Current Performance of DVB-T
Demodulators
Min-Chen Ho
ITE Tech, Inc.
Outline
2

DVB-T Physical Layer – EN 300744

Standardized DVB-T Testing

DVB-T Field Testing
DVB-T Physical Layer – EN300744
Block Diagram from EN 300 744
(204,188)
Reed-Solomon
QPSK, 16QAM,
64QAM
4
64-state R=1/2
convolutional code
DVB Transmission Modes

5
There are many modes in DVB transmission

Bandwidth: 5MHz, 6MHz, 7MHz, 8MHz.

FFT Size: 2K, 4K, 8K

Modulation: QPSK, 16QAM, 64QAM, non-uniform 16QAM with =1 or =2,
non-uniform 64QAM with =1, =2, or =4.

Code Rate: 1/2, 2/3, 3/4, 5/6, 7/8

Guard Interval: 1/4, 1/8, 1/16, 1/32

Different modes have different performance

It is very important to make sure that the correct mode is selected for
testing.
OFDM Parameters

Comments


6
Longer GI supports longer channel

For 2K, GI=1/32, the channel must be shorter than 7s

For 8K, GI=1/4, the channel can be as long as 256 s

With the same GI ratio, 8K mode can support longer channels than 2K mode.
Shorter Tu has better inter-carrier interference (ICI) tolerance

Sub-carriers are further apart when Tu is small.

2K has better ICI tolerance than 8K.

Channel variation is a major cause of ICI, therefore 2K has better mobility
support than 8K.
Signal Spectra I
S pectrum Analyzer
5 57 FJ2
R ef Level :
-4 0 .0
533 545 557
581 593
CTV PTS FTV 569 TTV CTS599
M1: -63.40 dB m @ 556.7 MH z
-4 0
dB m
dB / D iv :
-5 0
1 0 .0 d B
M2: -76.26 dB m @ 554.0 MH z
-6 0
-7 0
dB m
-8 0
-9 0
-1 00
-1 10
-1 20
-1 30
M2
M1
-1 40
5 04
7
5 16
C F: 5 5 7.0 M Hz
R B W: 10 0 kHz
St d: C DM A20 0 0 C l a ss 6 IM T
M i n Swe e p T i m e : 1 .0 0 M i l l i Se c
Da t e : 0 6/ 1 8/ 2 0 08
M od e l : M S2 7 11 D
5 28
5 40
5 52
5 64
5 76
Freq ue n c y (4 9 7.0 - 6 1 7.0 MH z )
SPAN: 1 20 .0 0 M Hz
VB W: 30 k Hz
T i m e : 1 4: 5 2: 39
Se ri a l #: 00 63 9 12 5
5 88
6 00
6 12
At t e nu a t i on : Dyn a m i c
De t e c t i o n: R M S Av e ra ge
Pre a m p: Dyn a m i c
Signal Spectra II
S pectrum Analyzer
5 57 C HUN
R ef Level :
-4 0 .0
-4 0
dB m
dB / D iv :
-5 0
1 0 .0 d B
-6 0
-7 0
S pectrum Analyzer
5 57 -12 0 C HUN
R ef Level :
-4 0 .0
dB m
-8 0
-4 0
-1 00
-5 0
-1 10
-6 0
-1 20
dB m
dB / D iv :
1 0 .0 d B
-1 30
-7 0
5 5 4 .0
5 6 0 .0
-1 40
-8 0
dB m
-9 0
5 48
5 50
-9 0
C F: 5 5 7.0 M Hz
R B W: 30 k Hz
C h a n Pwr: -71 .96 dB m
St d: C DM A20 0 0 C l a ss 6 IM T
M i n Swe e p T i m e : 1 .0 0 M i l l i Se c
Da t e : 0 6/ 1 8/ 2 0 08
M od e l : M S2 7 11 D
-1 00
-1 10
-1 20
-1 30
5 54
5 56
5 58
5 60
Freq ue n c y (5 4 7.0 - 5 6 7.0 MH z )
SPAN: 2 0.00 M Hz
VB W: 10 k Hz
C h a n Pwr De n si t y : -13 9.75 d B m / Hz
-1 40
5 04
5 16
C F: 5 5 7.0 M Hz
R B W: 10 0 kHz
St d: C DM A20 0 0 C l a ss 6 IM T
M i n Swe e p T i m e : 1 .0 0 M i l l i Se c
Da t e : 0 6/ 1 8/ 2 0 08
M8
od e l : M S2 7 11 D
5 28
5 40
5 52
5 64
5 76
Freq ue n c y (4 9 7.0 - 6 1 7.0 MH z )
SPAN: 1 20 .0 0 M Hz
VB W: 30 k Hz
T i m e : 1 3: 2 0: 34
Se ri a l #: 00 63 9 12 5
5 88
6 00
6 12
At t e nu a t i on : Dyn a m i c
De t e c t i o n: R M S Av e ra ge
Pre a m p: Dyn a m i c
5 52
T i m e : 1 2: 5 0: 03
Se ri a l #: 00 63 9 12 5
5 62
5 64
5 66
At t e nu a t i on : Dyn a m i c
De t e c t i o n: R M S Av e ra ge
INT B W: 6 M Hz
Pre a m p: Dyn a m i c
Standardized DVB-T Testing
Purpose of Standardized Testing
10

