Current Performance of DVB-T Demodulators

Current Performance of DVB-TCurrent Performance of DVB-TDemodulatorsDemodulators

Min-Chen Ho

ITE Tech, Inc.

2

OutlineOutline

DVB-T Physical Layer – EN 300744

Standardized DVB-T Testing

DVB-T Field Testing

DVB-T Physical Layer – EN300744DVB-T Physical Layer – EN300744

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)

Standardized DVB-T TestingStandardized DVB-T Testing

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

DVB-T Field TestingDVB-T Field Testing

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

19

London MapLondon Map

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

23

Paris MapParis Map

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

26

Paris (474MHz)Paris (474MHz)

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

28

Barcelona MapBarcelona Map

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

31

Barcelona (858MHz)Barcelona (858MHz)

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

33

Berlin MapBerlin Map

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

37

Berlin (506MHz)Berlin (506MHz)

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.

Thanks !Thanks !