Australian DTTB Field Trial

1
Australian DTTB Field Trial

• SMPTE Presentation
• 29 June 1998
• HDTV into the HOME

Compiled by Wayne Dickson SMIREE MIEAust CPEng.
Member SMPTE
2
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
• Urban
• Suburban
• Industrial suburban
• Hills
• Harbour - across water

• Beach areas
• Rural
• Translator areas
• Distribution systems
• Near Airports
• Near highways

3
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.

4
Australian DTTB Field Trial Overall Objectives

• GSM Mobile Telephones are the publics 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.

5
Australian DTTB Field Trial Unique
Charactercompared to other international Trials

• Both ATSC and DVB-T Systems _at_ the
  SAME TIME AND LOCATION
• VHF 7MHz Trial - UHF in Europe and USA
• Adjacent Channels - both upper and lower
• Reception matching Consumers 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

6
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

7
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

8
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

9
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

10
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

11
Australian DTTB Field Trial Trial Statistics
Field Trail
Sydney statistics

• 13,500 square Km
• 3.9 million people
• 1.3 million dwellings

• 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/Ss 30 to 90 dBuV/m
• PAL F/Ss 40 to 105 dBuV/m
• DTTB Av. F/S 68 dBuV/m
• PAL Av. F/S 82 dBuV/m

approximate
12
Australian DTTB Field Trial Transmission
Spectrums
13
DTTB Transmission8VSB
Spectrum Analyser display
Dependent upon Resolution B/W setting.
Vision Carrier
D 11.3 dB
CH7
CH9
CH8
Sound Carriers
A
Chroma
DTTB (8VSB)
PAL
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
14
DTTB TransmissionCOFDM
Spectrum Analyser display
Dependent upon Resolution B/W setting.
Vision Carrier
CH7
CH9
CH8
Sound Carriers
A
Chroma
DTTB (COFDM)
PAL
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
15
Australian DTTB Field Trial Reception Antennas
The following Antennas were used at heights from
2.5m to 10m determined by the Consumers antenna
heights at the location.

• VHF Band III antenna with a nominal gain of 7
  dBd and a front to back ratio of gt 20 dB
• A folded Dipole with a nomimal gain of 0 dBd

16
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.

17
Australian DTTB Field Trial Summary
ResultsCOVERAGE

• 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.

18
Australian DTTB Field Trial Summary
ResultsCOVERAGE

• 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 ResultsPAL
Receive Margin
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Australian DTTB Field Trial Summary ResultsDTTB
compared to PAL
21
Australian DTTB Field Trial Summary Results8VSB
Decoder Margin
22
Australian DTTB Field Trial Summary
ResultsCOFDM Decoder Margin
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Australian DTTB Field Trial Summary
ResultsCOVERAGE
For High Gain (7 dB nom.) Antenna and receiver NF
3.5 dB

• Typical F/S of PAL for 30 dB S/N 55 dBuV/m (30
  dB S/N is a noisy picture)
• _at_ -14 dB DTTB to PAL
• The worse typical failure of DTTB system occurred
  when PAL S/N was
• 30 dB for 8VSB ie F/S of 41 dBuV/m
• 32 dB for COFDM ie F/S of 43 dBuV/m

24
Australian DTTB Field Trial Summary
ResultsCOVERAGERoof antenna
DTTB to PAL Ratio
System Required F/S
Margin of Safety
Required F/S for Reliable Coverage
Rx. NF
0 dB
PAL 55 dBuV/m 0 dB 55
dBuV/m
-11 dB
8VSB 41 dBuV/m 3 dB 44
dBuV/m
3 dB
-9 dB
COFDM 43 dBuV/m 3 dB 46
dBuV/m
PAL 57 dBuV/m 0 dB 57
dBuV/m
5 dB
0 dB
8VSB 47 dBuV/m 3 dB 50
dBuV/m
9 dB
-7 dB
COFDM 45 dBuV/m 3 dB 48
dBuV/m
5 dB
-9 dB
25
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 Conditions
• Fixed reception

27
Field Trial Multipath Character
(Conditions Static multipath, Equal Rx NF, No
Co-channel or impulse interference)
Indoor Antenna
Outdoor Antenna
35
8VSB
COFDM
C/N Threshold (dB)
(64QAM,2/3,1/8)
Picture
(above curve)
19
15
SYDNEY FIELD TRIAL TESTS
No Picture
15
0
3
30
(Below curve)
Multipath Level ( - dB) (Single Echo)

