Transcript Digital Television Talk v3

Communications Laboratory
Australian
DTTB Lab Tests,
Methodology &
Results Summary
http://www.commslab.gov.au/
Presentation by: Neil Pickford
1
Overview
Digital Television Objectives & Technology
 DTTB Transmission Technology
 The Australian Test Program
 Laboratory Tests - Test Rig
 Laboratory Tests - Main Results
 Field Test Objectives & Equipment
 Summary Field Test Results
 Selection Process & Criteria
 Selection Result & Future

2
Digital Television
Why digital?
To Overcome Limitations
of Analog Television
 Noise free pictures
 Higher resolution images
Widescreen / HDTV
 No Ghosting
 Multi-channel, Enhanced
Sound Services
 Other Data services.
3
World TV Standards
NTSC
PAL
SECAM
PAL/SECAM
Unknown
4
Australia like China & Malaysia are PAL
Transmission Bandwidth - VHF
6 MHz
7 MHz
8 MHz
Not in Use
5
Australia & Malaysia are 7 MHz,
China is 8 MHz
Transmission Bandwidth - UHF
6 MHz
7 MHz
8 MHz
Not in Use
6
Australia is Alone using 7 MHz on UHF
Australian Population Distribution
Uneven
Population
distribution
Wide areas
where few
people live
Noise Limited
Transmission
environment
7
Free To Air Television (FTA)
8

5 Networks - 3 Commercial, 2 Government

Important part of Australian entertainment

Majority of Australian audience is watching

No television receiving licences

National broadcasters funded from taxation
Pay TV - Cable, MDS & Satellite
Only a small business in Australia
 Less then 400,000 subscribers
 Less than 7% of households

Indoor reception
Around
30% of Australians watch FTA using
indoor antennas
9
Program Quality Vs Quantity
Australians have a low number of
available television channels
Television program budget is spread between
fewer programs
Australians used to watching high quality
programming at high technical quality.
10
MP@ML
MP@HL
All decoders sold in Australia will
be MP@HL capable allowing all
viewers access to HD resolution
when it becomes available
11
Enabling Technologies
 Source
digitisation (Rec 601 digital studio)
 Compression technology (MPEG, AC-3)
 Data multiplexing (MPEG)
 Display technology (large wide screens)
Transmission
12
technology
(modulation)
Transmission Technology
The transmission system is used to transport the
information to the consumer.
 The system protects the information being
carried from the transmission environment
 Current Australian analog television uses the
PAL-B AM modulation system

13
Digital TV Transmission
Technology
The transmission
system is a
“data pipe”
 Transports data rates
of around 20 Mb/s
 Transports data in
individual containers
called packets

14
Digital TV Transmission Systems
Australia has been following Digital TV & HDTV
 Europeans
- Digital SDTV
- 8 MHz on UHF
- DVB-T (COFDM)
 Americans
- Digital HDTV
- 6 MHz VHF/UHF
- ATSC (8-VSB)
 Japanese
- Integrated Broadcasting
- ISDB (BST-OFDM)
15
8-VSB - USA


Developed by the advance television systems
committee - ATSC
Developed for use in a 6 MHz channel
A7





16
MHz variant is possible.
Uses a single carrier with pilot tone
8 level amplitude modulation system
Single Payload data rate of 19.39 Mb/s
Relies on adaptive equalisation
Existing AM technology highly developed
COFDM - Europe





Developed by the digital video
broadcasting project group - DVB
Uses similar technology to DRB
Uses 1705 or 6817 carriers
Variable carrier modulation types are defined allowing
Payload data rates of 5-27 Mb/s in 7 MHz
Developed for 8 MHz channels
A7


17
MHz variant has been produced and tested
Can use single frequency networks - SFNs
New technology with scope for continued
improvement & development
The Australian DTTB Test Program
Australia is interested in a Digital HDTV Future
 Australia has a Unique Broadcasting
Environment
 Overseas Digital TV Developments were
interesting but the results could not be directly
related to Australia.
 To make informed decisions we needed to
collect information relevant to our situation.
 We had a few Questions.

18
Aims of Australian DTTB Testing-1
Australia needed to know:
 How does DTTB perform with VHF PAL-B?
 What Protection does PAL require from the
DTTB service for:
 Co-Channel?
 Adjacent
Channel?
 Is Signal level a factor?
19
Subjective Assessment
Aims of Australian DTTB Testing-2
How Quickly does the system degrade?
 What are the real system thresholds?

 Signal
Level
 Carrier to Noise
 Payload Data Rate in 7 MHz
How does DTTB cope with Interference?
 What is a typical Noise Figure for a DTTB Rx

20
Aims of Australian DTTB Testing-3

What Protection does DTTB require from the
PAL-B service for:
 Co-Channel?
 Adjacent
Channel?
 Is Signal level a factor?

21
What Protection does DTTB require from other
DTTB services?
Aims of Australian DTTB Testing-4
How does DTTB perform in a 7 MHz
Channel Environment?
 How sensitive is DTTB to practical
Transmission Equipment?

How important is:
 Transmitter Linearity?
 Transmitter Precorrection?
 Transmitter Output Filtering?
 Combined Feeder/Antenna Systems?
22
Aims of Australian DTTB Testing-5

Is DTTB affected by Multipath Echoes?
 Are
Pre-Echoes a Problem?
 What happens past the Guard interval?
Is DTTB affected by Doppler Shift?
 Is DTTB affected by Dynamic Flutter?
 Is DTTB affected by Impulsive Interference?
 How does DTTB perform in the Field cw PAL

Lots of Questions but
Few Definitive Answers!
23
Scope of Tests
The test program began with the aim of
answering these questions for DVB-T
 During the early stages of testing ATSC was
floated as a Candidate Digital TV System
 The test program’s scope was increased and a
comparative focus adopted.
 All tests were designed to be as generally
applicable as possible to any Digital TV
Modulation System.

