Current Performance of DVB-T Current Performance of DVB-T Demodulators Demodulators Min-Chen Ho ITE Tech, Inc.
Dec 20, 2015
Current Performance of DVB-TCurrent Performance of DVB-TDemodulatorsDemodulators
Min-Chen Ho
ITE Tech, Inc.
4
Block Diagram from EN 300 744Block Diagram from EN 300 744(204,188)
Reed-Solomon64-state R=1/2
convolutional code
QPSK, 16QAM, 64QAM
5
DVB Transmission ModesDVB Transmission Modes 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.
6
OFDM ParametersOFDM Parameters Comments
Longer GI supports longer channel For 2K, GI=1/32, the channel must be shorter than 7s 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 supp
ort than 8K.
7
Signal Spectra ISignal Spectra I
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
504 516 528 540 552 564 576 588 600 612
Ref Level :
-40.0 dBm
dB / Div :
10.0 dB
M1M2
Spectrum Analyzer557FJ2
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 06/18/2008 Time: 14:52:39Min Sweep Time: 1.00 Milli SecStd: CDMA2000 Class 6 IMTRBW: 100 kHz VBW: 30 kHz Detection: RMS AverageCF: 557.0 MHz SPAN: 120.00 MHz Attenuation: Dynamic
dBm
Frequency (497.0 - 617.0 MHz)
M1: -63.40 dBm @ 556.7 MHz M2: -76.26 dBm @ 554.0 MHz533CTV
545PTS
557FTV 569
581TTV
593CTS599
8
Signal Spectra IISignal Spectra II
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
548 550 552 554 556 558 560 562 564 566
Ref Level :
-40.0 dBm
dB / Div :
10.0 dB
554.0 560.0
Spectrum Analyzer557CHUN
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 06/18/2008 Time: 12:50:03Min Sweep Time: 1.00 Milli SecStd: CDMA2000 Class 6 IMTChan Pwr: -71.96dBm Chan Pwr Density: -139.75dBm/Hz INT BW:6 MHzRBW: 30 kHz VBW: 10 kHz Detection: RMS AverageCF: 557.0 MHz SPAN: 20.00 MHz Attenuation: Dynamic
dBm
Frequency (547.0 - 567.0 MHz)
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
504 516 528 540 552 564 576 588 600 612
Ref Level :
-40.0 dBm
dB / Div :
10.0 dB
Spectrum Analyzer557-120CHUN
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 06/18/2008 Time: 13:20:34Min Sweep Time: 1.00 Milli SecStd: CDMA2000 Class 6 IMTRBW: 100 kHz VBW: 30 kHz Detection: RMS AverageCF: 557.0 MHz SPAN: 120.00 MHz Attenuation: Dynamic
dBm
Frequency (497.0 - 617.0 MHz)
10
Purpose of Standardized TestingPurpose of Standardized Testing 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)
11
AWGN PerformanceAWGN 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
Frequency
Input Signal Power
Reception OK
Sig
nal
Pow
er (
dBm
)
Bad Reception
System Noise Floor
C/N
Injected Noise Power
Frequency
Pmin (sensitivity)
Sig
nal
Pow
er (
dBm
)Pmax (strong signal)
Reception OK
Signal too weak
Signal too strong
Input Signal Power
System Noise Floor
12
Multipath Performance (Echo)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
SensitivityP0X(t-T0)
P1X(t-T1)P2X(t-T2)
X(t)
Transmitter Receiver
13
Multipath Performance (Echo)Multipath Performance (Echo) Example: 2-path 0-dB echo
time
X(t)
time
P0X(t – T0)P1X(t – T1)
-4 -3 -2 -1 0 1 2 3 4-350
-300
-250
-200
-150
-100
-50
0
50
Frequency (MHz)
Channel M
agnitude R
esponse (
dB
)
Frequency
Ave. Input Signal Power
Reception OK
Sig
nal
Pow
er (
dBm
)
System Noise Floor
C/N
Injected Noise Power
Frequency
Pmin (sensitivity)
Sig
nal
Pow
er (
dBm
)
Reception OK
Input Signal Power
System Noise Floor
14
Immunity Against Interference – ACI and CCIImmunity 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) 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 Immunity against interference – 干擾可以到多強還不會被蓋台
Desired
Interferer
N N+1Channel No.
