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DTTB Field trial Explanations

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					              Australian DTTB Field Trial

                  SMPTE Presentation
                                    29 June 1998

                      HDTV into the HOME


      Compiled by Wayne Dickson
      SMIREE MIEAust CPEng. Member SMPTE
28 June                                            1
             Australian DTTB Field Trial
                    What was it !
          A DTTB Field Trial is study of Failure !!
          • In comparison with current PAL television
          • In various reception conditions :
                •   City                     •   Beach areas
                •   Urban                    •   Rural
                •   Suburban                 •   Translator areas
                •   Industrial suburban      •   Distribution systems
                •   Hills                    •   Near Airports
                •   Harbour - across water   •   Near highways


28 June                                                                 2
              Australian DTTB Field Trial
                  Overall Objectives
          • Provide, as part of the selection criteria for a
            choice between 8VSB and COFDM systems, the
            difference in the reception character of the two
            systems.
          • Provide, to the system planners, some of the
            information for design to allow reliable reception
            by the viewing public.
          • Use upmost care to provide credible data.
28 June                                                          3
          Australian DTTB Field Trial
              Overall Objectives
    • GSM Mobile Telephones are the public’s first
      example of DIGITAL communications and the
      characteristic “cliff edge”.
    • “We” in Australia will plan to minimise the impact
      of the “cliff edge” by first ignoring the “marketing”
      and then embarking upon testing and analysing
      phases to select the best parameters to provide
      reliable HDTV into the homes of Australia.
28 June                                                   4
             Australian DTTB Field Trial
                  Unique Character
                 compared to other international Trials
          • Both ATSC and DVB-T Systems @ the
            SAME TIME AND LOCATION
          • VHF 7MHz Trial - UHF in Europe and USA
          • Adjacent Channels - both upper and lower
          • Reception matching Consumer’s Antenna
          • Static and Dynamic (Flutter) ECHOES (multipath)
          • Current Analogue (PAL) character records
          • Multiple test methods used :
               • Two Threshold C/N generation methods
28 June        • Two DTTB power Measurement methods           5
            Australian DTTB Field Trial
                  Technical Aims
    • Compare DTTB to Analogue (PAL) for :
          – COVERAGE study and prediction
          – ROBUSTNESS study under conditions such as :
            •   Level variations
            •   Static Echoes
            •   Dynamic (varying) Echoes - eg Aircraft
            •   Impulsive noise
    • Develop reliable field trial techniques for DTTB
28 June                                                   6
              Australian DTTB Field Trial
                    Technical Aims
    • Analyse to obtain character of the :
          – ATSC 8VSB system
          – DVB-T COFDM system
    • Analyse to provide “Infrastructure” needs
          –   DTTB transmission power requirements
          –   Translator or “Gap filler” requirements
          –   Margins for reliable reception
          –   Requirements for the minimum DTTB receiver
28 June                                                    7
              Australian DTTB Field Trial
                       Limitations
          The Field Trial did not cover :
    •     UHF Bands IV & V (for Regions and translators)
    •     Co-channel interference
    •     Long term level variations (seasonal)
    •     Variable weather conditions eg rain and lightening
    •     Performance in MATV and cabled systems
    •     In-door reception eg via “rabbit ear antennas”
    •     Portable and Mobile reception
28 June                                                        8
          Australian DTTB Field Trial
                Systems Tested
    • ATSC                                • DVB-T
          •   8VSB modulation                 •   COFDM modulation
          •   6 MHz nominal bandwidth         •   7 MHz nominal bandwidth
          •   Useful Bitrate 19.39 Mbps       •   Useful Bitrate 19.35 Mbps
          •   FEC 2/3                         •   FEC 2/3
          •   RS (207,187)                    •   RS (204,188)
          •   Equaliser range of 23uSec       •   Guard interval 1/8(32uSec)
          •   Co-channel comp. off.           •   DMV V1.0 Eq. Software
          •   “Blue racks” decoder            •   DMV V2.0 Sys. Software



