Single transmission for fixed, vehicular and handheld receivers

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Single transmission for fixed, vehicular and
handheld receivers
ISDB-T Transmission Technology
27 September 2007

• Kazunori Yokohata
• NHK (Japan Broadcasting Corporation)
• Science and Technical Research Laboratories

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Contents

• The schedule for transition to DTTB in Japan
• Features of ISDB-T
• Key technology for ISDB-T
• OFDM
• Frequency Time interleaving technology
• Hierarchical transmission
• Mobile reception of ISDB-T
• One-segment service for handheld receivers
• Emergency warning system (EWS)
• HDTV vehicular technology
• Single Frequency Network (SFN)
• Broadcast wave relays
• Technical features of DTTB systems in the world
• Summary of ISDB-T

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Schedule for transition to DTTB in Japan
2000
2003
2006
2011
Fully digital
Launched on Dec. 1, 2003
Digital Terrestrial TV (ISDB-T)
Terrestrial TV
Tokyo, Nagoya, Osaka Metro Area
Receivable throughout Japan
Other prefectural capital cities (As of Dec. 2006)
Service for handheld receivers commenced in April
2006
Conventional Analog TV
Switch-over on July 24, 2011
Complete transition to DTTB (End of analog TV
broadcasting service)
Analog-to-Analog Conversion Commenced on Feb. 9,
2003
Digital Terrestrial Audio (ISDB-TSB)
Experimental broadcasts commenced in Oct. 2003 in
Tokyo, Osaka
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Schedule for DTTB roll-out
Tokyo

• Expansion of DTTB coverage (number of households)
  
• 2003 25 (12 million) Commencement of DTTB

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Schedule for DTTB roll-out
Tokyo

• Expansion of DTTB coverage (number of households)
  
• 2003 25 (12 million) Commencement of DTTB
• 2004 38 (18 million)
• 2005 57 (27 million)

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Schedule for DTTB roll-out
Tokyo

• Expansion of DTTB coverage (number of households)
  
• 2003 25 (12 million) Commencement of DTTB
• 2004 38 (18 million)
• 2005 57 (27 million)
• 2006 84 (39.5 million) Commencement in all
  prefectural capital cities

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Complete transition to DTTB by 2011

• Distribution of DTTB signals throughout Japan
• Requires a large number of relay stations.

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Features of ISDB-T

• High quality TV and sound (HDTV) or
  Multi-broadcasting program
• Robustness for interferences
• OFDM
• Time and frequency interleaving technology
• Hierarchical transmission up to 3 layers
• Modulation, coding rates, length of time
  interleaving
• Parameters are sent in TMCC (transmission and
  multiplexing configuration control) signal
• Multimedia Services
• Data broadcasting Regional information service
• Interaction Quizzes, questionnaires, requests,
  voting
• Combined with communication services
• Inter-operability with Other Broadcasting Media
• ISDB-S (for satellite) and ISDB-C (for cable)
• Partial reception with handheld receivers
• Simultaneous with HDTV service
• Mobile reception with vehicular receivers
• SFN Operation

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Outline of ISDB-T transmission scheme
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Receiving environment for terrestrial TV
broadcasting
Fixed reception
Vehicular reception

• Multipath interference
• Fading interference
• Impulse, man-made noise
• Shadowing

Handheld reception
Receiving environment is very severe.
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Key technologies for ISDB-T

• To overcome the terrestrial severe receiving
  environment
• OFDM
• Frequency Time-interleaving
• To realize the effective and smart transmission
• Hierarchical transmission by Band Segmented
  Transmission OFDM
• Realization of One-Segment service for handheld
  reception

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OFDM signal

• OFDM is
• Multi-carrier modulation
• More than 2,000 carriers in a 6MHz TV channel
• Long symbol duration compare to single-carrier
  transmission system
• Multipath proof modulation
• by adding guard interval
• Modulation/demodulation can be processed by
  IFFT/FFT.