W.T.Dickson 29 March 98
28
DTTB System Multipath Character - Unequal NF
(Conditions Static multipath,Unequal Rx NF, No
Co-channel or impulse interference)
Indoor Antenna
Outdoor Antenna
(31)
35
8VSB
With NF(X4)dB
COFDM
With NFXdB
(64QAM,2/3,1/8)
Picture
C/N Threshold (dB)
(above curve)
(15)
19
No Picture
(Below curve)
15
0
3
30
Multipath Level ( - dB) (Single Echo)

W.T.Dickson 29 March 98
29
DTTB System Multipath Performance Improvement
(Conditions Static multipath, Equal Rx NF, No
Co-channel or impulse interference)
Indoor Antennas
Outdoor Antennas
35
8VSB
COFDM
(64QAM,2/3,1/8)
COFDM
(Nov. 1997)
Picture
C/N Threshold (dB)
(above curve)
Current implementations
(April 1998)
19
15
No Picture
(Below curve)
15
0
3
30
Multipath Level ( - dB) (Single Echo)

W.T.Dickson 16 April 98
30
DTTB Field trialExplanations

• Multipath
• Dynamic Conditions
• Fixed reception

31
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.
32
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
8VSB
with flutter
Dependent upon flutter level (amplitude and
doppler shift)
COFDM
C/N Threshold (dB)
(64QAM,2/3,1/8)
Picture
With or without flutter
(above curve)
19
15
No Picture
15
0
3
30
(Below curve)
Multipath Level ( - dB) (Single Echo)

W.T.Dickson 29 March 98
33
DTTB Systems Doppler Performance Limits
for current implementations
300
250
UHF
200
DOPPLERSHIFT(?Hz)
COFDM 2K, 3dB degrade
140
VHF - Band III
COFDM 2K
100
50
0
0
1000
500
100
200
300
400
600
700
800
900
ATSC see separate curves
SPEED (Km/Hr)
AIRCRAFT
Vehicles
Over Cities
COFDM implementations will inherently handle post
and pre-ghosts equally within the selected guard
interval.
34
ATSC 8-VSB Doppler Performance Limits
for current implementations
10
UHF
VHF - Band III
DOPPLERSHIFT(?Hz)
8VSB, Fast Mode, 3dB degrade
5
8VSB
1
0
0
100
30
23
10
6
2
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.
35
Doppler Echo
DTTB system Laboratory Doppler Tests
0
-5
-10
EchoLevel(dB)
-15
COFDM
-20
8-VSB
-25
0
100
300
500
-100
-200
-300
-400
-500
200
400
Doppler Frequency (Hz)
8VSB standard mode (1Hz nom.) Fast mode - not
shown (5Hz nom.)
36
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.

37
DTTB Field trialExplanations

• Interference
• Power Line, Industrial Home Appliance Fixed
  reception

38
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 level and character of impulse
noise (up to 10 dB higher than 8VSB)
8VSB
COFDM
With impulse noise
Picture
C/N Threshold (dB)
COFDM
(above curve)
(64QAM,2/3,1/8)
19
15
No Picture
(Below curve)
15
0
3
30

Multipath Level ( - dB) (Single Echo)
W.T.Dickson 29 March 98
39
DTTB system Laboratory Tests
Impulse Noise Performance
40
DTTB Field trialExplanations

• Powers

41
Analogue TVPeak 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.
42
COFDMPeak 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
43
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
44
DTTB Peak Amplitude Distribution
45
PAL-DTTB _at_ -14 dB Transmitter Powerin the Field
trials
Peak
3dB
6 KW(CW)
0dB
Average
-4.5dB
-7dB
Analogue
(Peak Sync.)
10 KW
400W
400W
-14dB
-14dB
COFDM
8VSB
ERP 100 KW 4 KW 4 KW
46
PAL-DTTB _at_ -10 dB Transmitter Powerpossible at
DTTB introduction
Peak
3dB
6 KW(CW)
0dB
Average
-0.5dB
-3dB
Analogue
(Peak Sync.)
1KW
1KW
10 KW
-10dB
-10dB
COFDM
8VSB
ERP 100 KW 10 KW 10 KW
47
Selection of COFDMModulation Parametersa
possible Scenariofor a softer cliff edge and
extended coverage
Use Hierarchical Modulation - with alpha1
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/NT20
dB - all available to HDTV
video and sound (Field Trial Scenario 64QAM,FEC
2/3 19.3 Mbps C/NT19 dB)
48
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)

49
Australian HDTV
As you can all see we are not finished !