28 June                                                                        9
           Australian DTTB Field Trial
           Contributing Organisations
          • Australian          • NDS
            Broadcasting        • ZENITH Electronics
            Authority (ABA)       Corp.
          • DCA Communication   • Harris Corp.
            Laboratory          • RFS
          • FACTS               • NEC
          • TEN Network         • Hewlett Packard
          • NINE Network        • Rohde & Schartz
          • SEVEN Network
28 June                                                1
              Australian DTTB Field Trial
                     Trial Statistics
          Sydney statistics * :      Field Trail :
           • 13,500 square Km        •   3 Oct. to 14 Nov. 1998
           • 3.9 million people      •   27 days of testing
           • 1.3 million dwellings   •   108 Sites
                * approximate        •   125 Tests
                                     •   0.4 Km to 100 Km
                                     •   4 KW erp DTTB
                                     •   100 KW erp PAL
                                     •   DTTB F/S’s 30 to 90 dBuV/m
                                     •   PAL F/S’s 40 to 105 dBuV/m
                                     •   DTTB Av. F/S 68 dBuV/m
28 June
                                     •   PAL Av. F/S        82 dBuV/m   1
          Australian DTTB Field Trial



           Transmission Spectrums




28 June                                 1
               DTTB Transmission
                    8VSB
                   Spectrum Analyser display :
          Dependent upon
          Resolution B/W                      Vision Carrier
                            D + 11.3 dB
          setting.

             CH7                   A   CH8         CH9       Sound Carriers
                                                        Chroma

                               DTTB
             PAL               (8VSB)                PAL

           D = DTTB to PAL ratio D = 14 dB for the Trial
                   DTTB power = average heating power

                   PAL power = the equivalent CW power of
                               peak sync Vision Carrier power
28 June                                                                       1
            DTTB Transmission
                COFDM
              Spectrum Analyser display :
                 Dependent upon
                 Resolution B/W
                                             Vision Carrier
                 setting.

          CH7                   A   CH8           CH9         Sound Carriers
                                                       Chroma

                              DTTB
           PAL              (COFDM)                  PAL
          D = DTTB to PAL ratio D = 14 dB for the Trial
                DTTB power = average heating power

                PAL power = the equivalent CW power of
                            peak sync Vision Carrier power
28 June                                                                        1
              Australian DTTB Field Trial
                 Reception Antennas
          The following Antennas were used at heights from 2.5m to 10m
          determined by the Consumer’s antenna heights at the location.

      • VHF Band III antenna with a nominal gain of
        7 dBd and a front to back ratio of > 20 dB

      • A folded Dipole with a nomimal gain of 0 dBd


28 June                                                                   1
            Australian DTTB Field Trial
                    Observations
          With DTTB power 1/25th (-14 dB) of PAL,
          when there was noticeable :

          • Grain (noise) and some echoes (multipath)
            on Analogue PAL picture, 8VSB and
            COFDM failed.
          • “Flutter” 8VSB reception failed.
          • Impulsive noise and some grain in picture,
            COFDM reception failed.
28 June                                                  1
          Australian DTTB Field Trial
               Summary Results
                 COVERAGE
  • Judgement of the coverage of DTTB compared to PAL
    is complex, as comparison has to be between a “cliff
    edge” failure of DTTB to a gradual failure of PAL.
  • A margin of safety has to be allowed, for DTTB reliable
    reception, further complicating decisions on equivalent
    coverage.
  • Coverage is also influenced by Receiver performance,
    especially NF.
28 June                                                       1
          Australian DTTB Field Trial
               Summary Results
                 COVERAGE
   • The following graphically presented data represents a
     fraction of the that being studied. Other data is yet to
     be analysed.
   • By investigating both the character of PAL “failure”
     against that of the individual character of the DTTB
     systems failure, an idea of the required power for
     reliable “equivalent” coverage can be envisaged.
   • A brief pointing to the following graphs may help later
     study.
28 June                                                         1
                                  Australian DTTB Field Trial
                                       Summary Results
                                     PAL Receive Margin
              (d B )
              IN




                                                                         PAL - SITE RECEIVE MARGIN
                                                                                      Facts DTTB Trial Sites
              A R G




                  40

                                                                               for HIGH GAIN ANTENNA
                  35
              M
              R E C E IV E




                  30                       Minimum F/S = 55dBuV/m
                                                                                                                         Receiver limitations
                  25
                                                       Margin to minimum acceptable
                                                       picture w/o multipath

