Integrated Services Digital Broadcasting

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A picture of ISDB-T (taken during a tour of the NHK Osaka broadcasting station)
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A picture of ISDB-T (taken during a tour of the NHK Osaka broadcasting station)

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.

Contents

[edit] Introduction

ISDB is maintained by the Japanese organisation ARIB. The standards can be obtained for free at the Japanese organization 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. 1seg is the name of an ISDB-T service for reception on cell phones, laptop computers and vehicles.

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 standard DVB-T. ISDB-T operates on unused TV channels, an approach taken by other countries for TV but never before for radio.

[edit] Video and audio compression

ISDB has adopted the MPEG-2 video and audio compression system. ATSC and DVB also adopted the same system. DVB and ISDB also provide for other video compression methods to be used, including JPEG and MPEG-4, although JPEG is only a required part of the MHEG standard.

[edit] 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.

[edit] 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).

[edit] 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 MULTI2 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, only moved to another copy-protected media - and this move operation marks content “Copy one generation”, which permanently prevents further copying. “Copy never” programming may only be timeshifted and cannot be permanently stored. Currently Japanese government is evaluating using DTCP 'Encryption plus Non-Assertion' mechanism to allow making multiple copies of digital content between compliant devices[1].

[edit] 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 the 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:

  • B-CAS card interface to de-scramble.
  • IR interface jack for controlling a VHS or DVD player.

[edit] Problems

Though ISDB is a feature-rich system, many problems have surfaced recently.

[edit] Copy Protection Technology

Every TV broadcast (including free TV) is encrypted with "Copy-Once", which allows users to record to a digital media (D-VHS, DVD, HDD, etc) but does not allow dubbing to another digital media. On the other hand, the "Copy-Once" technology does not prohibit all types of dubbing. It is possible to dub to an analog media (such as standard VHS) and if recorded to an HDD, it will allow users to "Move" the contents to a D-VHS, but not copy. In contrast, 1seg digital broadcasts which are for low-bandwidth mobile reception and occupy 1/13th of a digital channel, are transmitted 'in the clear' and do not carry copy protection information.

Many users are also very worried about the recent news of severe protection in the future. There are modes in ISDB to now allow the output of signal from an Analog connector (D-connector, Component, Composite, S-Video, etc). There are already plans to not allow analog output for "Copyright Protection" reasons. (Same as Blu-ray and HD-DVD) This will make all currently sold STB Tuners, and the majority of LCD/Plasma TVs without HDMI inputs unusable. Plus all analog VHS, D-VHS that can only record via analog input, and all DVD players will also become unusable. These more limiting copy protection technologies will all start after analog broadcasting ends (when there won't be any choice for viewers). Currently, no financial assistance schemes have been announced, and viewers without proper devices will be forced to buy a new compatible TV or set top box in order to view ISDB broadcasts. Though not clear, it is said that there are also plans to protect all programs with "Copy-Never".

[edit] B-CAS Card

The B-CAS card is required to decode all broadcasts. These cards are included with every digital TV or Tuner at no charge. To use this card, you must agree to the statement written on the registration card. Despite the fact that the card must be inserted to watch TV, if you don't agree to the statement, then the user cannot watch digital broadcasts. Essentially, users are "forced" to agree with the statement. Though registration is not required, it is recommended to fully enjoy interactive programs. Unregistered B-CAS card displays a watermark in a corner of the screen, suggesting the user to register. However, many viewers worry about the leaking of personal information, and the power/rights the TV stations have to access personal information for almost every citizen in Japan. In case of loss or destruction, or buying second-hand equipment, new B-CAS card can be issued for a fee of 3,000 Yen[2].

[edit] Services

  1. One HDTV or up to three SDTV services within one channel.
  2. Provides Data broadcasting.
  3. Interactive services such as games or shopping, via telephone line or broadband internet.
  4. EPG (Electronic Program Guide)
  5. Ability to send firmware patches for the TV/tuner over the air.

[edit] ISDB-S

[edit] History

Japan started digital broadcasting using the DVB-S standard by PerfecTV in October/1996, and DirecTV in December/1997, with communication satellites. Still, DVB-S did not satisfy the requirements of Japanese broadcasters, such as NHK, key commercial broadcasting stations like Nippon Television, TBS, Fuji Television, tv asahi, TV Tokyo, and WOWOW (Movie-only Pay-TV broadcasting). Consequently, ARIB developed the ISDB-S standards. The requirements were HDTV capability, interactive services, network access and effective frequency utilization, and other technical requirements. The DVB-S standard allows the transmission of a bit stream of roughly 34 Mbit/s with a satellite transponder, which means the transponder can send one HDTV channel. Unfortunately, the NHK broadcasting satellite had only four vacant transponders, which led ARIB and NHK to develop ISDB-S: The new standard could transmit at 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 1 December 2000. Today, SKY PerfecTV!, successor of Skyport TV, and Sky D, CS burn, Platone, EP, DirecTV, J Sky B, and PerfecTV!, adopted the ISDB-S system for use on the 110 degree (east longitude) wide-band communication satellite.