Purpose of standardized testing is to measure the performance of a
DVB receiver under certain assumptions.

In practice

If these assumptions hold, then the performance of a DVB receiver can be
predicted using standardized testing results. (Very rare)

If these assumptions do not hold, then standardized testing results only
provides a reference. (Most of the time)
AWGN Performance


AWGN assumptions

Injected noise power 和 [頻率或時間] 無關

Signal power 和 [頻率或時間] 無關
AWGN performance measures

C/N – 訊號強度應比雜訊強度高多少才能正常收訊

Sensitivity (弱信號) – 訊號強度最弱可到多弱還能正常收訊

Strong signal (強信號) – 訊號強度最強可到多少還能正常收訊
11
Input Signal Power
C/N
Bad Reception
Injected Noise Power
Reception OK
Signal Power (dBm)
Signal Power (dBm)
Signal too strong
Pmax
(strong signal)
Reception OK
Input Signal Power
Pmin (sensitivity)
Signal too weak
System Noise Floor
System Noise Floor
Frequency
Frequency
Multipath Performance (Echo)



Multipath Assumptions

Injected noise power 和 [頻率或時間] 無關

Signal power 隨 [頻率] 做某種規律之改變，但不隨時間改變
Multipath specification

Number of echos (2-path, 3-path, etc)

Echo attenuation (P0, P1, …) and delay (T0, T1 …)

Echo channels

Inside Guard Interval ( < GI)

Outside Guard Interval ( > GI)
Performance measures


C/N
P1X(t-T1)
X(t)
Sensitivity
Transmitter
12
P0X(t-T0)
Receiver
P2X(t-T2)
Multipath Performance (Echo)

Example: 2-path 0-dB echo
50
X(t)
time
P1X(t – T1)
time
Signal Power (dBm)

13
-50
-100
-150
-200
-250
-300
-350
-4
Ave. Input Signal Power
C/N
Injected Noise Power
Reception OK
-3
Signal Power (dBm)
P0X(t – T0)
Channel Magnitude Response (dB)
0
-2
-1
0
1
Frequency (MHz)
2
3
Reception OK
Input Signal Power Pmin (sensitivity)
System Noise Floor
System Noise Floor
Frequency
4
Frequency
Immunity Against Interference – ACI and CCI

Adjacent Channel Interference (ACI)

本身頻道符合 AWGN assumption，但其他頻道有極強之訊號

其他頻道之訊號如為類比電視訊號則稱為 Analog ACI

其他頻道之訊號如為數位電視訊號則稱為 Digital ACI
Co-Channel Interference (CCI)

Immunity against interference – 干擾可以到多強還不會被蓋台
Signal Power (dBm)

本身頻道除收到符合 AWGN assumption之數位訊號外，也同時收到同頻道
之類比電視訊號
ACI
Immunity
Interferer
Desired
N
14
Signal Power (dBm)

N+1
Channel No.
Desired
CCI
Immunity
Interferer
N
Channel No.
Immunity Against Interference – ACI and CCI

Example – CCI (可能發生在不同播放區的邊界)
spectrum of ADC output, MT tuner
spectrum of ADC output, MT tuner
60
60
Video
40
40
Color
NICAM
0
20
magnitude (dB)
20
magnitude (dB)
Audio (FM)
-20
-40
0
-20
-40
-60
-60
-80
-15
-10
-5
0
frequency (MHz)
5
PAL BG spectrum
15
10
15
-80
-15
-10
-5
0
frequency (MHz)
5
10
DVB-T Signal with PAL BG
15
DVB-T Field Testing
Field Testing

Not part of standardized testing.

