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.