Digital TV: An Introduction
Gregory Bensberg
UK DTT 81Main and
Relay Sites
CP5 Before
CP5 After
Current use of grouped aerials in the UK
21 31 36 38 42 62 68
UHF - channel numbers
Group A 21 - 37
Group B 35 - 53
Group C/D 48 - 68
Group W 21 - 68
Group E 35 - 37Group K 21 - 48
London Frequencies Manchester Frequencies
Digital Satellite CoverageDSAT Study:UK coverage map.Shadow regions due to terrain
Predicted UK CoverageDSAT StudyExtrapolated UK coverage
UHF spectrum now - Winter Hill
21 31 36 38 42 62 68
UHF - channel numbers
Interleaved spectrumAnalogue TV DTT
DTT – other sites
Group C/D 48 - 68
3 Conversion plan
• Convert 3 analogue networks for DTT• 6 multiplexes - 3 PSB, 3 commercial• Assume 16QAM rate 3/4 or 64 QAM Rate 2/3 for all
muxes • Support regional services • Release 14 channels i.e. 32 chs retained
Post switchover - 3 conversions
21 31 36 38 42 62 68
UHF - channel numbers
Interleaved spectrum Converted DTT
DTT – other sites
Cleared spectrum
Group C/D 48 - 68
Alois Bock’s notes
Basic video compression techniques
Basic video compression techniques
Basic video compression techniques
Motion estimation on source or reconstructed
0
2
4
6
8
10
12
1 2 3 4 5 6 7 8
Bit rate (Mbit/s)
PS
NR
-25
(dB
)
rec
src
Basic video compression techniques
Layer 1
Basic video compression techniques
Layer 2
Basic video compression techniques
Layer 3
Basic video compression techniques
Layer 4
Basic video compression techniques
Example hierarchical ME
Basic video compression techniques
Example exhaustive ME
Basic video compression techniques
Computational cost of MENormalised CPU Time
0
100
200
300
400
500
600
0 10 15 20 30 40 50 60 70 80 90 100
Search Range
exh
hier
Basic video compression techniques
B frame predictions
I frame B frame B frame P frame
Display order
Adrian Turner’s notes
Single Carrier QAM
sin
cos
x
x
+
Re(M(t))
Im(M(t))
f c
Frequency
Power Spectral Density
fc1/Ts
Ts
Constellations (2)Constellations (2)
QPSK2 bits/symbolM(n) = ±1 ±j
16 QAM4 bits/symbol
64 QAM6 bits/symbol
im
j
-j-j
-1 1 re
Mapping data to the constellation
Example - Gray coded 16QAM
0000
0001
0011
0010
0100
0101
0111
0110
1100
1101
1111
1110
1000
1001
1011
1010
OFDM
Time domain Frequency domain
TS
11-1-111......
Generating OFDM (1)Generating OFDM (1)
Frequency DomainFrequency DomainModulationModulation
Symbols (QPSK example)Symbols (QPSK example)
rere imim rere imim
Time DomainTime DomainSamplesSamples
FFTFFTFFTFFT-1-1
jjjj-j-j......
..
..
..
..
..
..
..
..
..
..
..
..
Fast Fourier TransformsComputational complexity
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 2000 4000 6000 8000 10000
N
Op
era
tio
ns
, mill
ion
s
DFT
FFT
The DVB-T pilot structure
Modulated carrier (QAM)Scattered or Continual PilotTPS carrier
Frequency
Time
Transport Streamsand Service Discovery
Guy Hirson, BroadLynx Limited
[email protected] course
Guildford University 2005
Transport StreamMPEG: Program Specific Information(CAT, PAT, PMT, NIT (?))Information for the decoder
DVB: Service InformationBAT, EIT, NIT, RST, SDT, TDT & TOTInformation for the user and service
Services (DVB speak) orPrograms (MPEG speak)carrying Elementary streams
Private CA data in Tables
Other private data (in Tables, Elementary Streams, etc.)
