28 June 1998
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Australian DTTB Field Trial
SMPTE Presentation29 June 1998
HDTV into the HOME
Compiled by Wayne DicksonSMIREE MIEAust CPEng. Member SMPTE
28 June 1998
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Australian DTTB Field Trial What was it !
• In comparison with current PAL television• In various reception conditions :
• City• Urban• Suburban• Industrial suburban• Hills• Harbour - across water
A DTTB Field Trial is study of Failure !!
• Beach areas• Rural• Translator areas• Distribution systems• Near Airports• Near highways
28 June 1998
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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 1998
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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 1998
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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• Two DTTB power Measurement methods
28 June 1998
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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 1998
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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
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Australian DTTB Field Trial Limitations
• 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
The Field Trial did not cover :
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Australian DTTB Field Trial Systems Tested
• ATSC• 8VSB modulation• 6 MHz nominal bandwidth• Useful Bitrate 19.39 Mbps• FEC 2/3• RS (207,187)• Equaliser range of 23uSec• Co-channel comp. off.• “Blue racks” decoder
• DVB-T• COFDM modulation• 7 MHz nominal bandwidth• Useful Bitrate 19.35 Mbps• FEC 2/3• RS (204,188)• Guard interval 1/8(32uSec)• DMV V1.0 Eq. Software• DMV V2.0 Sys. Software
28 June 1998
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Australian DTTB Field Trial Contributing Organisations
• Australian Broadcasting Authority (ABA)
• DCA Communication Laboratory
• FACTS• TEN Network• NINE Network• SEVEN Network
• NDS• ZENITH Electronics
Corp.• Harris Corp.• RFS• NEC• Hewlett Packard• Rohde & Schartz
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Australian DTTB Field Trial Trial Statistics
• 13,500 square Km• 3.9 million people• 1.3 million dwellings
Sydney statistics * :• 3 Oct. to 14 Nov. 1998• 27 days of testing• 108 Sites• 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• PAL Av. F/S 82 dBuV/m
Field Trail :
* approximate
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Australian DTTB Field Trial
Transmission Spectrums
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DTTB Transmission8VSB
Spectrum Analyser displaySpectrum Analyser display : :
DTTB(8VSB)
Vision Carrier
Sound CarriersChroma
PAL
Dependent upon Resolution B/W setting.
A
D = DTTB to PAL ratio D = 14 dB for the TrialDTTB power = average heating power
PAL power = the equivalent CW power of peak sync Vision Carrier power
D + 11.3 dB
PAL
CH7 CH9CH8
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DTTB TransmissionCOFDM
Spectrum Analyser displaySpectrum Analyser display : :
DTTB(COFDM)
Vision Carrier
Sound CarriersChroma
PAL
Dependent upon Resolution B/W setting.
A
D = DTTB to PAL ratio D = 14 dB for the TrialDTTB power = average heating power
PAL power = the equivalent CW power of peak sync Vision Carrier power
PAL
CH7 CH9CH8
28 June 1998
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Australian DTTB Field Trial Reception Antennas
• 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
The following Antennas were used at heights from 2.5m to 10mdetermined by the Consumer’s antenna heights at the location.
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Australian DTTB Field Trial Observations
• 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.
With DTTB power 1/25th (-14 dB) of PAL, when there was noticeable :
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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.
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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.
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Australian DTTB Field Trial Summary Results
PAL Receive Margin
0
5
10
15
20
25
30
35
40
Site
REC
EIVE
MAR
GIN
(dB
)
45 50 55 60 65 70 75 80 85 90 95 100 105 110 Site Field Strenght (dBuV/m)
PAL - SITE RECEIVE MARGINFacts DTTB Trial Sites
PAL on CH9
Plisch Receiver
W.T.D. 5 JUNE 1998
Nominal conditions : 7 dB gain Antenna + 2 dB leed loss @ CH9
MINIMUM ACCEPTABLE PICTURE
Minimum F/S = 55dBuV/m
Margin to minimum acceptablepicture w/o multipath
for HIGH GAIN ANTENNA
Receiver limitations
Effective decoder Noise Figure (NF) = 5 dB
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Australian DTTB Field Trial Summary Results
DTTB compared to PAL
-45
-40
-35
-30
-25
-20
-15
Vide
o S/
N o
f PAL
@ D
TTB
THRE
SHO
LD (
dB)
