The ISDB-T System

Masafumi Saito NHK Science & Technical Research Laboratories (Japan Broadcasting Corporation)

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) MPEG-2 Video

Satellite Error correction RS(204,188)

Coding

Modulation TC-8PSK

Cable Audio

Coding

Multiplexing

Error correction RS(204,188)

Modulation 64QAM

Terrestrial Data

Error correction RS(204,188) +Conv. code

Coding

Modulation Segmented OFDM

Package Media, Communication Systems or 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

frequency OFDM Segment

429 kHz

o

Bandwidth of an OFDM segment is 6/14 MHz (≅ 429 kHz).

o

All segments have a common structure.

Number of OFDM segments is 13 for wide-band ISDB-T and 1 or 3 for narrow-band ISDB-T. o

Multiplexing and Spectrum of ISDB-T Wideband ISDB-T Audio Program

HDTV Program

Audio SDTV for SDTV for Stationary Program Mobile Reception Reception

Narrow band ISDB-T (ISDB-TSB) Audio Audio Program Program Data

Multiplexing

Spectrum 5.6 MHz

5.6 MHz

429 kHz 1.3 MHz

OFDM Segments

Wideband Receiver (Integrated Receiver)

Narrow band Receiver (Pocket-size)

Service Examples Example 1

Example 2 Mobile Reception

Stationary Reception

Example 3

Mobile Reception

Stationary Reception

Mobile Reception

HDTV SDTV

or 3 SDTV Programs

+

Data

Integrated Receiver (all services)

+

Audio and Data

Car Receiver (Audio and Data)

SDTV

+

Data

+

+

Still Picture Data

Mobile Receiver (SDTV, Audio and Data)

+

Data

Pocket-size Receiver (Audio and Data)

Parameters of ISDB-T Parameters

Number of OFDM segments Useful bandwidth Carrier spacing Number of active carriers Modulation Number of symbols per frame

Active symbol duration Guard interval duration Inner code Outer code Time interleaving Useful bit rate

(6MHz Bandwidth)

Mode 2 Mode 3 13 5.575 MHz 5.573 MHz 5.572 MHz 1.984 kHz 3.968 kHz 0.992 kHz 1405 2809 4992 QPSK , 16QAM , 64QAM , DQPSK 204 252ｵs 504ｵs 1.008 ms Mode 1

1/4 , 1/8 , 1/16 , 1/32 of active symbol duration

Convolutional code (1/2 , 2/3 , 3/4 , 5/6 , 7/8)

RS (204,188) 0 ~ 0.44 s 3.651 Mbps ~ 23.234 Mbps

Channel Coding - Single TS - Constant clock rate inserting null-TSP

TS

ReMultiplexer

Outer coder RS (204,188)

Coded stream is divided into up to three layers

Splitter

Energy Dispersal

Delay Adjustment

Byte-wise Interleaving

Convulutional coder

Energy Dispersal

Delay Adjustment

Byte-wise Interleaving

Convulutional coder

Energy Dispersal

Delay Adjustment

Byte-wise Interleaving

Convulutional coder

Code rate: 1/2, 2/3, 3/4, 5/6, 7/8 Compensating for the delay difference among three layers caused by Byte-wise interleaving

Modulation Length of time interleaving: 0 ms, 110 ms, 220 ms, 440 ms, 880 ms Bit Interleaving

Pilot and Control signals

Mapping

Bit Interleaving

Mapping

Bit Interleaving

Mapping

Time Interleaving

Frequency Interleaving

Frequency Interleaver consists of Intra-Segment Interleaver and Inter-Segment Interleaver

- TMCC (Transmission and Multiplexing Configuration Control) - SP (Scattered Pilot) - CP (Continual Pilot) - AC (Auxiliary Channel) OFDM Frame

IFFT

Guard Interval Insertion

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) Tokyo Pilot Experiments 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 TOWER

Transmitting Station of Tokyo Pilot Experiments

Tx Antenna (261 m)

UHF 15 ch (485.15 MHz) Tx power: 100 W ERP: 395W

Field Trials (Fixed Reception)

BER (measured) BER?2e-4 BER> 2e-4 Field Strength (calculated) >70dBµV/m >60dBµV/m >50dBµV/m 0

50 km

Correct Reception Rate (Fixed Reception) Correct Reception Location Rates (%)

100 95 90 85 80 75

Mode 3, 64QAM, 5/6, 13 Seg. Mode 2, DQPSK, 1/2, 1 Seg. Mode 2, 64QAM, 7/8 12 Seg.

