Transcript
DVB-T2: Technical overview DVB-T2 block diagram
DVB-T2 frame structure
PLP 0
BB header insertion
CRC8
BB scramb.
Padding
The DVB-T2 frame structure consists of superframes that are divided into two or more T2 frames of several OFDM symbols. A superframe may carry T2 frames and FEF parts. The T2 frame always begins with a P1 preamble symbol, followed by one or more P2 preamble symbols carrying L1 signaling data and followed by a configurable number of data symbols carrying the data of the PLPs.
BB frames
Mode adaptation + stream adaptation
Max: TSF = 63.75 s [no FEF] Max: TSF = 127.50 s [with FEF] FEF interval
PLP n ISSY PLP 0
Stream adaptation
Null packet deletion
CRC8
In-band sig. or padding
T2-MI
BB header insertion
Scheduler
(ASI/IP)
T2-MI ON/OFF
Mode adaptation (GATEWAY)
BB scramb.
DVB-T2 frame
FEF length
FEF interval
FEF part
DVB-T2 frame
DVB-T2 frame
FEF length
FEF part
DVB-T2 frame
FEF length
FEF interval
DVB-T2 frame
FEF part
DVB-T2 frame
Max: TF = 250 ms
P1
Common PLP
P2
Data PLPs, type 1
Data PLPs, type 2
Auxiliary stream
Dummy cells
BB frames P1 signaling
BICM Time interl.
Configurable
Guard insert.
PAPR
P1 insert.
to TX
L1 padding
Time
Time
Cell index
IFFT
Mobile DTV 1
Pilot pattern
MISO
CRC
The P1 and P2 symbols and the parallel PLPs are combined into a T2 frame in the frame builder.
SDTV 1
Freq. interl.
Extension
T2 frame structure
HDTV 1
Frame builder
Dynamic
Physical layer pipes (PLPs)
SDTV 2
Frame builder + OFDM generation
HDTV 1
Cell interl.
Mobile DTV 1
Const. rotation
Mapper
SDTV 1
Demux
HDTV 1
Bit interl.
L1 postsignaling
Data volume
BCH/ LDPC
L1 presignaling
P1
P2
P2
Data
Data
Data
Data
Key L1 pre L1 post
Multiplexing of transport streams (TS) and composing of a T2-MI signal (example)
Transposer e.g. R&S®XLx8000
Common PLPs
Statistical multiplexer Elementary streams multiplexed to SPTS
SPTS multiplexed to MPTS, MPTS multiplexed to Big TS
PLPs of one group are related to one Big TS. For each group, a common PLP is generated.
RE-MUX Data Video Audio PSI/SI Data Video Audio PSI/SI
Multiplex
SPTS1
Data Video Audio PSI/SI
Multiplex
Data Video Audio PSI/SI
Multiplex
SPTS2
SPTS3
Data PLPs, type 2
T2 gateway
SD/HD
T2-MI signaling and specific data inserted once but periodically
MPTS1 SPTS1
Multiplex
Data PLPs, type 1
Transmitter TV analyzer e.g. R&S®ETL
Big TS1 = Group1
SPTS2
Big TS1
MPTS2
PLP1
PLP2
MPTS2
MPTS1
MPTS2
SPTS1
SPTS3
SPTS1
SPTS3
SPTS2
SPTS4
SPTS2
SPTS4
SPTS4
T2-MI (ASI or IP)
SPTSn
Data Video Audio PSI/SI
Multiplex
Multiplex
SPTSn
SPTSn+1
Primary distribution
Transmitter TV analyzer e.g. R&S®ETL
Big TS2
PLP3 MPTSn
PLP4 MPTSn+1
MPTSn
MPTSn+1
MPTSn+1
SPTSn
SPTS
SPTSn
SPTS
SPTS
SPTS n+1
SPTS
SPTS n+1
SPTS
Transposer e.g. R&S®XLx8000
Common PLP
SPTS
SD/HD
1K mode 853 n/a
2K mode 1705 n/a
4K mode 3409 n/a
8K mode 6817 6913
16K mode 13633 13 921
32K mode 27265 27 841
Duration TU Duration TU 1) Carrier spacing 1/TU (Hz) 2, 3) normal carrier mode Spacing between carriers 2) Kmin and Kmax: (Ktotal – 1)/TU 1) extended carrier mode Elementary period as a function of bandwidth: Bandwidth Elementary period T
1024 T 112 8929 7.61 MHz n/a
2048 T 224 4464 7.61 MHz n/a
4096 T 448 2232 7.61 MHz n/a
8192 T 896 1116 7.61 MHz 7.71 MHz
16384 T 1792 558 7.61 MHz 7.77 MHz
32768 T 3584 279 7.61 MHz 7.77 MHz
1.7 MHz 71/131 μs
5 MHz 7/40 μs
6 MHz 7/48 μs
7 MHz 1/8 μs
8 MHz 7/64 μs
10 MHz 4) 7/80 μs
3) 4)
This value is used in the definition of the pilot sequence in both normal and extended carrier mode. This configuration is only intended for professional applications and is not expected to be supported by domestic receivers.