Containers fordata carriageMPEG table section
PES Packets
Transport Stream Packets
Data Streams•PSI: PAT, PMT & CAT•SI: NIT, SDT, EIT•DSM-CC•MHP AIT
Media Streams•Video•Audio•Subtitles•Legacy Teletext
Protecting the Packet
header payload RS
188 bytes
204 bytes
Transport Stream Packetheader payload header payload header payload
Sync byte
Transport Error
Indicator
Payload unit start indicator
Transport priority
PID Transport Scrambling
Control
Adaptation Field
Control
Continuity Counter
Adaptation Field
8 1 1 1 2 4 N213
Adaptation field length
Discontinuity indicator
Random access
indicator
ES priority
indicator 5 flags
Optional fields
Stuffing bytes
8 1 1 NN51
PCR OPCR Splice countdown
TS private data length
adaptation field extension
length
3 flags Optional fields
42 42 8 NN58
TS private data
TS packet
PCR insertion in the multiplexer
27 MHzcounter
PCR
42 bit
hdr payload hdr payload payloadhdr hdr payload hdr payload
TS packet TS packet TS packet TS packet
Video timebase
TS packet
PCR extraction in the demultiplexer
27 MHzcounter
PCR
42 bit
hdr payload hdr payload payloadhdr hdr payload hdr payload
TS packet TS packet TS packet TS packet
Video timebase (1Hz in 27MHz, 10ppb/s)
compare42 bit
errorfilter
Frequency control
PES packets for synchronised dataheader payload header payload
Packet start code prefix
Stream_id PES packet length
Optional PES header
PES packet data bytes
24 8 N NN16
‘10’ PES priority
Data alignment indicator
Original or copy
Stuffing bytes
2 NN
PES scrambling
control
copyright flags PES header data len
Optional fields
2 1 1 1 1 8 8
PTS
DTS
ESCR ES Rate Additional copy info
2
DSM Trick mode
Previous PES CRC
PES extension
2 1 1 1 1 8 8
MPEG sectionsTable id Section
syntax indicator
Private indicator
Private section length
8 1 121
N private data bytes
1
Table_id extension
Current next
indicator
16
Version number
Section number
Private data
5 8 32
2
2
Last Section number
CRC32
1 8
The guts of an Integrated
Receiver/Decoder
CPU
CA
Tra
nsp
ort
AudioDecode
VideoDecode
GPU
DAC
PALEncode
RCModem
SC
I/O
Demod FEC
1 2 34 5 67 8 9
Networks, Bouquets, Services and Events
TS 1
TS 2
TS 3
Network
Bouquet
Service
Event
Programs and their componentsMPEG-2 Transport Stream
Program 1 Program 2 Program nPSIData
ElementaryStream 1(Video)
ElementaryStream 2(Audio1)
ElementaryStream n(Subtitles)
CA
The inter-linking of PSI Tables and Programs
Program 1Program 2
Program n
PAT ECMES 1ES 2ES 3
ECM 3ES 4
PMT (2)MPEG-2 TS
CAS ID 1CAS ID 1
CAS ID x
CAT
Selecting a Service byLogical Channel
Number
CPU
Tra
nsp
ort
Demod FEC
1 2 34 5 67 8 9
ProgramSI filters
RetrieveBAT, SDT, EITs
Build tableof services
SI Processing
NIT => list of services+ tuning data
SDT => Service names
EITs => Event info
Select “channel”
Tune to TSProgramPSI filtersfor PAT
RetrievePAT
ProgramPSI filtersfor PMT
RetrievePMT
Set up toretrieve
A/V
VideoDecode
AudioDecode
Selecting an EventEvent NameDescriptionAttributes
Event NameDescriptionAttributes
Event NameDescriptionAttributes
Event NameDescriptionAttributes
Data from EIT database
Service ID etc.
