- The
following articles are licensed under the
GNU
Free Documentation License.
DVB short
for Digital Video Broadcasting, is a suite of
internationally accepted, open
standards for digital
television maintained by the DVB Project, an
industry consortium with more than 270 members, and published
by a Joint Technical Committee (JTC) of European
Telecommunications Standards Institute (ETSI), European
Committee for Electrotechnical Standardization (CENELEC)
and European
Broadcasting Union (EBU). The standards can be obtained
for free at the ETSI
website after registration.
How the several DVB sub-standards
interact is described in the DVB Cookbook (DVB-Cook).
DVB-S
is the Digital
Video Broadcasting standard for satellite
television. It is used through all of Europe
and most of the rest of the world. This is even true in North
America, where it pre-dates the use of ATSC
by several years. DVB-S is used in both SCPC
and MCPC
modes for broadcast
network feeds,
as well as for direct
broadcast satellite services like Astra
in Europe, Dish
Network in the U.S.,
and Bell
ExpressVu in Canada.
While the transport
stream is essentially the same as other forms of DVB, it
uses QPSK
modulation
instead.
DVB-S2
is a newer specification of the DVB-S standard, ratified by ETSI
in March
2005. The main use for this is HDTV,
while the original standard was mainly for SDTV.
DVB-S2 is tightly tied with the introduction of HDTV and H.264
(MPEG-4)
video
codecs.
The authors claim that DVB-S2
performance gain over DVB-S is around 30%, in addition to
improvements in the video
compression.
DVB-S2 is being introduced now in
Europe. Since November
2005, two transponders on Astra at 19.2°E send in DVB-S2.
DirecTV
is also introducing it in the U.S., although its original
system was Digital
Satellite System (DSS), which uses MPEG-2
but with a different transport stream.
DVB-C stands for Digital Video Broadcasting - Cable
and it is the DVB
European consortium standard for the broadcast transmission of
digital
television over cable.
This system transmits an MPEG-2
family digital audio/video stream, using a QAM
modulation with channel
coding.
DVB-T stands for Digital Video Broadcasting -
Terrestrial and it is the DVB
European consortium standard for the broadcast transmission of
digital
terrestrial television. This system transmits a compressed
digital audio/video stream, using OFDM
modulation with concatenated channel
coding (i.e. COFDM). The adopted source coding methods are
MPEG-2
and, more recently, H.264.
DVB-H stands for Digital
Video Broadcasting - Handheld.
DVB-H is a technical specification for bringing broadcast
services to handheld receivers and was formally adopted as ETSI
standard EN 302 304 in November 2004. The DVB-H specification
(EN 302 304) can be downloaded from the DVB-H Online website.
The major competitor of this technology is DMB.
MPEG-2 is the designation for a group of coding and compression
standards for Audio and Video (AV), agreed upon by MPEG
(Moving Picture Experts Group), and published as the ISO/IEC
13818 international standard. MPEG-2 is typically used to
encode audio and video for broadcast signals, including direct
broadcast satellite and Cable
TV. MPEG-2, with some modifications, is also the coding format
used by standard commercial DVD
movies. Using MPEG2 requires paying licensing fees to the
patent holders via the MPEG Licensing Association.
MPEG-2 includes a Systems part (part 1) that defines two
distinct (but related) container formats. One is Transport
Stream, which is designed to carry digital video and audio
over somewhat-unreliable media. MPEG-2 Transport Stream is
commonly used in broadcast applications, such as ATSC
and DVB.
MPEG-2 Systems also defines Program Stream, a container format
that is designed for reasonably reliable media such as disks.
MPEG-2 Program Stream is used in the DVD
and SVCD
standards.
The Video part (part 2) of MPEG-2 is similar to MPEG-1,
but also provides support for interlaced
video (the format used by analog broadcast TV systems). MPEG-2
video is not optimized for low bit-rates (less than 1 Mbit/s),
but outperforms MPEG-1 at 3 Mbit/s and above. All
standards-conforming MPEG-2 Video decoders are fully capable
of playing back MPEG-1 Video streams.