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Frequency and time interleaving (I)
Original data
Suitable for multipath interference. But,
ineffective to flat-fading and impulse noise.
Suitable for fading and impulse
interference. But, ineffective to multipath
interference.
Suitable for all kinds of interference.
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Frequency and time interleaving (II)
Burst errors
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Effect of frequency and time interleaving
Laboratory test results
Without time-interleaver (Error remains even in
high C/N)
With time-interleaver (No error at more than
C/N20dB)
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Hierarchical transmission examples (Band
Segmented Transmission - OFDM and services in
ISDB-T)
Digital Terrestrial Sound Broadcasting (ISDB-TSB)
Digital Terrestrial Television Broadcasting
(ISDB-T)
1-segment Service (Partial reception)
SDTV for Mobile Reception
SDTV for fixed Reception
1-segment Service (Partial reception)
HDTV Program
Audio Program
Audio Program
Data
Multiplexing
Layer C
Layer B
Layer B
Layer A
Layer A
Spectrum
5.6 MHz
5.6 MHz
429 kHz
1.3 MHz
OFDM Segments
handheld Receiver
Fixed / vehicular Receiver
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Multi-broadcasting and multi-view service

• Multi-broadcasting service

Portable-receiver services
HDTV Movie
HDTV Movie (low bit rate)
HDTV
Baseball
SDTV Baseball (special channel)
Time
Viewers switch to subchannel
Changes automatically to next program

• Multi-view service

Portable-receiver services
HDTV
SDTV (Golf, main program)
HDTV
SDTV (Golf, 17th hole)
Next program
Golf
SDTV (Golf, 18th hole)
Time
Changes automatically to next program
Viewers switch to subchannel
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For flexible broadcasting services

• Hierarchical transmission
• Transmission segment groups with different
  transmission parameters
• Maximum of three layers can be transmitted
  simultaneously in a channel
• Possible to select parameters to adjust services
  such as HDTV, vehicular and so on

ISDB-T in Japanese 6MHz system
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Broadcasting services for mobile receivers

• Single transmission for fixed, mobile (vehicular
  and handheld) receivers
• Receiving both digital terrestrial data
  broadcasting (partial reception)
• and Internet service via wireless communications

Digital Terrestrial Broadcasting
Fixed Receiver
Handheld Receiver
Internet, etc.
Vehicular Receiver
Example of bandwidth assignment Video 244
kbps Audio 55 kbps Data 55 kbps
EPG 20 kbps PSI / SI 37 kbps
Mode 3, GI ratio 1/8, QPSK 2/3 Data bit-rate
416 kbps
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Handheld receivers for ISDB-T One-Seg in Japanese
market
Service commenced in April 2006
SoftBank 905SH
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Handheld receivers

• Get information related to a program from data
  broadcasting or Internet with low bit-rate video

Low-bit-rate video from broadcasting channel

• Video AVC/H.264 (about 244 kbps)
• Audio AAC-SBR (about 55 kbps)
• Data broadcasting
• Closed caption
• Wake up function in case of
• emergency

Information from broadcasting and communication
channel
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Service model of One-Segment service for
handheld communication terminals

• Various types of services can be realized using
  functionalities
• combining One-segment service reception and
  mobile communication

Linkage from broadcasting to communication
Link to web sites
Mobile data online
Data broadcasting view
Broadcasting program view
NHK
NHK
BML
BML
Receive and watch TV program via Broadcasting
Receive and browse data broadcasting via
Broadcasting
TV program is received via Broadcasting
(top), data is received via mobile Internet
(bottom)
Mobile Internet services of various provider
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Emergency Warning System for broadcasting

• Remote activation of Radio TV ready for EWS
• AM, FM Radio TV Control signal and Alert
  Sound
• Digital Broadcasting (ISDB-T) Emergency Warning
  Control Flag
• In Japan, EWS for analog broadcasting has been
  operated since September 1985
• EWS test signals are monthly broadcasted in Japan

Automatic Activation
Alert
EWS
Meteorological Agency
Broadcasting Station
Broadcasting Service Area
Transmitter
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Research Development of handheld receivers with
EWS signal in ISDB-T
Wake-up handheld receiver
Receive only EWS Signal
Emergency warning broadcast
The system does not employ FFT, but instead stays
on stand-by for the EMS signal component.
Low power consumption stand-by mode
Active mode to receive emergency warning
broadcast
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The activation flag for alert broadcasting in
ISDB-T for handheld receivers
bit 203
TMCC Transmission and Multiplexing Configuration
Control (204 bits/frame)
bit 26
??????
??????
??????
bit 0
Time
???
???
???