Sig
nal
Pow
er (
dBm
)
ACI Immunity Desired
Interferer
NChannel No.
Sig
nal
Pow
er (
dBm
)CCI Immunity
15
Immunity Against Interference – ACI and CCIImmunity Against Interference – ACI and CCI
Example – CCI ( 可能發生在不同播放區的邊界 )
-15 -10 -5 0 5 10 15-80
-60
-40
-20
0
20
40
60
frequency (MHz)
magn
itude
(dB)
spectrum of ADC output, MT tuner
Video
Color
Audio (FM)
NICAM
-15 -10 -5 0 5 10 15-80
-60
-40
-20
0
20
40
60
frequency (MHz)
ma
gn
itu
de
(d
B)
spectrum of ADC output, MT tuner
PAL BG spectrum DVB-T Signal with PAL BG
17
Field TestingField 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 fro
m actual performance. Lab 中得到的 mobile performance 數據僅能供參考用
18
Transmitter @ London, UKTransmitter @ London, UK Location: Crystal Palace Park
Height: 219 m
Built: 1956
Transmission PAL-I Analog TV
DVB-T
FM
Measured Channel Power p_inband ~ -40 dBm
p_total ~ -20 dBm
路測道具
20
London - Frequency TableLondon - Frequency Table
Channel No. Freq (MHz)Power (kW)
Type MUX Modulation
22 482 20 D MUX2 8M,64QAM,2K,2/3,1/32
23 487.25 1000 A ITV
25 506 20 D MUX1 8M,16QAM,2K,3/4,1/32
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 8M,64QAM,2K,2/3,1/32
33 567.25 1000 A BBC2
34 578 20 D MUX5 8M,16QAM,2K,3/4,1/32
37 599.25 1000 A C5
21
London: UHF SpectraLondon: UHF Spectra
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
476 490 504 518 532 546 560 574 588 602
Ref Level :
-10.0 dBm
dB / Div :
10.0 dB
M1
Spectrum AnalyzerUK-CRP-140
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 03/18/2009 Time: 01:50:43Min Sweep Time: 1.00 Milli SecStd: AMPS / EIA 553RBW: 300 kHz VBW: 100 kHz Detection: RMS AverageCF: 540.0 MHz SPAN: 140.00 MHz Attenuation: Dynamic
dBm
Frequency (470.0 - 610.0 MHz)
M1: -62.54 dBm @ 502.55 MHz
482506 530 538 562 578
22
Transmitter @ Paris, FranceTransmitter @ 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
24
Paris: Frequency TableParis: Frequency Table
Channel No.