With some enhancements, MPEG-2 Video and Systems are also
used in most HDTV
transmission systems.
The MPEG-2 Audio part (defined in Part 3 of the standard),
enhances MPEG-1's audio by allowing the coding of audio
programs with more than two channels. Part 3 of the standard
allows this to be done in a backwards compatible way, allowing
MPEG-1 audio decoders to decode the two main stereo components
of the presentation.
Part 7 of the MPEG-2 standard specifies a rather different,
non-backwards-compatible audio format. Part 7 is referred to
as MPEG-2 AAC.
While AAC is more efficient than the previous MPEG audio
standards, it is much more complex to implement, and somewhat
more powerful hardware is needed for encoding and decoding.
SMPTE- The Society
of Motion Picture and Television Engineers (pronounced "simptee" or sometimes "sumptee")
is an international professional association, based in
the United
States of America, of engineers working in the motion
imaging industries. An internationally-recognized standards
developing organization, SMPTE has over 400 standards,
Recommended Practices and Engineering Guidelines for
television, motion pictures, digital cinema, audio and medical
imaging. In addition to development and publication of
standards documents, SMPTE publishes a journal, provides
assistance to members with employment, and performs other
industry-related functions.SMPTE standards documents are copyrighted and may be
purchased from the SMPTE website, or other distributors of
technical standards. Standard documents may be purchased by
the general public. Significant standards promulgated by SMPTE
include:
- All film and television transmission formats and media,
including digital.
- Physical interfaces for transmission of television
signals and related data (such as SMPTE
time code)
- The SMPTE
color bar test
pattern and other diagnostic tools
- The Material eXchange Format, or MXF
SDI- Serial Digital Interface,
standardized in ITU-R
BT.656 and SMPTE-259M,
is a digitized video
interface used for broadcast
grade video. A related standard, known as High Definition
Serial Digital Interface (HD-SDI) is standardized in
SMPTE-292M; this provides a nominal date rate of 1.485 Gbit/s.
An emerging interface, commonly known in the industry as dual
link and consisting essentially of a pair of SMPTE 292M
links, is standardized as SMPTE 372M; this provides a nominal
2.97 3 Gbit/s nominal interface used in applications (such as digital
cinema) which require greater fidelity and resolution than
standard HDTV can provide. A more recent interface, consisting
of a single 2.97 Gbit/s serial link, is standardized by SMPTE
424M,
These standards are used for transmission of uncompressed,
unencrypted digital television signals (optionally including
audio) within television facilities; they can also be used for
packetized data. They are designed for operation over short
distances; due to their high bitrates they are inappropriate
for long-distance transmission. SDI and HD-SDI are currently
only available in professional video equipment; various
licensing agreements, restricting the use of unencrypted
digital interfaces to professional equipment, prohibit their
use in consumer equipment. (There are various mod
kits for existing DVD
players and other devices, which allow a user to add a
serial digital interface to these devices).
PCI-
Peripheral Component Interconnect standard (in
practice almost always shortened to PCI) specifies a computer
bus for attaching peripheral
devices to a computer
motherboard.
These devices can take any one of the following forms:
The PCI bus is common in modern PCs,
where it has displaced ISA
and VESA
Local Bus as the standard expansion bus, but it also
appears in many other computer types. The bus will eventually
be succeeded by PCI
Express and other technologies, which have already started
to appear in new computers.
The PCI specification covers the physical size of the bus
(including wire spacing), electrical characteristics, bus
timing, and protocols. The specification can be purchased from
the PCI
Special Interest Group (PCISIG).
USB-
Universal Serial Bus is a serial
bus
standard to interface
devices. It was designed for computers
such as PCs
and the Apple
Macintosh,
but its popularity has prompted it to also become commonplace
on video
game consoles, PDAs,
cellphones;
and even devices such as televisions
and home stereo equipment (e.g., mp3
players), and portable
memory devices.
