28 June 1998

1

Australian DTTB Field Trial

SMPTE Presentation29 June 1998

HDTV into the HOME

Compiled by Wayne DicksonSMIREE MIEAust CPEng. Member SMPTE

28 June 1998

2

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

28 June 1998

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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 :

28 June 1998

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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

28 June 1998

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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

28 June 1998

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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.

28 June 1998

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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.

28 June 1998

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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

28 June 1998

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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

28 June 1998

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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

28 June 1998

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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

28 June 1998

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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

28 June 1998

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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

28 June 1998

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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.

28 June 1998

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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)

28 June 1998

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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

28 June 1998

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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)

28 June 1998

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Impulse Noise Performance

DTTB system Laboratory Tests

28 June 1998

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DTTB Field trialExplanations

Powers

28 June 1998

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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)

28 June 1998

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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

28 June 1998

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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

28 June 1998

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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)

28 June 1998

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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