Freq. (MHz)Power (kW)
Type MUX Modulation
21 474 23 D R2 8M,64QAM,8K,2/3,1/32
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 8M,64QAM,8K,2/3,1/32
28 527.25 500 A France-3
29 538 20.9 D R5 8M,64QAM,8K,3/4,1/8
30 543.25 100 A France-5
32 562 23 D R6 8M,64QAM,8K,2/3,1/32
33 567.25 100 A M6
35 586 41 D R1 8M,64QAM,8K,3/4,1/8
25
Paris: UHF Spectra (Star Hotel)Paris: UHF Spectra (Star Hotel)
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
471.2 483.6 496.0 508.4 520.8 533.2 545.6 558.0 570.4 582.8
Ref Level :
-10.0 dBm
dB / Div :
10.0 dB
M1
Spectrum AnalyzerFR-STAR-FULL
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 03/20/2009 Time: 06:01:55Min Sweep Time: 1.00 Milli SecStd: AMPS / EIA 553RBW: 10 kHz VBW: 3 kHz Detection: RMS AverageCF: 530.0 MHz SPAN: 124.00 MHz Attenuation: Dynamic
dBm
Frequency (468.0 - 592.0 MHz)
M1: -97.87 dBm @ 590.14 MHz
474 490 498 522 538 562 586
27
Transmitter @ Barcelona, SpainTransmitter @ 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
29
Frequency Table (Bercelona)Frequency Table (Bercelona)Channel
No.Freq. (MHz)
Power (kW)
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
30
Barcelona: UHF SpectraBarcelona: UHF Spectra
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
475.2 514.8 554.4 594.0 633.6 673.2 712.8 752.4 792.0 831.6
Ref Level :
-10.0 dBm
dB / Div :
10.0 dB
M1
Spectrum AnalyzerSP-TIBI-FULL
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 03/22/2009 Time: 18:31:21Min Sweep Time: 50.00 Micro SecStd: AMPS / EIA 553RBW: 10 kHz VBW: 3 kHz Detection: RMS AverageCF: 666.0 MHz SPAN: 396.00 MHz Attenuation: Dynamic
dBm
Frequency (468.0 - 864.0 MHz)
M1: -85.88 dBm @ 548.19 MHz
482
498514 570 650
690794 818
834~858
32
Transmitter @ Berlin, GermanyTransmitter @ Berlin, Germany Location: Fernsehturm Berlin
(near Alexanderplatz)
Height: 368 m
Built: 1969
Transmission DVB-T
FM
Measured Channel Power p_inband ~ -40 dBm
p_total ~ -30 dBm
34
Berlin: Frequency TableBerlin: Frequency Table
Channel No.
Freq.
(MHz)
Power
(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
35
Berlin: VHF SpectraBerlin: VHF Spectra
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
156 162 168 174 180 186 192 198 204 210
Ref Level :
0.0 dBm
dB / Div :
10.0 dB
M1M2
Spectrum AnalyzerDE-ALE-VHF
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 03/27/2009 Time: 21:36:22 Average:10Min Sweep Time: 50.00 Micro SecStd: AMPS / EIA 553RBW: 100 kHz VBW: 30 kHz Detection: RMS AverageCF: 184.5 MHz SPAN: 60.00 MHz Attenuation: Dynamic
dBm
Frequency (154.5 - 214.5 MHz)
M1: -86.57 dBm @ 214.5 MHz M2: -86.57 dBm @ 214.5 MHz
177.5 191.5
177.5N+2 DACI (191.5)191.5:N-2 DACI (177.5)
36
Berlin: UHF SpectraBerlin: UHF Spectra
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
499.2 537.6 576.0 614.4 652.8 691.2 729.6 768.0 806.4 844.8
Ref Level :
0.0 dBm
dB / Div :
10.0 dB
M1M2
Spectrum AnalyzerDE-ALE-UHF
Model: MS2711D Serial #: 00639125 Preamp: DynamicDate: 03/27/2009 Time: 21:34:55 Average:5Min Sweep Time: 50.00 Micro SecStd: AMPS / EIA 553RBW: 300 kHz VBW: 100 kHz Detection: RMS AverageCF: 666.0 MHz SPAN: 384.00 MHz Attenuation: Dynamic
dBm
Frequency (474.0 - 858.0 MHz)
M1: -80.91 dBm @ 637.2 MHz M2: -80.91 dBm @ 637.2 MHz
506:N+2 DACI (522)522:N-2 DACI (506)570:N-6 DACI (522)658:N-11 DACI (570)N+12 DACI (754)
506 522 570 658
754 778
38
Summary – Signal ConditionsSummary – Signal Conditions
Ch Type London Paris Barcelona Berlin
Analog TV PAL-I (5 chs)SECAM-L
(5 chs)
PAL-B
(tons of chs)No
Digital TV UHF (6 chs) UHF (7 chs) UHF (12 chs)VHF (2 chs)
UHF (6 chs)
Others FM FMFM (Strong!)
DAB (~200MHz)FM
39
Lessons LearnedLessons Learned 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.