However, field testing is the most realistic way of performance
evaluation.

Key difference between field testing and standardized lab testing


Standardized testing tests performance under certain assumptions.

Field testing tests performance in real situations.
Real situations are very different from standardized testing
assumptions. Therefore:

Standardized tests 通過了並不代表在任何時間任何地點都能收訊

Mobile performance predicted using standardized tests is very different
from actual performance.

17
Lab 中得到的 mobile performance 數據僅能供參考用
Transmitter @ London, UK

Location: Crystal Palace Park

Height: 219 m

Built: 1956

Transmission

18

PAL-I Analog TV

DVB-T

FM
Measured Channel Power

p_inband ~ -40 dBm

p_total ~ -20 dBm
路測道具
London Map
19
London - Frequency Table
Channel No.
20
Freq (MHz) Power (kW) Type
MUX
Modulation
8M,64QAM,2K,2/3,1/32
22
482
20
D
MUX2
23
487.25
1000
A
ITV
25
506
20
D
MUX1
26
511.25
1000
A
BBC1
28
530
20
D
MUX4
8M,16QAM,2K,3/4,1/32
29
538
20
D
MUX6
8M,16QAM,2K,3/4,1/32
30
543.25
1000
A
C4
32
562
20
D
MUX3
33
567.25
1000
A
BBC2
34
578
20
D
MUX5
37
599.25
1000
A
C5
8M,16QAM,2K,3/4,1/32
8M,64QAM,2K,2/3,1/32
8M,16QAM,2K,3/4,1/32
London: UHF Spectra
S pectrum Analyzer
UK-C R P-1 40
R ef Level :
-1 0 .0
-1 0
M1: -62.54 dB m @ 502.55 MH z
dB m
dB / D iv :
-2 0
1 0 .0 d B
-3 0
-4 0
dB m
-5 0
-6 0
506
530 538
562
578
482
-7 0
-8 0
-9 0
-1 00
M1
-1 10
4 76
4 90
C F: 5 4 0.0 M Hz
R B W: 30 0 kHz
St d: AM PS / E IA 55 3
M i n Swe e p T i m e : 1 .0 0 M i l l i Se c
Da t e : 0 3/ 1 8/ 2 0 09
M od e l : M S2 7 11 D
21
5 04
5 18
5 32
5 46
5 60
Freq ue n c y (4 7 0.0 - 6 1 0.0 MH z )
SPAN: 1 40 .0 0 M Hz
VB W: 10 0 kHz
T i m e : 0 1: 5 0: 43
Se ri a l #: 00 63 9 12 5
5 74
5 88
6 02
At t e nu a t i on : Dyn a m i c
De t e c t i o n: R M S Av e ra ge
Pre a m p: Dyn a m i c
Transmitter @ Paris, France

Location: La Tour Eiffel

Height: 324 m

Built: 1889

Transmission


SECAM-L Analog TV

DVB-T

FM
Measured Channel Power

p_inband ~ -40 dBm

p_total ~ -30 dBm
路測車
22
Paris Map
23
Paris: Frequency Table
Channel No. Freq. (MHz) Power (kW) Type
24
MUX
Modulation
8M,64QAM,8K,2/3,1/32
21
474
23
D
R2
22
479.25
500
A
France-2
23
490
5
D
L8
8M,16QAM,8K,2/3,1/32
24
498
23
D
R4
8M,64QAM,8K,2/3,1/32
25
503.25
500
A
TF1
27
522
23
D
R3
28
527.25
500
A
France-3
29
538
20.9
D
R5
30
543.25
100
A
France-5
32
562
23
D
R6
33
567.25
100
A
M6
35
586
41
D
R1
8M,64QAM,8K,2/3,1/32
8M,64QAM,8K,3/4,1/8
8M,64QAM,8K,2/3,1/32
8M,64QAM,8K,3/4,1/8
Paris: UHF Spectra (Star Hotel)
S pectrum Analyzer
FR -ST AR -FUL L
R ef Level :
-1 0 .0
-1 0
M1: -97.87 dB m @ 590.14 MH z
dB m
dB / D iv :
-2 0
1 0 .0 d B
-3 0
-4 0
dB m
-5 0
-6 0
-7 0
474
522
490 498
538
562
586
-8 0
-9 0
-1 00
M1
-1 10
4 7 1 .2
4 8 3 .6
4 9 6 .0
C F: 5 3 0.0 M Hz
R B W: 10 k Hz
St d: AM PS / E IA 55 3
M i n Swe e p T i m e : 1 .0 0 M i l l i Se c
Da t e : 0 3/ 2 0/ 2 0 09
M od e l : M S2 7 11 D
25
5 0 8 .4
5 2 0 .8
5 3 3 .2
5 4 5 .6
Freq ue n c y (4 6 8.0 - 5 9 2.0 MH z )
SPAN: 1 24 .0 0 M Hz
VB W: 3 kHz
T i m e : 0 6: 0 1: 55
Se ri a l #: 00 63 9 12 5
5 5 8 .0
5 7 0 .4
5 8 2 .8
At t e nu a t i on : Dyn a m i c
De t e c t i o n: R M S Av e ra ge
Pre a m p: Dyn a m i c
Paris (474MHz)
26
Transmitter @ Barcelona, Spain

