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architecture Container High-speed InternetDVB Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02Unidirectional distribution systems DAB6.1Mobile CommunicationsChapter 6: Broadcast Systems
wireless networks with base station and mobile terminalsz client-server environments (diskless terminal)z cable TV with set-top boxz information services (pager, SMS)zbandwidth limitations of the transmission mediumdepends on applications, type of informationexamplesMC SS026.2a sender can optimize transmitted information only for one group ofusers/terminalsz functions needed to individualize personal requirements/applicationszhigh bandwidth from server to client (downstream), but no bandwidth viceversa (upstream)problems of unidirectional broadcast systemsProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ Special case: unidirectional distribution systems Asymmetric communication environmentsUnidirectional distribution systems
AB unidirectionaldistributionmediumAProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/optimized for expectedaccess patternof all userssenderservice providerUnidirectional distributionBBAAAMC SS02individual accesspattern of one userAAB6.3receiver.receiverreceiverservice user
Amulti-diskBAABCCCAAABBACMC SS026.4cost-based strategy: what are the costs for a user (waiting time) if a data blockhas been requested but is currently not cachedz application and cache have to know content of data blocksand access patterns of user to optimizezuse of cachingAskewed diskBProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ Aflat diskcyclic repetition of data blocksdifferent patterns possible (optimization possible only if the content isknown)Receiver SenderStructuring transmissions - broadcast disks
COFDM (Coded Orthogonal Frequency Division Multiplex)SFN (Single Frequency Network)192 to 1536 subcarriers within a 1.5 MHz frequency bandfirst phase: one out of 32 frequency blocks for terrestrial TVchannels 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)MC SS026.5Sending power: 6.1 kW (VHF, Ø 120 km) or4 kW (L-band, Ø 30 km)Date-rates: 2.304 Mbit/s (net 1.2 to 1.536 Mbit/s)Modulation: Differential 4-phase modulation (D-QPSK)Audio channels per frequency block: typ. 6, max. 192 kbit/sDigital services: 0.6 - 16 kbit/s (PAD), 24 kbit/s (NPAD) Frequencies Media accessProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ DAB: Digital Audio Broadcasting
carries control informationconsists of FIB (Fast Information Block)each FIB 256 bit (incl. 16 bit checksum)defines configuration and content of MSCtransfer addressable packetsProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02transparent data transmission with a fixed bit ratePacket mode Stream mode 6.6carries 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 eachFIC (Fast Information Channel) MSC (Main Service Channel)DAB transport mechanisms
phasereferencesymbol12.FICfast informationFIC channeldatasymbolTuProf. Dr.-Ing. Jochen Schiller, nnelnullsymbolLsymbolL0datasymbol6.7main servicechanneldatasymbolL-1MC SS02MSCguard interval Tdframe duration TFTransmission frame1
ChannelCoderPacketMuxMSCMultiplexerFICODFMRadio FrequencyTransmitterMC SS026.8fcarriers1.5 MHzDAB SignalFIC: Fast Information ChannelMSC: Main Service ChannelOFDM: Orthogonal Frequency Division MultiplexingTransmissionMultiplexerProf. Dr.-Ing. Jochen Schiller, derAudioAudioServices EncoderMultiplexInformationServiceInformationDAB sender
MC SS02User Interface(partial)MSCProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/Control BusTunerODFMDemodulatorDAB receiver6.9IndependentDataServiceAudioService
audio transmission almost with CD qualityrobust against multipath propagationminimal distortion of audio signals during signal fading MC SS026.10transmission of digital data using long symbol sequences, separated byguard spacesz delayed symbols, e.g., reflection, still remain within the guard spacezfully digital audio signals (PCM, 16 Bit, 48 kHz, stereo)MPEG compression of audio signals, compression ratio 1:10redundancy bits for error detection and correctionburst errors typical for radio transmissions, therefore signalinterleaving - receivers can now correct single bit errors resultingfrom interferencelow symbol-rate, many symbolsMechanisms GoalProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ Audio coding
MC SS026.11a DAB ensemble combines audio programs and data serviceswith different requirements for transmission quality and bit ratesthe standard allows dynamic reconfiguration of the DABmultiplexing scheme (i.e., during transmission)data rates can be variable, DAB can use free capacities for otherservicesthe multiplexer performs this kind of bit rate management,therefore, additional services can come from different providersProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ Bit rate management