24
Order of Measurements
FACTS Advanced TV Specialists Group
directed the priority of Testing
 Laboratory Tests First
 DTTB into PAL protection
 DTTB System Parameters
 PAL into DTTB protection
 Other Interferers & Degradations
 Field Tests Later

25
TektronixTSG-271 PAL
PALTest Generator
Tv Ant
MUF2-Z2
Plisch SBUF
PAL Stereo IF
Modulator
PAL
SonyDVW-A500P
Digital Betacam
UnwantedSignal Path
PAL RF
PAL IF
+21.7 dB
ZSC-2-4
SDI
PAL LO
-2.4
dBm
AR2098
Amp
+8.0 dBm
Ch 7-9
BW 13MHz
CW/ SCM
DMV
MCC
RS232
9600
Baud
DMVMPEG
Coder
235.150 MHz
-13 dBm
PAL LO
226.800 MHz
+0 dBm
DTTB LO
VT-100
RS422
Taxi
Ch 7-9
BW 13MHz
10baseT
Ethernet
DMV Multiplexer
DMV 2k
COFDM
Modulator
RS422
Taxi
Ch8
Cofdm
-16.5
dBm
-13.4 dBm
DTTB Cal
Level Adjust
-21.4
dBm
+17.9 dB
+6.8 dBm
PAL/ CW
Signal
Level
-10 dB
Switch
D/ U
Combiner
ZSC-2-4
DTTB
Signal
Level
TransmissionEquipment
LocatedinMainLaboratory
Pal
HP8663A
COFDM 226.800 MHz
8-VSB 235.500 MHz
NEC+6.2 dBm
Harris +7.0 dBm
DTTB Tx LO
Power Levels for two Test Modes Shown
3 W+33 dBm for Link Echo Tests
75 W+48.6 dBm for Coax Echo Tests
75 W Input
RG-213 Coaxial Delay On Laboratory Roof
-30 dBm
-18 dBm
26
DTTB Receiver
-27.6 dBm
TTL Clock
& data
Yellow Shaded Items are under Control of HP9836 via HPIB
-27.6 dBm
HP9836
Controller
Pal TV Under
Test
Anritsu ME520B
Bit Error Rate Meter
Link
Echo/ Doppler
0 dB
HPIB Coax
Comms Link
HP37204
HPIB Extender
HP5383A
Frequency
Meter
GPS
Frequency
Reference
10 MHz
10 MHz
450 MHz
+7 dBm
Mix Up LO
ZFSC-2-4
-48.6 dBm
Direct/ Echo
-19
Combiner
dBm
-18 dBm
HP37204
HPIB Extender
Hills Ch 8-11TV antenna
~3 W
-22 dBm
Direct
Signal
-18.5
dBm
+7 dBm
-50
dBm
MAV-11
Amp
-38 dBm
UHF Ch 44
641.5 MHz
+27 dB
+12 dB
191.5 MHz
BW 7 MHz
L-Band
GPS
-50
ZFM-11 dBm
HP8447C
Amp
Translator LinkEquipment
At Universityof Canberra
+22 dB
-16 dB
-23 dBm
-27 dBm
-42.8
dBm
HP8447E
Amp
-19
dBm
+4
AR
10W100
Amp
-19 dBm
Echo
Signal
Power
+48.55 dBm
GPS
10 MHz GPS
Reference
228..150 MHz
+7 dBm
Echo LO
VHF Ch 8
191.500 MHz
BW 7MHz
+18.55 dBm
+11 dBm
RG-6 Cable Loss 3.85 dB
HPIB
10 MHz
Doppler LO228.150 MHz
Ch 44 LO678.150 MHz
+7 dBm
Echo
LO
HP-436A
Power
Meter
10 MHz
Reference
Coax Echo
-10 dBm
ZFM-11
200 m
-24.5 dBm
-17 dBm
DTTB IF
36.65 MHz
IF
-8 dBm
-41
IF amp
dBm ZFM-11
8 MHz IF Filter
L-Band
GPS
UHF Ch 44
641.5 MHz
-35 dBm
HPAmp
-20 dB
Plisch TV Receiver
Coax
Doppler
GPS
Frequency
Reference
10 MHz
LinkUHFReceiveEquipment Near Roof
+7 dBm
IF=36.15 MHz
Ch 8
DTTB
+30 dB
HP8447C
Amp
Combined DTTB Signal
-23.8 dBm
HPIB
500W
30dB
Attenuator
300 m
0 dB
0 dB
Coax
Echo/ Doppler
RS232
19.2 Kb/ s
HP 70000
Spectrum Analyser
2 km VHF Link
Tx Filter
VHF Ch 8
BW 7MHz
dBm
900 m
+30 dB
HP8447C
0 dBm
Amp
Spectrum
Analyser
HPIB
DUT
Port
3 Element VHF
Ch 8 Beam
Transmitter
Test
Under
-14
dBm
Test
-0.8 dBm 2.1 dB -17
3 W Input
-23.8 dBm
Measure
Port
Test
Splitter
ZSC-2-4
HPIB To/ From Other Yellow Shaded Equipment
20.4 dB Link
7.0 dB Coax
O/ P
Ethernet
DesiredSignal Path
Direct
Calibrate
Tx
LO
RxControl
PC
0 dB Cal Level for DTTB Rx -23.75 dBm
0 dB Cal Level for Pal TV Rx -27.6 dBm
-16.4 dBm
HP3708
-15.9
Carrier to Noise
dBm
Test Set
+5.4 dBm
Off air PAL
Video
PAL/ CW+DTTB
HP8447C
Amp
+29.3 dB
Manual
Tx Drive
HP-436A
Power Meter
-22.8 dB
-16.5 dBm
-23 dBm
50 Ohm
-10 dB
Min
-23.8 dBm
Dash-Dot LineIndicates
ModulationEquipment
Under Test
Rig/ Tx -15.3
Select dBm
-14.7
dBm
ZHL-1AAmp
-32.6
dBm
Tx Drive
Level
35.3 MHz
Cofdm IF
DMV MPEG
Coder
191.500 MHz
-20.1 dBm
SCM/ CW
All theEquipment Withinthis
DashedBoxisinsideShieldedroom
withtheDTTBModulator
Rig LO
All Equipment within Da
Box is in Separate Shie
Room with DTTB Recei
+10.2 dB
PAL/ CW
HP8447E
-23.8 dBm Amp
Off Air 7 & 9 Test
-20 dBm
-60 dBm
-57 dBm
MAV-11
Amp
-69 dBm
Laboratory Tests - Test Rig
C/N Set & Attenuators
Control
Domestic
Computer Television
Receiver
27
Modulator
Control
Computers
EUT
PAL & CW
Spectrum Analysers
Plot &
Printing
Test Rig - Modulation Equipment
Power Meter
RF LO
PAL & CW
Interference
Generators
COFDM
Modulator
MPEG Mux
MPEG Mux
MPEG Encoder
MPEG Encoder
28
8-VSB
Modulator
Laboratory Tests - Transmitters
Loads
Echo Combiner
Harris
1 kW
Tx
Power Meter
Digital CRO
Tx LO
Spectrum
Analyser
29
Harris
Exciter
NEC 200 W Tx
Digital Transmitters TCN-9 Sydney
30
Lab Tests - VHF/UHF Transposer
Level Adjust
UHF Amps
Power Supply
VHF Input Filter
RF Amp
RF LO
10 Watt UHF
Amplifier
31
UHF BPF Filter
Mixer
COFDM - Commercial Receiver

