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Integrated Services Digital Broadcasting

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`Integrated Services Digital Broadcasting (ISDB) is the digital television (DTV) and digital audio broadcasting (DAB) format that Japan has created to allow radio and television stations there to convert to digital.

Missing image
ISDB-T.jpg
A picture of ISDB-T (taken during a tour of the NHK Osaka broadcasting station)
Contents

Introduction

ISDB is maintained by ARIB. The standards can be obtained for free at the DiBEG website and at ARIB.

The core standards of ISDB are ISDB-S (satellite television), ISDB-T(terrestrial), ISDB-C (cable) and 2.6GHz band mobile broadcasting which are all based on MPEG-2 video and audio coding as well as the transport stream described by the MPEG-2 standard, and are capable of high definition television (HDTV). ISDB-T and ISDB-Tsb are for mobile reception in TV bands.

The concept was named for its similarity to ISDN, because both allow multiple channels of data to be transmitted together (a process called multiplexing). This is also much like another digital radio system, Eureka 147, which calls each group of stations on a transmitter an ensemble; this is very much like the multi-channel digital TV standards ATSC and DVB-T. ISDB-T operates on unused TV channels, an approach taken by other countries for TV but never before for radio.

Video and audio compression

ISDB has adopted the MPEG-2 video and audio compression system. ATSC and DVB also adopted the same system.

Transmission

The various flavors of ISDB differ mainly in the modulations used, due to the requirements of different frequency bands. The 12 GHz band ISDB-S uses PSK modulation, 2.6 GHz band digital sound broadcasting uses CDM and ISDB-T (in VHF and/or UHF band) uses COFDM with PSK/QAM.

Interaction

Besides audio and video transmission, ISDB also defines data connections (Data broadcasting) with the internet as a return channel over several media (10Base-T/100Base-T, Telephone line modem, Mobile phone, Wireless LAN (IEEE 802.11) etc.) and with different protocols. This is used, for example, for interactive interfaces like data broadcasting (ARIB STD B-24) and electronic program guides (EPG).

Interfaces and Encryption

ISDB describes a lot of (network) interfaces, but most importantly the Common Interface for Conditional Access (ARIB STD-B25) with the Common Scrambling Algorithm (Multi-2) required for (de-)scrambling TV.

The ISDB CAS system is operated by a company named B-CAS in Japan; the CAS card is called B-CAS card. The Japanese ISDB signal is always encrypted by the B-CAS system even if it is a free TV program. That is why it is commonly called "Pay per view system without charge". An interface for mobile reception is under consideration.

ISDB supports RMP (Rights management and protection). Since all DTV systems carry digital data content, a DVD or HD recorder could easily copy content losslessly, so that a great deal of pirated content could be circulating the market. Hollywood requested copy protection; this was the main reason for RMP. The content has three modes: “Copy once”, “Copy free” and “Copy never”. In “Copy once” mode a program can be stored on a hard disc recorder, but cannot be copied.

Receiver

There are two types of ISDB receiver: TV and STB (Set top box). The aspect ratio of ISDB television is 16:9; televisions fulfilling these specs are called Hi-vision TVs. There are three tv types: CRT (Cathode ray tube), PDP (Plasma display panel) and LCD (Liquid crystal display), with LCD being most popular Hi-Vision format on the Japanese market right now.

LCD share as measured by JEITA in November 2004 was about 60 %. While PDP set occupies the high end market with units that are over 50 inches (1270 mm), PDP and CRT set shares are about 20% each. CRT set are considered low end for Hi-Vision.

STB is sometimes referred to as digital tuner. High-end ISDB STB have several interfaces:

