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Introduction to DVB-T2 „Second Generation Digital Terrestrial Video Broadcasting“ © Copyright: Rohde&Schwarz Training Center Munich
Introduction toDVB-T2
„Second Generation DigitalTerrestrial Video Broadcasting“
© Copyright: Rohde&SchwarzTraining Center Munich
1MAT-Fi, 13.01.2010 | DVB-T2 | 2
What is DVB-T2 …
It is not DVB-T using MPEG-4 encoding …
It is a new DVB transmission standard forthe terrestrial world …
It is not backward-compatible to DVB-T …
It offers 30 … 50 % higher data rates than DVB-T.
1MAT-Fi, 13.01.2010 | DVB-T2 | 3
MPEG-4 within DVB-T
MPEG-4 AVC and MPEG-4 AAC encodingwithin DVB-T is of course possible …
DVB-T is only a transmission standard.
Countries installing DVB-T now are usingMPEG-4.
1MAT-Fi, 13.01.2010 | DVB-T2 | 4
DVB History
Source: DVB project
1MAT-Fi, 13.01.2010 | DVB-T2 | 5
DVB-TBaseband
signalForward Error
CorrectionModulation
MPEG-2 TS-packet structure-short packets ofconst. length
-asynchronous
ConcatenatedFEC:-scrambler,RS block code,convolutionalcoder withpuncturing
- short timeinterleaver
-COFDM usingQPSK, 16QAM, 64QAM
-absolute mapping-pilots for channel correction
2K mode-wide carrierspacing (4kHz)
-short symbols-short guard
8K mode-close carrierspacing (1kHz)
-long symbols-long guard
each packetheader has tobe analyzed(PID)
bad mobilereceptioncapability
bad mobilereceptioncapability, butgood for SFN‘s
better mobilereceptioncapability as 8K,but expensiveto build SFN‘s
powerintensive
1MAT-Fi, 13.01.2010 | DVB-T2 | 6
DVB-T -> DVB-HBaseband
signalForward Error
CorrectionModulation
MPEG-2 TS-packet structure-short packets ofconst. length
-asynchronous
ConcatenatedFEC:-scrambler,RS block code,convolutionalcoder withpuncturing
- short timeinterleaver
-COFDM usingQPSK, 16QAM, 64QAM
-absolute mapping-pilots for channel correction
2K mode-wide carrierspacing (4kHz)
-short symbols-short guard
8K mode-close carrierspacing (1kHz)
-long symbols-long guard
each packetheader has tobe analyzed(PID) bad mobile
receptioncapability
bad mobilereceptioncapability, butgood for SFN‘s
better mobilereceptioncapability as 8K,but expensiveto build SFN‘s
powerintensive
time slicingin-depthinterleaving+ add. FEC 4K mode
1MAT-Fi, 13.01.2010 | DVB-T2 | 7
DVB-T2
DVB-T2
„Second generation digital terrestrial televisionbroadcasting system“
Draft ETSI EN 302 755Draft finished in May 2008
1MAT-Fi, 13.01.2010 | DVB-T2 | 8
DVB-T2
•New DVB-T standard: ETSI EN 302 755(April 2008)
•Pushed by BBC.
•Higher data rates, better FEC (similar to DVB-S2),better mobile reception capability.
1MAT-Fi, 13.01.2010 | DVB-T2 | 9
DVB-T2 Overview•Multiple MPEG-2 transport stream inputs ormultiple generic stream inputs
•Same FEC as DVB-S2 (BCH+LDPC)•COFDM (1K, 2K, 4K, 8K, 16K and 32K mode)•QPSK, 16QAM, 64QAM, 256QAM•Bandwidth 10, 8, 7, 6, 5, 1.7 MHz•Q-delayed and rotated constellation diagrams•PLP = physical layer pipes / time slicing•Flexible pilot structure (8 pilot pattern)•Time interleaving•MISO and SISO mode•PAPR = peak average power reduction•Future extension frames
1MAT-Fi, 13.01.2010 | DVB-T2 | 10
From DVB-T to DVB-T2 …
From DVB-T to DVB-T2Data rates and required C/N
1MAT-Fi, 13.01.2010 | DVB-T2 | 11
Shannon‘s Law
);1(log 2 NSBC
Channel Capacity
);log(10][
;31
NSdBSNR
SNRBC
C[bit/s/Hz]
SNR[dB]Claude Elwood Shannon, USA 1948The Bell System Technical Journal„A Mathematical Theory of Communication“
S/N>>1:
C[bit/s]=Channel CapacityB[Hz]=Channel BandwidthS/N=Signal to Noise Ratio
1MAT-Fi, 13.01.2010 | DVB-T2 | 12
DVB-T2 … more Capacity …Shannon limit … channel capacity
C~=1/3 * SNR * B;
„Fixed antenna“ receptionSNR = 20 … 30 dB
„Portable indoor“ receptionSNR = 10 … 20 dB
B = 6/7/8MHz
using 8 MHz bandwidth:10 dB … 26.7 Mbit/s15 dB … 40 Mbit/s20 dB … 53.3 Mbit/s30 dB … 80 Mbit/s
Theoreticalmax. data rates
1MAT-Fi, 13.01.2010 | DVB-T2 | 13
DVB-T Datarates (8 MHz)Modulation Code rate Guard 1/4 Guard 1/8 Guard 1/16 Guard 1/32
Mbit/s Mbit/s Mbit/s Mbit/s
QPSK 1/2 4.976471 5.529412 5.854671 6.032086
2/3 6.635294 7.372549 7.806228 8.042781
3/4 7.464706 8.294118 8.782007 9.048128
5/6 8.294118 9.215686 9.757785 10.05348
7/8 8.708824 9.676471 10.24567 10.55617
16QAM 1/2 9.952941 11.05882 11.70934 12.06417