Header
Seg 0 (429 kHz)
The activation flag for alert broadcasting
Frequency
Digital terrestrial broadcasting for handheld
receiver
seg 0 (429 kHz)
seg 11 (429 kHz)
seg 9 (429 kHz)
seg 7 (429 kHz)
seg 5 (429 kHz)
seg 3 (429 kHz)
seg 1 (429 kHz)
seg 2 (429 kHz)
seg 4 (429 kHz)
seg 6 (429 kHz)
seg 8 (429 kHz)
seg 10 (429 kHz)
seg 12 (429 kHz)
Frequency
DTTB full service (6 MHz/channel)
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EWS low power consumption technology for
handheld receivers
LCD 2.5
Cell phone that be connected small prototype
receiver
Small prototype receiver that detect the
activation flag for alert broadcasting
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HDTV vehicular reception technology for ISDB-T

• Conventional reception
• Robust modulation (16QAM ½ or QPSK)
• 1 receiving antenna
• SDTV
• Diversity reception
• 64QAM (transmission same as in fixed reception)
• 2-4 branches (number of receiving antennas)
• HDTV
• Diversity reception technology for motor vehicles
• Space diversity
• HDTV programs are available in a vehicle with
  high quality, clear and noiseless image
• A HDTV vehicular system based on the diversity
  reception technology is already on sale in Japan

Already on sale in Japan
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Diversity reception system for mobile reception

• After multiplying weight vector, the signals at
  each branch are diversity combined for each
  sub-carrier to maximize the C/N in each
  sub-carrier
• The weight vector is computed from scattered
  pilot (SP) signals contained in the ISDB-T signal

Weight vector
Branch
1
FFT 1
D(0)

FFT 2
2
3
FFT 3
D(i)

Spectrum of diversity combined signal
FFT 4
4
0 1 2 3 ????????? k carrier
D(k-1)
Spectra of receiving OFDM signal
Block diagram of diversity reception system
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Result of vehicle reception field experiment
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SFN Single Frequency Network

• ISDB-T enables SFN
• Addition of guard interval of OFDM
• Robustness to multipath interference
• Effective utilization of frequency channel
• NHK has recently developed and put into service
  SFN On-air (broadcast-wave) relays technology for
  more effective frequency utilization and
  equipment cost reduction

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The first practical SFN in Ibaraki prefecture
Juo Sta.
Hitachi-kamine Fx.
Yamagata Sta.
Hitachi Sta.
Mito Sta.
24.2 km
Kaba-san Fx.
53.6km
Mito Studio
Shoubu-Kuki Fx.
47.3 km
Main transmitter (Tokyo Tower)
Tokyo Studio
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On-air relays (Broadcast-wave relays)

• On-air relays
• On-air waves from a station of the previous stage
  are received and retransmitted.
• This is the same method as that for a
  conventional analog TV broadcasting.
• On-air relays have the advantage of lower
  equipment cost.
• Japanese DTTB requires a large number of relay
  stations.
• A dedicated link, such as a microwave link, is
  not required.
• Securing frequency resources for the dedicated
  link is also not required.
• Not only MFN but also SFN is desired for on-air
  relays.

Main transmitter
Relay station
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Problem with On-air relays

• Interferences in reception at relay stations
• Multipath
• Fading
• Co-channel interference (analog/digital) from
  other stations
• Coupling loop interference( C L I ) feed back
  loop in SFN relay

Multipath
C L I
Desired wave
T T L
Co-channel interference
Large area SFN relay station
SFN relay station
S T L
Co-channel interference
Desired wave
Desired wave
Main transmitter
Multipath fading
Broadcasting station
Multipath
Sea / Lake
reflection
Large area MFN relay station
MFN relay station
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Compensation technologies for reducing
interference
? excellent, ? good, ineffective
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Technical features of DTTB systems
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Summary of ISDB-T Transmission system

• ISDB-T promises flexible broadcasting services
  through hierarchical transmission
• ISDB-T is robust for interferences because of
  OFDM, time and frequency interleaving technology
• ISDB-T has technological advantages in mobile
  reception
• HDTV and mobile service can be transmitted
  simultaneously
• one-segment service for handheld receivers
• HDTV vehicular system using diversity reception
  technology
• The same HDTV broadcasted for fixed receiver can
  be viewed in motor vehicle
• EWS (Emergency Warning System)
• Handheld receivers woken up by EWS signal alerts
  the user quickly of earthquake and tsunami
  warnings
• SFN for effective frequency utilization
• On June 29, 2006, Brazil decided to adopt a DTTB
  system based on ISDB-T

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• Yokohata.k-jm_at_nhk.or.jp
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