Ser
vice
sel
ectio
n
Select from menu
Data Carousel
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DDB
DII transaction_id
mi mi mi
DII transaction_id
mi mi mi
Block
ModuleGroup
DSI transaction_id
gi gi
48
Digital Terrestrial Television:Domestic and MATV
Reception
Peter BarnettConsultant
Tel: +44 (0)1794 341053E-mail: [email protected]
www.dtg.org.uk
DTT reception
Domestic
MATV IRS
Typical UHF spectrum
Aerials
Group A
AnalogueDigital
CH
21 C
H6
8CH
37
Group AGroup B
Group C/D
Group EGroup K
Group W
Aerials
Group W
CH
21 C
H6
8Group A
Group BGroup C/D
Group EGroup K
Group W
AerialsGroup A
Group BGroup C/D
Group EGroup K
Group W
Pre-switchover
Post-switchover
Receiver operating window
30 40 50 60 70 80Signal level (dBV)
Analoguesignal
Digitalsignal
Difference inreceived levels
Marginaloperation
Effects of pre-amplifiers
30 40 50 60 70 80Signal level (dBV)
Analoguesignal
Digitalsignal
Difference inreceived levels
Upgrading systems
Digital
Analogue
-50
-40
-30
-20
-10
0
Channel changing in MATV systems
Intermodulation in amplifiers
Intermodulation in amplifiers
LNB interference into DTT
Low band High band
10.7GHz 11.7GHz 12.75GHz
0 950MHz 2150MHz
Local oscillator
UHF interference into satellite
Measurements
A
B
C
University of SurreyDTT : An Overview
Receivers (Hardware) Nov 2005 v2.0Peter Lewis
Philips Semiconductors Technology Center
SouthamptonUK
Inside a ‘Set Top Box’RF in from
aerial
Picture & Sound out to
TV set
Channel Decoding Stage
Source Decoding Stage
Tuner
Demodulator
Tuner Phase Noise
1116 Hz (8k)
4464 Hz (2k)
NB Carrier Separation Phase noise spreads the carriers
So they interfere with each other
Tuner Step SizeANALOGUE DIGITAL
RF from VCRs etc is imprecise RF from digital TXs is precise but may be offset ± 1/6MHz
Therefore a fine tuning resolution is needed
Therefore a 1/6MHz tuning resolution is needed
The adjacent channel problem
Chan NChan N-1
Peak sync power
total power in channel
Up to 35dB !
Lower adjacent sound, and SAW profile
Chan N
WANTED DVB-T SIGNAL
+10 dB
+20 dB
+30 dB
0 dB
SAW IF Filter Profile
FM sound NICAM sound
(Levels plotted as though
with 100kHz BW S/A)
Attenuation of NICAM by one SAW
Chan N
EFFECTIVE NICAM LEVEL WITHOUT ANY FILTERING
EFFECTIVE NICAM LEVEL WITH ONE SAW FILTER
WANTED DVB-T SIGNAL
+10 dB
+20 dB
+30 dB
0 dB
The more distant channel problem
Chan N-x
Up to 50dB !
Chan N
SAW filter profile for distant channels
Chan N-x Chan N
Interference from distant channels
Chan N-x Chan N
X
X
XX
F1
F2 F4
F3
Traditional High Quality Front-End
TUNER2 SAW FILTERS
1st IF AMP
2nd IF Filter ?
DOWN-CONVERTER &
AGC AMP
DEMODULATOR
Gain control
Modern High Quality Front-End
TUNER
IF / AGC AMP, in tuner
Single SAW, in tuner
DEMODULATOR, containing digital filtering that replaces
one SAW filter
Gain control
Channel decoder stage - demod IC
Tuner IF filter
Local Oscil.
1st IF (~36MHz) 2nd IF (~5MHz)
Down conversion IC
NB Down conversion is optional. Gain control is not !
DVB-T Channel demodulator & decoder IC
ADCDigital
front endFFT
Chan est. & correct.
Error Correct.
Etc.
