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Fragmented Broadcast World: Myth or Reality?

DVB-T deployed

DVB-T2 adopted

DVB-T adopted

ISDB-T adopted

CTTB, CMMB (China)

ATSC, T-DMB (Korea)

ATSC, ATSC M/H

ISDB-T deployed

DVB-T, a Digital Terrestrial Television (DTT) standard, was first published in 1997 and broadcasted in the UK in 1998. Since this date, many new Digital TV & Radio standards appeared in several countries as seen on the following world map:

This landscape may seem, at first glance, as a nightmare for chipset and device manufacturers who must invest significant amounts of money to develop devices for each standard with a relatively limited market opportunity. However a comparative analysis of the DTT standards structures shows that there is more convergence than it would appear to be at first. Despite this so-called fragmented Broadcast World, it is possible to find strong commonalities between the various standards thus allowing manufacturers to implement all these standards into a single programmable chip with minimum overhead costs as what has been previously done with modulators chipsets.

Most of the DTT standards use the same frequency band, and the

In order to facilitate the comparison between all the DTT standards, the set of configurable parameters (M-QAM, FFT size, Guard Interval, Inner and Outer codes rates, bandwidth) are listed in columns in the next two pages, together with the bit rate calculation formulas. In addition, the last column shows that some standards offer the possibility of In-band Mobile TV applications thanks to availability of sub-channels or Multi-Pipes.

In practice, the last table synthesizes the performances of the most used DTT configuration in the World and a final graph compares their spectrum efficiency versus the carrier-to-noise signal C/N required.

RF + Filters + A/D

Demodulation / Equalization(VSP)

M-QAM : 2 to 256SC; COFDM

FFT : 0.25k to 32kDiversity

Channel Decoding(Distributed CPUs + HW blocks)

Inner FEC: Turbo Codes, LDPC, Treillis,..Outer FEC : RS, BCH,..

De-Interleavers

Interfaces+ Control+ CAS

same modulation scheme composed of COFDM Multi-carriers or Single Carrier modulated in M-QAM, associated with inner code (Viterbi, Turbo code or LDPC) and outer code (Reed Solomon or BCH).

The following Block-diagram shows the required range of parameters of a programmable “multistandards” chipset, capable of demodulating in one IC, all the existing DTT World Standards. For any given standard to work, the receiver only has to download the associated microcode. There is therefore no need to change the Hardware.

White paper n°8 - Oct. 2011-Version 2b

World DTT Standards parameters

Standards FFT Symbol Rate [Msymbol/s] Inner FEC Outer FEC M-QAM Data_rate (Mbit/s) Multiple sub-channels or Pipes

DVB-T2k8k

{1/2; 2/3; 3/4; 5/6; 7/8} log2(M)No

GI= {1/32;1/16;1/8;1/4} BW[MHz]={6;7;8} Viterbi (CR) Reed-Solomon M= {4; 16; 64} Du_Max= 31.7 Mbit/s (in 8 MHz)

ISDB-T nSEGn = [1,2,….,13]

2k4k8k

{1/2; 2/3; 3/4; 5/6; 7/8} log2(M)Yes

13 SEG

SEG parameters :(M; CR; I, NSEG)GI= {1/32; 1/16; 1/8; 1/4 } BW= {6,8} Viterbi (CR) M= {2, 4, 16} Du_Max= 23.2 Mbit/s (in 6MHz)

CMMB4k; 8MHz

1k4k

5.46048 {1/2; 3/4} log2(M)Yes

40 slots

PLP parameters :(M; CR; I, Nslots)

39 x 0.13824 + 0.06912 BW= 8MHz LDPC M= {2, 4, 16} Du_Max= 16.4 Mbit/s (in 8 MHz)

CMMB1k; 2MHz

1.092096 {1/2; 3/4} log2(M)

Du_1k= Du_ 4k / 5 BW= 2MHz LDPC M= {2, 4, 16}

CTTB (DTMB)PN420

C=1(Single carrier)

or

C= 3780(4k)

Gi = Du_Max= 32.5 Mbit/s

NoCTTB (DTMB)PN595

GI = {47/117; 47/78; 94/117}{ “0.4”; “0.6”; “0.8”} 1 log2(M)

CTTB (DTMB)PN945

GI = LDPC + BCH M= {4; 16; 32; 64}Du_Max= 32.5 Mbit/s

DVB-T2

1k2k4k8k

16k32k

{1/2; 3/5; 2/3; 3/4; 4/5; 5/6} log2(M)

Yes

PLP parameters :(M; CR; I, bit rate)