                  20


                  15
              S i t e




                  10


                       5                                                                                                     PAL on CH9


                       0
                             45     50         55        60         65        70           75       80         85   90          95        100      105                    110
                                                                                   Site Field Strenght (dBuV/m)
                             MINIMUM ACCEPTABLE PICTURE
                                                                                                                                      Plisch Receiver
          Nominal conditions :           7 dB gain Antenna + 2 dB leed loss @ CH9
                                              Effective decoder Noise Figure (NF) = 5 dB
                                                                                                                                                   W. T. D. 5 JUNE 1998




28 June                                                                                                                                                                         1
                                  Australian DTTB Field Trial
          ( d B )
          T H R E S H O L D


                                       Summary Results
                                   DTTB compared to PAL
                                                                       PAL VIDEO S/N @ DTTB THRESHOLD
                                                                                    @ 14dB nominal DTTB to PAL ratio
          D T T B




               -15



                                                                                                                                                    8VSB
               -20
          @
          P A L




               -25
          o f




               -30
          S / N




               -35
                                                                                                                                         COFDM (64QAM,2/3,1/8)
          V id e o




                                      Average S/N @ Threshold of :                              8VSB = -24.2dB unwtd (PAL)
               -40
                                                                                             COFDM = -28.7dB unwtd (PAL)

                                                                Note : 8VSB Launch power on average was 0.8dB higher than COFDM Launch power
               -45
                              0   5      10    15    20    25     30     35    40      45    50    55    60       65   70    75    80     85   90    95    100   105             110   115
                                                                                                    TEST #
                                                                                                                                               FACTS DTTB Trial Sites


                                                                                            System Noise Method
                                                                                                                                                                  W.T.D. 15 Jan 1998




28 June                                                                                                                                                                                      2
                 Australian DTTB Field Trial
                      Summary Results
                   8VSB Decoder Margin
          ( d B )




                                                                   8VSB SITE DECODE MARGIN
                                                                                FACTS DTTB Trial Sites
          A R G I N




             60


                                                                         for a HIGH GAIN ANTENNA

             50
                                 Minimum F/S = 37 dBuV/m                                        Margin @ Threshold C/N
          M




                                      without multipath                                         w/o multipath
          C O D E




                                      and 3 dB margin
             40



                                              Minimum F/S = 47 dBuV/m
             30                               with multipath allowance
          D E




                                                  and 3 dB margin
                                                                                                                         Margin @ threshold C/N
                                                                                                                         with multipath
          i t e




             20
          S




                                                                                                                             8VSB

             10

                                                                                                                         Decoder NF = 9 dB

                0
                      25    30         35           40        45        50           55         60          65     70         75         80       85                            90
              NO PICTURE                                                     Site Field Strenght (dBuV/m)
                                                                                                                                   System Noise Method
                           Nominal conditions :     7 dB gain Antenna + 2 dB leed loss
                                                  Effective decoder Noise Figure (NF) = 9 dB
                                                                                                                                                         W. T. D. 7 JUNE 1998




28 June                                                                                                                                                                              2
                 Australian DTTB Field Trial
                      Summary Results
                  COFDM Decoder Margin
           ( d B )




                                                            COFDM SITE DECODE MARGIN
           I N




                                                                          FACTS DTTB Trial Sites

             60
           A R G




                                                                      for a HIGH GAIN ANTENNA
             50
                                                                                              Margin @Threshold C/N
           M




                                Minimum F/S = 37 dBuV/m
                                                                                              w/o multipath
                                    without mutipath
           D E




             40                     and 3 dB margin
           D E C O




                                          Minimum F/S = 45 dBuV/m
             30                           with multipath allowance
                                              and 3 dB margin
                                                                                                               Margin @ Threshold C/N
                                                                                                               with Multipath
           S i t e




             20



                                                                                                               COFDM (64QAM,2/3,1/8)
             10


                                                                                                               Decoder NF = 5 dB

                0

                     25   30       35        40        45        50           55            60        65       70       75         80    85                 90
          NO PICTURE                                                  Site Field Strenght (dBuV/m)
                                                                                                                        System Noise Method
             Nominal conditions : 7 dB gain Antenna + 2 dB leed loss @ CH8
                                          Effective decoder Noise Figure (NF) = 5 dB                                                              . .   NE
                                                                                                                                              W. T D 5 JU 1998




