Digital TV over Cable
A Recommended Standard for Singapore
National Cable Standards Committee
DTV Technical Working Committee
SUMMARY
In view of the rapid and advent developments of digital TV technology
around the world, a Technical Working Committee (TWC) was formed by the
Singapore National Cable Standard Committee (NCSC) in August this year to
recommend a digital cable standard for Singapore. Two key digital cable TV
standards were included in the study and comparison, namely European
Digital Video Broadcast for Cable (DVB) and American Open Cable standard.
To ensure an objective assessment of each of the standards, both standards
were studied along a number of key technical areas, namely standard
maturity, content acquisition, baseband processing, transmission, conditional
access, consumer interfaces, and interactive channels. In addition, a market
update on the cable home passed, subscribers take-up, and digital
deployment, mainly in North America and Europe markets were also
included.
The committee noted that Open Cable is still at the evolutionary stage, while
it provides better noise immunity through its trellis coding, supports
emergency alert system, and a more secured POD module, the study
revealed that DVB offers a number of strengths over Open Cable. These
includes a more comprehensive and complete set of International standards
covering all programme delivery media, support of 8 MHz channelisation, in-
band signaling, simulcrypt and multicrypt conditional access, better
compatibility with satellite and terrestrial transmissions. The market study
also revealed that United States and Europe have an almost equivalent
market size based on cable TV penetration. The North American market
reported about 12-13 million digital STBs deployment today, mostly
proprietary but with partial compliance to Open Cable. The European
market, on the other hand, recorded a total of about 10 million DVB
compliant STBs (including cable, satellite & terrestrial), out of which about 2
million are DVB-C cable boxes.
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The NCSC TWC recommended DVB-C as the digital television standard of
digital video broadcast transmission over cable in Singapore. This
recommendation also includes DVB standards for multiplexing, subtitling,
conditional access, and interfacing. For support of interactive applications,
the NCSC TWC recommends leaving the option of the return channel open
for commercial considerations, acknowledging that interactivity on television
is still in the evolutionary stage today.
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LIST OF TABLES
Table 2-1 MPEG PSI and DVB SI Tables ........................................................................................................9
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LIST OF FIGURES
Figure 2-1 DVB Cable System Overview Block Diagram...............................................................................7
Figure 2-2 DVB-C Transmission Conceptual Block Diagram.................................................................... 10
Figure 3-1 The Open Cable Architecture........................................................................................................ 18
Figure 3-2 POD Module Block Diagram........................................................................................................ 19
Figure 3-3 Channel Types of OpenCable........................................................................................................ 22
Figure 3-4 FAT Digital Protocol Stack ........................................................................................................... 23
Figure 3-5 Open Cable Transmission Conceptual Block Diagram............................................................ 24
Figure 4-1 Breakdown of Cable Modems and STB return Channels......................................................... 34
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TABLE OF CONTENT
SUMMARY................................................................................................................................................................I
LIST OF TABLES ............................................................................................................................................... III
LIST OF FIGURES............................................................................................................................................. IV
TABLE OF CONTENT...............................................................................................................................V
ACKNOWLEDGEMENTS..................................................................................................................................1
INTRODUCTION.........................................................................................................................................2
1.1 OVERVIEW ................................................................................................................................................2
1.2 BACKGROUND ..........................................................................................................................................4
1.2.1 A Brief Look on Television ...............................................................................................................4
DVB OVERVIEW .........................................................................................................................................6
2.1 INTRODUCTION ........................................................................................................................................6
2.2 STANDARDS OVERVIEW .........................................................................................................................7
2.3 CONTENT A CQUISITION ..........................................................................................................................8
2.4 BASEBAND PROCESSING .........................................................................................................................8
2.5 TRANSMISSION .......................................................................................................................................10
2.6 CONDITIONAL A CCESS ..........................................................................................................................11
2.7 INTERFACES............................................................................................................................................11
2.7.1 Professional Interfaces................................................................................................................... 11
2.7.2 Consumer Interfaces ....................................................................................................................... 12
2.8 INTERACTIVE CHANNEL .......................................................................................................................13