2/3 13.27059 14.74510 15.61246 16.08556
3/4 14.92941 16.58824 17.56401 18.09626
5/6 16.58824 18.43137 19.51557 20.10695
7/8 17.41765 19.35294 20.49135 21.11230
64QAM 1/2 14.92941 16.58824 17.56401 18.0926
2/3 19.90588 22.11765 23.41869 24.12834
3/4 22.39412 24.88235 26.34602 27.14439
5/6 24.88235 27.64706 29.27336 30.16043
7/8 26.12647 29.02941 30.73702 31.66845
Portableindoor
Fixedantennaoutdoor
1MAT-Fi, 13.01.2010 | DVB-T2 | 14
DVB-T and DVB-T2
DVB-T, Germany portable indoor: 13.27 Mbit/s
DVB-T, fixed antenna: 22.39 Mbit/s
DVB-T2: 30 … 50 % more data rate:
an coarse estimation …
17 … 20 Mbit/s portable indoor
29 … 33 Mbit/s fixed antenna
1MAT-Fi, 13.01.2010 | DVB-T2 | 15
Example: DVB-T2 Capacity
8 MHzchannel,32K mode,g=1/128,PP7
Source:DVB-T2ImplementationGuidelinesA133February 2009
2026050.325/6256QAM
2026048.274/5256QAM
2026045.243/4256QAM
2026040.212/3256QAM
2026036.143/5256QAM
2026030.081/2256QAM
1516037.625/664QAM
1516036.094/564QAM
1516033.823/464QAM
1516030.062/364QAM
1516027.023/564QAM
1516022.481/264QAM
1016025.165/616QAM
1016024.144/516QAM
1016022.623/416QAM
1016020.112/316QAM
1016018.073/516QAM
1016015.041/216QAM
506012.465/6QPSK
506011.954/5QPSK
506011.203/4QPSK
50609.952/3QPSK
50608.943/5QPSK
50607.441/2QPSK
FEC blocks per frameFrame length[symbols]
Bitrate [Mbit/s]CoderateModulation
1MAT-Fi, 13.01.2010 | DVB-T2 | 16
Fall-off-the-Cliff
A digital TV transmission runs til fall-off-the-cliff, thatmeans go or no-go.
All interferences causesmore or less bit errors.If the bit error ratio is toohigh, then the FEC in thereceiver will fail. Thatmeans no-go or fall-off-the-cliffif there are to many bit errors.
go no-go
1MAT-Fi, 13.01.2010 | DVB-T2 | 17
C/N Limits @ DVB-TTyp of modulation Code rate Gaussian channel Rice channel Rayleigh channel
[dB] [dB] [dB]QPSK 1/2 3.1 3.6 5.4
2/3 4.9 5.7 8.43/4 5.9 6.8 10.75/6 6.9 8.0 13.17/8 7.7 8.7 16.3
16-QAM 1/2 8.8 9.6 11.22/3 11.1 11.6 14.23/4 12.5 13.0 16.75/6 13.5 14.4 19.37/8 13.9 15.0 22.8
64-QAM 1/2 14.4 14.7 16.02/3 16.5 17.1 19.33/4 18.0 18.6 21.75/6 19.3 20.0 25.37/8 20.1 21.0 27.9
portableindoor
fixed
1MAT-Fi, 13.01.2010 | DVB-T2 | 18
C/N Limits @DVB-T2 @ BER=10-4 after LDPC
25.725.322.321.85/6
24.424.221.521.14/5
22.522.520.219.73/4
20.020.017.817.52/3
18.218.116.015.63/5
15.315.413.312.81/2256QAM
20.119.917.216.65/6
18.919.016.415.94/5
17.317.515.314.93/4
15.115.413.613.22/3
13.613.812.111.73/5
11.511.710.09.61/264QAM
14.214.411.811.25/6
13.213.411.110.64/5
11.912.210.39.83/4
10.210.58.98.62/3
8.89.17.77.43/5
7.07.36.15.71/216QAM
7.27.25.65.05/6
6.46.85.04.54/5
5.55.94.33.93/4
4.24.63.32.92/3
3.03.42.42.13/5
1.51.81.00.81/2QPSK
C/N 0dB EchoChannel @ 90% GI[dB]
C/N Rayleigh Channel[dB]
C/N Ricean Channel[dB]
C/N GaussianChannel[dB]
CoderateModulation
LDPCblocklength64800bits
1MAT-Fi, 13.01.2010 | DVB-T2 | 19
C/N Limits @DVB-T2 @ BER=10-4 after LDPC
25.925.622.522.05/6
24.324.221.721.24/5
22.722.620.419.93/4
20.320.318.117.72/3
18.818.816.916.53/5
14.314.412.412.11/2256QAM
20.320.317.416.85/6
18.919.116.616.14/5
17.617.815.615.23/4
15.515.713.813.42/3
14.014.212.412.03/5
10.510.79.18.71/264QAM
14.414.612.011.45/6
13.313.611.310.84/5
12.112.410.510.03/4
10.410.79.18.82/3
9.09.37.97.53/5
6.36.65.55.21/216QAM
7.47.85.75.15/6
6.56.95.14.64/5
5.76.04.54.03/4
4.44.73.43.12/3
3.23.52.42.23/5
1.21.50.70.41/2QPSK
C/N 0dB EchoChannel @ 90% GI[dB]
C/N Rayleigh Channel[dB]
C/N Ricean Channel[dB]
C/N GaussianChannel[dB]
CoderateModulation
LDPCblocklength16200bits
1MAT-Fi, 13.01.2010 | DVB-T2 | 20
BER after LDPC and after BCH
BER = 10-4 after LDPCcorresponds to a BER = 10-7 after BCH
BER = 10-7 after LDPCcorresponds to a BER = 10-11 after BCH
1MAT-Fi, 13.01.2010 | DVB-T2 | 21
Block Diagram of a DVB-T2 Modulator
Inputpre-pro-
cessor(s)
MultipleTS or GSstreams
Inputprocessing
Bit inter-leaved
coding &modulation
Framebuilder
COFDMgeneration
Up to 255 input streams
1MAT-Fi, 13.01.2010 | DVB-T2 | 22
Stream Adaptation, DVB-T2 Input Mode B
Sch
edul
er
PLP0
PLP1
PLPn
……
..Framedelay
BBscrambler
In-bandsignalling/padding
Frame m Frame m-1
ToBICM
module
L1 dynPLP0(m)
L1 dynPLP0-n(m)
Dynamicschedulinginformation
Framedelay
BBscrambler
In-bandsignalling/padding
L1 dynPLPn(m)
Framedelay
BBscrambler
In-bandsignalling/padding
L1 dynPLP1(m)
…..