28 June                                                                                                                                                          2
           Australian DTTB Field Trial
                Summary Results
                  COVERAGE
                          Roof antenna
                                                                      DTTB
    Rx.   System   Required F/S   Margin       Required F/S
                                              for Reliable Coverage
                                                                      to PAL
    NF                            of Safety
                                                                       Ratio
           PAL     55 dBuV/m       0 dB          55 dBuV/m             0 dB
   3 dB   8VSB     41 dBuV/m        3 dB         44 dBuV/m            -11 dB
          COFDM    43 dBuV/m       3 dB          46 dBuV/m             -9 dB
   5 dB    PAL     57 dBuV/m       0 dB          57 dBuV/m             0 dB
   9 dB   8VSB     47 dBuV/m        3 dB         50 dBuV/m            -7 dB
   5 dB COFDM      45 dBuV/m        3 dB         48 dBuV/m             -9 dB
28 June                                                                        2
           Australian DTTB Field Trial
             Required DTTB Power
                    (VHF roof top Antenna)
          • To provide approximate equivalent coverage
            to current FTA transmission (nominal ERP of
            100 KW), the DTTB ERP is estimated to be :
            – Equal Receiver NF :
               • 8VSB          8 KW ERP
               • COFDM 12.5 KW ERP
            – Receivers as expected to be implemented :
               • 8VSB         20 KW ERP
               • COFDM 12.5 KW ERP
28 June                                                   2
          DTTB Field trial
           Explanations

             Multipath
           Static Conditions
            Fixed reception



28 June                        2
                                        Field Trial
                                    Multipath Character
            (Conditions: Static multipath, Equal Rx NF, No Co-channel or impulse interference)

                                     Indoor Antenna      Outdoor Antenna
                               35
                                                 8VSB
          C/N Threshold (dB)




                                                            COFDM
                                                            (64QAM,2/3,1/8)
                                                                                          Picture
                                                                                          (above
                                                                                           curve)
                               19
                               15               SYDNEY FIELD TRIAL TESTS
                                                                                          No Picture
                                 0      3              15                      30        (Below
                                              Multipath Level ( - dB)                     curve)

28 June
                                                 (Single Echo)                W.T.Dickson 29 March 98   2
                                  DTTB System Multipath
                                  Character - Unequal NF
                         (Conditions: Static multipath,Unequal Rx NF, No Co-channel or impulse interference)

                                             Indoor Antenna       Outdoor Antenna
                               35 (31)
          C/N Threshold (dB)




                                                           8VSB With NF=(X+4)dB

                                                              COFDM        With NF=XdB
                                                              (64QAM,2/3,1/8)                             Picture
                                                                                                          (above
                                                                                                           curve)

                               19 (15)
                                                                                                          No Picture
                                                                                                         (Below
                                                               15                                         curve)
                                         0     3                                               30
                                                      Multipath Level ( - dB)
28 June
                                                          (Single Echo)                       W.T.Dickson 29 March 98   2
               DTTB System Multipath
              Performance Improvement
          (Conditions: Static multipath, Equal Rx NF, No Co-channel or impulse interference)

                                     Indoor Antennas         Outdoor Antennas
                               35
                                                   8VSB
          C/N Threshold (dB)




                                                   COFDM
                                                   (64QAM,2/3,1/8)
                                                       (Nov. 1997)                                      Picture
                                                                        COFDM                           (above
                                                                     Current implementations
                                                                             (April 1998)                curve)

                               19
                               15                                                                       No Picture
                                                                                                       (Below
                                                         15                                             curve)
                                 0        3                                                  30
                                                Multipath Level ( - dB)
28 June
                                                  (Single Echo)                             W.T.Dickson 16 April 98   2
          DTTB Field trial
           Explanations

             Multipath
          Dynamic Conditions
            Fixed reception



28 June                        3
                               Aircraft Flutter

                                                          Va


                                                              
                                                 Far               Das
                                       Dar
                                                                          Fas

                                                  D                          F




      Fas = F - F * Cos  * Va / c + F * Cos  * Va / c            tg = ( Dar + Das - D ) / 0.3 uSec
                             Doppler shift
          NOTE : There are competing doppler shifts.

