ACMProfessional services
Backwards compatible modes
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What isWhat isDVBDVB--S2 ?DVB-S2 is the “second generation” DVB system for broadband satellite servicesUnder ETSI editorial revision before Public EnquiryDRAFTEN 302 307
slide 4
DVBDVB--S2 in the DVB chainS2 chainDVB-S2IRDsDVB-S2 MODMPEG-TSInteraction channelDVB-RCS,DVB-PSTN, DVB-RCC, ….DVB-S DVB-S2DVB-S DVB-S2High capacity forward link by satellite
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DVB-S2 application scenarios
Broadcast Applications(DTV):
Non backwards compatible
Backwards compatible with DVB-S
Interactive Applications (including rate adaptation ACM) for corporate and consumer applications
Professional Systems (DSNG, Internet trunking, cable feeds, ...
slide 6
What’s DVB-S2
The DVB-S2 tool-kit:
Advanced coding and modulation
Perfornance
(Block diagram)
Broadcast services (CCM & VCM)
Interactive services
Professional Services
Backwards compatible modes
slide 7
The tool-kit approachDVB-S2 is a single system for the various application scenariosCost reductiondue to massproductionDVB-S2Broadcast ProfileInteractive Profile(ACM)Professional Profile(ACM)Back-compatibleprofile
slide 8
Forward Error CorrectionWhat is FEC?
It is the subsystem performing error correction in the receiver.
Therefore a quasi-error-free stream is recovered even in presence of weak or interfered signals
FEC is the system engine
slide 9
ForwardErrorCorrectionThe Selection processoFour“rounds”basedon computer simulationsSeven competitors, using “turbo-code” families:Serial and parallel convolutionalcodes (+ RS)Product CodesLow Density Parity Check (LDPC) codesVery low performance difference: 0.1 -0.8 dB.
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ForwardErrorCorrectionAfter 1 milionGbit, 40.000 days simulations .... The “revenge”of block codes... The Winner was:LDPC codes concatenated with BCHHuge code block dimension:64800 bit (or 16200)
Many available code rates:
1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, 9/10
... LDPCswere invented by Gallagerin 1960!!!
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The DVBThe DVB--S2 system engineS2 engineThe receiving chipThe chipThe BCH outer code: a “cheap ensurance” against error floors at very low BERs(where simulations cannot investigate)Periodic structures facilitating parallel decoding; about 50 decoding iterationsThe receiving chip complexity target : < 10 mm2 with today 0.09 μm technology10 mm2
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The DVBThe DVB--S2S2system “wsystem whheels”eels”ModulaModulationtionoFour formats, all optimised to operate on non-linear transponders (external points on circles): oQPSK (2 bit/s/Hz)o8PSK(3 bit/s/Hz)o16APSK (4 bit/s/Hz): 4-12-APSKo32APSK (5 bit/s/Hz):4-12-16 APSKoThree wheel profiles:roll-off o0.35o0.25o0.20
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Capacity & C/N requirementsC/requirementsThe Transmission modesThe modes Spectrumefficiency versus required C/N on AWGN channel0,00,51,01,52,02,53,03,54,04,5-3-2-101234567891011121314151617C/N [dB] in RsRu[bit/s] per unit Symbol Rate RsQPSK8PSK16APSK32APSKDVB-SDotted lines= modulation constrained Shannon limitDVB-DSNG30%0.5 4.518 dB
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Adaptive Coding and Modulation FFramingraming: the “lorries queue”: queue”oThe transmission is organised inFRAMES (sequence of lorries)Error protection and modulation may change frame-by-frame, according to expected reception conditions (clear sky, rain,...)oThe Header (lorry numberplate) contains:synchronisation and signalling signalsFEC FRAMEFEC FRAMEHFEC FRAMEHPL FRAME8PSK 5/6QPSK 2/316APSK 3/4HUsefuldataFECredundancyReceivingconditions
slide 15
FlexibilityoDVB-S2 may transport single or multiple input streams:oMPEG-TS format ogeneric format (e.g. IP,..)oSuitable for MPEG-2 TV and HDTV as well as for the new coding systems (e.g. H264/AVC, VC9, ....)oEach stream may be protected in a different way
slide 16
Capacity & C/N requirementsC/requirementsDVB-S2 compared with DVB-S:bit-rate capacity gain (same C/N and symbol-rate):25-35% depending on modes and applicationsLarge flexibility to potentially match any transponder characteristics:Spectrum efficiencies from 0.5 to 4.5 bit/s/HzC/N range from –2 to +16 dB(AWGN)0.7 –1dB from the Shannon limit probably means that: “In the course of our lifetime we will never have to design another systemfor satellite broadcasting”