1MAT-Fi, 13.01.2010 | DVB-T2 | 23
DVB-T2: Mode A and Mode BMode A:•Single PLP (Physical Layer Pipe)•Only one input stream (MPEG-2 TS or generic)•One or several services in the input stream•Simple structure similar to DVB-T•Equal error protection
Mode B:•Multiple PLP•Several input streams (MPEG-2 TS or generic)•One or several services in each input stream•Complex structure•Variable Coding and Modulation (VCM)
1MAT-Fi, 13.01.2010 | DVB-T2 | 24
T2-MI – Modulator Interface
Sch
edul
er
PLP0
PLP1
PLPn
……
..Framedelay
BBscrambler
In-bandsignalling/padding
Frame m Frame m-1
ToBICM
module
L1 dynPLP0(m)
L1 dynPLP0-n(m)
Dynamicschedulinginformation
Framedelay
BBscrambler
In-bandsignalling/padding
L1 dynPLPn(m)
Framedelay
BBscrambler
In-bandsignalling/padding
L1 dynPLP1(m)
…..
T2-MI
Padding
Padding
Padding
T2gateway Modulator
1MAT-Fi, 13.01.2010 | DVB-T2 | 25
T2-MI Packet Structure
T2-MIheader
Payload
48 bits Payload length bits
Packettype
Packetcount
Superframeindex Reserved
Payloadlength
Pad CRC32
0…7 bits 32 bits
1MAT-Fi, 13.01.2010 | DVB-T2 | 26
T2-MI Packet Type
Reserved for future useAll other values
FEF part: I/Q data0x31
FEF part: Null0x30
Individual addressing0x21
DVB-T2 timestamp0x20
L1 future0x11
L1 current0x10
Auxilliary stream I/Q data0x01
Baseband frame0x00
DescriptionT2-MI packet type
1MAT-Fi, 13.01.2010 | DVB-T2 | 27
DVB-T2 Modulator Interface
ETSI TS 102 773
„T2-MI“
Modulator Interface
ASI
RTPUDPIP
Ethernet
MPEG-2 TS/GSETS data (BB frames)
T2-MI packetsDVB Data Piping
DVB/MPEG-2 TS
DVB-IP Phase 1(MPEG TS over IP)
L1, SFN info,Aux DataStreams
1MAT-Fi, 13.01.2010 | DVB-T2 | 28
Data Piping: T2-MI in MPEG-2 TS
Payload Payload PayloadH H H
T2-MI packet T2-MI packet
PointerPayload unit start indicator = 1
1MAT-Fi, 13.01.2010 | DVB-T2 | 29
DVB-T2 Network Structure (SFN)
DVB-T2Gateway
DVB-T2mod.&Tx
DVB-T2mod.&Tx
DVB-T2mod.&Tx
T2-MI
In 0
In 1
In n
RF
RF
RF
1MAT-Fi, 13.01.2010 | DVB-T2 | 30
DVB-T2 Block Diagram
DVB-T2 Block Diagram
1MAT-Fi, 13.01.2010 | DVB-T2 | 31
DVB-T2 Block DiagramPLP 0
PLP n
Mod
e/st
ream
adap
tatio
n
FECCell
builder MapperCell
inter-leaver
Timeinter-leaver
Freq
uenc
yin
terle
aver
FECCell
builder MapperCell
inter-leaver
Timeinter-leaver
MISOproc.
Pilotinsert.
IFFT PAPRred.
Guardinterv.insert.
P1symbolInsert.
DA Tx1
Pilotinsert.
IFFT PAPRred.
Guardinterv.insert.
P1symbolInsert.
DA Tx2
(optional)
......
......
Fram
ebu
ilder
Totransmitters
1MAT-Fi, 13.01.2010 | DVB-T2 | 32
DVB-T2 Block Diagram (Gateway + Modulator)PLP 0
PLP n
Mod
e/st
ream
adap
tatio
n
FECCell
builder MapperCell
inter-leaver
Timeinter-leaver
Freq
uenc
yin
terle
aver
FECCell
builder MapperCell
inter-leaver
Timeinter-leaver
MISOproc.
Pilotinsert.
IFFT PAPRred.
Guardinterv.insert.
P1symbolInsert.
DA Tx1
Pilotinsert.
IFFT PAPRred.
Guardinterv.insert.
P1symbolInsert.
DA Tx2
(optional)
......
......