Transport stream
RF
AGC amp
Channel decoder stage - digital F/E
Tuner IF filter
Local Oscil.
1st IF (~36MHz) 2nd IF (~5MHz)
Down conversion IC
NB Down conversion is optional. Gain control is not !
DVB-T Channel demodulator & decoder IC
ADCDigital
front endFFT
Chan est. & correct.
Error Correct.
Etc.
Transport stream
RF
AGC amp
Process that may be in the ‘Digital Front End’
Digital Frequency Adjustment
ADCDigital AGC
AGC detector
analogue or digital
IF
correction required
Gain control to RF/IF stages
I & Q data at baseband
shift
= correction x t
data in data out
One method of identifying the symbol start
correlation
one full symbolguard interval
threshold
current samplefuturepast
TuTu
Channel decoder stage - FFT
Tuner IF filter
Local Oscil.
1st IF (~36MHz) 2nd IF (~5MHz)
Down conversion IC
NB Down conversion is optional. Gain control is not !
DVB-T Channel demodulator & decoder IC
ADCDigital
front endFFT
Chan est. & correct.
Error Correct.
Etc.
Transport stream
RF
AGC amp
Conversion from time samples to frequency
values.
frequency
2048 complex values for ‘2k’
8192 complex values for ‘8k’
I
-32953213395-3232-9532
13395
-32-32133
Q
95-95950329532-95-95
095
32950
time
2048 complex values for ‘2k’
8192 complex values for ‘8k’
Q
-30-7012698080106470
1010
-78-30-9
I
20-9078564012-56-4020
8090
-491062
FFT window timing error
ideal FFT window
actual FFT window
freq component A
freq component B
one full symbol
guard interval
timing error, terr
phase error = terr x A
phase error = terr x B
OFDM demod. stage - time corrector
Digital Time AdjustmentFFT
shift
= t correction x
data in data out
The principle is the same as for frequency adjustment in the
frequency domain
I & Q time data
I & Q frequency data
Channel decoder stage - Chan. est. & corr.
Tuner IF filter
Local Oscil.
1st IF (~36MHz) 2nd IF (~5MHz)
Down conversion IC
NB Down conversion is optional. Gain control is not !
DVB-T Channel demodulator & decoder IC
ADCDigital
front endFFT
Chan est. & correct.
Error Correct.
Etc.
Transport stream
RF
AGC amp
Echoes and Pilots
Phase of echo
Effect of echo
Only first 200+ carriers shown.
Continues on ….
echo adds
echo subtracts
Continual Pilot Scattered Pilot
Example of single echo with 1 usec delay
Channel estimation from pilots
interpolate through
timeinterpolate through frequency
symbol N
symbol N+1
symbol N+2
symbol N+3
to get estimates of channel response for every carrier
scattered pilot
Channel equalisation
Channel Estimation
frequency data corrupted by
channel, etc., effects
frequency data
corrected
CPE Detection
confidence
CPE detection
Channel Estimation
frequency data corrupted by
channel, etc., effects
frequency data
corrected
CPE Detection
confidence
Common Phase Error - CPEPhase Error
Time
one symbol
phase noise
mixer
local oscillator
part of tunerRF IF
+1kHz-1kHz
example of cause
CPE Detection using continual pilots
Continual Pilots
mean = CPE
symbol N
symbol N + 1
etc...
phase change between symbols
etc...
CPE detection
Channel Estimation
frequency data corrupted by
channel, etc., effects
frequency data
corrected
CPE Detection
confidence
Channel decoder stage: de-mapping, de-
interleaving & error correction
Tuner IF filter
Local Oscil.
1st IF (~36MHz) 2nd IF (~5MHz)
Down conversion IC
NB Down conversion is optional. Gain control is not !
DVB-T Channel demodulator & decoder IC
ADCDigital
front endFFT
Chan est. & correct.
Error Correct.
Etc.