2.9 BILLING AND OPERATIONAL SUPPORT ...............................................................................................14
2.10 INTEROPERABILITY................................................................................................................................15
2.11 SUMMARY...............................................................................................................................................15
OPEN CABLE OVERVIEW ................................................................................................................... 17
3.1 INTRODUCTION ......................................................................................................................................17
3.2 STANDARDS OVERVIEW .......................................................................................................................18
3.3 CONTENT A CQUISITION ........................................................................................................................20
3.4 BASEBAND PROCESSING .......................................................................................................................20
3.5 TRANSMISSION .......................................................................................................................................22
3.6 CONDITIONAL A CCESS ..........................................................................................................................24
3.7 INTERFACES............................................................................................................................................25
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3.7.1 Professional Interfaces................................................................................................................... 25
3.7.2 Consumer Interfaces ....................................................................................................................... 26
3.8 INTERACTIVE CHANNEL .......................................................................................................................27
3.9 BILLING AND OPERATIONAL SUPPORT ...............................................................................................27
3.10 INTEROPERABILITY................................................................................................................................28
3.11 SUMMARY...............................................................................................................................................28
MARKET STUDY............................................................................................................................................... 30
4.1 INTRODUCTION ......................................................................................................................................30
4.2 UNITED STATES CABLE M ARKET SUMMARY....................................................................................30
4.3 EUROPEAN CABLE MARKET SUMMARY .............................................................................................31
4.4 A SIA-PACIFIC CABLE MARKET ...........................................................................................................32
4.5 INTERACTIVE CHANNEL M ARKET SUMMARY ...................................................................................33
DISCUSSION AND RECOMMENDATIONS ................................................................................... 35
5.1 LIMITATIONS OF THE STUDY................................................................................................................35
5.2 DISCUSSION AND RECOMMENDATIONS..............................................................................................35
5.2.1 Standard Maturity and Comprehensiveness............................................................................... 35
5.2.2 Key strengths and weaknesses ...................................................................................................... 36
5.2.3 Recommendation One..................................................................................................................... 37
5.2.4 Recommendation Two .................................................................................................................... 38
REFERENCES ..................................................................................................................................................... 39
GLOSSARY OF ABBREVIATION............................................................................................................... 44
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ACKNOWLEDGEMENTS
The Chairman, TWC would like to thank the following companies, academia
and organisation for their assistance in the preparation of this report.
Chan Meng Tuck ATS
Lee Siak Hong Barco
Peter Avis Barco
Steven Luys Barco
Norman Lim Cisco
Ong Beng Hui Cisco
Kapil Sharma IDA
Lee Kian Soon IDA
Lim Yew Gee IDA
Ong Kian Lin IDA
Kelvin Wong Motorola
Lee Peng Chong Motorola
Narisa Chu Motorola
Juhu Nieminen Nokia
James Sinclair NTL
Keith Jennings NTL
Edward Pan NTU, CSP
Lim Keng Pang NTU, CSP
Lim Chin Siang SBA
Dale Hoefer Scientific Atlanta
Ng Chin Bong SCM Microsystems
Foo Ming Jap SCV
Lu Jin SCV
Tay Seng Choon SCV
Desmond Poon SCV (TWC Secretary)
December 2000
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INTRODUCTION
1.1 Overview
The study “Digital TV over Cable – A Standard for Singapore” was carried out
by the Technical Working Committee (TWC) formed by the Singapore
National Cable Standard Committee (NCSC) in August this year.
In view of the rapid and advent developments of digital TV technology
around the world, NCSC recognised the importance of the cable industry in
providing broadband services to the Singaporean. The committee has
decided that it was timely to conduct the study, with the objective of
recommending a suitable digital cable standard for Singapore.
The TWC committee, chaired by the Senior VP, Broadband Engineering
Services of the Singapore Cable Vision - Thomas Ee, comprises of members
from the industry, government agencies, academia and the broadcaster.
Under the charter of TWC, the committee is committed to the following terms
of reference:
• To study the technical pros and cons of the various standards based on
results of the trials, simulation and laboratory evaluation
• To survey the existing status of implementation in other parts of the
world
• To study the compatibility and interoperability issues of emerging digital
cable systems with existing cable network infrastructure
• To ascertain the availability and scalability of head-end system, network
and consumer premise equipment
• To study the interoperability with DTV Terrestrial system, Internet and
Singapore One (S1) broadband network
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Since its formation, the committee has been actively involved in a series of
consultation process with the industry. Three working groups were formed to
cover the different areas, namely: DVB, Open Cable and the Cable Industry
Market.