32
News Data Systems - System 3000
COFDM - Test Rx Hardware
33
34
8-VSB - Test Receiver Hardware
Main Results - Lab Tests
C/N ATSC 4 dB better than DVB-T.
This Advantage offset by Poor Noise Figure
 DVB-T is better than ATSC for Multipath
 ATSC is better than DVB-T for Impulse Noise
 ATSC cannot handle Flutter or Doppler Echoes
 ATSC is very sensitive to Transmission system
impairments and IF translation
 DVB-T is better at handling Co-channel PAL
 DVB-T is better rejecting on channel
interference (CW)

35
8-VSB & COFDM - Spectrum
8-VSB
COFDM
36
Digital Modulation - 8-AM
+7
+5
+3
+1
-1
-3
-5
-7
Before Equaliser
After Equaliser
8-VSB - Coaxial Direct Feed through Tuner on Channel 8 VHF
37
3 Bits/Symbol
Spectrum of COFDM DTTB
7 MHz Carrier Spacing
2k Mode 3.91 kHz
8k Mode 0.98 kHz
Almost
Rectangular
Shape
1705 or 6817 Carriers
6.67 MHz in 7 MHz Channel
7.61 MHz in 8 MHz Channel
38
7 MHz COFDM Modulator Spectrum
00
-10
-10
Power spectrum density (dB)
Power Spectrum Density (dB)
7 MHz Theoretical DVB Transmission signal spectrum
-20
-20
-30
-30
-40
-40
-50
-50
2k 1/32 Guard
-60
-8
-7
-6
-5
-4
-3
-2
-1
-8
-7
-6
-5
-4
-3
-2
-1
00 11 22 33
Frequency relative to centre frequency fc (MHz)
Frequency Offset (MHz)
39
44
55
66
77
88
64-QAM - Perfect & Failure
42
Channel Estimation & Equalisation
ATSC
Time
Frequency Spectrum
DVB-T
Time
43
Data
Continuous Pilot
Occasional Pilot
Special Data
General Parameters - Aust Tests
Parameter
DVB-T
Data Payload
19.35 Mb/s 19.39 Mb/s
Carriers
1705
1
Symbol Time
256 us
93 ns
Time Interleaving
1 Symbol 4 ms
Reed Solomon code rate
188/204
IF Bandwidth (3 dB)
6.67 MHz 5.38 MHz
44
ATSC
187/207
General Parameters
45
Parameter
DVB-T
ATSC
IF centre Frequency
35.3 MHz 44.0 MHz
Receiver AFC range
11.5 kHz
Latency including MPEG
coding SDTV 8 Mb/s
37 Frames
359 kHz
Payload Bitrate Mb/s
COFDM FEC
Sys Min Sig
Calc
Guard Guard Guard Guard
MOD
Code C/N
Level
Rx NF
1/4
1/8
1/16
1/32
TYPE
Rate (dB) (dBuV)
(dB)
(Mb/s) (Mb/s) (Mb/s) (Mb/s)
QPSK
1/2
5.4
11.7
4.8
4.35
4.84
5.12
5.28
QPSK
2/3
6.6
13.2
5.1
5.81
6.45
6.83
7.04
QPSK
3/4
7.6
14.8
5.7
6.53
7.26
7.68
7.92
QPSK
5/6
8.7
16.8
6.6
7.26
8.06
8.54
8.80
QPSK
7/8
9.5
19.2
8.2
7.62
8.47
8.96
9.24
16-QAM
1/2
11.2
17.7
5.0
8.71
9.68 10.25 10.56
16-QAM
2/3
13.0
19.6
5.1
11.61 12.90 13.66 14.07
16-QAM
3/4
14.1
20.9
5.3
13.06 14.51 15.37 15.83
16-QAM
5/6
15.5
22.9
5.9
14.51 16.13 17.08 17.59
16-QAM
7/8
16.3
24.9
7.1
15.24 16.93 17.93 18.47
64-QAM
1/2
16.8
23.3
5.0
13.06 14.51 15.37 15.83
64-QAM
2/3
19.1
25.2
4.6
17.42 19.35 20.49 21.11
64-QAM
3/4
20.6
27.5
5.4
19.59 21.77 23.05 23.75
64-QAM
5/6
22.2
30.0
6.3
21.77 24.19 25.61 26.39
64-QAM
7/8
23.7
32.4
7.2
22.86 25.40 26.89 27.71
8-VSB
2/3
15.1
27.2
11.2
19.39
Blue Payload Figures are 188/204 scaled from actual measurement
Red Figures are calculated from the 1/32 Guard interval data
46
AWGN Receiver Performance
Parameter
DVB-T
ATSC
Carrier to Noise Threshold
(in native system BW)
19.1 dB
15.1 dB
Simulated Theoretical C/N
for optimum system
16.5 dB
14.9 dB
Minimum Signal Level
25.2 dBuV 27.2 dBuV
Receiver noise figure
4.6 dB
Rx Level for 1 dB C/N Loss 34 dBuV
47
11.2 dB
35 dBuV
Receiver Parameters