Transport stream
RF
AGC amp
Stages of ‘Error Correction Etc’DVB-T Channel demodulator & decoder IC
ADCDigital
front endFFT
Chan est. & correct.
Error Correct.
Etc.
Transport stream
de-mapping, de-interleaving,
etc.de-coding
De-mapping, etc, stage
de-mapping, de-interleaving,
etc.de-coding
What is the basic job to be done?
DE-MAPPING, DE-INTERLEAVING, etc.
MAIN INPUT IS I & Q DATA STREAMS REPRESENTING
THE MODULTION ON ALL THE USEFUL DATA CARRIERS
I
Q
confidence
confidence
MAIN OUTPUT IS A BITSTREAM WITH
CONFIDENCE INFO.
data
de-mapper
symbol* de-
interleaver
bit de-interleaver
De-mapping & Inner De-interleaving:
muxdataI
Qconfidence
confid-ence
order may be reversed
* data on each carrier (not OFDM symbols)
de-mappersymbol
de-interleaver
bit de-interleaver
demapper
muxdataI
Qconfidence
confid-ence
Mapping: 16QAM exampleEach point represents
4 bits
A, B, C, D
A=0
B=0D=0
D=0
C=0C=0
Note that crossing one
boundary changes only
one bitC=1
D=1
A=1
B=1
e.g. ‘0,0,1,1’
I
Q
1,0,0,11,1,1,00,0,0,00,1,1,0
Demapping, to symbol vectors Simple Symbol
Value VectorI
Q
I
Q
I
Q
I
Q
carrier n
carrier n+1
carrier n+2
carrier n+3
etc.
1(110), 0(101), 0(011), 1(001)
Demapping, including confidenceFull Symbol Metrics Vector
I
Q
Bit valuesConfidence in
each bitcarrier n
1 (100), 1 , 1 , 0(111) (010) (110)
0 (110), 0 , 0(110) (101) (101), 0
0 (011), 1 , 0(111) (100) (111), 1
Demapping: separating vectors to metric streams
Symbol VectorValue (Confidence) 1
0
0
111
010
110
100
1
1
1
0
110
101
101
110
0
0
0
0
111
100
111
011
0
1
1
0
stream 0
stream 1
stream 2
stream 3
1 (110), 0 , 0 , 1(101) (011) (001)
1 (100), 1 , 1 , 0(111) (010) (110)
0 (110), 0 , 0(110) (101) (101), 0
0 (011), 1 , 0(111) (100) (111), 1
101
011
001
110
1
de-mappersymbol
de-interleaver
bit de-interleaver
demapper
muxdataI
Qconfidence
confid-ence
1 0 1 0 1 1 111 0 0 0 1 1 111 1 0 0 0 1 111 1 1 0 1 1 11
x 2, 4, or 61Data
Confidence
de-mapper
symbol de-
interleaver
bit de-interleaver
Symbol de-interleaver
muxdataI
Qconfidence
confid-ence
1 0 1 0 1 1 111 0 0 0 1 1 111 1 0 0 0 1 111 1 1 0 1 1 11
1Data
Confidence
x 2, 4, or 6
‘Symbol’ de-interleaving
1512 or 6048 metrics de-interleaved to undo the corresponding process at the transmitter.
metrics (data + confidence) for one
complete OFDM symbol de-
interleaved into original order
metrics (data + confidence) for one
complete OFDM symbol as received
from de-mapper
de-mapper
symbol de-
interleaver
bit de-interleaver
Symbol de-interleaver
muxdataI
Qconfidence
confid-ence
1 0 1 0 1 1 111 0 0 0 1 1 111 1 0 0 0 1 111 1 1 0 1 1 11
1Data
Confidence
1 0 1 1 1 0 001 0 1 1 1 0 001 1 0 1 0 1 011 1 1 1 1 1 01
re-arranged
x 2, 4, or 6 x 2, 4, or 6
de-mapper
symbol de-
interleaver
bit de-interleaver
bit de-interleaver
muxdataI
Qconfidence
confid-ence
1 0 1 1 1 0 001 0 1 1 1 0 001 1 0 1 0 1 011 1 1 1 1 1 01
x 2, 4, or 6
Bit de-interleaving, e.g. substreams 0 & 1.