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The System Block Diagram
BBFRAMEPLFRAME FEC ENCODING MODULATION PL FRAMING BCH outer LDPC inner PL Signalling Pilot symbols BB Filter& Quadrature Modulation QPSK, 8PSK, 16APSK, 32APSK constel-lations1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, 9/10 α=0,35, 0,25, 0,20 to the RF satellite channelMAPPINGSCRAMBLER Dummy FRAMELP stream for BC modes MODE & STREAM ADAPTATION STREAM ADAPTERBBSignallingMerger SlicerInput interface & adaptation tools #1 Single Input Stream Multiple Input Streams DATA ACM COMMAND CRC-8 Encoder Input interface & adaptation tools #n BB Header (10bytes)(LDPC-protected)Input adaptation descriptionMerger: definesthe input polling strategyPL Header (7 bits)(64,7)-protected(MODCOD, TYPE)Multiple input streamsPadding bits when requiredPadding frameBlock code: 64800 (16200) bits
slide 18
What’s DVB-S2
The DVB-S2 tool-kit:
Broadcast services (CCM & VCM)
Interactive services
Professional Services
Backwards compatible modes
slide 19
Capacity & C/N requirementsC/requirementsEXAMPLES:EXAMPLES:DVB-S2 for broadcastingSatellite EIRP (dBW)51SystemDVB-SDVB-S2Symbol-rate MBaud27.5 (α=0.35)30.9 (α=0.20)Modulation & coding(C/N=5.1dB@27.5 MHz)QPSK 2/3QPSK 3/4Useful bit-rate Mbit/s33.846(gain 39%)Number of SDTV programmes(*)7 MPEG-2;15 AVC10 MPEG-221 AVCNumber of HDTV programmes(*)1-2MPEG-2;3-4AVC2MPEG-25AVC
(*) Video bit-rates(Mbit/s): MPEG-2: SDTV=4.4; HDTV=18; AVC: SDTV= 2.2; HDTV=9
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Capacity & C/N requirementsC/requirementsEXAMPLES:EXAMPLES:DVB-S2 for broadcastingSatellite EIRP (dBW)53.7SystemDVB-SDVB-S2Symbol-rate MBaud27.5 (α=0.35)27.9 (α=0.25)Modulation & coding(C/N=5.1dB@27.5 MHz)QPSK 2/3APSK 2/3Useful bit-rate Mbit/s44.458.8(gain 32%)Number of SDTV programmes(*)10 MPEG-2;20 AVC13 MPEG-226 AVCNumber of HDTV programmes(*)2MPEG-2;5AVC3MPEG-26AVC
(*) Video bit-rates(Mbit/s): MPEG-2: SDTV=4.4; HDTV=18; AVC: SDTV= 2.2; HDTV=9
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EXAMPLESEXAMPLESSDTV and HDTV broadcastingSDTV broadcastingTwoinput transport streams, two protection levels(VCM)C/NDifference:around 5 dB2xHDTVbit-rate 40 Mbit/s8PSK 3/4 3xSDTVbit-rate 12 Mbit/sQPSK 2/3,MUX1MUX2DVB-S2Rs=27.5 MbaudSingle carrierSDTV offers a
higher availability (
e.g. 99.6%) thanHDTV (
e.g. 90%)
slide 22
What’s DVB-S2
The DVB-S2 tool-kit:
Broadcast services (CCM & VCM)
Interactive services
ACM
Cost Comparison
Professional Services
Backwards compatible modes
slide 23
Strengths & Weakness of Broadband Satellite Interactive ServicesPros:wide coverage and fast deploymentdo not require expensive terrestrial infrastructures:ideal to cover rural areas or developing Countries Cons:satellite capacity impactson the service cost for 30% -50%Terrestrial ADSL cost is falling sharply
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Requirements for new generation Broadband Satellite Interactive ServicesSatellite ServicesCOST SAVINGthrough a cocktail of technologies: Multispot coverage, DVB-S2 (Improved FEC and ACM), DVB-RCS interactive channelMulti-spot coverage:The satellite power is concentrated towards the users’ region only
slide 25
Adaptive Coding and ModulationAdaptive ModulationUnicasting versus BroadcastingUnicasting BroadcastingCurrently the DVB IP/Unicastservices by satellite make use of DVB-S in the forward pathDVB-S has been developed for broadcasting applicationswhere the errorprotection is constant for every service and is constant in time (link optimisation for the worst case: worst service, worst minute , worst location)Large C/N margins for a large percentage of time
slide 26
Adaptive Coding and ModulationAdaptive ModulationUnicasting versus BroadcastingUnicasting BroadcastingThe DVB-S2 ACM technologyallows FEC/modulation adaptation according to the propagation conditions(rain/clear sky, beam centre or beam contour, ....)each usermay operate with very low C/N margins, thus maximising the satellite throughputThe gain of ACM increases with frequency (C, Ku, Ka): less crowded Ka band needs ACM!
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Adaptive Coding and Modulation
How does it work?