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 #
PAL VIDEO S/N @ DTTB THRESHOLD@ 14dB nominal DTTB to PAL ratio
System Noise Method
8VSB
COFDM (64QAM,2/3,1/8)
Note : 8VSB Launch power on average was 0.8dB higher than COFDM Launch power
Average S/N @ Threshold of :8VSB = -24.2dB unwtd (PAL)COFDM = -28.7dB unwtd (PAL)
FACTS DTTB Trial Sites
W.T.D. 15 Jan 1998
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Australian DTTB Field Trial Summary Results
8VSB Decoder Margin
0
10
20
30
40
50
60
Site
DEC
OD
E M
ARG
IN (d
B)
25 30 35 40 45 50 55 60 65 70 75 80 85 90 Site Field Strenght (dBuV/m)
8VSB SITE DECODE MARGINFACTS DTTB Trial Sites
8VSB
System Noise MethodW.T.D. 7 JUNE 1998
Nominal conditions : 7 dB gain Antenna + 2 dB leed lossEffective decoder Noise Figure (NF) = 9 dB
NO PICTURE
Minimum F/S = 37 dBuV/m without multipath and 3 dB margin
Margin @ Threshold C/Nw/o multipath
Decoder NF = 9 dB
for a HIGH GAIN ANTENNA
Minimum F/S = 47 dBuV/mwith multipath allowance and 3 dB margin Margin @ threshold C/N
with multipath
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Australian DTTB Field Trial Summary Results
COFDM Decoder Margin
0
10
20
30
40
50
60
Site
DEC
OD
E M
ARG
IN (
dB)
25 30 35 40 45 50 55 60 65 70 75 80 85 90 Site Field Strenght (dBuV/m)
COFDM SITE DECODE MARGINFACTS DTTB Trial Sites
COFDM (64QAM,2/3,1/8)
System Noise Method
W.T.D. 5 JUNE 1998
Nominal conditions : 7 dB gain Antenna + 2 dB leed loss @ CH8Effective decoder Noise Figure (NF) = 5 dB
NO PICTURE
Minimum F/S = 37 dBuV/m without mutipath and 3 dB margin
Margin @Threshold C/Nw/o multipath
Decoder NF = 5 dB
for a HIGH GAIN ANTENNA
Minimum F/S = 45 dBuV/mwith multipath allowance and 3 dB margin
Margin @ Threshold C/Nwith Multipath
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Australian DTTB Field Trial Summary Results
COVERAGERoof antenna
System Required F/S Marginof Safety
PAL 55 dBuV/m 0 dB 55 dBuV/m
8VSB 41 dBuV/m 3 dB 44 dBuV/m
COFDM 43 dBuV/m 3 dB 46 dBuV/m
PAL 57 dBuV/m 0 dB 57 dBuV/m
8VSB 47 dBuV/m 3 dB 50 dBuV/m
COFDM 45 dBuV/m 3 dB 48 dBuV/m
Required F/Sfor Reliable Coverage
Rx.NF
3 dB
5 dB
9 dB
5 dB
DTTBto PAL Ratio0 dB
-11 dB
-9 dB
0 dB
-7 dB
-9 dB
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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
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DTTB Field trialExplanations
Multipath Static ConditionsFixed reception
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Field Trial Multipath Character
0 3 15 30
1519
35
Multipath Level ( - dB) (Single Echo)
8VSB
COFDM(64QAM,2/3,1/8)
C/N
Thr
esho
ld (d
B)
Indoor Antenna Outdoor Antenna
W.T.Dickson 29 March 98
(Conditions: Static multipath, Equal Rx NF, No Co-channel or impulse interference)
Picture
No Picture
(above curve)
(Below curve)
SYDNEY FIELD TRIAL TESTS
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DTTB System Multipath Character - Unequal NF
0 3 15 30
(15)19
35
Multipath Level ( - dB) (Single Echo)
8VSB
COFDM(64QAM,2/3,1/8)
C/N
Thr
esho
ld (d
B)
Outdoor Antenna
W.T.Dickson 29 March 98
(Conditions: Static multipath,Unequal Rx NF, No Co-channel or impulse interference)
(31)With NF=(X+4)dB
With NF=XdBPicture
No Picture
(above curve)
(Below curve)
Indoor Antenna
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DTTB System Multipath Performance Improvement
0 3 15 30
1519
35
Multipath Level ( - dB) (Single Echo)
8VSB
COFDM(64QAM,2/3,1/8)
C/N
Thr
esho
ld (d
B)
Indoor Antennas Outdoor Antennas
W.T.Dickson 16 April 98
(Conditions: Static multipath, Equal Rx NF, No Co-channel or impulse interference)
COFDMCurrent implementations
(April 1998)
(Nov. 1997) Picture
No Picture
(above curve)
(Below curve)
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DTTB Field trialExplanations
MultipathDynamic Conditions
Fixed reception
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Aircraft Flutter
D
DarDasFar
F
Fas
Fas = F - F * Cos * Va / c + F * Cos * Va / c
Va
Doppler shift
tg = ( Dar + Das - D ) / 0.3 uSec
NOTE : There are competing doppler shifts.
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DTTB System Dynamic Multipath Character
0 3 15 30
1519
35
Multipath Level ( - dB) (Single Echo)
8VSB
COFDM(64QAM,2/3,1/8)
C/N
Thr
esho
ld (d
B)
Indoor Antenna Outdoor Antenna
W.T.Dickson 29 March 98
(Conditions: Dynamic multipath (flutter), Equal Rx NF, No Co-channel or impulse interference)
8VSBw/o flutter
with flutterDependent upon flutter level (amplitude and doppler shift)
With or without flutterPicture
No Picture
(above curve)
(Below curve)
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VHF - Band III
UHF
DOPPLERSHIFT(Hz)
140
300
00 1000500100 200 300 400 600 700 800 900
100
50
200
250
COFDM 2K, 3dB degrade
COFDM 2K
SPEED (Km/Hr)AIRCRAFTVehicles
Over Cities
for current implementations
ATSCsee separate curves
COFDM implementations will inherently handle post and pre-ghosts equally within the selected guard interval.