00 01 19 20 21 22 40 41 42 43 61 62 63 64 82 83 84 85 103 104 105 106 124 125... .. .. .. .. ..
00 01 19 20 21 22 40 41 42 43 61 62 63 64 82 83 84 85 103 104 105 106 124 125... .. .. .. .. ..
00 01 19 20 21 22 40 41 42 43 61 62 63 64 82 83 84 85 103 104 105 106 124 125... .. .. .. .. ..
00 01 19 20 21 22 40 41 42 43 61 62 63 64 82 83 84 85 103 104 105 106 124 125... .. .. .. .. ..
i/p stream 0 (bits b0,0 - b0,125)
o/p stream 0 (bits a0,0 - a0,125)
i/p stream 1 (bits b1,0 - b1,125)
o/p stream 1 (bits a1,0 - a1,125)
de-mapper
symbol de-
interleaver
bit de-interleaver
bit de-interleaver
muxdataI
Qconfidence
confid-ence
1 0 1 1 1 0 001 0 1 1 1 0 001 1 0 1 0 1 011 1 1 1 1 1 01
0 0 1 0 1 0 001 0 1 0 1 0 000 1 1 0 1 1 010 1 0 1 0 1 10
re-arranged more
x 2, 4, or 6 x 2, 4, or 6
de-mapper
symbol de-
interleaver
bit de-interleaver
multiplexer
muxdataI
Qconfidence
confid-ence
1 0 1 1 1 0 001 0 1 1 1 0 001 1 0 1 0 1 011 1 1 1 1 1 01
2, 4, or 6 streams
0 1 1 1 1 1 010 1 1 1 1 1 001 1 0 1 1 0 111 1 1 0 1 1 11
1 0 0 1 0 1 011 0 1 1 0 0 001 1 1 1 1 1 010 0 1 1 1 0 11
0 1 1 0 1 1 000 1 1 1 1 1 100 1 0 1 0 0 111 1 1 1 1 1 10
1 stream
De-coding stage:
de-mapping, de-interleaving,
etc.de-coding
What is the basic job to be done?
DECODING
OUTPUT IS A TRANSPORT STREAM
confidence
MAIN INPUT IS A BITSTREAM WITH CONFIDENCE INFO.
data
convolutional
inner decoder
outer de-interleaver
block outer
decoder
De-coding sub-stages:
energy dispersal removal
data
confid-ence
MPEG2 t/s
(Viterbi) (RS)
BER less than 2 x 10-4 BER near zero
convolutional
inner decoder
outer de-interleaver
block outer
decoder
Convolutional Decoder (Viterbi):
energy dispersal removal
data
confid-ence
MPEG2 t/s
1 0 0 1 0 0 11
0 1 1 0 0 1 001 1 1 0 0 1 100 1 0 1 1 0 110 1 1 1 1 1 11
Convolutional coding used in DVB-T
1 bit delay
1 bit delay
1 bit delay
1 bit delay
1 bit delay
+
+
switches at twice input
bit rate
1 bit delay
INPUT BIT STREAM
FINAL OUTPUT BIT STREAM
(twice rate of input)
Modulo 2 adder
Modulo 2 adder
X OUTPUT BIT STREAM
Y OUTPUT BIT STREAM
A simple convolutional coder
+
switches at twice input
bit rate
1 bit delay
INPUT BIT STREAM
FINAL OUTPUT BIT STREAM
(twice rate of input)
Modulo 2 adder
Y OUTPUT BIT STREAM
X OUTPUT BIT STREAM
Example output of simple convolutional coder
Input Bits
Output Bits
0 0 1 0 1 1 0 0 1 0
10 0 0 1 1 0 0 10
1
Y
1
Y
0 00 0
Y YX X
1
X
0
X
1 1 0 0 1 01 0 1 0 1 1
Y Y Y Y Y YX X X X X X
Delayed Input Bits+ +
Options for ‘correcting’ an error and get a valid
sequence0 0 1 0 1 1 0 0 1 00 0 1 1 1 0 1 0 1 1
0 0 1 1 1 1 0 0 1 00 0 1 0 0 0 1 0 1 1
0 0 0 1 1 1 0 0 1 00 0 0 1 0 0 1 0 1 1
0 0 1 0 1 1 0 0 1 00 0 1 1 1 0 1 0 1 1
0 0 1 0 0 1 0 0 1 00 0 1 1 0 1 1 0 1 1
0 0 1 0 0 0 0 0 1 00 0 1 1 0 0 0 0 1 1
Tx.