Guard interval
 Affects
payload data rate and echo performance
 No impact on general receiver parameters such as
C/N & Signal level.

48
COFDM Transmission Parameter Signalling
(TPS) - receiver automatically determines
the modulation type, FEC & Guard Interval
DTTB System Multipath Character
Indoor Antenna
Outdoor Antenna
C/N Threshold (dB)
35
8VSB
COFDM
(64QAM, 2/3, 1/8)
19
15
0
49
3
15
Multipath Level ( - dB)
(Conditions: Static multipath, Equal Rx NF,
No Co-channel or impulse interference)
25
AWGN Performance
51

C/N 4 dB more power required for DVB-T to
achieve the same coverage as ATSC.

Better C/N performance ATSC offset by
poor receiver noise figure

ATSC C/N is very close to the theoretical
DVB-T implementation is still over 2.5 dB
higher than the simulated margin.

Other DVB-T modes have different C/N
Thresholds and Data Rates
Multipath & Flutter Measurements
Parameter
DVB-T
ATSC
7.2 us Coax pre ghost
0 dB
-13.5 dB
7.2 us Coax post ghost
0 dB
-2.2 dB
Echo correction range
32 us
Doppler single echo performance
(-3 dB echoes)
140 Hz
52
+3 to -20 us
1 Hz
Doppler Echo - 7.5 us Coax
DTTB 7.5 us Single Coax Doppler Echo
0
0
COFDM
8-VSB
COFDM Post Echo
8-VSB Post Echo
-5
-10
Echo Level E/D (dB)
Echo Level E/D (dB)
-5
-10
-15
-15
-20
-20
-25
-500
-25
-500
53
-400
-300
-200
-200
0
200
Frequency Offset (Hz)
-100
0
100
Frequency Offset of Echo (Hz)
200
300
400
500
500
Multipath & Flutter - Overview

ATSC system 2 Equaliser modes
 Rx
Eq switches to fast mode when short variable
echoes are detected.
 Lab Tests - slow equalisation mode.
54

8 VSB degrades more rapidly when
multipath echo exceeds -7 dB

COFDM works up to 0 dB in a white noise
environment but in this condition is very
fragile.
Transmitter Performance Sensitivity
Parameter
55
DVB-T
ATSC
Transmitter/Translator Linearity
& Inter-mod Sensitivity
Low
High
Group Delay / Combiner /
Filter Sensitivity
< 50 ns
Low
Transmission Strategies - 1
Suggested Transmission System
performance maintenance strategy
56

DVB-T - Manual Maintenance and
static pre-correction - same as PAL

ATSC - Automatic Dynamic pre-corrector
Measures performance and makes
pre-correction adjustments on-line
Transmission Strategies - 2
Gap Fill coverage - System Strategy

DVB-T  IF
Translator
 Non

Regenerative On Channel Repeater (OCR)
 Digital
Repeater
 Single
Frequency Network
ATSC  Digital
 Non
57
Repeater
Regenerative OCR (Low Signal Environs)
Transmission Performance - 1
58

ATSC very sensitive to transmission
impairments as it uses up correction
capacity in the receiver equaliser.

ATSC equaliser has to correct the response
characteristic of the whole channel.

DVB-T equaliser uses pilot carriers spread
throughout the spectrum to equalise the
channel in small 16-50 kHz sections.
Transmission Performance - 2
59

ATSC Dynamic Pre-corrector will be difficult
to apply in the combined antenna systems
used in Australia

Zenith suggest transmission without using a
transmitter output filter to avoid group delay
problems with 8-VSB.

ATSC 6 MHz system operating in a 7 MHz
channel helps this situation.
Impulse Noise - Results

Impulse Sensitivity
(Differential to PAL grade 4)
 DVB-T
 ATSC
61
9 -14 dB
17-25 dB

Difficult to measure & characterise.

Mainly affects the lower VHF frequencies

ATSC is 8 to 11 dB better at handling
impulsive noise than DVB-T
Impulse Noise - Plot
COFDM
8-VSB
62
Impulse Noise - Overview
63