Glossary: ASI = Asynchronous Serial Interface; BB = Baseband; BCH = Bose-Chaudhuri-Hocquenghem Code; BICM = Bit-Interleaved Coded Modulation; CRC8 = Cyclic Redundancy Check; DTV = Digital Television; DVB-T2 = Digital Video Broadcasting-Terrestrial; FEF = Future Extension Frame; HDTV = High Definition (HD) Television; IFFT = Inverse Fast Fourier Transformation; IP = Internet Protocol; ISSY = Input Stream Synchronizer; LDPC = Low-Density Parity Check Codes; MISO = Multiple Input Single Output; MPEG = Moving Picture Experts Group; MPTS = Multi Program Transport Stream; OFDM = Orthogonal Frequency Division Multiplex; PAPR = Peak-to-Average Power Ratio; PLP = Physical Layer Pipe; QAM = Quadrature Amplitude Modulation; QPSK = Quadrature Phase Shift Keying; SDTV = Standard Definition (SD) Television; SFN = Single Frequency Network; SISO = Single Input Single Output; SPTS = Single Program Transport Stream; T2-MI = T2 Modulator Interface
MISO
Values for 8 MHz channels. Numeric values in italics are approximate values.
FFT size
SISO
Parameter (OFDM parameter) Number of carriers Ktotal normal carrier mode (Kmin = 0; Kmax = Ktotal – 1) extended carrier mode
2)
This rotated constellation allows improved, more robust detection of the constellation points.
Mobile and SD/HD TV reception
Big TS2 = Group2
SPTS n+1
16QAM constellation after rotation
SD/HD
Transmitter TV analyzer e.g. R&S®ETL
1)
Frame-closing symbol
SPTS3 SPTS4
Dummy cells
Transposer e.g. R&S®XLx8000
MPTSn Data Video Audio PSI/SI
Mobile and SD/HD TV reception
Common PLP
MPTS1
Auxiliary streams
Mobile and SD/HD TV reception Example: DVB-T2 constellation with C/N = 21 dB.
Guard interval 1/128
1/32 PP4 PP6
1/16 PP2 PP8 PP4 PP2 PP8 PP4 PP5
19/256 PP2 PP8 PP4 PP2 PP8 PP4 PP5
32k
PP7
16k
PP7
PP7 PP4 PP6
8k
PP7
PP7 PP4
PP8 PP4 PP5
4k, 2k
n/a
PP7 PP4
1k
n/a
32k
1/8
19/128 PP2 PP8
1/4 n/a
PP2 PP3 PP8
PP2 PP3 PP8
PP1 PP8
PP8 PP4 PP5
PP2 PP3 PP8
PP2 PP3 PP8
PP1 PP8
PP4 PP5
n/a
PP2 PP3
n/a
PP1
n/a
PP4 PP5
n/a
PP2 PP3
n/a
PP1
PP8 PP4 PP6
PP8 PP4
PP2 PP8
PP2 PP8
n/a
n/a
n/a
16k
PP8 PP4 PP5
PP8 PP4 PP5
PP3 PP8
PP3 PP8
PP1 PP8
PP1 PP8
n/a
8k
PP8 PP4 PP5
PP8 PP4 PP5
PP3 PP8
PP3 PP8
PP1 PP8
PP1 PP8
n/a
4k, 2k
n/a
PP4 PP5
PP3
n/a
PP1
n/a
n/a
1k
n/a
n/a
PP3
n/a
PP1
n/a
n/a
DVB-T2 spectrum If a large number of OFDM carriers are used, the spectrum falls sharply toward the band edge. This effect is utilized by DVB-T2 with the 8k extended, 16k extended and 32k extended IFFT modes.
Source: ETSI EN 302 755
DVB-T2 lite not possible with bold-marked pilot pattern.
Rohde & Schwarz solutions for DVB-T2
¸SFC compact modulator
¸EFL340 portable TV test receiver
¸XLx8000 transposer MFN and SFN solutions for DVB-T2
R&S®BTC broadcast test center
¸SFE broadcast tester
¸ETL TV analyzer
Full range of Rohde & Schwarz DVB-T2 transmitters (DVB-T2 exiters)
PD 5213.9686.82.82 V 05.00
¸DVMS digital TV monitoring system family
5213968682
¸THU9 transmitter (19" Rack, full height)
www.rohde-schwarz.com/technology/DVB-T2
DVBT-T2_po_en.indd 1
13.01.2015 15:54:23