T2-MI
Stre
amad
apta
tion
part
2
Fram
ebu
ilder
Totransmitters
T2 gateway
1MAT-Fi, 13.01.2010 | DVB-T2 | 33
Comparison: DVB-T Modulator & Transmitter (1)
FEC LPSymbolInter-leaver
FrameAdapt. IFFT
GuardInterv.Insert.
Pre-Corr.
FIRFilter
FEC HP(Option)
Dem
ux BitInter-leaver
Band-PassFilter
IF
RF
Map
per
PowerAmpl.
TS1
TS2
Pilots, TPS
C(oded) O(rthogonal) F(requency) D(ivision) M(ultiplex)
(2, 4, 6)
1MAT-Fi, 13.01.2010 | DVB-T2 | 34
Comparison: DVB-T Modulator & Transmitter (2)
Base-bandInterf.
SyncInvers.
EnergyDisp.
Reed-Solom.Enc.
Conv.Inter-leaver
Conv.Coder
Puncturing
Synchronization
Inv. Sync.
TS In
same as DVB-C
same as DVB-S
Code Rate1/2...(3/4)...7/8
FEC1/OuterCoder
FEC2/InnerCoder
Data Rate In
= Date Rate Out[2.17...(1.63)...1.36]
x 204/188 x 2 x (1.5-Code Rate)
CodedDataOut
1MAT-Fi, 13.01.2010 | DVB-T2 | 35
DVB-T2 Forward Error Correction
DVB-T2 Forward Error Correction
1MAT-Fi, 13.01.2010 | DVB-T2 | 36
Forward Error Correction @ DVB-T2
Basebandscrambler
BCHencoder
LDPCencoder
Bitinterleaver
BCH=Bose-Chaudhuri-HocquenghemLDPC=Low Density Parity Check Code
Same FEC as in DVB-S2
1MAT-Fi, 13.01.2010 | DVB-T2 | 37
FEC Frame
Data fieldBasebandheader
80 bits
Padding
BCH
LDPC
Outer FEC: BCH coding
Inner FEC: LDPC coding
kBCH
DFL
Data from MPEG-2 TS or generic data
16*tBCH bits
tBCH=8,10,12
64800 or 16200 bits FEC frame
kLDPC = code rate * FEC frame Coderate
1MAT-Fi, 13.01.2010 | DVB-T2 | 38
Coderates
5/6
4/5
3/4
2/3
3/5
1/2
Coderate
Data rates from7.49 Mbit/s (QPSK, CR=1/2)
up to50.32 Mbit/s (256QAM, CR=5/6)
1MAT-Fi, 13.01.2010 | DVB-T2 | 39
DVB-T2 Modulation Pattern
DVB-T2 Modulation Pattern
1MAT-Fi, 13.01.2010 | DVB-T2 | 40
Definition of a Cell
A cell is a mapped IQ value
n bits
Mapping
2n = N constellation pointsCell
I Q
n=2, 4, 6, 8
N=4, 16, 64, 256
1MAT-Fi, 13.01.2010 | DVB-T2 | 41
Modulation Pattern
QPSK 16QAM 64QAM 256QAM
Gray coded constellation diagrams(QPSK, 16QAM, 64QAM indentical to DVB-T)
1MAT-Fi, 13.01.2010 | DVB-T2 | 42
Rotated and Q-delayed Constellation Diagram
I
Q
1MAT-Fi, 13.01.2010 | DVB-T2 | 43
Rotated Constellation Diagram
Rotation of constellation diagram gives differentprojection points on I and Q axis for each constellationpoint instead of same projection point in case ofnon-rotated diagram.
This can be used for soft-decision.
atan(1/16)8.616.829.0ΦΦ (degrees)
256QAM64QAM16QAMQPSKMod.
Ration angle for each modulation type:
1MAT-Fi, 13.01.2010 | DVB-T2 | 44
Non-rotated Constellation Diagram
I
Q
1MAT-Fi, 13.01.2010 | DVB-T2 | 45
Rotated Constellation Diagram
I
Q
1MAT-Fi, 13.01.2010 | DVB-T2 | 46
Rotated Q-delayed Constellation Diagramn bits
Mapping
2n = N constellation pointsCell
I Q
n=2, 4, 6, 8
N=4, 16, 64, 256
Rotation
Cellk Cellk+1
I Q QQ-delayfromk-1
I
1MAT-Fi, 13.01.2010 | DVB-T2 | 47
Q-delayed Constellation Diagrams
Cell 4
I4 Q3
Cell 5
I5 Q4
Cell 6
I4 Q5
Cell 7
I4 Q6
Afterwards there is the cell interleaving.
1MAT-Fi, 13.01.2010 | DVB-T2 | 48
Rotated Q-delayed Constellation DiagramAdvantage:
Information of each constellation point is now bothon I and Q axis.
Q part is delayed on another cell.
Cells will be interleaved and the I part cariing cell isduring the transmission far away from the Q part carriingcell.
Frequency selective interferences can be bettercompensated.
1MAT-Fi, 13.01.2010 | DVB-T2 | 49
DVB-T2 COFDM Parameters
DVB-T2 COFDM Parameters
1MAT-Fi, 13.01.2010 | DVB-T2 | 50
COFDM Subcarriers
f
Channel bandwidthΔf
10, 8, 7, 6, 5, 1.7 MHz
1MAT-Fi, 13.01.2010 | DVB-T2 | 51
COFDM Symbols with Guard Interval
Symbol n+1Symbol nGuard interval
1MAT-Fi, 13.01.2010 | DVB-T2 | 52
DVB-T2 COFDM Parameters
8.9290.1121K
4.4640.2242K
2.2320.4484K
1.1160.8968K
0.5581.79216K
0.2793.58432K
CarrierSpacing[kHz]
Symbolduration[ms]
FFTsize
in 8 MHz channel bandwidth
8K, 16K and 32K mode: normal or extended carrier mode
1MAT-Fi, 13.01.2010 | DVB-T2 | 53
OFDM Spectrum
Δf
1MAT-Fi, 13.01.2010 | DVB-T2 | 54
Spectrum in 1K and 32K Mode
1MAT-Fi, 13.01.2010 | DVB-T2 | 55
Influence of No. of OFDM Carriers
Each carrier is a sin(x)/x function.