At the time of this report finding, two digital cable TV standards have evolved
sufficiently for our evaluation. Some cable operators in North America and
Europe have already started to deploy digital cable services for their
subscribers and many have planned to upgrade their cable plants to roll-out
digital cable services in 2001/2002 and beyond. Although the committee
findings have shown that a large number of cable operators had deployed
proprietary digital cable services for their subscribers as early as 1997, the
committee felt that proprietary systems would not enjoy sufficient economies
of scale and they would not be a long-term viable solution for the cable
operators. Therefore, we did not attempt to study them in detail.
This report is a 5-month collaborative effort from all the participants. The
report is basically organised into five major sections, with emphasis on the
following areas;
• European Digital Video Broadcast for Cable (DVB)
• American Open Cable standard
• Market Study
• Comparison and Analysis
• Discussion and Recommendations
It also covered the definitions, the detailed description and the comparison of
the two competing digital cable standards and provided a market update on
cable home passed, subscribers’ take-up and digital deployment, mainly in
North America and Europe markets. We have also identified some major
cable operators’ deployment of various set-top solutions, including the
propriety set-top boxes that are widely available today by a multitude of
vendors.
The committee compared and assessed the standards based on the
technology maturity, availability, scalability, interoperability and economies
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of the two compelling standards. Among these criteria, the ability to inter-
operate with the existing SCV’s cable network is of utmost consideration.
Consumer products and the availability of set-top boxes were also important
factors in determining the relevant digital cable standard for Singapore.
1.2 Background
1.2.1 A Brief Look on Television
Analogue TV transmission has been used for over 50 years for the mass
broadcasting of television pictures. However, all three of the main analogue
standards (PAL, SECAM and NTSC) have come to the end of their
development cycles, and it is becoming increasingly difficult to develop new
services. It is difficult to convert between the standards, and any conversion
results in picture degradation.
It has also proved to be difficult to adapt to new screen formats (such as
wide-screen for movies), new sound formats (such as stereo and surround
sound) and picture resolutions. These require complicated changes to the
transmission equipment, and even more complex analogue modulation
techniques.
Analogue transmission suffers from major inherent disadvantages, namely:
• Transmission is subject to degradation of quality at every stage in the
transmission process
• It uses scarce broadcast spectrum inefficiently
• Data transport cannot be easily integrated within analogue services
The advantage of digital television is brought about by the developments in
the digital video production, compression and transmission technologies.
These allow many more channels to become available to the broadcasters,
improve the quality of reception and make it possible to deliver multimedia
content to the consumers. With digital technology, it eases the integration of
systems, making it possible to offer consumers advanced interactive services
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such as pay-per-view, electronic programme guides and most importantly, T-
commerce to take off.
• Digital technology allows new types of broadcast by
• Removing the quality limitations
• Supporting a variety of screen formats
• Enables flexibility in programme delivery
• Uses channel space economically
• Allow audio video and data to be mixed together
• Enables interactive services easily
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DVB OVERVIEW
2.1 Introduction
DVB (Digital Video Broadcasting) is a consortium of around 300 companies
in the fields of Broadcasting, Manufacturing, Network Operation and
Regulatory matters that have come together to establish common
international standards for the move from analogue to digital broadcasting.
DVB systems are developed through consensus in the working groups of the
Technical Module. Members of the groups are drawn from the general
assembly of the project. Once standards have been published, through ETSI,
they are available at a nominal cost for anyone, world-wide. Open standards
free manufacturers to implement innovative and value added services.
For each specification, a set of User Requirements is compiled by the
Commercial Module. These are used as constraints on the specification. User
requirements outline market parameters for a DVB system (price-band, user
functions, etc.). The Technical Module then develops the specification,
following these user requirements. The approval process within DVB
requires that the Commercial Module support the specification before the
Steering Board finally approves it. Following approval by the Steering Board,
DVB specifications are offered for standardization to the relevant
international standards body (ETSI or CENELEC), through the
EBU/ETSI/CENELEC JTC (Joint Technical Committee), the ITU-R, ITU-T
and DAVIC.
