Download - Itu seminar isdb t 001108
The ISDB-T System
NHK Science & Technical Research Laboratories(Japan Broadcasting Corporation)
Masafumi Saito
Contents
1. Concept of ISDB
2. Requirements for ISDB-T
3. Transmission and Services
4. Experimental Results
5. Present Situation in Japan
6. Conclusions
Concept of ISDB (Integrated Services Digital Broadcasting)
Video
Audio
Data
Coding
Coding
Coding
Multiplexing
Error correctionRS(204,188)
Error correctionRS(204,188)
Error correctionRS(204,188)+Conv. code
ModulationTC-8PSK
Modulation64QAM
ModulationSegmented OFDM
Satellite
Cable
Terrestrial
MPEG-2
Package Media, Communication Systemsor Other Media (DVB and ATSC)
MPEG-2 TS
Requirements for ISDB-T(ISDB-Terrestrial)
ISDB-T should
- have the capability to provide various services, including
HDTV, multi-channel SDTV, data services, etc.
- have sufficient transmission quality for the portable
and mobile reception.
- ensure flexible use of transmission capacity.
- be able to achieve effective use of frequency using
SFN (Single Frequency Networks) technology.
Modulation Scheme of ISDB-T(Band Segmented OFDM)
5.6 MHz
frequency429 kHzOFDM Segment
o Bandwidth of an OFDM segment is 6/14 MHz (≅ 429 kHz).
o All segments have a common structure.
o Number of OFDM segments is 13 for wide-band ISDB-T and 1 or 3 for narrow-band ISDB-T.
Multiplexing and Spectrum of ISDB-T
HDTVProgram
Narrow band Receiver(Pocket-size)
Wideband Receiver(Integrated Receiver)
Multiplexing
AudioProgram
OFDM Segments
5.6 MHz 5.6 MHz 1.3 MHz
Wideband ISDB-TNarrow band ISDB-T
(ISDB-TSB)
429 kHz
SDTV forMobile
Reception
SDTV forStationary Reception
Data
Spectrum
AudioProgram
AudioProgram
AudioProgram
Service Examples
HDTV
or3 SDTV Programs
Stationary Reception
+
+
+
MobileReception
Example 1
+
+
Integrated Receiver(all services)
Car Receiver(Audio and Data)
Mobile Receiver(SDTV, Audio and Data)
Still Picture
+
Example 2 Example 3
DataAudioandData
SDTV
Data
StationaryReception
MobileReception
SDTV
Data Data
MobileReception
Pocket-size Receiver(Audio and Data)
Parameters of ISDB-T (6MHz Bandwidth)
QPSK , 16QAM , 64QAM , DQPSK
Convolutional code (1/2 , 2/3 , 3/4 , 5/6 , 7/8)
Parameters
Number of OFDM segmentsUseful bandwidth
Carrier spacingNumber of active carriers
ModulationNumber of symbols per frameActive symbol durationGuard interval duration
Inner code
Outer code
Useful bit rate
Mode 1 Mode 2 Mode 313
5.575 MHz 5.573 MHz 5.572 MHz3.968 kHz 1.984 kHz 0.992 kHz
1405 2809 4992
204252オs 504オs 1.008 ms
1/4 , 1/8 , 1/16 , 1/32 of active symbol duration
RS (204,188)0 ̃ 0.44 s
3.651 Mbps ̃ 23.234 Mbps
Time interleaving
Channel Coding
Re-Multiplexer
- Single TS- Constant clock rateinserting null-TSP
Compensating for the delay differenceamong three layers caused by Byte-wise interleaving
Code rate: 1/2, 2/3, 3/4, 5/6, 7/8
Outer coderRS (204,188)
EnergyDispersal
DelayAdjustment
Byte-wiseInterleaving
Convulutionalcoder
SplitterEnergy
Dispersal
EnergyDispersal
DelayAdjustment
DelayAdjustment
Byte-wiseInterleaving
Byte-wiseInterleaving
Convulutionalcoder
ConvulutionalcoderCoded stream is divided
into up to three layers
TS
Modulation
Length of time interleaving:0 ms, 110 ms, 220 ms, 440 ms, 880 ms
Frequency Interleaver consists ofIntra-Segment Interleaver andInter-Segment Interleaver
- TMCC (Transmission and MultiplexingConfiguration Control)
- SP (Scattered Pilot)- CP (Continual Pilot)- AC (Auxiliary Channel)Bit
Interleaving
Bit Interleaving
Bit Interleaving
Mapping
Mapping
Mapping
TimeInterleaving
FrequencyInterleaving
OFDMFrame
Pilot and Control signals
IFFT Guard IntervalInsertion
Guard Interval Ratio:1/32, 1/16, 1/8, and 1/4
Features of the Transmission Scheme of ISDB-T
o Different parameters can be set for each layer → Wide variety of services
o Robust against fading in mobile environment → Suitable for mobile reception
o Segment structure → Partial reception is possible
o OFDM modulation → Effective use of frequency by SFN (Single Frequency Networks)
Practical Experiments (Field Trials)
Phase 1 (November 1998 to March 1999)HDTV, Multi-channel SDTV, Mobile reception, etc.