ATSC only has a few data symbols affected
by any normal impulsive phenomenon

The DVB-T COFDM demodulation (FFT)
spreads the energy from a broad spectrum
impulse across all carriers leading to
massive data loss when the impulse is
large enough.
DTTB into PAL - Subjective
Grade
3
4
3
4
D T T B in to P A L B P ro te c tio n D /U (d B)
S y s te m T e s t D e s c rip tio n
M e a n S td D e v
D VB-T 7 M H z
Ch 7 lo w e r a d j. c h .
-9.5
3.3
T ro p o s p h e ric
Ch 8 Co -Ch a n n e l
35.8
1.4
In te rfe re n c e
Ch 9 u p p e r a d j. c h .
-10.6
4.9
D VB-T 7 M H z
Ch 7 lo w e r a d j. c h .
-5.3
3.8
Co n tin u o u s
Ch 8 Co -Ch a n n e l
41.1
2.0
In te rfe re n c e
Ch 9 u p p e r a d j. c h .
-6.4
4.3
D VB-T 7 M H z
Ch 7 lo w e r a d j. c h .
3.5
3.8
Limit o f
Ch 8 Co -Ch a n n e l
50.4
0.9
P e rc e p tib ility
Ch 9 u p p e r a d j. c h .
5.1
5.8
A T SC 6 M Hz
Ch 7 lo w e r a d j. c h .
-7.0
3.4
T ro p o s p h e ric
Ch 8 Co -Ch a n n e l
38.7
2.6
In te rfe re n c e
Ch 9 u p p e r a d j. c h .
-7.1
3.5
A T SC 6 M Hz
Ch 7 lo w e r a d j. c h .
-0.9
4.3
Co n tin u o u s
Ch 8 Co -Ch a n n e l
45.5
2.2
In te rfe re n c e
Ch 9 u p p e r a d j. c h .
-0.3
2.9
A T SC 6 M Hz
Ch 7 lo w e r a d j. c h .
5.0
4.4
Limit o f
Ch 8 Co -Ch a n n e l
51.4
2.5
P e rc e p tib ility
Ch 9 u p p e r a d j. c h .
5.4
3.1
64
Num
12
12
12
12
12
12
12
14
16
15
41
17
15
41
17
15
41
17
M in
-14.0
33.5
-20.0
-9.5
38.5
-14.0
-2.5
48.5
-1.0
-12.5
34.5
-14.0
-5.5
41.0
-5.5
0.0
47.0
0.0
M e d ia n
-10.0
36.0
-10.0
-6.5
40.8
-6.8
2.8
50.3
3.8
-7.0
38.5
-6.0
-2.0
45.0
0.0
4.0
51.5
4.5
M ax
-4.0
38.5
-3.0
2.5
45.0
1.0
10.0
52.0
20.0
-2.0
44.0
-3.5
8.0
50.5
3.0
13.0
56.5
10.5
DTTB into PAL - Overview
65

DVB-T marginally less interference to PAL

DTTB Co channel signals need to be kept
at least 46 dB on average below the
Wanted PAL level to ensure Grade 4
reception

DTTB Adjacent channel signals need to be
kept on average at or below the Wanted
PAL level to ensure Grade 4 reception
PAL into DTTB - Results
D T T B S y s t e m P a ra me t e rs
P A L in t o D T T B P ro t e c t io n (D / U )
D T T B T YP E C O N S T ELLA T IO N F EC
C o d e C h 7 Lo w e r C o C h a n n e l
Ch 9 U p p er
M O D U LA T IO N
Rate
A d j C h (d B )
(d B )
A d j C h (d B )
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D VB -T -7
D V B -T -7
D VB -T -7
D VB -T -7
D VB -T -7
A T S C -6
66
CO FD M Q PSK
CO FD M Q PSK
CO FD M Q PSK
CO FD M Q PSK
CO FD M Q PSK
C O F D M 16-Q A M
C O F D M 16-Q A M
C O F D M 16-Q A M
C O F D M 16-Q A M
C O F D M 16-Q A M
C O F D M 64-Q A M
C O FD M 6 4 -Q A M
C O F D M 64-Q A M
C O F D M 64-Q A M
C O F D M 64-Q A M
8 -V S B 8 -A M
1/ 2
2/ 3
3/ 4
5/ 6
7/ 8
1/ 2
2/ 3
3/ 4
5/ 6
7/ 8
1/ 2
2 /3
3/ 4
5/ 6
7/ 8
2 /3
-44.8
-44.5
-43.7
-42.3
-40.8
-43.5
-42.1
-40.2
-37.0
-35.2
-41.2
-3 5 .4
-35.0
-31.2
-28.9
-3 8 .6
-13.0
-8.4
-4.0
3.1
9.7
-8.8
-2.3
3.3
9.9
16.9
-3.1
1 .4
10.8
17.1
22.6
9 .1
-49.2
-47.0
-45.3
-43.3
-42.0
-46.1
-43.3
-41.2
-39.1
-37.3
-41.7
-3 7 .5
-35.9
-33.1
-30.8
-3 8 .7
PAL into DTTB - Protection Plot
10
Pal into DTTB Protection Ratio Comparison for 50 dBuV DTTB Signals
Protection Ratio D/U (dB)
10
5
00
-5
Protection Ratio D/U (dB)
-10
-10
-15
-20
-20
-25
-30
-30
8-VSB
8-VSB
COFDM
COFDM
-35
-40
-40
-45
-8
-7
-6
-5
-4
-3
-2
-1
0
-8
-7
-6
-5
-4
-3
-2
-1
11 22
Frequency0
Offset (MHz)
Frequency Offset (MHz)
67
33
44
55
66
77
88
Co Channel PAL into DTTB - Plot
DTTB Small Frequency Offset Co-channel Pal protection for 50 dBuV DTTB Signals
15
1010
Protection Ratio D/U (dB)
Protection Ratio D/U (dB)
15
8-VSB Pal Co-Channel
Protection
8-VSB
Co Channel
COFDM V2.1 EQ Pal Interference
COFDM
Co Channel
5
5
00
-5-5
-40
-40
68
-30
-30
-20
-20
-10
00
10
-10
10
Frequency Offset (kHz)
Frequency Offset (kHz)
20
20
30
30
40
40
Off Air PAL into DTTB - Plot
Pal into DTTB Protection with real Off Air Pal signals either side of DTTB Channel 8
5
Protection Ratio D/U (dB)
5
00
6 MHz 78-VSB
MHz COFDM
MHz 8VSB
7 MHz 6COFDM
-5-5
Protection Ratio D/U (dB)
-10
-10
Note: Channel 7 only has a
single monophonic Sound
carrier which is 10 dB below
the Vision carrier level
-15
-15
-20
-20
-25
-25
-30
-30
-35
-35
-40
-40
-2000
-2
69
-1500
-1000
-500
500
1000
-1.5
-1
-0.5
00
0.5
1
Channel 8 DTTB Frequency Offset (kHz)
Channel 8 DTTB Frequency Offset (MHz)
1500
1.5
2
2000
DTTB & PAL in Adjacent Channels
COFDM
70
PAL
0 dB Relative Levels - PAL/DTTB
COFDM
PAL into DTTB - Overview 1
71

The narrower ATSC system achieves very
similar out of band / adjacent channel
performance to DVB-T.