The DVB System provides a complete solution for digital television and data
broadcasting across the range of delivery media. All DVB systems are based
on MPEG-2 audio and video-compression. DVB adds to the MPEG transport
stream multiplex, the necessary elements to bring digital broadcast services
to the home through cable (DVB-C), satellite (DVB-S) and terrestrial
broadcast (DVB-T) systems.
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2.2 Standards Overview
DVB has provided specifications for a broad variety of digital transmission
systems concerning communication via satellite, cable and terrestrial
networks. These systems have been or are currently being standardized by
ESTI. The diagram below shows the standard interfaces between the
components of the cable system.
Satellite
(DVB-S)
Off-Air Descrambling Remultiplexing Scrambling Modulation Descrambling
(DVB-T) +
Consumer
SI Processing
Devices
Local (DVB-CA) (DVB- (DVB-CA) (DVB-C) (DVB-CA)
(DVB-C) Multiplexing)
PDH SDH
ATM
(DVB-ATM,
PDH, SDH)
Source: DVB
Figure 2-1 DVB Cable System Overview Block Diagram
DVB has incorporated an open service information system to accompany the
DVB signals, which can be used by the STB decoder and the user to navigate
through an array of services offered. These services could range from
interactive television to near video-on-demand to specialized programming.
To sort out the available offerings, the DVB-SI provides the elements
necessary for the development of an electronic program guide. Specifications
for the transmission of the baseband signals via all sorts of broadcast
delivery channels have been among the principal deliverables of the DVB
Project.
The cable network system, known as DVB-C, has the same core properties
as the satellite and terrestrial system, but the modulation is based on QAM
rather than QPSK. In addition, the DVB Project has designed an interface,
which will be used for connecting the world of DVB signals to PDH and SDH
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networks. A mechanism for distribution of digital multi-programme
television suitable for Satellite Master Antenna Television (SMATV) systems
under coaxial cable is also described in DVB-CS.
2.3 Content Acquisition
As shown in Figure 2-1, DVB has provided specifications for the delivery of
digital television over a broad variety of transmission systems including
satellite, cable and terrestrial networks. At the cable head-end, this enables
a seamless conversion from the various DVB sources to the DVB-C system.
For example, DVB-S or DVB-T based transport streams multiplexes received
via the satellite can be easily de-scrambled, cherry picked and re-
multiplexed with other DVB MPEG transport streams to create DVB-C
compliant streams suitable for carriage over the cable.
In addition, DVB has also specified the support of both Dolby AC-3 and
MPEG Layer II audio, providing an option to the consumer STB to support
both audio systems at the expense of additional costs to minimize
transcoding complexity at the head-end.
2.4 Baseband Processing
MPEG-2 was selected as the source coding of audio and video and for the
creation of programme elementary streams, Transport Streams (TS), etc., the
so-called Systems level. Additionally, a mechanism needs to be provided
which enables the delivery of "analogue" Teletext to the receiver via DVB.
This mechanism described in EN 300 472 [12] is known as "DVB-TXT". In
EN 300 743 [14], a mechanism is also described which allows the
transmission of all kinds of subtitles and graphic elements as part of the
DVB signals.
EN 301 192 [27] (DVB-DATA) defines the transmission of data services in
DVB bitstreams in five manners, including data piping, data streaming,
multiprotocol encapsulation, data carrousels and object Carrousels. This
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may be used to enable applications for the download of software, delivery of
Internet services over broadcast channels (IP tunnelling), interactive TV etc.
Purpose Table Link To
MPEG-PSI Tables
Lists the programs carried in the PAT PMT and CAT tables
current TS Program association table
Lists the audio and video PMT Elementary streams
components for a program in the Program map table
current TS
Lists the data streams with CAT EMM and ECM encryption data
access rights and keys for a Conditional access table
program in the current TS
DVB-SI Tables
Describes all the TSs composing BAT – bouquet association table SDT
the entire service NIT – network information table
(including a descriptor for the
modulation scheme and
parameters)
Describes the programs SDT EIT
contained in each TS Service description table
Describes the scheduled events EIT Present and following events
for each program enabling the Event information table
creation of EPG
Describes the changes in the RST
scheduled events Running status table
Date and time TDT – time and date table
TOT – time offset table
Table 2-1 MPEG PSI and DVB SI Tables
DVB services consist of a wide variety of programmes carried via a large
number of transmission channels. In order for the IRD to be able to tune to
such channels and in order for the DVB customer to be able to navigate the
profusion of programmes, powerful navigational aids need to be provided as
part of the DVB streams. The Service Information (SI) described in EN 300
468 [11] constitutes this set of aids, known as "DVB-SI". As part of DVB-SI,
DVB has specified additional SI to complement the MPEG-2 PSI by providing
data to aid automatic tuning of IRDs and additional data intended for
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display to the user. In addition to the network information table (NIT), DVB
has also specified seven more tables, three of which are mandatory and four
are optional. The additional SI can be used to provide information on
services and events carried by different multiplexes as well as other
networks. These tables are summarized in the Table 2-1. Along with the
above tables, a number of descriptors are also defined, including descriptors
for parental ratings, subtitling, multilingual etc.