DTTB Systems Doppler Performance Limits
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VHF - Band IIIUHF
00 100
8VSB, “Fast Mode”, 3dB degrade
SPEED (Km/Hr)Vehicles
8VSB
5
1
10
30231062
Aircraft
for current implementations
8VSB implementations of equalisers are likely to cater for post ghosts up to 30 uSec and pre-ghosts up to 3 uSec only.
DOPPLERSHIFT(Hz)
ATSC 8-VSB Doppler Performance Limits
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DTTB 7.5 us Single Coax Doppler Echo
-25
-20
-15
-10
-5
0
-500 -400 -300 -200 -100 0 100 200 300 400 500
COFDM Post Echo
8-VSB Post Echo
Doppler Echo
DTTB system Laboratory Doppler Tests
8VSB standard mode (1Hz nom.) Fast mode - not shown (5Hz nom.)
COFDM
8-VSB
EchoLevel(dB)
Doppler Frequency (Hz)0 100 200 300 400 500-100-200-300-400-500
-10
-15
-20
-25
-5
0
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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 1998
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DTTB Field trialExplanations
InterferencePower Line, Industrial & Home Appliance
Fixed reception
28 June 1998
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DTTB System Impulse Noise Character
0 3 15 30
1519
35
Multipath Level ( - dB) (Single Echo)
8VSB
COFDM(64QAM,2/3,1/8)
C/N
Thr
esho
ld (d
B)
Indoor Antenna Outdoor Antenna
W.T.Dickson 29 March 98
(Conditions: Static multipath, Equal Rx NF, No Co-channel, but with impulse interference)
COFDMWith impulse noise
Dependent upon level and characterof impulse noise(up to 10 dB higherthan 8VSB) Picture
No Picture
(above curve)
(Below curve)
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Impulse Noise Performance
DTTB system Laboratory Tests
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DTTB Field trialExplanations
Powers
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Analogue TVPeak & RMS Voltage
RMS voltage = 1
Peak voltage = 1.414
3 dB peak to average
That is :For the peak sync regionthe “peak to average” ratio,like a Sine Wave, is 3 dB andapplies to voltage & power.
Black(1.1)
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COFDMPeak to Average
RMS voltage = 1 (0dB)
Peak voltage = 3 (9.5dB) - COFDM ( for CDF = 95% peak voltage = 1.7 (4.7dB) )
( “CDF” - Cumultive Distribution Function )
( CDF = 99.99%)
DIGITAL TVDIGITAL TV
9.5 dB peak to average
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8-VSB Peak to Average
RMS voltage = 1 (0dB)
Peak voltage = 2.5 (7dB) - 8VSB ( for CDF = 95% peak voltage = 1.6 (4dB) )
(CDF = 99.99%)
DIGITAL TVDIGITAL TV
7 dB peak to average
28 June 1998
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DTTB Peak Amplitude Distribution
Peak Amplitude Distributionfor COFDM and 8VSB DTTB Systems
0
1
2
3
4
5
6
7
8
9
10
0 2 4 6 8 10 12 14 16 18 20
Probability of occurrence (100-CDF) %
Peak to Average ratio (dB)
Measurements by HP VSAExtrapolation
COFDM
8VSB
0.01% 9.63 dB
0.01% 7.14 dB
Noise
Average(RMS voltage)
Peak sinewave
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PAL-DTTB @ -14 dB Transmitter PowerTransmitter Powerin the Field trialsin the Field trials
0dB
-14dB -14dB
3dB
-4.5dB -7dBAnalogue
COFDM 8VSB
Average
Peak
(Peak Sync.)
6 KW(CW)
400W 400W10 KW
ERP = 100 KW 4 KW 4 KW
28 June 1998
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PAL-DTTB @ -10 dB Transmitter PowerTransmitter Power
possible at DTTB introductionpossible at DTTB introduction
0dB
-10dB -10dB
3dB
-0.5dB -3dBAnalogue
COFDM 8VSB
Average
Peak
(Peak Sync.)
6 KW(CW)
1KW 1KW10 KW
ERP = 100 KW 10 KW 10 KW
28 June 1998
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Selection of COFDMModulation Parameters
a possible Scenariofor a softer cliff edge and extended coverage
Use Hierarchical Modulation : - with alpha=1 and guard interval = 1/8 (32uSec)
SDTV + SI informationRobust level : QPSK, FEC 1/2 = 5 Mbps & C/NT =13dB - SDTV only with SI information on robust level HDTVLess 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)
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Further Testing to followfor 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)
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As you can all see we are not finished !
Australian HDTV