ATSC is nearly 8 dB worse than DVB-T
when subjected to interference from CoChannel PAL transmissions
PAL into DTTB - Overview 2
72

In situations where Co-Channel DTTB and
PAL signals exist the DTTB into PAL
interference will be the dominant factor,
providing directional antennas are used.

If a DTTB frequency offset was being
considered for use, the data indicates that
moving up in frequency is preferable to
moving down.
CW into DTTB - Protection Plot
CW Interferer into DTTB Protection Ratio Comparison for 50 dBuV DTTB Signals
15
5
00
-5
Protection Ratio D/U (dB)
Protection Ratio D/U (dB)
1010
-10
-10
-15
-20
-20
-25
-30
-30
8-VSB
8-VSB
COFDM
COFDM
-35
-40
-40
-45
-50
-50
-8
-7
-6
-5
-4
-3
-2
-1
-8
-7
-6
-5
-4
-3
-2
-1
00Offset (MHz)
11 22
Frequency
Frequency Offset (MHz)
73
33
44
55
66
77
88
CW into DTTB - Summary
74

DVB-T is on average 15.5 dB less sensitive
across the channel to general CW type
interferers than ATSC

The DVB-T orthogonal carrier spacing is
evident for DVB-T in this measurement with
a variation of over 8 dB. If known CW
interferers are likely then a frequency offset
of less than 4 kHz may assist system
performance.
CW into DTTB centre channel
DTTB Small Frequency Offset Co-channel CW Interference protection for 50 dBuV Signal
15
10
10
Protection Ratio D/U (dB)
Protection Ratio D/U (dB)
15
8-VSB CW Interference
Protection
8-VSB
CW Protection
COFDM V2.1 EQ CW Interference
COFDM
CW Protection
55
00
-5-5
-10
-10
-40
-40
75
-30
-30
-20
-20
-10
00
10
-10
10
Frequency Offset (kHz)
Frequency Offset (kHz)
20
20
30
30
40
40
CW into DTTB - Comment
76

ATSC has occasional peaks due to critical
equaliser responses.

The DVB-T response above was obtained
from the improved equaliser which was
provided near the end of the tests.
DTTB into DTTB - Overview
D TTB
TY P E
D V B -T -7
A T SC -6
C h 7 L ow er
A d j C h (d B )
-2 8 .3
-3 0 .4
C o C hannel C h 9 Upper
(d B )
A d j C h (d B )
20
-2 8 .5
1 4 .6
-3 2 .2
Adjacent channel performance of ATSC is
better than DVB-T
 The Co-channel protection of both digital
systems approximates to the system carrier
to noise threshold.

77
DTTB into DTTB - Protection Plot
DTTB into DTTB Protection
25
15
1010
5
Protection Ratio (dB)
Protection Ratio D/U (dB)
2020
00
-5
COFDM
8-VSB
8-VSB
COFDM
-10
-10
-15
-20
-20
-25
-30
-30
-35
-8
-7
-6
-5
-4
-3
-2
-1
-8
-7
-6
-5
-4
-3
-2
-1
00 11 22 33 44
Frequency offset of Unwanted DTTB signal (MHz)
Frequency Offset of Unwanted DTTB (MHz)
78
55
66
77
88
DTTB Field Testing Objectives
A DTTB Field Trial is study of Failure !!
In comparison with current PAL television
In various reception conditions :
Investigate the difference in reception character
for the two DTTB modulation systems.
 Provide information to DTTB system planners
 To provide Credible data.

79
Field Testing - Van

80
A field test vehicle was built in a small van.
Field Testing - On the Streets

81
Over 115 sites were measured
Field Test Vehicle Block Diagram
Ch 6-11 VHF
Antenna on
a 10 m Mast
Spectrum
Analyser
11.5 dB
NF 3.6 dB
11.5 dB
-20dB
Input
level
Noise
Injection
Noise
Source
82
Plisch PAL
Demodulator
5
way
split
-7 dB
DVB-T
Receiver
ATSC
Receiver
Vector Signal
Analyser
VM-700
PAL
Monitor
BER
Meter
CRO
Field Testing - Method
Field tests were conducted in Sydney over a
1 month period on VHF channel 8.
 Some simultaneous tests were conducted on
VHF channel 6
 Power level for the field test was 14 dB below
adjacent analog television channels 7 & 9
 Analog and digital television performance for
both systems were evaluated at each site.
 Conducted by Independent Consultant & Mr
Wayne Dickson of TEN

83
Field Test - Data Collected each Site
Common Masthead Amp used (NF ~ 3.6 dB)
 Analog PAL transmission character (7,9 & 10)
 Measure level, multipath, quality & Video S/N
 Measure DVB & ATSC reception (Ch 8)
 Record DTTB & Analog Spectrum
 Measure Noise Margin (C/N Margin)
 Measure Level Threshold (Signal Margin)
 Measure antenna off pointing sensitivity