Services

  1. ISDB provides HDTV and/or Multi-SDTV services within one channel.
  2. ISDB provides Data broadcasting.

ISDB-S

History

Japan started digital broadcasting using the DVB-S standard by PerfecTV in October/1996 and DirecTV in December/1997 with communication satellites. Still, the DVB-S did not satisfy the requirements of Japanese broadcasters, among others NHK and commercial broadcasting stations like NTV, TBS, Fuji TV, TV Asahi, TV Tokyo and WOWOW. Consequently, ARIB developed the ISDB-S standards. The requirements were, among others HDTV capability, interactive services, network access and effective frequency utilization. The DVB-S standard allows the transmission of a bit stream of roughly 34 Mbit/s with a satellite transponder, which means that the transponder can send a HDTV channel. Unfortunately, broadcasting satellite had only 4 vacant transponders, which led ARIB and NHK to develop ISDB-S: The new standard could transmit about 51 Mbit/s with a single transponder, which means that ISDB-S is 1.5 times more efficient than DVB-S and that one transponder can transmit two HDTV channels, along with other independent audio and data. Digital satellite broadcasting (BS digital) was started by NHK and followed commercial broadcasting stations on the 1st of December, 2000. Today, SkyperfecTV!, successor of Skyport TV, Sky D, CS burn, Platone, EP, DirecTV, J Sky B and PerfecTV!, adopted ISDB-S system at the east longitude 110 degree wide band communication satellite.

Technical specification

Summary of ISDB-S(Satellite digital broadcasting)

Transmission
channel coding
Modulation TC8PSK,QPSK,BPSK
(Hierarchical transmission)
Error correction coding Inner coding:Trellis [TC8PSK] and Convolution

Outer coding :RS(204,188);

TMCC:Convolution coding+RS
Time domain multiplexing TMCC
Conditional Access Mutli-2
Data broadcasting ARIB STD B-24(BML, ECMA script)
Service information ARIB STD B-10
Multiplexing MPEG-2 Systems
Audio coding MPEG-2 Audio(AAC)
Video coding MPEG-2 Video

Channel

Frequncy and channel specification of Japanese Satellite using ISDB-S

Method BS digital broadcasting Wide band CS digital broadcasting
Frequency band 11.7 to 12.2 GHz 12.2 to 12.75 GHz
Transmission bit rate 51 Mbit/s (TC8PSK) 40 Mbit/s (QPSK)
Transmission band width 34.5 MHz* 34.5 MHz
  • Compatible to 27 MHz band satellite transponder for analog FM broadcasting.

ISDB-T

History

HDTV was invented at NHK STRL. The research of HDTV started as early as in the 1960s, though onlyn in 1973 a standard was proposed to the ITU-R (CCIR). In the 1980's, the television camera, high definition cathode-ray tube, video tape recorder and editing equipment among others have developed. In 1982 NHK developed MUSE (Multiple sub-nyquist sampling Encoding), the first HDTV video compression and transmission system. MUSE adopted digital video compression system, but for transmission frequency modulation had been adopted after a digital-to-analog converter converted the digital signal. In 1987, NHK made demonstration of MUSE in the Washington D.C and NAB. The demonstration made great impression on the U.S.. As a result of this, the U.S. developed ATSC, the first terrestrial digital HDTV. Europe later also developed their own HDTV-system, DVB. Japan started R&D of a completely digital system in the 1980's that led to ISDB. Japan started terrestrial digital broadcasting using ISDB-T standard by NHK and commercial broadcasting stations on the 1st of December, 2003.

Feature

ISDB-T is characterized by the following features:

  • ISDB-T can transmit a HDTV channel and a mobile phone channel within the 6MHz bandwidth usually reserved for TV transmissions.
  • ISDB-T allows to switch to two or three SDTV channels instead of one HDTV channel (multiplexing SDTV channels).
  • The combination of these services can be changed at anytime.
  • ISDB-T provides interactive services with data broadcasting.
  • ISDB-T provides EPG (Electronic Program Guides).
  • ISDB-T supports internet access as a return channel that works to support the data broadcasting. Internet access is also provided on mobile phones.
  • ISDB-T provides SFN (Single frequency Network) and on-channel repeater technology. SFN makes effcient utilization of the frequency resource (spectrum).
  • ISDB-T provides robustness to multipath interference ("ghosting").
  • ISDB-T provides robustness to impulse noises that come from motor vehicles and power lines in urban environments.
  • ISDB-T allows HDTV to be received on moving vehicles at over 100 km/h; DVB-T can only receive SDTV on moving vehicles, while ATSC can not be received on moving vehicles at all.
  • ISDB-T can be received on mobile phones moving at a speed over 400 km/h.

Adoption

ISDB-T was adopted in commercial transmissions in Japan in December 2003. It comprises a market of about 100 million television sets. ISDB-T had 2 million subscribers as of end 2004.