Transport stream (TS) is a format specified in MPEG-2
Part 1, Systems (ISO/IEC standard 13818-1). Its design goal is
to allow multiplexing of digital video and audio and to
synchronize the output. Transport stream offers features for
error correction for transportation over unreliable media, and
is used in broadcast applications such as DVB
and ATSC.
BDA- Broadcast Driver Architecture is a
Microsoft standard for digital
video capture on their Windows operating systems. It
encompasses the ATSC
and DVB
standards and gives developers a standardised method of
accessing the TV cards.
Applications using BDA drivers: Windows
XP Media Center Edition, MediaPortal,
GB-PVR
LVDS - Low voltage differential signaling, is an
electrical signaling system that can run at very high speeds
over cheap, twisted-pair
copper cables. It was introduced in 1994,
and has since become very popular. LVDS is a differential signaling system, which means that
it transmits two different voltages which are compared at the
receiver.
LVDS uses the difference in voltage between two wires to
signal information. The transmitter injects a small current,
nominally 3.5 milliamperes,
into one wire or the other, depending on the logic level to be
sent. The current passes through a resistor of about 100 to
120 ohms (matched to the characteristic
impedance of the cable) at the receiving end, then returns
in the opposite direction along the other wire. From Ohm's
law, the voltage difference across the resistor is
therefore about 350 millivolts.
The receiver senses the polarity of this voltage to determine
the logic level. (This is a type of current
loop signaling).
The small amplitude
of the signal and the tight electric- and magnetic-field
coupling between the two wires reduces the amount of radiated
electromagnetic noise.
The low common-mode voltage (the average of the voltages on
the two wires) of about 1.25 V allows LVDS to be used with a
wide range of integrated circuits with power supply voltages
down to 2.5 V or lower. The low differential voltage, about
350 mV as stated above, causes LVDS to consume very little
power compared to other systems. For example, the static power
dissipation in the LVDS load resistor is 1.2 mW, compared to
the 90 mW dissipated by the load resistor for an RS-422
signal. This power efficiency is maintained at high
frequencies because of the low voltage swing.
Bitrate- In telecommunications
and computing,
bitrate (sometimes written bit rate, or as a variable
Rbit) is the number of bits
that are conveyed or processed per unit of time. In digital multimedia,
bitrate is the number of bits used per unit of time to
represent a continuous medium such as audio
or video.
It is quantified using the bit per second (bit/s)
unit or some derivative such as Mbit/s.
While often referred to as "speed", bitrate does
not measure distance/time but quantity/time, and
thus should be distinguished from the "propagation
speed" (which depends on the transmission medium and
has the usual physical meaning).
Symbol rate- In
digital
communications, the symbol rate is the bit
rate divided by the number of bits transmitted in each symbol.
Symbol rate is measured in symbols-per-second, hertz
(Hz), or baud
(Bd).
The term baud
rate is synonymous with symbol rate, but is less
frequently used today as it has in the past been commonly
misused to mean bit
rate or data
rate.
COFDM- Orthogonal
frequency-division multiplexing, also
sometimes called discrete multitone modulation
(DMT), is a complex modulation
technique for transmission based upon the idea of frequency-division
multiplexing (FDM) where each frequency channel is
modulated with a simpler modulation.
In OFDM the frequencies and modulation of FDM are arranged to
be orthogonal
with each other which almost eliminates the interference
between channels. Although the principles and some of the
benefits have been known for 40 years, it is made popular
today by the lower cost and availability of digital
signal processing components.