84
A R G IN
(d B )
Australian DTTB Field Trial
PAL Receive Margin
PAL - SITE RECEIVE MARGIN
Facts DTTB Trial Sites
40
for HIGH GAIN ANTENNA
R E C E IV E
M
35
30
Minimum F/S = 55dBuV/m
Receiver limitations
Margin to minimum acceptable
picture w/o multipath
25
20
S it e
15
10
PAL on CH9
5
0
45
50
55
60
MINIMUM ACCEPTABLE PICTURE
65
70
75
Nominal conditions : 7 dB gain Antenna + 2 dB leed loss @ CH9
Effective decoder Noise Figure (NF) = 5 dB
85
80
85
90
95
100
105
Site Field Strenght (dBuV/m)
Plisch Receiver
W . T. D. 5 J UNE 1 9 98
110
T H R E S H O L D
Australian DTTB Field Trial
DTTB compared to PAL
D T T B
PAL VIDEO S/N @ DTTB THRESHOLD
@ 14dB nominal DTTB to PAL ratio
-15
8VSB
o f P A L
@
-20
-25
S /N
-30
-35
V id e o
COFDM (64QAM,2/3,1/8)
Average S/N @ Threshold of :
-40
8VSB = -24.2dB unwtd (PAL)
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
TEST #
65
70
75
80
85
90
95
100
105
110
FACTS DTTB Trial Sites
System Noise Method
W. T. D. 15 Jan 1998
86
115
(d B )
Australian DTTB Field Trial
8VSB Decoder Margin
8VSB SITE DECODE MARGIN
A R G IN
FACTS DTTB Trial Sites
60
for a HIGH GAIN ANTENNA
50
D E C O D E
M
Minimum F/S = 37 dBuV/m
without multipath
and 3 dB margin
40
Margin @ Threshold C/N
w/o multipath
Minimum F/S = 47 dBuV/m
with multipath allowance
and 3 dB margin
Margin @ threshold C/N
with multipath
S it e
30
20
8VSB
10
Decoder NF = 9 dB
0
25
30
NO PICTURE
35
40
45
50
55
Nominal conditions : 7 dB gain Antenna + 2 dB leed loss
Effective decoder Noise Figure (NF) = 9 dB
87
60
Site Field Strenght (dBuV/m)
65
70
75
80
85
90
System Noise Method
W . T. D. 7 J UNE 1 9 98
(d B
)
Australian DTTB Field Trial
COFDM Decoder Margin
G IN
COFDM SITE DECODE MARGIN
FAC TS D TTB Tr ia l Site s
60
A
R
for a HIGH GAIN ANTENNA
M
50
Margin @Threshold C/N
w/o multipath
E
Minimum F/S = 37 dBuV/m
without mutipath
and 3 dB margin
O D
40
E C
Minimum F/S = 45 dBuV/m
with multipath allowance
and 3 dB margin
D
30
S it e
Margin @ Threshold C/N
with Multipath
20
COFDM (64QAM,2/3,1/8)
10
Decoder NF = 5 dB
0
25
NO PICTURE
30
35
40
45
50
55
Nominal conditions : 7 dB gain Antenna + 2 dB leed loss @ CH8
Effective decoder Noise Figure (NF) = 5 dB
88
60
Site Field Strenght (dBuV/m)
65
70
75
80
85
90
System Noise Method
W . T. D. 5 J UNE 1 9 98
DTTB Systems Doppler
Performance Limits
for current
implementations
300
250
DOPPLER
SHIFT
(Hz)
UHF
200
VHF - Band III
COFDM 2K, 3dB degrade
140
COFDM 2K
100
50
0
ATSC
see separate curves
0
100
300
400
500
600
700
800
900
SPEED (Km/Hr)
Vehicles
89
200
AIRCRAFT
Over Cities
COFDM implementations will inherently handle post and
pre-ghosts equally within the selected guard interval.
1000
ATSC 8-VSB
Doppler Performance Limits
for current
implementations
10
UHF
DOPPLER
SHIFT
(Hz)
VHF - Band III
8VSB, “Fast Mode”, 3dB degrade
5
8VSB
1
0
0 2 6 10
23
30
SPEED (Km/Hr)
Vehicles
8VSB implementations of equalisers are likely to cater for
post ghosts up to 30 uSec and pre-ghosts up to 3 uSec only.
90
100
Aircraft
Field Test - Observations
At -14 dB DTTB power when there was a
reasonable PAL picture both 8-VSB & COFDM
worked at the vast majority of Sites
 When PAL had:

 Grain
(noise) and some echoes (multipath),
both 8-VSB & COFDM failed
 Flutter, caused by aircraft or vehicles, 8-VSB failed
 Impulsive noise & some grain, COFDM failed
91
Results Conclusion
92

The assessment of the results presented in
this summary depends largely on the
SPECIFIC system REQUIREMENTS of the
broadcaster and the viewers.

The implementation and performance of
both digital terrestrial transmission systems
are still being improved, however the
DVB-T system shows more scope for
achieving future advances.
The Selection Committee

A selection committee was formed
from FACTS ATV specialists group
Representing:
 National
broadcasters (ABC and SBS)
 The commercial networks (7,9 & 10)
 The regional commercial broadcasters
 The Department of Communications
and the Arts
 The Australian Broadcasting Authority
93
Selection Panel - Responsibility
94

Analysing the comparative tests and other
available factual information

Establishing the relevance of the
performance differences to Australian
broadcasting