Location: Torre de Collserola (on Tibidabo)

Height: 288.4 m

Built: 1992

Transmission


PAL-B Analog TV

DVB-T

FM
Measured Channel Power

p_inband ~ -40 dBm

p_total ~ -20 dBm
路測車
27
Barcelona Map
28
Frequency Table (Bercelona)
Channel Freq. Power
No.
(MHz) (kW)
29
Type
Network
Modulation
22
482
D
Abertis Telecom
8M,QPSK,8K,1/2,1/8
24
498
D
MARESMEDIGITAL TV
8M,64QAM,8K,2/3,1/4
26
514
D
Barcelona TV
8M,64QAM,8K,2/3,1/4
33
570
D
EDC
8M,64QAM,8K,2/3,1/4
43
650
D
TVC
8M,64QAM,8K,2/3,1/4
48
690
D
Harmonic
8M,64QAM,8K,2/3,1/4
61
794
D
TVC
8M,64QAM,8K,2/3,1/4
64
818
D
RTVE
8M,64QAM,8K,2/3,1/4
66
834
D
RTVE
8M,64QAM,8K,2/3,1/4
67
842
D
La Sexta
8M,64QAM,8K,2/3,1/4
68
850
D
TELECINCO
8M,64QAM,8K,2/3,1/4
69
858
D
ANTENA3 TELEVISION
8M,64QAM,8K,2/3,1/4
Barcelona: UHF Spectra
S pectrum Analyzer
SP-T IB I-FUL L
R ef Level :
-1 0 .0
-1 0
M1: -85.88 dB m @ 548.19 MH z
dB m
dB / D iv :
-2 0
1 0 .0 d B
-3 0
-4 0
dB m
-5 0
-6 0
498
514
570
650
834~858
794 818
690
-7 0482
-8 0
-9 0
-1 00
M1
-1 10
4 7 5 .2
5 1 4 .8
5 5 4 .4
C F: 6 6 6.0 M Hz
R B W: 10 k Hz
St d: AM PS / E IA 55 3
M i n Swe e p T i m e : 5 0.00 M i c ro Se c
Da t e : 0 3/ 2 2/ 2 0 09
M od e l : M S2 7 11 D
30
5 9 4 .0
6 3 3 .6
6 7 3 .2
7 1 2 .8
Freq ue n c y (4 6 8.0 - 8 6 4.0 MH z )
SPAN: 3 96 .0 0 M Hz
VB W: 3 kHz
T i m e : 1 8: 3 1: 21
Se ri a l #: 00 63 9 12 5
7 5 2 .4
7 9 2 .0
8 3 1 .6
At t e nu a t i on : Dyn a m i c
De t e c t i o n: R M S Av e ra ge
Pre a m p: Dyn a m i c
Barcelona (858MHz)
31
Transmitter @ Berlin, Germany

Location: Fernsehturm Berlin
(near Alexanderplatz)