28 June                                                                                                3
                               DTTB System Dynamic
                                Multipath Character
                                    (Conditions: Dynamic multipath (flutter), Equal Rx NF,
                                            No Co-channel or impulse interference)

                                          Indoor Antenna           Outdoor Antenna
                               35
                                                          8VSB w/o flutter
          C/N Threshold (dB)




                                                            8VSB with flutter
                                                              Dependent upon flutter level (amplitude and doppler shift)

                                                                                COFDM
                                                                               (64QAM,2/3,1/8)                 Picture
                                                                              With or without flutter          (above
                                                                                                                curve)
                               19
                               15
                                                                                                               No Picture
                                 0           3                 15                                    30       (Below
                                                      Multipath Level ( - dB)                                  curve)

28 June
                                                         (Single Echo)                               W.T.Dickson 29 March 98   3
                              DTTB Systems Doppler
                               Performance Limits
                                           for current implementations
                     300

                     250                                  UHF

                     200
    DOPPLER
     SHIFT                                           COFDM 2K, 3dB degrade
                     140
      (Hz)                                                     VHF - Band III
                     100                        COFDM 2K

                         50
                         0
          ATSC                0     100   200   300 400   500 600    700 800 900 1000
   see separate curves                    SPEED (Km/Hr)
                              Vehicles                     AIRCRAFT
                                           Over Cities
                                  COFDM implementations will inherently handle post and
                                  pre-ghosts equally within the selected guard interval.
28 June                                                                                    3
                     ATSC 8-VSB
               Doppler Performance Limits
                                 for current implementations
              10

                          UHF                  VHF - Band III

    DOPPLER
                                                8VSB, “Fast Mode”, 3dB degrade
     SHIFT     5
      (Hz)


                                                 8VSB
               1
               0
                0 2 6 10           23 30                                    100
                                SPEED (Km/Hr)
                                           Vehicles                               Aircraft
                   8VSB implementations of equalisers are likely to cater for
                   post ghosts up to 30 uSec and pre-ghosts up to 3 uSec only.
28 June                                                                                      3
                                             DTTB system
                                        Laboratory Doppler Tests
                                                              Doppler Echo
                                                                   DTTB 7.5 us Single Coax Doppler Echo
                   00
                                                                                                                 COFDM Post Echo

                                                                                                                 8-VSB Post Echo


               -5 -5
                Echo Level E/D (dB)




      Echo    -10
                -10


      Level
      (dB)    -15
                -15


                                                                                                                                     COFDM
              -20
                -20
                                                                                                                                     8-VSB

              -25
                -25
                   -500                     -400    -300    -200        -100          0            100    200   300       400       500
                -500                       -400    -300    -200        -100
                                                                          Frequency Offset of Echo100
                                                                                      0           (Hz)    200   300       400      500
                                                            Doppler Frequency (Hz)
                                      8VSB standard mode (1Hz nom.) Fast mode - not shown (5Hz nom.)
28 June                                                                                                                                      3
                  Aircraft Flutter & Doppler
                  Performance Conclusion
          DTTB system performance :

          • The COFDM 2K system is OK for VHF and UHF reception conditions.

          • The COFDM 8K system is OK for VHF reception conditions.

          • The 8VSB system is highly susceptible to any flutter from either
            Aircraft or vehicles.




28 June                                                                        3
                   DTTB Field trial
                    Explanations

                     Interference
          Power Line, Industrial & Home Appliance
                       Fixed reception



28 June                                             3
                                   DTTB System Impulse
                                     Noise Character
          (Conditions: Static multipath, Equal Rx NF, No Co-channel, but with impulse interference)

                                         Indoor Antenna        Outdoor Antenna
                                   35                                          Dependent upon
                                                     8VSB
              C/N Threshold (dB)



                                                                               level and character
                                                                               of impulse noise
                                                          COFDM                (up to 10 dB higher
                                                          With impulse noise   than 8VSB)        Picture
                                                                  COFDM                               (above
                                                                   (64QAM,2/3,1/8)                     curve)