FFT & PPcan be different in

DVB-T2 and DVB-T2 Lite frames

GI= {1/128; 1/32;1/16; 19/256; 1/8; 19/128; 1/4}

Na= Cdata(PPn,FFT) in Table 42 of DVB-T2 standard

(ETSI EN 302755v1.1.1)

BW[MHz]= {1.7; 5; 6;

7; 8}

Normal LDPC= {1/2 ; 3/5 ; 3/4; 4/5 ; 2/3 ; 5/6}Nldpc= 64800Nbch-Kbch=192 for LDPC= {1/2; 3/5; 3/4; 4/5}Nbch-Kbch=160 for LDPC= {2/3; 5/6}

Short LDPC= {4/9; 3/5; 2/3; 11/15 ; 7/9 ; 37/45 }Nldpc=16200Nbch-Kbch= 168

M= {4; 16; 64; 256}

+ Rotated constellations

Du_Max= 50.6 Mbit/s Du_Max= 32.5 Mbit/s

Note :

Does not include the P1 and P2 overhead (~ -0.3%)See § 6.3 of DVB Bluebook A133 ( Implementation Guideline for DVB-T2)

DVB-T2 Lite

2k4k8k

16k

Idem DVB-T2 except:no PP8

IdemDVB-T2

Short LDPC only

CR = {1/3; 2/5; 4/9; 3/5; 2/3; 11/15}

M= {4; 16; 64; 256} forLDPC= {1/3; 2/5; 4/9; 3/5}

M= {4; 16; 64} forLDPC= {2/3; 11/15}

ATSCSingle Carrier

10.6762774 2/3 187/207 log2(M) 19.289506No

BW= 6 MHz CR= Treillis Code M= 8Log2(M)= 3

ATSC-MH/CMM

Single Carrier

SCCC RS log2(M)= 3 0.152 Mb/s < PDR < 2.500 Mb/s0.9 Mb/s < MDRL < 7.3 Mb/s

Yes

associated with ATSC frameCR= {(2/3)x{1/2); (2/3)x(1/4)} PDR= Payload Data Rate (ATSC-MH)

MDRL= Main Data Rate Losses (ATSC)

204188

204188

}{240

240 ;224;192; 176

( )LDPCNldpcKbchNbchBCH

×−

−=1( )GIFFTNa

+1112

( ) ( )MCRBWGI 2log

204188

8175.6

××××+

( ) ( )MCRBWGI

n2log

204188

61218

××××+

( )MRSLDPC 2log46048.5 ×××

( )MRSLDPC 2log092096.1 ×××

( ) ( )MBCHLDPCBWGIFFT

Na2log

81112××××

+

( ) ( )MBCHLDPCBWGIFFT

Na2log

81112××××

+

235187;

223187;

211188

=RS

Radio/TVStandards FFT Symbol Rate [Msymbol/s] Inner FEC FEC Padding Outer FEC M-QAM Data_rate (Mbit/s) Multiple sub-

channels or Pipes

DVB-SHA

1k2k4k8k

{ 1/5; 2/9; 1/4; 2/7; 1/3 ;2/5 ;1/2; 2/3 } 1 log2(M)

No

GI= {1/32; 1/16; 1/8; 1/4}BW[MHz]= {1.7; 5; 8}

1.7 for 1k onlyTurbo code (TC)

Tc Ncu

2/7 798

1/4; 1/2 816

others 810

M= {4;16} Du_Max=17.2 Mbit/s (in 8 MHz)

DABDAB+TDMB

0,25k0,5k1k2k

1.152 CR 1 RS log2(M)= 2Yes

Sub-channels parameters:(CR, bit rate) FFT= {0.25k; 0.5k; 1k ; 2k}

CR_Viterbi :

Long_A: CR= {1/4; 3/8; 1/2; 3/4}Long_B: CR= {4/9; 4/7; 4/6; 4/5}Short : CR= {1/3;2/5;1/2;3/5;3/4}

RS=1 for DABRS= 110/ 120 for DAB+RS= 188/ 204 for T-DMB(for T-DMB add extra

losses up to 25% due to overhead of MPEG4

encapsulation into MPEG2)

M= 4

D - QPSK

p = 8 for Long_Ap = 32 for Long_B

integer part

Du_Max = 1.84 Mbit/s

( ) ( )MNcuTCBWGI 2log

189188

8168175.6

×××××+

pRSCRp

×

× 10002304

=.