The main idea behind OFDM is that since low-rate
modulations (i.e modulations with relatively long symbols
compared to the channel time characteristics) are less
sensitive to multipath, it should be better to send a number
of low rate streams in parallel than sending one high rate
waveform. This is exactly what OFDM is doing. It divides the
frequency spectrum in subbands small enough so that the
channel effects are constant (flat) over a given subband. Then
a "classical" IQ modulation (BPSK, QPSK, M-QAM, etc)
is sent over the subband. If designed correctly, all the fast
changing effects of the channel (multipath) disappear as they
are now occurring during the transmission of a single symbol
and are thus treated as flat fading at the received.
Classical signal processing such as channel coding, power
allocation, adaptive modulation and coding can be applied for
a given subband or over the subbands. Multiuser allocation is
also possible, either using time, coding or frequency
separation of the users.
QAM- Quadrature amplitude modulation is a modulation
scheme which conveys data
by changing (modulating) the amplitude
of two carrier
waves. These two waves, usually sinusoids,
are out
of phase with each other by 90°
and are thus called quadrature
carriers — hence the name of the scheme.
As with all modulation
schemes, QAM conveys data
by changing some aspect of a carrier signal, or the carrier
wave, (usually a sinusoid)
in response to a data signal. In the case of QAM, the
amplitude of two quadrature waves is changed (modulated
or keyed) to represent the data signal.
Phase
modulation (analogue PM) and phase-shift
keying (digital PSK) can be regarded as a special case of
QAM, where the amplitude of the modulating signal is constant,
with only the phase varying. This can also be extended to frequency
modulation (FM) and frequency-shift
keying (FSK), as this can be regarded as a special case of
phase modulation.
Although analogue QAM is possible, this article focuses on
digital QAM. Analogue QAM is used in NTSC
and PAL
television systems, where the I- and Q-signals carry the
components of chroma (colour) information. "Compatible
QAM" or C-QUAM
is used in AM
stereo radio
to carry the stereo
difference information.
As for many digital modulation schemes, the constellation
diagram is a useful representation and is relied upon in
this article.
In QAM, the constellation points are usually arranged in a
square grid with equal vertical and horizontal spacing,
although other configurations are possible (see e.g. Cross-QAM).
Since in digital telecommunications
the data is usually binary,
the number of points in the grid is usually a power of 2
(2,4,8...). Since QAM is usually square, some of these are
rare — the most common forms are 16-QAM, 64-QAM, 128-QAM and
256-QAM. By moving to a higher-order constellation, it is
possible to transmit more bits
per symbol.
However, if the mean energy of the constellation is to remain
the same (by way of making a fair comparison), the points must
be closer together and are thus more susceptible to noise
and other corruption; this results in a higher bit
error rate and so higher-order QAM can deliver more data
less reliably than lower-order QAM.
If data-rates beyond those offered by 8-PSK
are required, it is more usual to move to QAM since it
achieves a greater distance between adjacent points in the I-Q
plane by distributing the points more evenly. The complicating
factor is that the points are no longer all the same amplitude
and so the demodulator
must now correctly detect both phase
and amplitude,
rather than just phase.
64-QAM and 256-QAM are often used in digital
cable television and cable
modem applications. In the US,
64-QAM and 256-QAM are the mandated modulation schemes for digital
cable, as standardised by the SCTE
in the standard ANSI/SCTE
07 2000. Note that many marketing people will refer to
these as QAM-64 and QAM-256. In the UK,
16-QAM and 64-QAM are currently used for digital
terrestrial television (Freeview
and Top
Up TV).
QPSK- Sometimes known as
quaternary or quadriphase PSK or 4-PSK, QPSK uses four points
on the constellation diagram, equispaced around a circle. With
four phases, QPSK can encode two bits per symbol, shown in the
diagram with Gray
coding to minimize the BER — twice the rate of BPSK.
Analysis shows that this may be used either to double the data
rate compared to a BPSK system while maintaining the bandwidth
of the signal or to maintain the data-rate of BPSK but halve
the bandwidth needed.