                                   19
                                   15                                                                 No Picture
                                                                                                     (Below
                                                           15                                         curve)
                                     0     3                                               30
                                                  Multipath Level ( - dB)
28 June
                                                      (Single Echo)                       W.T.Dickson 29 March 98   3
             DTTB system
            Laboratory Tests
          Impulse Noise Performance




28 June                               3
          DTTB Field trial
           Explanations

              Powers




28 June                      4
             Analogue TV
          Peak & RMS Voltage

                              Peak voltage = 1.414
                 Black(1.1)
                                RMS voltage = 1


                                        3 dB peak to average

                        That is :
                        For the peak sync region
                        the “peak to average” ratio,
                        like a Sine Wave, is 3 dB and
                        applies to voltage & power.
28 June                                                        4
             COFDM
          Peak to Average
               ( CDF = 99.99%)
             Peak voltage = 3 (9.5dB) - COFDM
               ( for CDF = 95% peak voltage = 1.7 (4.7dB) )
               ( “CDF” - Cumultive Distribution Function )

               RMS voltage = 1 (0dB)

                                 9.5 dB peak to average


                         DIGITAL TV


28 June                                                       4
              8-VSB
          Peak to Average
               (CDF = 99.99%)
             Peak voltage = 2.5 (7dB) - 8VSB
             ( for CDF = 95% peak voltage = 1.6 (4dB) )

               RMS voltage = 1 (0dB)

                                7 dB peak to average


                         DIGITAL TV



28 June                                                   4
                                   DTTB Peak Amplitude
                                      Distribution
                                            Peak Amplitude Distribution
                                                    for COFDM and 8VSB DTTB Systems

                          10
                                   0.01% 9.63 dB
                          9
                          8
                                    0.01% 7.14 dB
                          7
                                             COFDM
                          6
          Peak to Average                                     Noise
                          5
            ratio (dB)
                          4                 8VSB
                Peak      3
             sinewave                        Measurements by HP VSA
                          2
                                                                                            Extrapolation
                          1
             Average      0
          (RMS voltage)        0        2           4     6           8    10       12       14         16   18   20
                                                          Probability of occurrence (100-CDF) %


28 June                                                                                                                4
                       PAL-DTTB @ -14 dB
                        Transmitter Power
                         in the Field trials
          Peak
                 3dB
    Average 0dB 6 KW(CW)

                    Analogue     -4.5dB              -7dB
                  (Peak Sync.)
                    10 KW
                                 -14dB       400W   -14dB     400W
                                          COFDM             8VSB
             ERP = 100 KW                  4 KW             4 KW
28 June                                                              4
                 PAL-DTTB @ -10 dB
                   Transmitter Power
             possible at DTTB introduction
          Peak
                 3dB
    Average 0dB 6 KW(CW)
                                 -0.5dB            -3dB
                    Analogue
                  (Peak Sync.)
                    10 KW        -10dB     1KW    -10dB   1KW

                                          COFDM        8VSB
             ERP = 100 KW                 10 KW       10 KW
28 June                                                         4
                Selection of COFDM
                Modulation Parameters
                 a possible Scenario
          for a softer cliff edge and extended coverage
    Use Hierarchical Modulation :
    - with alpha=1 and guard interval = 1/8 (32uSec)

    SDTV + SI information
    Robust level :          QPSK, FEC 1/2 = 5 Mbps & C/NT =13dB
                 - SDTV only with SI information on robust level
    HDTV
    Less robust level :     64QAM,FEC 2/3 = 13.6 Mps & C/NT=20 dB
                 - all available to HDTV video and sound
    (Field Trial Scenario : 64QAM,FEC 2/3 = 19.3 Mbps & C/NT=19 dB)

28 June                                                           4
                Further Testing to follow
                    for example of :
          •   Set top or indoor Antennas
          •   Transmitters & Translators
          •   Digital receivers as they appear
          •   Portable & Mobile reception
          •   2 K / 8 K & Hierarchical modes
          •   Planning problems - eg :
                • DTTB to PAL (eg CH6 & CH8 in Melbourne)
28 June                                                     4
                    Australian HDTV



          As you can all see we are not finished !




28 June                                              4