( )GI+175.6

8BW

X

( )GIn+121

86

BWX

6BW

X

X

X

8BW

X

( )GI+175.6

8BW

712.1BW

189188

816×

Ncu

AcronymsNa = Number of data carriers

GI = Guard Interval

I = Interleaving

Ts = Symbol Duration

CR = Code Rate

FEC = Forward Error Correction

QAM = Quadrature Amplitude

Modulation

M = Number of Constelation points

SEG = Segment

SC = Single Carriers

Du = Data User Rate

2 3© Copyright DiBcom - MK1011 - DTT Broadcast world

19

.420=

3780

17108

595=

3780

1 4

945=

3780

( )BW

GI 81.7.488

×+

( )BW

GI 81.7.488

×+

( )MLDPC 2log××BWGI 81

.7.488

Du_Max= 32.5 Mbit/s

ConclusionThis paper shows similarities between the world DTT standards, allowing the design of a programmable “multistandard“ chipset that can cover all standards with minimum overhead.

For manufacturers, the fragmented Broadcast world is no longer a challenge, but an opportunity. In the very near future, one might think of a car that can drive anywhere and be capable of receiving all Radio and TV standards wherever it is driving, one might dream of a Tablet

It has to be noted that the chosen configurations are the most used, but they are not necessarily optimal in terms of spectral efficiency. Also, it appears clearly on this graph that the new DVB-T2 is the standard which has the best performance with respect to the spectral efficiency criteria.

In the next figure the spectral efficiency of DTT standards configurations analysed in the previous table are plotted versus their required Gaussian C/N and compared to the theoretical Shannon limit.

Currently deployed bit rates and Gaussian (C/N) by standard in some countries

In the following table the previous formulas are used to calculate the bit rate of most used DTT configurations used in the World. Some specified/measured values of C/N (Gaussian and TU6@10Hz Doppler) are also given in the last columns.

0

1

2

3

4

5

6

7

0 2 4 6 8 10 12 14 16 18 20

ISDB-T 12 SEG

DVB-T2 UK

DVB-T 64QAM 3/4

DVB-T 16QAM 2/3

ISDB-T 1 SEG CMMB DAB

CTTB SC 0.8

ATSC

DVB-T2 Lite 16QAM DVB-T2 Lite QPSK

CTTB 4k 0.6

CTTB 4k 0.8

DVB-SH

Spectral Efficiency C/N

(C/N) ______ [dB]

Spec

tral

Effi

cien

cy (b

it/s/

Hz)

that can receive HD TV signals anywhere without the constraints of which standard is available in that area. Despite the initial industry and political lobbying, one can see that Digital Communications always end up with somewhat the same scheme. And as history shows, sooner or later, semiconductor designers can implement everything at a reasonable consumer cost.

FECModul. BW

[MHz] Du [Mb/s]Spectral

efficiency(bit/s/Hz)

CountryC/N [dB]

Standards FFT GI inner outer Gaussian TU6_10Hz

DVB-T8k 1/4 2/3 188/204 16-QAM 8 13.27 1.66 Germany 11.8 22.5

8k 1/8 3/4 188/204 64-QAM 8 24.88 3.11 France 18.9

ISDB-T

Layer A NSEG=18k

1/8 2/3 188/204 QPSK 6 0.41617.27 2.88 Japon

5.5

Layer B NSEG=12 1/8 3/4 188/204 64-QAM 6 16.85 19.4 25.1

Layer A NSEG=18k

1/8 2/3 188/204 QPSK 6 0.44118.28 3.05 Brazil

5.5

Layer B NSEG=12 1/16 3/4 188/204 64-QAM 6 17.84 19.4 25.1

CMMB 4k 1/2 192/240 QPSK 8 4.37 0.55 Shanghaï 1.6 9.7

CTTB

PN420 4k 1/9 0.8 16-QAM 8 21.66 2.71 Beijing 12.8 20.6

PN595 SC 17/108 0.8 16-QAM 8 20.79 2.6 Shanghaï 13.1

PN945 4k 1/4 0.6 16-QAM 8 14.44 1.8 Shanghaï 10.4

ATSC SC 8-VSB 6 19.29 3.22 US 15

DVB-T2 32k ext 1/128 2/3 BCH 256-QAM 8 40.21 5.03 UK 17.8

DVB-T2 Lite + DVB-T2

Mobile Fix (HD)

8k 1/32 4/9 BCH QPSK 8 1.0234.38

0.754.30 UK trials

0.7

32k ext 1/128 2/3 BCH 256-QAM 8 33.36 5.03 17.8

DVB-T2 Lite + DVB-T2

Mobile Fix (HD)

8k 1/32 4/9 BCH 16-QAM 8 2.0435.40

1.54.43

5.5

32k ext 1/128 2/3 BCH 256-QAM 8 33.36 5.03 17.8

DVB-SH Satelite 2k 1/4 1/2 QPSK 5 3.36 0.67 Trials 2 6.5

DAB+ Radio 2k 1/2 RS D-QPSK 1.71 1.12 0.65 Germany 6.4 10.7

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Gaussian