The shoulders are an overlay of all sin(x)/x functions ofall carriers out of band.
The shoulder is more and more suppressed the moreOFDM carriers are in use.
1K, 2K, 4K, 8K, 16K, 32K mode
Higher shoulder Lower shoulder
1MAT-Fi, 13.01.2010 | DVB-T2 | 56
Extended Carrier Mode
In 8K, 16K and 32K mode a wider spectrumcan be used because of the lower shoulder.
This is called extended carrier mode.
The data rate in extended carrier mode ishigher than in normal carrier mode.
1MAT-Fi, 13.01.2010 | DVB-T2 | 57
32K Mode and 32K Extended Carrier Mode
1MAT-Fi, 13.01.2010 | DVB-T2 | 58
32K Mode and 32K Extended Carrier Mode
256QAMCR=3/5PP7
32K:35.246Mbit/s
32K extended:36.140 Mbit/s
1MAT-Fi, 13.01.2010 | DVB-T2 | 59
32K extended and non-critical Mask Filter
1MAT-Fi, 13.01.2010 | DVB-T2 | 60
DVB-T2 COFDM Parameters
X--X--X----0.1121K
X--X--XX--0.2242K
X--X--XX--0.4484K
XXXXXXX0.8968K
XXXXXXX1.79216K
--XXXXXX3.58432K
g=1/4
g=19/128
g=1/8
g=19/256
g=1/16
g=1/32
g=1/128
Symbolduration[ms] in8 MHz
FFTsize
Guard interval sizes
1MAT-Fi, 13.01.2010 | DVB-T2 | 61
DVB-T2 Spectrum
Center carrier
Channelbandwidth
IFFTbandwidth
Signalbandwidth
Carrier # 0 Carrier # n
1MAT-Fi, 13.01.2010 | DVB-T2 | 62
OFDM Parameters in a 8 MHz Channel
7.777.777.71NANANASignal bandwidth inextended carrier mode[MHz]
7.617.617.617.617.617.61Signal bandwidth innormal mode [MHz]
0.2790.5581.1162.2324.4648.929Carrier spacing [kHz]
35841792896448224112Symbol duration [us]
32768163848192409620481024IFFT
59628896000Additional carriers inextended carrier mode
27841139216913NANANANo. of carriers inextended carrier mode
2726513633681734091705853No. of carriers innormal mode
32K mode16K mode8K mode4K mode2K mode1K modeParameter
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Channel Bandwidth
9.517.616.665.714.761.54Signal bandwidth innormal carrier mode[MHz]
7/807/641/87/487/4071/131Elementary period [us]
1087651.7Bandwidth [MHz]
1MAT-Fi, 13.01.2010 | DVB-T2 | 64
Frame Builder
Frame Builder
1MAT-Fi, 13.01.2010 | DVB-T2 | 65
T2 Frame Structure
P1 P2 Payload symbols PLPx
T2 frame
P2 symbols containing signalling data
P1 symbol for synchronization and frame detection
from each input there is one PLP = PhysicalLayer Pipe, which can be differently modulated
1MAT-Fi, 13.01.2010 | DVB-T2 | 66
T2 Frame Structure
P1 P2 Payload symbols PLPx
T2 frame
P2 symbols containing signalling data
P1 symbol for synchronization and frame detection
From each input there is one PLP = PhysicalLayer Pipe, which can be modulated usingdifferent modulation parameters.
PLP0 PLP1
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P1 SymbolP1 = preamble symbol 1
•Initial signal for T2 frame detection•Signalling of basic transmission parameters•Frequency and time synchronization
•1K symbol with two ½ guard-like portions before andafter the symbol•Good, double correlation, quick detection of P1-symbol•Carriers are DBPSK modulated (differential infrequency (carrier) direction)
GuardGuard P1524samples
482samples
1024samples
+Δf+Δf
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P1 Symbol
7 bits signalling:
SISO/MISO/future useFFT size + partial guard interval informationUse of FEF = Future Extension Frames
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P2 SymbolContains L1 (layer 1) signalling (physical transmissionparameters of Physical Layer Pipes = PLP)
There is not only one P2 symbol; the no. of P2 symbolsdepends on the FFT mode (1 … 16 P2 symbols).
A P2 symbol consists of a L1 pre-signalling and aL2 post signalling part.