70 65 60 35

40

45

50

55

60

65

70

75

Measured Field Strength (dB ｵ V/m)

80

85

Field Trials (Mobile Reception)

Total measured distance - about 3000 km

BER (measured) BER?2e-4 BER> 2e-4 Field Strength (calculated) >70dBµV/m >60dBµV/m >50dBµV/m 0

50 km

Correct Reception Time Rates (%)

Effect of Time Interleaving (Mobile Reception) 100 99%

95 90 85

Mode 2, DQPSK, 1/2 , 13 seg.

80

Depth of time interleaving: 500ms With Time Interleaving Without Time Interleaving

75 70 35

40 45 50 55 60 Measured Field Strength (dBｵ V/m)

65

Pilot Experiments in 11 Areas in Japan Started in April 1999 Purposes: ｷ Development of new services suitable for each region ｷ Confirmation of receiving area ｷ Training engineers, etc.

Sapporo

Sendai

Kanazawa

Nagano

Hiroshima

Tokyo Nagoya Fukuoka Osaka Naha

Takamatsu

Study on Single Frequency Networks (Development of coupling cancelers) q Distribution methods of ISDB-T signals from main transmitters to relay transmitters n Micro Wave l Frequency for this purpose is necessary n Optical Fiber l Construction and running cost is high n Relay Networks l Low cost l Interference by coupling waves is the problem

Coupling Waves at Relay Stations Transmitting Antenna

Mountains, Buildings, etc. Wave from the main transmitter

Coupling Waves f 1 f1 f1

f1 Receiving Antenna NHK

SFN Relay Station

Principle of Coupling Cancelers Receiving Antenna

Wave from Main Station

Coupling: C (? )

Transmitting Antenna

Amplifier: G (? )

+ _ _

W (? ) Transversal Filter

Coupling Canceler Condition for canceling: W (? ) = G (? ) C (? )

Output Signal

Result of Field Trials (Effect of Coupling Cancelers) 10-1 -2

BER

10

BER=7ﾗ 10

Mode 3 Guard Interval 1/8

-3

D/U=-6dB

10-3

D/U=8

D/U=0dB

-4

10

64QAM-OFDM, Without FEC

10-5

20

25 30 C/N [dB]

35

Number of Transmission Stations for Analogue TV

Frequency Allocation in Japan ISDB-T channels (An example)

700

Adjustment of analogue channels

600 … 500 13 14 15 16 17 18 19 … … … 25 26 27 28 29 30 31 32

UHF lower channels (Initial Allocation)

400

Adjustment of analogue channels except for major stations

300

200

100

0

1

2

3

4

5

6

7

8

VHF

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

Channels

UHF

Schedule of Channel Planning in Japan January 1999: Start of a consortium on channel plan April 2000: Draft channel assignment for main stations all over Japan By the end of 2001 Draft channel assignment for major relay stations

Schedule of Implementation of ISDB-T in Japan 1999 2000 2001 2002 2003 2004 2005 2006 2007

Service

Final Standard ? May

Service Start in Tokyo, Osaka and Nagoya (2003) ?

Pilot Experiments on a practical scale Field Experiments

Frequency Planning

Channel Plan for Main Stations ? Apr.

Channel Plan for Major Relay Stations ?

Service Start in other areas (2006) ?

Conclusions n ISDB-T system based on Band Segmented OFDM

was developed in Japan. n The ISDB-T system was standardized as the

digital terrestrial television broadcasting system in 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 the

year 2003.