2.5 Transmission
EN 300 429 [10] describes channel coding and modulation for DVB signal
delivery on cable (CATV) systems; known as "DVB-C". Conceptual block
diagram of DVB-C is shown below.
Data Baseband Outer Interleaver
Physical Energy
Interface Dispersal Coding I = 12
and Syn
Clock
QAM Modulator
Cable Baseband
IF Physical
Network Shaping
Interface
Source: DVB
Figure 2-2 DVB-C Transmission Conceptual Block Diagram
The baseband interfacing and sync unit adapts the data structure to the
format of the signal source. The framing structure is in accordance with
MPEG-2 transport layer including sync bytes. The scrambler inverts the
Sync 1 byte according to the MPEG-2 framing structure, and randomizes the
data stream for spectrum shaping purposes. Outer coding unit applies a
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shortened Reed-Solomon (RS) code to each randomized transport packet to
generate an error-protected packet. Convolutional interleaving unit performs
a depth I = 12 convolutional interleaving of the error-protected packets.
Baseband shaping unit performs mapping from differentially encoded m-
tuples to I and Q signals and a square-root raised cosine filtering of the I and
Q signals prior to Quadrature Amplitude Modulation (QAM) 16, 32, 64, 128,
or 256 modulation. Finally, a system receiver performs the inverse signal
processing in order to recover the baseband signal.
2.6 Conditional Access
DVB-based services will either be of the "pay" type or will at least include
some elements, which are not supposed to be freely available to the public.
DVB has defined a standard for a "Common Interface for Conditional Access
and other Digital Video Broadcasting Decoder Applications" to enable an
Integrated Receiver Decoder (IRD) to de-scramble programmes which have
been broadcast in parallel, using different CA systems. By way of inserting a
PCMCIA module into the common interface, different CA systems can be
addressed sequentially by that IRD. It is important to note that the ability for
MultiCrypt and SimulCrypt provides significant flexibility for the cable
operator.
2.7 Interfaces
2.7.1 Professional Interfaces
The EN 50083 series of the DVB standards deal with cable networks for
television signals, sound signals and interactive services including
equipment, systems and installations using all applicable transmission
media.
• for head-end reception, processing and distribution of television and
sound signals and their associated data signals and
• for processing, interfacing and transmitting all kinds of signals for
interactive services
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EN 50083-9 [1] defines the interfaces for CATV/SMATV head-ends and
similar professional equipment for DVB/MPEG-2 transport streams. Three
interfaces and two serial transmission media are specified as follows:
• SPI (Synchronous Parallel Interface);
• SSI-C (Synchronous Serial Interface on coaxial cable);
• SSI-O (Synchronous Serial Interface on optical fibre);
• ASI-C (Asynchronous Serial Interface on coaxial cable);
• ASI-O (Asynchronous Serial Interface on optical fibre).
2.7.2 Consumer Interfaces
ETR 154 [4] (DVB-MPEG) has specified the minimum requirement of MPEG-
2 functionalities that all IRDs of a particular class are required to either
meet or exceed. The IRDs are classified as those that can support either "25
Hz" or "30 Hz" nominal video frame rates. Those that support either "SDTV"
or "HDTV" and finally those that support "Baseline" or "with digital interface"
in which case digital bitstream can be stored.
The source picture format, encoded picture format and display picture
format do not need to be identical in DVB systems. For example, the HDTV
signal source may be down-converted to SDTV resolution before it is
broadcast. Upon receiving the incoming signal, a HDTV IRD can then up-
convert it to HDTV resolution before displaying.
