The ISDB-T System. Masafumi Saito. NHK Science & Technical Research Laboratories (Japan Broadcasting Corporation)

Transcription

1 The ISDB-T System Masafumi Saito NHK Science & Technical Research Laboratories (Japan Broadcasting Corporation)

2 Contents 1. Concept of ISDB 2. Requirements for ISDB-T 3. Transmission and Services 4. Experimental Results 5. Present Situation in Japan 6. Conclusions

3 Concept of ISDB (Integrated Services Digital Broadcasting) Video Audio Data MPEG-2 Coding Coding Multiplexing Coding Satellite Error correction RS(204,188) Cable Error correction RS(204,188) Terrestrial Error correction RS(204,188) +Conv. code Modulation TC-8PSK Modulation 64QAM Modulation Segmented OFDM Package Media, Communication Systems or Other Media (DVB and ATSC) MPEG-2 TS

4 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.

5 Modulation Scheme of ISDB-T (Band Segmented OFDM) 5.6 MHz OFDM Segment 429 khz frequency Bandwidth of an OFDM segment is 6/14 MHz ( 429 khz). 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.

6 Multiplexing and Spectrum of ISDB-T Wideband ISDB-T Narrow band ISDB-T (ISDB-TSB) Audio Program HDTV Program Audio Program SDTV for Mobile Reception SDTV for Stationary Reception Audio Program Audio Program Data Multiplexing Spectrum OFDM Segments 5.6 MHz 5.6 MHz 429 khz 1.3 MHz Wideband Receiver (Integrated Receiver) Narrow band Receiver (Pocket-size)

7 Service Examples Example 1 Example 2 Example 3 Stationary Reception HDTV or 3 SDTV Programs Data Mobile Reception Audio and Data SDTV Stationary Reception Data SDTV Mobile Reception Data Mobile Reception Still Picture Data Integrated Receiver (all services) Car Receiver (Audio and Data Mobile Receiver (SDTV, Audio and Data) Pocket-size Receiver (Audio and Data)

8 Parameters of ISDB-T (6MHz Bandwidth) 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 Mode 1 Mode 2 Mode MHz MHz MHz khz khz khz QPSK, 16QAM, 64QAM, DQPSK s 504s ms 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) s Mbps Mbps

9 Channel Coding - Single TS - Constant clock rate inserting null-tsp Energy Dispersal Delay Adjustment Byte-wise Interleaving Convulutional coder TS Re- Multiplexer Outer coder RS (204,188) Splitter Energy Dispersal Delay Adjustment Byte-wise Interleaving Convulutional coder Coded stream is divided into up to three layers Energy Dispersal Delay Adjustment Byte-wise Interleaving Convulutional coder Compensating for the delay difference among three layers caused by Byte-wise interleaving Code rate: 1/2, 2/3, 3/4, 5/6, 7/8

10 Modulation Length of time interleaving: 0 ms, 110 ms, 220 ms, 440 ms, 880 ms Bit Interleaving Mapping Pilot and Control signals - TMCC (Transmission and Multiplexing Configuration Control) - SP (Scattered Pilot) - CP (Continual Pilot) - AC (Auxiliary Channel) Bit Interleaving Mapping Time Interleaving Frequency Interleaving OFDM Frame IFFT Guard Interval Insertion Bit Interleaving Mapping Frequency Interleaver consists of Intra-Segment Interleaver and Inter-Segment Interleaver Guard Interval Ratio: 1/32, 1/16, 1/8, and 1/4

11 Features of the Transmission Scheme of ISDB-T Different parameters can be set for each layer Wide variety of services Robust against fading in mobile environment Suitable for mobile reception Segment structure Partial reception is possible OFDM modulation Effective use of frequency by SFN (Single Frequency Networks)

12 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.

13 TOKYO TOWER Transmitting Station of Tokyo Pilot Experiments Tx Antenna (261 m) UHF 15 ch ( MHz) Tx power: 100 W ERP: 395W

14 Field Trials (Fixed Reception) BER (measured) BER2e-4 BER 2e-4 Field Strength (calculated) >70dBµV/m >60dBµV/m >50dBµV/m 0 50 km

15 Correct Reception Rate (Fixed Reception) 100 Correct Reception Location Rates (%) Mode 3, 64QAM, 5/6, 13 Seg. Mode 2, DQPSK, 1/2, 1 Seg. 70 Mode 2, 64QAM, 7/8 12 Seg Measured Field Strength (db V/m)

16 Field Trials (Mobile Reception) Total measured distance - about 3000 km BER (measured) BER2e-4 BER 2e-4 Field Strength (calculated) >70dBµV/m >60dBµV/m >50dBµV/m 0 50 km

17 Effect of Time Interleaving (Mobile Reception) Correct Reception Time Rates (%) % Mode 2, DQPSK, 1/2, 13 seg. Depth of time interleaving: 500ms With Time Interleaving Without Time Interleaving Measured Field Strength (db V/m)

18 Pilot Experiments in 11 Areas in Japan Started in April 1999 Purposes: Development of new services suitable for each region Confirmation of receiving area Training engineers, etc. Fukuoka Hiroshima Naha Sapporo Kanazawa Sendai Nagano Tokyo Nagoya Osaka Takamatsu

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

20 Coupling Waves at Relay Stations Transmitting Antenna Mountains, Buildings, etc. Wave from the main transmitter Coupling Waves f 1 f 1 f 1 Receiving Antenna f 1 SFN Relay Station

21 Principle of Coupling Cancelers Receiving Antenna Coupling: C ( ) Transmitting Antenna Wave from Main Station + W ( ) Transversal Filter Amplifier G ( ) Output Signal Coupling Canceler Condition for canceling: W ( ) = G ( ) C ( )

22 Result of Field Trials (Effect of Coupling Cancelers) 10-1 BER D/U= BER= D/U=-6dB Mode Guard Interval 1/ QAM-OFDM, Without FEC D/U=0dB C/N [db]

23 Frequency Allocation in Japan Number of Transmission Stations for Analogue TV ISDB-T channels (An example) UHF lower channels (Initial Allocation) Adjustment of analogue channels Adjustment of analogue channels except for major stations VHF Channels UHF

24 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

25 Schedule of Implementation of ISDB-T in Japan Service Final Standard May Service Start in Tokyo, Osaka and Nagoya (2003) Service Start in other areas (2006) Field Experiments Pilot Experiments on a practical scale Frequency Planning Channel Plan for Main Stations Apr. Channel Plan for Major Relay Stations

26 Conclusions ISDB-T system based on Band Segmented OFDM was developed in Japan. The ISDB-T system was standardized as the digital terrestrial television broadcasting system in Japan in May Pilot experiments of ISDB-T are carried out in 11 major cities in Japan. ISDB-T services are planned to start before the year 2003.