Brazil, which currently uses an analogue TV system (PAL-M) that slightly differs from any other country's, is also considering ISDB-T for its DTV format. Other than that, there are no other countries that are considering ISDB, although it does seem to have an advantage over ATSC and DVB-T in reception tests. The ABERT/SET group in Brazil did system comparison tests of DTV under the supervision of the CPqD foundation. The comparison tests were done under the direction of a work group of SET (the Brazilian Engineers Society of Television) and ABERT (the Brazilian Association of the broadcaster of Radio and Television). The ABERT/SET group selected ISDB-T as the best in the digital broadcasting systems among ATSC, DVB-T and ISDB-T. ISDB-T was pointed out as the most flexible of all for better answering the necessities of mobility and portability. It is most efficient for mobile and portable reception.

Technical specification

Segment struture

ARIB has developed the segment structure called OFDM (see figure). ISDB-T divides the frequency band of one channel into thirteen segments. Broadcaster can select the combination of segments to use: this choice of segment structure allows for flexibility of services. For example, ISDB-T can transmit a LDTV and a HDTV using one TV channel or change to 3 SDTV, a switch that can be performed anytime. ISDB-T can also change the modulation scheme at the same time.

Seg.13 Seg.11 Seg.9 Seg.7 Seg.5 Seg.3 Seg.1 Seg.2 Seg.4 Seg.6 Seg.8 Seg.10 Seg.12
FIGURE Spectrum segment structure of ISDB-T

Summary of ISDB-T

Transmission
channel coding
Modulation 64QAM-OFDM,

16QAM-OFDM,
QPSK-OFDM,
DQPSK-OFDM

(Hierarchical transmission)
Error correction coding Inner coding,

Convolution 7/8,3/4,2/3,1/2

Outer coding :RS(204,188)
Guard interval 1/16,1/8,1/4
Interleaving Time, Frequency, bit, byte
Frequency domain multiplexing BST-OFDM (Segmented structure OFDM)
Conditional Access Mutli-2
Data broadcasting ARIB STD B-24(BML, ECMA script)
Service information ARIB STD B-10
Multiplexing MPEG-2 Systems
Audio coding MPEG-2 Audio (AAC)
Video coding MPEG-2 Video MPEG-4 AVC /H.264*
  • H.264 used in one segment broadcasting for Mobile phone.

Channel

Specification of Japanese terrestrial digital broadcasting using ISDB-T

Method terrestrial digital broadcasting
Frequency band VHF/UHF,Super high band
Transmission bit rate 19 Mbit/s(64QAM)
Transmission band width 5.6 MHz*
  • Compatible to 6 MHz band terrestrial analog TV broadcasting.

2.6 GHz Satellite Sound digital broadcasting

MobaHo! is the name of the services that uses the Mobible satellite digital audio broadcasting specifiecations. MobaHo! started its service on 20th October, 2004.

ISDB-Tsb

ISDB-Tsb the is terrestrial digital sound broadcasting specification. The technical specification is the same as ISDB-T. ISDB-Tsb supports the coded transmission of OFDM siginals.

ISDB-C

ISDB-C is cable digital broadcasting specification. The technical specification is developed by JCTEA.

Standards

ARIB and JCTEA developed the following standards. Some part of standards are located on the pages of ITU-R and ITU-T.

Channel Communication Satellite television digital broadcasting Broadcasting

/Communication
Satellite
television

digital
broadcasting
Terrestrial television digital broadcasting Satellite Sound digital broadcasting Terrestrial Sound digital broadcasting Cable

television

digital broadcasting
Nick name - ISDB-S ISDB-T 2.6GHz mobile broadcasting ISDB-Tsb 64QAM,

Trans-modulation

(ISDB-C)
Transmission DVB-S ARIB

STD-B20,

ITU-R BO.1408
ARIB

STD-B31,

ITU-R BT.1306-1
ARIB STD-B41 ARIB STD-B29, ITU-R BS.1114 ITU-T J.83 Annex C, J.183
Receiver ARIB STD-B16 ARIB STD-B21 ARIB STD-B42 ARIB STD-B30 JCTEA STD-004, STD-007
Server type broadcasting - ARIB STD-B38 -
Conditional access - ARIB STD-B25 (Muti-2) JCTEA STD-001
Service information - ARIB STD-B10 JCTEA STD-003
Data broadcasting - ARIB STD-B24 (BML), ARIB STD-B23 (EE or MHP like) -
Video/Audio compression and multiplexing MPEG-2 ARIB STD-B32 (MPEG) -
Technical report - ARIB TR-B13 ARIB TR-B14 - - -


See also

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