Although QPSK can be viewed as a quaternary modulation, it
is easier to see it as two independently modulated quadrature
carriers. With this interpretation, the even (or odd) bits are
used to modulate the in-phase component of the carrier, while
the odd (or even) bits are used to modulate the quadrature-phase
component of the carrier. BPSK is used on both carriers and
they can be independently demodulated.
PSK- Phase-shift keying is a digital
modulation
scheme that conveys data
by changing, or modulating, the phase
of a reference signal
(the carrier
wave).
Any digital modulation scheme uses a finite
number of distinct signals to represent digital data. In the
case of PSK, a finite number of phases are used. Each of these
phases is assigned a unique pattern of binary
bits.
Usually, each phase encodes an equal number of bits. Each
pattern of bits forms the symbol
that is represented by the particular phase. The demodulator,
which is designed specifically for the symbol-set used by the
modulator, determines the phase of the received signal and
maps it back to the symbol it represents, thus recovering the
original data. This requires the receiver to be able to
compare the phase of the received signal to a reference signal
— such a system is termed coherent.
Alternatively, instead of using the bit patterns to set
the phase of the wave, it can instead be used to change
it by a specified amount. The demodulator then determines the changes
in the phase of the received signal rather than the phase
itself. Since this scheme depends on the difference between
successive phases, it is termed differential phase-shift
keying (DPSK). DPSK can be significantly simpler to
implement than ordinary PSK since there is no need for the
demodulator to have a copy of the reference signal to
determine the exact phase of the received signal (it is a
non-coherent scheme). In exchange, it produces more erroneous
demodulations. The exact requirements of the particular
scenario under consideration determine which scheme is used.
8VSB is the 8-level vestigial
sideband modulation method adopted for terrestrial
broadcast of the ATSC
digital
television standard in the United
States and Canada.In
the 6MHz (megahertz)
channel used for broadcast ATSC, 8VSB carries 19.39Mb (megabits)
of usable data per second, although the actual transmitted bit
rate is significantly higher due to the addition of forward
error correction codes. The eight signal levels are
selected with the use of a trellis
encoder. There are also the similar modulations 2VSB,
4VSB,
and 16VSB.
16VSB was notably intended to be used for ATSC digital
cable, but quadrature
amplitude modulation (QAM) has become the industry
standard instead.
PES- Defined
by MPEG
communication protocol. An Elementary
stream is packetized by adding a packet header. The output
of a video encoder is an elementary stream which is then
packetized. Packet protocol allows:
1-
Multiplexing
of the data and to minimize the size of buffers (reduce cost) in receivers.
2-
Error detection and control.
An elementary stream contains
only one kind of data, for example audio or video. The output
of a video encoder is an elementary stream. The output of an
audio encoder is also an elementary stream. Sometimes referred
to as "elementary", "data",
"audio", or "video" bitstreams
or streams. The format of the elementary stream depends upon
the codec or data carried in the stream.
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.
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.
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.
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 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.
Problems
Though ISDB is a
feature-rich system, many problems have surfaced recently.
Copy Protection
Technology
Almost every TV
broadcast (including free TV) are 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.
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".
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. 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.
Services
-
One HDTV or up
to three SDTV services within one channel.
-
Provides Data
broadcasting.
-
Interactive
services via Telephone Line or 10Base-T Broadband Internet.
-
EPG
(Electronic
Program Guide)
-
Ability to send
firmware patches for the TV/tuner
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, 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.
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
|
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.
ISDB-T
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.
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 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.
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 no other countries
that are considering ISDB. Possibly because ISDB Tuners and TVs
are way too expensive compared to other formats. However, 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 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.
-
Argentina (and
other south-american countries) may adopt the Brazilian model
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
Summary of ISDB-T
Transmission
channel coding
|
Modulation
|
64QAM-OFDM,
16QAM-OFDM,
QPSK-OFDM,
DQPSK-OFDM
(Hierarchical
transmission)
|
|
Error correction
coding
|
| |