D2D3PADD4PADD5D6PADD7PADD2D3D4D5D6Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/D1MC SS026.12D9PADPADD8Audio 896 kbit/sAudio 796 kbit/sD9PADD7D8Audio 1Audio 2Audio 3Audio 4Audio 5192 kbit/s 192 kbit/s 128 kbit/s 160 kbit/s 160 kbit/sPADPADPADPADPADD10 D11DAB - Multiplex - reconfiguredD1PADAudio 1Audio 2Audio 3Audio 4Audio 5Audio 6192 kbit/s 192 kbit/s 192 kbit/s 160 kbit/s 160 kbit/s 128 kbit/sDAB - MultiplexExample of a reconfiguration
broad range of receiver capabilitiesaudio-only devices with single/multiple line text display, additional colorgraphic display, PC adapters etc.different types of receivers should at least be able to recognize all kinds ofprogram associated and program independent data and process some ofitMC SS026.13common standard for data transmission: MOTimportant for MOT is the support of data formats used in other multimediasystems (e.g., online services, Internet, CD-ROM)DAB can therefore transmit HTML documents from the WWW with verylittle additional effortProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ Solution ProblemMultimedia Object Transfer Protocol (MOT)
MHEG, Java, JPEG, ASCII, MPEG, HTML, HTTP, BMP, GIF, .size of header and body, content type7 byteheadercorearbitrary dataheaderextensionobjects, segments, headersProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02body6.14handling information, e.g., repetition distance, segmentation,priorityinformation supports caching mechanismsDAB allows for many repetition schemes Body Header extension Header core MOT formatsMOT structure
SatellitesTerrestrialReceiverCableB-ISDN, ADSL,etc. DVD, etc.IntegratedReceiver-Decodersatellite transmissioncable network technologylater also terrestrial transmissionMultipointDistributionSystem MC SS02DVBDigital VideoBroadcasting6.15Multimedia PCSDTVEDTVHDTV1991 foundation of the ELG (European Launching Group)goal: development of digital television in Europe1993 renaming into DVB (Digital Video Broadcasting)goal: introduction of digital television based onProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ Digital Video Broadcasting
enhanced definitionhigh definition televisionSDTVMPEG-2/DVBcontainerMC SS02standard definitionmultiple channelsProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/multiple channelsEDTVsingle channelHDTVMPEG-2/DVBcontainer6.16data broadcastingmultimediaMPEG-2/DVBcontainerNIT (Network Information Table): lists the services of a provider,contains additional information for set-top boxesz SDT (Service Description Table): list of names and parameters for eachservice within a MPEG multiplex channelz EIT (Event Information Table): status information about the currenttransmission, additional information for set-top boxesz TDT (Time and Date Table): Update information for set-top boxeszhigh flexibility for the transmission of digital datano restrictions regarding the type of informationDVB Service Information specifies the content of a containerMPEG-2/DVBcontainer DVB transmits MPEG-2 containerDVB Container
TCP/IPInternetProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/serviceproviderDVB-S adapterPCMC SS02leased EG2 multiplexsimultaneous to digital TVdownlink: DVB receiver, data rate per user 6-38 Mbit/sreturn channel from user to service provider: e.g., modem with 33kbit/s, ISDN with 64 kbit/s, DSL with several 100 kbit/s etc.satellite receiver Asymmetric data exchangeExample: high-speed Internet access
mobile operatorInternetdataMUXProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ISPTV broadcasterTVMC SS02mobileterminal6.18GSM/GPRS,UMTS(IP data)onitacrein tchannelsbroadcastDVB-T, DAB(TV plus IP data)Example: mobile Internet services using IP over GSM/GPRS or UMTS asinteraction channel for DAB/DVBDefinition of interaction channels Interacting/controlling broadcast via GSM, UMTS, DECT, PSTN, Convergence of broadcasting and mobile comm.
Telecom,licensed5 MHz30-300 kbit/s(per user)Low to highVoice, dataLocal to wideVery highRegulationBandwidthEffectivethroughputMobility supportApplicationCoverageDeployment costfor wide coverageLow to high5-30 Mbit/s(shared)8 MHzBroadcast,licensed130-260,430-862 (UK)DVBLowWideMC SS02Low6.19WideAudio, pushHigh res. video,Internet, images, audio, push Internetlow res. videoVery high1.5 Mbit/s(shared)1.5 MHzBroadcast,licensed1140-1504,220-228 (UK)DABProf. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/2000 (terrestrial),2500 (satellite)Spectrum bands(depends onnationalregulations) [MHz]UMTSComparison of UMTS, DAB and DVB
return channel from user to service provider: e.g., modem with 33 kbit/s, ISDN with 64 kbit/s, DSL with several 100 kbit/s etc. DVB-S adapter PC Internet TCP/IP leased line service provider satellite provider information provider satellite receiver DVB/MPEG2 multiplex simultaneous to digital TV