P2 P2
L1 pre-signalling
L1 post-signalling
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L1 Signalling inside P2 Symbol
Part 1 (const. length)
L1 pre-signalling:
Guard intervalPilot patternCell IDNetwork IDPAPR useNumber of data symbolsL1 post signalling parameters(FEC and mod. of L1 post)
Part 2 (var. length):
L1 post-signalling:
Number of PLP‘sRF frequenciesPLP ID‘sPLP signalling parameter(FEC and mod. of PLP)
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FEC and Modulation of P2 Symbols
P2 pre-signalling part:
Mod: BPSK
FEC: BCH + 16K LDPCLDPC-CR=1/4
P2 post-signalling part:
Mod.: BPSK, QPSK,16QAM, 64QAM
FEC: BCH + 16K LDPCLDPC-CR = ½, ¼ if BPSKLDPC-CR = ½ if QPSK,16QAM, 64QAM
P2 P2
L1 pre-signalling
L1 post-signalling
(P2 symbols also contain some PLP data cells)
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No. of P2 Symbols
132K
116K
28K
44K
82K
161K
No. of P2symbols
FFT size
The capacity of a P2 symbol depends on FFT size, that is thereason why the no. of P2 symbols depends on FFT size:
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Variable Coding and Modulation
Time
Datarate
HD
TV1
SD
TV1
HD
TV2
Rad
io1
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DVB-T2 Frame Structure
Super Frame Super Frame Super Frame
T2-frame 0 T2-frame 1 T2-frame 2 T2-frame NT2-1FEF FEF
P1P20
P2NP2-1
Datasymb.
0
Datasymb.
1
Datasymb.Ldata-1
TSF
TF
TSTSTP1
… …
…
…
FEF = Future Extension Frame
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T2 Frame Structure
P1 P2
T2 frame
CommonPLP‘s
Data PLP‘stype 1
Data PLP‘stype 2
Auxillarydata
Dummycells
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Maximum DVB-T2 Frame Length
1784NA1982NA2098NANA1121K892NA991NA10491081NA2242K446NA495NA524540NA4484K2232422472592622702768968K
111121123129131135138179216KNA606064646668358432K
g=1/4
g=19/128
g=1/8
g=19/256
g=1/16
g=1/32
g=1/128
Symbolduration[us]
FFTsize
Max. frame length in no. of OFDM symbols
Max. DVB-T2 frame length = 250 ms
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Maximum Length of a Super Frame
Max. length of a super frame:
No FEF‘s in use: 64 s or 255 frames of 250 ms
FEF‘s in use: 128 s
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Interleaving in DVB-T2
Interleaving in DVB-T2
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Interleaving in DVB-T2
DVB-T2 uses 4 different interleavers:
1) Bit interleaver after FEC based on a LDPC word2) Cell interleaver after mapping based on a FEC frame3) Time interleaver after cell interleaver based on a TI frame4) Frequency interleaver before IFFT based on a symbol
1) and 3) are block interleavers
2) and 4) are pseudo random permutation interleavers
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Interleaver in DVB-T2
FEC Bitinterleaver
MappingCell
interleaverTime
interleaver
Frequencyinterleaver IFFT
I
Q
PLP0
FEC Bitinterleaver
MappingCell
interleaverTime
interleaver
I
Q
PLP1
FEC Bitinterleaver
MappingCell
interleaverTime
interleaver
I
Q
PLPn Fram
ebu
ilder
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Task of Interleavers in DVB-T2
1) Bit interleaver interleaves code bits in a LDPC word
2) Cell interleaver interleaves mapped IQ values in a FEC frame
3) Time interleaver is a protection against long impulsive interferers
4) Frequency interleaver is a protection against frequencyselective interferers (e.g. notches)
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Comparison with DVB-T
DVB-T:
1) Convolutional interleaving between FEC1 and FEC22) Bit and symbol interleaving before mapping (=
frequency interleaver)
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DVB-T2 Time Interleaver
DVB-T2 timer interleaver
-DVB-T2 time interleaver is a block interleaver.-Operates on PLP level.-A integer no. of FEC blocks from the cell interleaveris grouped into interleaving frames.
-No. of FEC blocks per interleaving frame: 0 … 1023
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DVB-T2 Time InterleaverFEC blocksof one PLP
TI block
Timeinterleaver
Interleaving frame
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Configuration Parameters of Time Interleaver
TI configuration parameters:
TIME_IL_TYPE (1 bit) 0 or 1TIME_IL_LENGTH (8 bit) in blocks per interleaving frameFRAME_INTERVAL (8 bit) in framesPLP_NUM_BLOCKS_MAX (10 bit) 0 … 1023
The TI configuration parameters are signalled inthe L1-post signalling part of P2 symbols.They are independent for each PLP.
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Time Interleaver Configuration
1) 1 TI block in 1 interleaving frame mapped in 1 T2 frame(TIME_IL_TYPE = 0, TIME_IL_LENGTH = 1)
2) 1 TI block in 1 interleaving frame mapped in more thanone T2 frame with at distance of n frames(TIME_IL_TYPE = 1, FRAME_INTERVAL = n)
3) m TI blocks in 1 interleaving frame mapped in 1 T2 frame(TIME_IL_TYPE = 0, TIME_IL_LENGTH = m)
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Time Interleaver Configuration (1)
TI block
Interleavingframe
T2 frame T2 frame T2 frame
TI block
Interleavingframe
TI block
Interleavingframe
k FEC blocks
0 < k < PLP_NUM_BLOCKS_MAXk is a varying number
TIME_IL_TYPE = 0
Application:mode Amediumdata rateormode Bhigh datarate
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Time Interleaver Configuration (2)
TI block
Interleavingframe
T2 frame T2 frame T2 frame
k FEC blocks
0 < k < PLP_NUM_BLOCKS_MAXk is a varying number
FRAME_INTERVAL = 2
TIME_IL_TYPE = 1
Application:mode Blowdata rate;bestinterleaving
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Time Interleaver Configuration (3)
TIblock 0
Interleavingframe
T2 frame T2 frame T2 frame
TIblock 3
TI2 TIME_IL_LENGTH = 3
TIME_IL_TYPE = 0
Application:mode A singlePLP, BBC modeor high datarates in mode B
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Sub-Slicing
Sub-Slicing in DVB-T2
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Sub-Slices
Sub-Slicing:
•A PLP can be devided into several sub-slices (2 … 6480).•PLP‘s containing sub-slices are called „Type 2 PLP‘s“.