[edit] 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 Multi-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

[edit] Channel

Frequency and channel specification of Japanese Satellites 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 with 27 MHz band satellite transponder for analog FM broadcasting.

[edit] ISDB-T

[edit] History

HDTV was invented at NHK STRL. The research of HDTV started as early as in the 1960s, though only 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 were 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, a terrestrial digital DTV system. Europe also developed their own DTV system, DVB. Although the DVB-T service started operating a few weeks later than the ATSC system, it quickly outstripped ATSC in terms of user base. Japan started R&D of a completely digital system in the 1980s that led to ISDB. Japan started terrestrial digital broadcasting using ISDB-T standard by NHK and commercial broadcasting stations on the 1 December 2003.

[edit] Feature

ISDB-T is characterized by the following features:

  • ISDB-T can transmit a HDTV channel and a mobile phone channel within the 6 MHz 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 efficient utilization of the frequency resource (spectrum).
  • ISDB-T can be received indoors with a simple indoor antenna.
  • 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.
  • 1seg is a mobile terrestrial digital audio/video broadcasting service in Japan.

[edit] 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 10 million subscribers by the end of April 2005. Along with the wide use of ISDB-T, the price of STB is getting low. The price of ISDB-T STB in lower end of the market is ¥19800 that is worth $169 at 19 April 2006. (Japanese) uniden

Brazil*, which currently uses an analogue TV system (PAL-M) that slightly differs from any other country's, has chosen ISDB-T for its DTV format, calling it SBTVD-T Sistema Brasileiro de Televisão Digital- Terrestre. Other than that, there are few countries, mainly from Mercosur, such as Argentina and Venezuela strongly considering ISDB-T in order to enjoy common market benefits from the local development of technology instead of imported as it is the case with the other standards. Also, it seems 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 Television Engineering Society) and ABERT (the Brazilian Association of Radio and Television Broadcasters). 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. In June 29, 2006, Brazil announced ISDB as the chosen standard for Digital TV transmissions, to be fully implemented until 2016. See SBTVD.

[edit] 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.

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

[edit] 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.

[edit] 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.

[edit] 2.6 GHz Mobile satellite digital audio/video broadcasting

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

[edit] ISDB-Tsb

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

[edit] ISDB-C

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

[edit] 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 2.6 GHz 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 - - -

[edit] Table of terrestrial HDTV transmission systems


Table 1: Main characteristics of three DTTB systems
Systems ATSC 8-VSB DVB COFDM ISDB BST-COFDM
Source coding
Video Main profile syntax of ISO/IEC 13818-2 (MPEG-2 - video)
Audio ATSC Standard A/52 (Dolby AC-3) ISO/IEC 13818-2 (MPEG-2 – layer II audio) and Dolby AC-3 ISO/IEC 13818-7 (MPEG-2 – AAC audio)
Transmission system
Channel coding
Outer coding R-S (207, 187, t = 10) R-S (204, 188, t = 8)
Outer interleaver 52 R-S block interleaver 12 R-S block interleaver
Inner coding Rate 2/3 trellis code Punctured convolution code: Rate 1/2, 2/3,3/4, 5/6, 7/8 Constraint length = 7, Polynomials (octal) = 171, 133
Inner interleaver 12 to 1 trellis code interleaver Bit-wise interleaving and frequency interleaving Bit-wise interleaving, frequency interleaving and selectable time interleaving
Data randomization 16-bit PRBS 16-bit PRBS 16-bit PRBS
Modulation 8-VSB and 16-VSB COFDM
QPSK, 16QAM and 64QAM
Hierarchical modulation: multi-resolution constellation (16QAM and 64 QAM)
Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol
2 modes: 2k and 8k FFT		 BST-COFDM with 13 frequency segments
DQPSK, QPSK, 16QAM and 64QAM
Hierarchical modulation: choice of three different modulations on each segment
Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol
3 modes: 2k, 4k and 8k FFT


[edit] See also

General category

Transmission technology

[edit] External links

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