Height: 368 m

Built: 1969

Transmission

32

DVB-T

FM
Measured Channel Power

p_inband ~ -40 dBm

p_total ~ -30 dBm
Berlin Map
33
Berlin: Frequency Table
Channel No.
34
Freq. Power
(MHz) (kW)
Type Network Name
Modulation
5
177.5
D
ARD
7M,16QAM,8K,3/4,1/8
7
191.5
D
ARD
7M,16QAM,8K,2/3,1/8
25
506
D
RTL World
8M,16QAM,8K,2/3,1/8
27
522
D
ARD
8M,16QAM,8K,2/3,1/8
33
570
D
ZDFMobile
8M,16QAM,8K,2/3,1/4
44
658
D
ProSiebenSat.1
8M,16QAM,8K,2/3,1/8
56
754
D
BetaDigital
8M,16QAM,8K,2/3,1/8
59
778
D
RTL World
8M,16QAM,8K,2/3,1/8
Berlin: VHF Spectra
S pectrum Analyzer
DE -AL E -VHF
R ef Level :
0 .0
M1: -86.57 dB m @ 214.5 MH z
0
M2: -86.57 dB m @ 214.5 MH z
177.5
N+2 DACI
(191.5)
191.5:
N-2 DACI
(177.5)
dB m
dB / D iv :
-1 0
1 0 .0 d B
-2 0
-3 0
dB m
-4 0
-5 0
177.5
191.5
-6 0
-7 0
-8 0
-9 0
M1
M2
-1 00
1 56
1 62
1 68
C F: 1 8 4.5 M Hz
R B W: 10 0 kHz
St d: AM PS / E IA 55 3
M i n Swe e p T i m e : 5 0.00 M i c ro Se c
Da t e : 0 3/ 2 7/ 2 0 09
M od e l : M S2 7 11 D
35
1 74
1 80
1 86
1 92
1 98
2 04
2 10
Freq ue n c y (1 5 4.5 - 2 1 4.5 MH z )
SPAN: 6 0.00 M Hz
At t e nu a t i on : Dyn a m i c
VB W: 30 k Hz
De t e c t i o n: R M S Av e ra ge
T i m e : 2 1: 3 6: 22
Se ri a l #: 00 63 9 12 5
Av e ra g e : 1 0
Pre a m p: Dyn a m i c
Berlin: UHF Spectra
S pectrum Analyzer
DE -AL E -UHF
R ef Level :
0 .0
M1: -80.91 dB m @ 637.2 MH z
0
M2: -80.91 dB m @ 637.2 MH z
506:
N+2 DACI (522)
522:
N-2 DACI (506)
570:
N-6 DACI (522)
658:
N-11 DACI (570)
N+12 DACI
(754)
dB m
dB / D iv :
-1 0
1 0 .0 d B
-2 0
-3 0
dB m
-4 0
506 522 570
658
-5 0
754 778
-6 0
-7 0
-8 0
-9 0
M 2M 1
-1 00
4 9 9 .2
5 3 7 .6
C F: 6 6 6.0 M Hz
R B W: 30 0 kHz
St d: AM PS / E IA 55 3
M i n Swe e p T i m e : 5 0.00 M i c ro Se c
Da t e : 0 3/ 2 7/ 2 0 09
M od e l : M S2 7 11 D
36
5 7 6 .0
6 1 4 .4
6 5 2 .8
6 9 1 .2
7 2 9 .6
Freq ue n c y (4 7 4.0 - 8 5 8.0 MH z )
SPAN: 3 84 .0 0 M Hz
VB W: 10 0 kHz
T i m e : 2 1: 3 4: 55
Se ri a l #: 00 63 9 12 5
7 6 8 .0
8 0 6 .4
8 4 4 .8
At t e nu a t i on : Dyn a m i c
De t e c t i o n: R M S Av e ra ge
Av e ra g e : 5
Pre a m p: Dyn a m i c
Berlin (506MHz)
37
Summary – Signal Conditions
Ch Type
Analog TV
38
London
PAL-I (5 chs)
Paris
Barcelona
SECAM-L
PAL-B
(5 chs)
(tons of chs)
Digital TV
UHF (6 chs)
UHF (7 chs)
Others
FM
FM
UHF (12 chs)
FM (Strong!)
DAB (~200MHz)
Berlin
No
VHF (2 chs)
UHF (6 chs)
FM
Lessons Learned
39

Good sensitivity helps when input signal is weak.

Near ACI detection should be robust.

At some locations (fixed-point), signal changes quite fast.

All tuners need RF backed off significantly at Barcelona

[ACI] Field and Nordig/MBRAI conditions are very different

In the field, I/C ~ 10-30 dB; Nordig/MBRAI, I/C ~ 30-50 dB

In the field, many interference channels; Nordig/MBRAI, up to 2 channels.
Thanks !