Also, a single MPEG-2 Transport Stream (TS) may contain programme
material intended for more than one type of IRD. The simulcasting of SDTV
and HDTV video signals is a good example whereby an SDTV IRD will decode
and display SDTV pictures whilst an HDTV IRD will decode and display
HDTV pictures from the same TS.
EN50201 [2] (DVB-IRD) specification defines the recommended interfaces for
connection of DVB Integrated Receiver Decoder equipment. It includes RF
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input/output interface, modem interface, video and audio interface, data
signal interface, control signal interface, and CA module interface.
Analogue video signal output can be either baseband in RGB, Y/C (S-VHS)
or CVBS format, or modulated on an RF carrier. Audio signal output can be
either analogue or digital linear PCM coded audio signal format. Three
interface options are defined for data signal output, i.e. RS232 for low
bitrates, IEEE 1284 for bitrates up till about 10 Mbit/s, and IEEE 1394 for
bitrates of 100 Mbit/s or more such as MPEG-2 compressed streams or
other multimedia data streams.
2.8 Interactive Channel
In DVB the tools for enabling interaction have generally been split into two
sets. One is network-independent and can be regarded as a protocol stack
which extends approximately via ISO/OSI layers two to three (see ETS 300
802 [20]). An important part of this stack was derived from the Digital
Storage Media Command Control (DSM-CC) protocols created by MPEG (see
ISO/IEC 13818-6 [69]). This work has been further evolved into an
independent DVB standard named the DVB-MHP.
The second group of DVB specifications relates to the lower layers
(approximately one to two) of the ISO/OSI model and therefore specifies the
network-dependent tools for interactivity. ETS 300 800 [18], more commonly
know as DVB-RCC, defines a standard for cable modem. Other interactive
channels consist of PSTN/ISDN (DVB-RCP, ETS 300 801 [19]), DECT (DVB-
RCD, EN 301 193 [28]), LMDS (DVB-RCL, EN 301 199 [35]), GSM (DVB-RCG,
EN 301 195 [30]), SMATV (DVB-RCCS, TR 101 201 [37]) and Satellite (DVB-
RCS, EN 301 790 [39]).
DVB-RCC
The specification DVB-RCC (return channel for cable) covers all aspects for
bi-directional communications over CATV network including physical layer,
the medium access control layer, mid layer interfaces, Quality of Service
(QoS) and security aspects. Its first version was already standardized by
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ETSI (EN/ETS 300 800 [18]) in July 1998 as well as by ITU (ITU-T J.112
annex A [72]). This version was further developed by the DVB Project with
strong support of EuroCableLabs and several manufacturers as part of
EuroModem.
In the system model, two channels are established between the Service
provider and the User, Broadcast channel (BC) and Interaction channel (IC).
The interactive system is composed of Forward Interaction path
(downstream) and Return Interaction path (upstream). The general concept
is to use downstream transmission from the INA (Independent Network
Adapter) to the NIUs to provide synchronization and information to all NIUs.
This allows the NIUs to adapt to the network and send synchronised
information upstream. Upstream transmission is divided into time slots
which can be used by different users, using the technique of Time Division
Multiple Access (TDMA). One downstream channel is used to synchronise up
to 8 upstream channels, which are all divided into time slots. A counter at
the INA is sent periodically to the NIUs, so that all NIUs work with the same
clock. This gives the opportunity to the INA to assign time slots to different
users.
Three major access modes are provided with this system. The first one is
based on contention access, which lets users send information at any time
with the risk to have a collision with other user’s transmissions. The second
and third modes are contention-less based, where the INA either provides a
finite amount of slots to a specific NIU, or a given bit rate requested by a NIU
until the INA stops the connection. These access modes are dynamically
shared among time slots, which allows NIUs to know when contention based
transmission is or is not allowed. This is to avoid a collision for the two
contention-less based access modes.
2.9 Billing and Operational Support
No interface has been defined in DVB for billing and operational support as
it was understand that some proprietary interface is normally implemented
between the CA (Conditional Access) system and the cable operator’s own
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subscriber management system. The intricacy of the commercial
requirements has prevented the definition of a standardized interface in view
of the intricate commercial requirements.