DVB-S2DEMACM MODReturn channelC/N+IMeasurementbit-rateControl High protectionQPSK, RATE 1/2Low Protection8PSK rate 5/6FOR ONE-TO-ONE and INTERACTIVESERVICES ONLYPotential ACM gain (ESA source): bit-rate x2in Ka band (Europe)DVB-S2-ACMgain versus DVB-S: bit-rate x 1.30 (FEC) x2(ACM)=2.6
slide 28
Fast Internet Services Comparison of DVBComparison DVB--S2 space segment cost and ADSLADSL
Transponder cost : 2.6 M€/year
(National Ka-bandSpot-beam, BW=72 MHz)
2.6 M€/ year8500 users= 306€/year (satellite capacity only)DVB-S2.6 M€/ year22000 users= 118€/year(satellite capacity only)DVB-S2
ADSL(flat) = 444 €/year(full service)
A recent commercial study forecasts revenuesfor1.3 BillionUS$ in 2005-2009 by DVB-S2 equipment (70% for Interactive services)
slide 29
What’s DVB-S2
The DVB-S2 tool-kit:
Broadcast services (CCM & VCM)
Interactive services
ACM
Cost Comparison
Professional Services
Distribution of DTT Multiplexes
DSNG
Backwards compatible modes
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EXAMPLE
Distribution of two MPEG
MUXes to DTT transmittersDVB-TMUX1MUX2DVB-S224 Mbit/s24 Mbit/sQPSK 5/6C/N=6 dBMUX1MUX2Rs=30 MbaudSingle carrierBW=36 MHzDVB-S would require2 carriers per transponder:•about20% more BW•4-5 dB more power
slide 31
EXAMPLE
DSNG Links Using ACM
Rs=7.5 MbaudEta=20%Multiple carriersC/N = 3 -9 dBBW=36 MHzClear sky:17 Mbit/s @ C/N=9 dBHeavy storm:10 Mbit/s @ C/N= 3 dBFor the same availability,DVB-S carries 7 Mbit/s only!!!RCS return channelVBR encoder
slide 32
What’s DVB-S2
The DVB-S2 tool-kit:
Broadcast services (CCM & VCM)
Interactive services
ACM
Cost Comparison
Professional Services
Distribution of DTT Multiplexes
DSNG
Backwards compatible modes
slide 33
BBackwardackwardss--compatible modesmodesA bridge between present and futureA futureAlthough the full benefits of DVB-S2 are associated to incompatible modes....Backwards compatible modes allow:legacy DVB-S receivers to correctly decode PART OF the DVB-S2 signals
slide 34
Hierarchical modulations allow transmission of backward-compatible signalsnon uniform 8PSK constelationThe high-priority(HP) stream may convey backward compatible DVB-SinformationThe low-priority (LP) stream may convey incompatible S2information(using code rates 1/4, 1/3, 1/2, 3/5)IQABCCOD1Non Uniform 8PSK mapperTS-MUX 1COD2TS-MUX 2DVB-S convolut. codeDVB-S2P1,P2,P3P4,P5,P6ϕϕDVB-SDVB-S2
slide 35
Backwards Backwards-Compatible modes
(same availability HP HP-LP)
Significant capacitygainsof BC-modes are associated to high C/N ratios (High power satellites) and to spectum efficiencies > 1,6 -i.e., DVB-S(7/8) 0,51,01,52,02,54 5 67891011C/N [dB] η(HP+LP) [bit/s/Hz] LP1/4LP3/5LP1/2LP1/3DVB-Sonly HP7/8Range of interestforBC modesLarger capacity gains may be achieved for lower LP availability
slide 36
Backwards Backwards-Compatible modes
Small Impact on DVB DVB-S2
2θDVB-S outer & inner coding EN 300421 DVB-S2 outer & inner coding PL Header insertion EN 302307 Hierarchicalmapper Is,Qs bits Spectrum shaping (α=0,35) QuadraturemodulationHP TS MUX LP TS MUX
slide 37
Conclusions (1)The DVB Project doesn't see DVB-S2 replacing DVB-S in the short term for TV broadcasting. Millions of DVB-S decoders are already operating reliably, contributing to successful digital satellite businesses around the world. DVB-S2 will do what DVB-S could never have done for new applications: delivery of HDTV and IP based services professional applications
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Conclusions (2)Two examples can summarisethe DVB-S2 revolution:Combining DVB-S2 and new video and audio coding schemes (H264/AVC or VC9) a conventional 36 MHz transponder may carry:20-25 SDTV5-6 HDTV Combining the DVB-S2 ACM technology with multi-spot Ka band satellites, current satellite capacity prices for Fast Internet connections can be reduced by a factor of 10. This may re-open the competition with terrestrial ADSL, at least in rural areas and developing Countries.
slide 39
Commercial Requirements(Document CM 373r1): ADVANCED CODING and MODULATION Schemes for Broadband Satellite Services, introducing improved performance over DVB-S and DVB-DSNG:-CAPACITY INCREASE > 30% under the same transmission conditions or...-RUGGEDNESS INCREASE for the same spectrum efficiency (by using state of the art channel coding and modulations)Adaptive Coding and Modulation for INTERACTIVE services, to allow maximum usage of the transponder resourcesFlexibility to convey:transport streams generic streams (e.g. IP)
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