Phase 2 (April 1999 to March 2000)Data broadcasting, Multimedia services, EPG, etc.
Phase 3 (April 2000 to March 2002)Gap-fillers, Multimedia services, etc.
Tokyo Pilot Experiments
Tx Antenna (261 m)
TOKYO TOWER
UHF 15 ch (485.15 MHz)
Tx power: 100 W
ERP: 395W
Transmitting Station of Tokyo Pilot Experiments
Field Trials (Fixed Reception)
0 50 km
>70dBµV/m
>60dBµV/m
>50dBµV/m
BER?2e-4BER> 2e-4
BER (measured)
Field Strength (calculated)
60
65
70
75
80
85
90
95
100
35 40 45 50 55 60 65 70 75 80 85
Measured Field Strength (dB オ V/m)
Cor
rect
Rec
epti
on L
ocat
ion
Rat
es (%
)
Mode 3, 64QAM, 5/6, 13 Seg.Mode 2, DQPSK, 1/2, 1 Seg.Mode 2, 64QAM, 7/8 12 Seg.
Correct Reception Rate(Fixed Reception)
Field Trials (Mobile Reception)
Total measured distance- about 3000 km
0 50 km
>70dBµV/m
>60dBµV/m
>50dBµV/m
BER?2e-4BER> 2e-4
BER (measured)
Field Strength (calculated)
Effect of Time Interleaving(Mobile Reception)
70
75
80
85
90
95
100
35 40 45 50 55 60 65Measured Field Strength (dBオ V/m)
Cor
rect
Rec
epti
on T
ime
Rat
es (%
)
With Time Interleaving Without Time Interleaving
Mode 2, DQPSK, 1/2 , 13 seg.
99%
Depth of time interleaving: 500ms
Pilot Experiments in 11 Areasin Japan
Sapporo
Sendai
Nagano
Kanazawa
Nagoya
Osaka
Hiroshima
Fukuoka
Naha Takamatsu
Started in April 1999
Tokyo
Purposes:キ Development of new servicessuitable for each region
キ Confirmation of receiving areaキ Training engineers, etc.
Study on Single Frequency Networks(Development of coupling cancelers)
q Distribution methods of ISDB-T signals from main transmitters to relay transmittersn Micro Wave
l Frequency for this purpose is necessaryn Optical Fiber
l Construction and running cost is highn Relay Networks
l Low costl Interference by coupling waves is the problem
Coupling Waves at Relay Stations
SFN Relay Station
f 1Mountains, Buildings, etc.
NHK
Receiving Antenna
Transmitting Antenna
f 1
f 1Wave from the main transmitter
f 1
Coupling Waves
Principle of Coupling Cancelers
Coupling Canceler
Condition for canceling: W (? ) = G (? ) C (? )
+
_
_W (? )
Amplifier:G (? )
Coupling: C (? )Receiving Antenna
Wave from Main Station
Transmitting Antenna
TransversalFilter
Output Signal
Result of Field Trials(Effect of Coupling Cancelers)
20 25 30 3510-5
10-4
10-3
10-2
10-1
C/N [dB]
BER=7ラ 10-3
D/U=-6dB
D/U=0dB
D/U=8
64QAM-OFDM,Without FEC
BE
R
Mode 3Guard Interval 1/8
Frequency Allocation in JapanN
umbe
r of T
rans
mis
sion
Sta
tions
for A
nalo
gue
TV
0
100
200
300
400
500
600
700
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62
VHF Channels
UHF lower channels(Initial Allocation)
Adjustment of analoguechannels except formajor stations
Adjustment ofanalogue channels
13 14 15 16 17 18 19 … … … 25 26 27 28 29 30 31 32
ISDB-T channels (An example)
…
UHF
Schedule of Channel Planning in Japan
January 1999:Start of a consortium on channel plan
April 2000: Draft channel assignment for main stationsall over Japan
By the end of 2001Draft channel assignment for major relaystations
Schedule of Implementation of ISDB-T in Japan
1999
?Final Standard
?May
Pilot Experimentson a practical scale
Service Start in Tokyo, Osaka and Nagoya (2003)
Service
FrequencyPlanning
FieldExperiments
?Apr.
Channel Plan for Main Stations
?
2000 2001 2002 2003 2004 2005 2006 2007
Service Start in other areas (2006)
?
Channel Plan for Major Relay Stations
Conclusions
n ISDB-T system based on Band Segmented OFDM was developed in Japan.
n The ISDB-T system was standardized as thedigital terrestrial television broadcasting systemin Japan in May 1999.
n Pilot experiments of ISDB-T are carried out in 11 major cities in Japan.
n ISDB-T services are planned to start before theyear 2003.