Less sub-slices More sub-slices
Less time diversityMore power savingin Rx possible
More time diversityLess buffer memory
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Sub-Slicing
1 2 3 … M 1 2 3 … M 1 2
Sub-sliceinterval
T2-frame
Sub-slice
In sub-slicing mode a PLP is not transmittedin one portion but in small portions.
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Time Frequency Slicing
Time Frequency Slicing (TFS):
DVB-T2 standard also decribes possibily todistribute PLP‘s over 2 … n RF channels.
2 tuners would be required in the receiver.
NorDig spec for DVB-T2 talks about TFS.
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PLP Types
PLP Types
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PLP TypesPLP types:
Common PLP:PLP having one slice per T2-frame, transmitted justafter L1 signalling, which may contain data shared bymultiple PLP‘s.
Type 1 PLP:PLP having one slice per T2-frame,transmitted before any Type 2 PLP
Type 2 PLP:PLP having two or more sub-slices per T2-frame,transmitted after any Type 1 PLP.
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T2 Frame Structure
P1 P2
T2 frame
CommonPLP‘s
Data PLP‘stype 1
Data PLP‘stype 2
Auxillarydata
Dummycellsdata shared by
multiple PLP‘sone slice per
T2-frame
two or moresub-slices
per T2-frame
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Pilots
Pilots in DVB-T2
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Pilots in DVB-T2Purpose of pilots in COFDM:-Synchronization-Channel estimation
DVB-T uses 3 types of „special carriers“:-Continual pilots-Scattered pilots-TPS carriers
DVB-T2:-Edge pilots-Continual pilots-Scattered pilots (DVB-T2 offers 8 different pilot patterns)-Frame closing pilots-P2 pilots
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Scattered Pilot Patterns
166 (96)PP8424 (96)PP7224 (48)PP6412 (48)PP5212 (24)PP446 (24)PP326 (12)PP2
43 (12)PP1
Number of symbols d3forming one scatteredpilot sequence
Distance d1between pilotcarrier positions(anddistance d2 in onesymbol)
Pilot pattern
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Pilot Pattern Parameter
….
….
0 i
Frequency (carrier no.)
….
….
d1
d2
d3
d1 = distance between scattered pilot carrier positionsd2 = distance between scattered pilots in one symbold3 = symbols forming one scattered pilot sequence
Time
Edgepilot
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Scattered Pilot Pattern in SISO Mode
PP1NAPP2PP3
NAPP4PP5
NANA1K
PP1NAPP2PP3
NAPP4PP5
PP7PP4
NA4K, 2K
PP1PP8
PP2PP3PP8
PP2PP3PP8
PP8PP4PP5
PP8PP4PP5
PP7PP4
PP78K
PP1PP8
PP2PP3PP8
PP2PP3PP8
PP2PP8PP4PP5
PP2PP8PP4PP5
PP7PP4PP6
PP716K
NAPP2PP8
PP2PP8
PP2PP8PP4
PP2PP8PP4
PP4PP6
PP732K
g=1/4
g=19/128
g=1/8
g=19/256
g=1/16g=1/32
g=1/128
FFTsize
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Scattered Pilot Pattern in MISO Mode
NANAPP1NAPP3NANA1K
NANAPP1NAPP3PP4PP5
NA4K, 2K
NAPP1PP8
PP1PP8
PP3PP8
PP3PP8
PP8PP4PP5
PP8PP4PP5
8K
NAPP1PP8
PP1PP8
PP3PP8
PP3PP8
PP8PP4PP5
PP8PP4PP5
16K
NANANAPP2PP8
PP2PP8
PP8PP4
PP8PP4PP6
32K
g=1/4
g=19/128
g=1/8
g=19/256
g=1/16g=1/32
g=1/128
FFTsize
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Amplitudes of the Scattered Pilots
7.47/3PP5, PP6, PP7, PP84.97/4PP3, PP42.54/3PP1, PP2
Equivalent boost [dB]AmplitudeScattered pilot pattern
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PAPR (Peak to Average Power Ratio) Reduction
PAPRReduction
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Crest Factor
Cf = 20 * log(upeak/Urms);
CfOFDM = 10 * log(2 * N);
Theoretical crest factor of DVB-T: 36...41 dB
Practical values: approx. 15 dB (no clipping)approx. 11...13 dB (clipping inside power Tx)
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Efficiency of a Class AB Amplifier (typical)
Drain Efficiency %
0
5
10
15
20
25
30
35
0 10 20 30 40 50 60 70 80
Pout in W
Drai
nEf
ficie
ncy
%
Drain Efficiency %
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PAPR
Peak to Average Power Reduction
ACEActive Constellation
Extension
TRTone Reservation
Modificationof constellation
Using addionalreserved carriers
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PAPR – ACM – Active Constellation ExtensionACM: outer constellation points can be shifted outwardwithout increasing the BER in order to decrease the crest factor.
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PAPR – TR – Ton Reservation
Reserved tones (carriers) can be switched on or ofand can be modified in amplitude and phaseto decrease the crest factor.
If TR is in use than the net data rate is reduced by0.4 … 0.8 Mbit/s up to some Mbit/s, depending onthe transmission parameters (IFFT mode, guard, CR).
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PAPR
Source:ETSI EN 302 755
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DVB-T2 Block DiagramPLP 0
PLP n
Mod
e/st
ream
adap
tatio
n
FECCell
builder MapperCell
inter-leaver
Timeinter-leaver
Freq
uenc
yin
terle
aver
FECCell
builder MapperCell
inter-leaver
Timeinter-leaver
MISOproc.