Recommending the system to be used
Selection Criteria
 Derived
a set of 50 selection criteria
relevant to the Australian transmission
environment
 Criteria were reduced to final 29 which
could impact on the final decision
 The criteria were weighted and an
overall average used to rank the
selection criteria
95
Selection Criteria - Groups
 Most
Important Criteria Groupings
Coverage
System
Design Elements
Operational Modes Supported
Overall System
Receivers
96
Selection Criteria - Analysis
 Assessed
each of the selection criteria
elements for each modulation system
Some criteria were put aside as it was
felt there was not enough information
to factually score those criteria
97
Criteria - Coverage
 Inner
and outer service areas
 Performance with Roof top antennas
 Performance with Set top antennas *
 Co-channel & Adjacent channel protection
 Mobile Reception
 Multipath (Ghosting, Doppler & Flutter)
 Immunity to impulse noise
98
Criteria - System Design Elements
 Combining
& use of common Tx Antenna
 Requirements for implementing translators
 Suitability for co-channel translators
 Ability to use existing transmitters
99
Criteria - Operational Modes Support
 HDTV
Support
 Support for closed captioning
 Multiple languages Audio
 Surround Sound Audio System
100
Criteria - Overall System
 Accepted
HDTV system
 Performance within 7 MHz channel
 Number useful Mb/s in 7 MHz
 Ability to fit in existing infrastructure
 Overall Modulation System Delay
 System Flexibility, Upgrade Capacity &
Future Development Capacity
101
Selection Criteria - Receivers
 Availability
(for HDTV) MP@HL
 Receiver Features & Cost
 PAL and DTTB capability
 Degree of customizing for Australia
 Receiver Applications Software
 Lock up time
 Australian channel selection
102
DTTB Choice Assessment Sheet
GROUP1 – COVERAGE
Element
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
103
ATSC DVB
IMPORTANCE
Element
Group
ATSC DVB
IMPORTANCE
Element
Group
ATSC DVB
IMPORTANCE
Element
Group
Group 4
Adoption of an accepted rather than unique (HDTV) system
Performance within 7 MHz channel
Number of useful Mbs/7MHz
Overall encode/decode delay
System upgrade & further development capability
GROUP 5 - RECEIVER ELEMENTS
Element
5.1
5.2
5.3
5.4
5.5
5.6
5.7
IMPORTANCE
Element
Group
Group 3
HDTV support
Support for closed captions
Support for multilingual audio
Audio System
GROUP 4 - OVERALL SYSTEM
Element
4.1
4.2
4.3
4.4
4.5
ATSC DVB
Group 2
Combining to use common transmit antennas
Ease of use and cost of implementing translators
Common channel translator capability
Ability to use existing transmitters
GROUP3 - OPERATIONAL MODES SUPPORTED
Element
3.1
3.2
3.3
3.4
IMPORTANCE
Element
Group
Group 1
Percentage of A coverage pop. served
Percentage of B coverage pop. served
Set top antennas
Mobile reception
Co-channel performance
Adjacent channel performance
Multipath Performance
Immunity to electrical interference
Ability to be conveyed in MATV and cabled systems
GROUP 2 - SYSTEM DESIGN ELEMENTS
Element
2.1
2.2
2.3
2.4
ATSC DVB
Group 5
Receiver availability, features & cost
Receiver and STB MP @ HL
Receivers with both PAL and DTTB capability
Receivers not specific design for Australia
Receiver applications software
Receiver lock-up time
Ability to provide automatic channel selection for Australian channelling
DTTB Choice Assessment Sheet
GROUP1 – COVERAGE
Element
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
104
IMPORTANCE
Element
Group
ATSC DVB
IMPORTANCE
Element
Group
Group 1
Percentage of A coverage pop. served
Percentage of B coverage pop. served
Set top antennas
Mobile reception
Co-channel performance
Adjacent channel performance
Multipath Performance
Immunity to electrical interference
Ability to be conveyed in MATV and cabled systems
GROUP 2 - SYSTEM DESIGN ELEMENTS
Element
2.1
2.2
2.3
2.4
ATSC DVB
Group 2
Combining to use common transmit antennas
Ease of use and cost of implementing translators
Common channel translator capability
Ability to use existing transmitters
Selection Result - June 1998
 The
selection committee
unanimously selected the
7 MHz DVB-T modulation
system for use in Australia

105
The criteria that were set aside would,
however, not have changed the selection
decision
Overall Selection Influences
A single system for All Free to Air Broadcasters
 Ability to meet Governments objectives for
coverage
 Able to deliver the HDTV quality objective
 Availability of consumer products at acceptable
costs
 Solid support from proponent
 Interoperability with other digital video platforms
 Confidence in the system meeting the business
objectives
106

More Selections

Sub-committees formed to investigate:
 Service
information data standard
 Multichannel audio system
 HDTV video production format

July 1998 3 further recommendations
 SI
data standard be based on DVB-SI
 AC3 multichannel audio is the
preferred audio encoding format
 1920/1080/50 Hz interlaced 1125 lines is the
preferred video production format
107
Frame Rate Video Format Decision
Examined 50 or 60 Hz based video formats
 Decided to stay with 25/50 Hz system:

108
 40+ years of 50 Hz Archive program material
 Overseas production available in 50 or 60 Hz
 Down-conversion is required for Legacy Rx
 Inappropriate to use incompatible frame rates
in the FTA broadcast community
 Production problems associated with 60 Hz
image capture in a 50 Hz power environment
 Broadcast / Consumer Manufacturers assurance
50 Hz equipment will be available
Australian Video Formats
Use of Progressive and Interlace video formats
 The Format selected to suit program content.
 Likely Video Formats
MP@HL,

 Film Material
 1920x1080/50I
 General Entertainment
 720x576/50P  Sports Coverage
 720x576/50I
 SDTV Program
 1920x1080/25P
MP@ML
109
DTTB Implementation Notes:
Although SFNs are of interest in Australia they
will be of little use during the simulcast period.
 Use may be made of Dual Frequency Networks
to increase spectrum efficiency
 The channel frequency matrix will be adjusted
when Analog TV services cease.
 Digital TV provides the capacity to repack the
television spectrum.

110
A Future Digital System Concept
MMDS
Satellite
Hypermedia
Integrated Receiver
Decoder (IRD)
Terrestrial
Cable
Broadcast
Interactivity
B-ISDN
XDSL
111
CD, DVD
DVC
The End
Thank you for your attention
Any questions?
112