0 0 1 0 1 1 0 0 1 00 0 1 1 0 0 1 0 1 1Rx.
Opt. A
Opt. B
Opt. C
Opt. D
Opt. E
Y Y Y Y Y Y Y Y Y YX X X X X X X X X X
convolutional
inner decoder
outer de-interleaver
block outer
decoder
Outer de-interleaver:
energy dispersal removal
data
confid-ence
MPEG2 t/s
1 0 0 1 0 0 11
Outer de-interleaving
204 byte TS like packets
204 byte blocks, but with bytes interleaved
Fifo shift registers
1 byte per position
No delay
17 bytes delay
2 x 17 bytes delay
3 x 17 bytes delay
11 x 17 bytes delay
17 complete ‘switch rotations’ per packet
RS parity bytes are now grouped at the end of each block.
Effectively the inverse of the interleaving process at the transmitter
convolutional
inner decoder
outer de-interleaver
block outer
decoder
Output of Outer de-interleaver:
energy dispersal removal
data
confid-ence
MPEG2 t/s
1 0 0 1 0 0 11
convolutional
inner decoder
outer de-interleaver
block outer
decoder
Input to Block decoder (Reed-Solomon):
energy dispersal removal
data
confid-ence
MPEG2 t/s
204 byte (corrupted ?) blocks
Reed-Solomon Error Correction for DVB
RSinc.
The Reed-Solomon error correction process can locate and correct up to 8 corrupted bytes in the block of 204 bytes
47,00,13,08,00,00,A3,C3,C0,00,00,23,74,F2,……,46,8A,9C,00,23,00,00,4C,…..,00,04,06,00,C0,00,34,42,B9,57,...,F5,9C,A3.
Possible Implementation of RS Error Corrector
47,00,13,08,00,00,A3,C3,C0,00,00,23,74,F2,……,46,8A,9C,00,23,00,00,4C,…..,00,04,06,00,C0,00,34,42,B9,57,...,F5,9C,A3.
Syndrome Calculation Error
Location Calculation
Error Calculation
Error Correction
47,00,13,08,00,00,A3,C3,C3,00,00,23,74,F2,……,46,8A,9C,00,37,00,00,4C,…..,00,04,7C,00,C0,00,34,42,B9,43,...,F7,9C,A3.
Input Block
Output Block
Parity bytes no longer needed
convolutional
inner decoder
outer de-interleaver
block outer
decoder
Output from Block decoder (Reed-Solomon):
energy dispersal removal
data
confid-ence
MPEG2 t/s
204 byte (corrupted ?) blocks
188 byte quasi error free blocks
convolutional
inner decoder
outer de-interleaver
block outer
decoder
Energy dispersion removal:
energy dispersal removal
data
confid-ence
MPEG2 t/s
Channel Decoder Stage Summary
Tuner IF filter
1st IF (~36MHz)
DVB-T Channel demodulator & decoder IC
ADCDigital
front endFFT
Chan est. & correct.
Error Correct.
Etc.
Transport stream
RF
AGC amp