Pilotinsert.
IFFT PAPRred.
Guardinterv.insert.
P1symbolInsert.
DA Tx1
Pilotinsert.
IFFT PAPRred.
Guardinterv.insert.
P1symbolInsert.
DA Tx2
(optional)
......
......
T2-MI
Stre
amad
apta
tion
part
2
Fram
ebu
ilder
Totransmitters
T2 gateway
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SISO / MISO
SISO / MISO
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SISO and MISO
DVB-T2 allows
SISO = Single Input Single Output
and
MISO = Multiple Input Single Output
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SISO Principle
Tx RxData Data
SISO = single input, single output
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Diversity Receiver: SIMO
Tx1 RxData Data
SIMO = single input, multiple output
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MISO Principle
Tx1
Tx2
RxData
Data
MISO = multiple input single output
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MIMO Principle
Tx1
Tx2
Data
MIMO = multiple input multiple output
Rx Data
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MISO: Space-Time Transmit Diversity
2 transmission antennas = space diversityConjugate symbols are repeated = time diversity
S/N improvement in fading environment
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Alamouti
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MISO Principle
FEC Mapper Sn Sn+1
1 -()*
1 ()*
RxData
Data
Tx1
Tx2
S1 -S2*
S2 S1*
Alamouti Matrix
S2 S1* S4 S3*
S1 -S2* S3 -S4*
S1S2
-S2*S1*
Symbol
Symbol
()*=conjugate complex
Path 1
Path 2
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MISO Receiver
Rx
S1S2
-S2*S1*
r1 r2
r1 r2
combiner
channelestimation
max. likelihooddetector
data
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MISO: Symbol Combining Rule in the Receiver
S1 -S2*
S2 S1*
Alamouti Matrix
received symbols:r1=s1+s2r2=-s2*+s1*
Combining rule in the receiver:
s1~=r1+r2*=(s1+s2)+(-s2*+s1*)*=s1+s1=2s1;
s2~=r1-r2*=(s1+s2)-(-s2*+s1*)*=s2+s2=2s2;
t1 t2time
path1
path2
()*=conjugate complex
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MISO: modified: DVB-T2
FEC Mapper Cn Cn+1
1 1
()* -()*
RxData
Data
Tx1
Tx2
S1 S2
S2* -S1*
Modified Alamouti Matrix
C2* -C1* C4* -C3*
C1 C2 C3 C4
C1C2*
C2-C1*
Cell
Symbol
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MISO in DVB-T2
… but the implementation guidelinesare talking about MISO in frequency direction …
… how is MISO really be implemented in DVB-T2 …
Space / frequency diversityinstead of
space / time diversity
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Original Text from the Standard …
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SISO / MISO @ DVB-T2
Using only path 1 = SISO
Using both path 1 and path 2 = MISO mode
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MISO @ DVB-T2
Co-located MISO: 2 antennas at the same transmittersite (horizontal and vertical polarization)
Distributed MISO: antennas in thedifferent transmitter sites inside a SFN
M1 M2
M1M2
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DVB-T2 Spectrum
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Fading inbetween two Tx in a SFN
+Transmitter 1 Transmitter 2
Result: deep notches
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Fading inbetween two Tx in a SFN using MISO
+Transmitter 1
MISO 1Transmitter 2
MISO 2
Result: no notchesDistributedMISO
No correlationbetweensignal M1and M2
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Scattered Pilot Pattern in MISO Mode
NANAPP1NAPP3NANA1K
NANAPP1NAPP3PP4PP5
NA4K, 2K
NAPP1PP8
PP1PP8
PP3PP8
PP3PP8
PP8PP4PP5
PP8PP4PP5
8K
NAPP1PP8
PP1PP8
PP3PP8
PP3PP8
PP8PP4PP5
PP8PP4PP5
16K
NANANAPP2PP8
PP2PP8
PP8PP4
PP8PP4PP6
32K
g=1/4
g=19/128
g=1/8
g=19/256
g=1/16g=1/32
g=1/128
FFTsize
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DVB-T2 – Further FeaturesAuxillary stream insertion-At the end of a DVB-T2 frame auxillary streamscan be inserted.-Auxillary streams will be ignored by a DVB-T2receiver.-“A sequence of cells carrying data of as yet undefinedmodulation and coding, which may be used for futureextensions or as required by broadcasters and networkoperators.“Future Extension Frames (FEF)-„An open door in the standard for the future …“- Data frames for future extensions- Unknown to a DVB-T2 receiver
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DVB-T2 – Further Features
T2-TX-SIG
Draft version for transmitter identification ina Single Frequency Network using signatures:
-using auxillary streams-using FEF‘s
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Measurements in a SFN
Playoutcenter
Tx1, RF1
Tx2, RF1Tx4, RF1
Tx5, RF1
Tx3, RF1
MP
MP =measurement
point
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Impulse Response Measurement in a SFN
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Example: Transmitter Identifaction Information in DAB
A comparison to DAB:TII = Transmitter Idenfication Information
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DAB Frame with Null SymbolsTIIno TII no TII
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DAB Spectrum with visible Null Symbol
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DAB Spectrum Zero Span
30 ms / Div
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FFT of a Null Symbol with TII
Signalling of TII Main ID (0…69) and TII Sub ID (1…23)
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DVB-T
In DVB-T there is a cell ID, whichidentifies a SFN cell.
Transmitter identification is not possiblein DVB-T.
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DVB-T2
30…50 % more data rate (LDPC, >8K modes)more flexibility (PLP, variable coding and mod.)better mobile reception capability
