, PSTN, …
    • Example: mobile Internet services using IP over GSM/GPRS or UMTS as interaction channel for DAB/DVB
  • 24. mobile terminal DVB-T, DAB (TV plus IP data) GSM/GPRS, UMTS (IP data) MUX Internet TV broadcaster ISP mobile operator TV data broadcast interaction channels

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