2.10 Interoperability
Because the standards are open, all the manufacturers making compliant
systems are able to guarantee that their DVB equipment will work with other
manufacturers' DVB equipment. Not only this, but because the standards
are designed with a maximum amount of commonality, and based on the
common MPEG-2 coding system, they may be effortlessly carried from one
medium to another, which is frequently needed in today's complex signal
distribution environment. DVB signals move easily and inexpensively from
satellite to cable, from cable to terrestrial.
In the complete DVB world, the lean approach of self-certification has been
applied to all kinds of DVB-Compliant equipment. Interoperability tests
carried out by manufacturers themselves are based on ETR 290 (DVB-
Measurement) [8] standard, which defines the measurement guidelines for
DVB systems. The process has been successful so far as the commercial
market will penalize vendor/manufacturers who fail to comply with the
standard. However, instances of non-interoperability are still prevalent in
view of the complexity of the specifications.
2.11 Summary
The work of the DVB Project has resulted in a comprehensive list of
technical and non-technical documents describing solutions required by the
market players in order for them to be able to make the best use of the new
technology of broadcasting digital signals. These documents are the result of
the co-operative efforts of many individuals who spent hours designing new
solutions to new problems.
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Several organizations in Europe have already started DVB transmissions via
satellite and on cable. New organizations are being founded in order to
facilitate the start of services soon. Outside Europe, DVB has also become
very popular. Currently services based on the DVB developments are being
initiated in many parts of the world, among others in Japan, Hong Kong,
Thailand, Indonesia, Australia, South Africa, Canada and the U.S.
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OPEN CABLE OVERVIEW
3.1 Introduction
The North American digital cable evolution has been campaigned by the US
Federal Communications Commission (FCC) under the direction of the
Telecom Reform Act 1996. Compatibility, competition and interoperability
are among the primary objectives promoted by FCC’s Open Cable policy. In
order to meet these regulatory requirements, 3 major industry efforts were
formed to make Open Cable a reality by July 1, 2000. These efforts are:
1. The Society of Cable Communications Engineers (SCTE) Digital Video
Subcommittee (DVS), an American National Standards Institute
(ANSI) accredited body for setting standards
2. The Advanced Television Systems Committee (ATSC) sponsored by the
Consumer Electronics Association (CEA);
3. OpenCable TM Forum sponsored by CableLabs which is funded by US
Cable Multiple System Operators (MSO).
Of the above 3, only the first organization is an officially recognized
standards setting body for the North America Cable Industry. Specifications
established by the other organizations are usually submitted to the SCTE for
ballot and approval.
While Open Cable standards were being developed by the SCTE, CableLabs
through the OpenCable TM Forum initiates many draft standards and
conducts the OpenCable TM certification process. The OpenCable™ initiative,
managed by the Advanced Platforms and Services group at Cable Television
Laboratories, Inc. (CableLabs), has produced a set of interface specifications
that define the next generation of digital cable television set-top boxes and
other digital devices to be deployed by cable operators in North America. In
addition to crafting the interface specifications, CableLabs has also created a
process and the facilities to test and certify the interoperability of
OpenCable™ devices. These test facilities enable designers and
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manufacturers to validate the functionality and performance of their
equipment in a real-world cable network environment that includes head-
end equipment and interconnected devices from multiple vendors. The ATSC
has, in parallel, also developed CEA’s version from the perspective of making
the digital television a viable cable service terminal device.
3.2 Standards Overview
The Open Cable reference architecture is shown in Figure 3-1 below. It
specifies a number of standard interfaces between the components of a
typical cable system. However, except for the OpenCable™ Interface-Network
(OCI-N [73]) which is defined between the cable head-end and OpenCable™
devices/set-top terminal, other interfaces are currently unspecified.
Conditional POD
Internet Access Module(s)
Content System
Video Headend
Content Digital
Cable- Compatible
Ready Devices *
Other Device*
Content Other (Host)
Headend
Other
Devices*
* Devices may be provided by consumer
Cable I-N equipment suppliers or cable operator.
Source: Adapted from OpenCable TM Architecture
Figure 3-1 The Open Cable Architecture
Key to these interface specifications is the definition of a removable security
module, which is the basis for making the devices fully portable from one
cable system to another regardless of the network operator. This point-of-
deployment (POD) module is a PCMCIA-format device supplied by the cable
operator, which provides two important functions:
Page 18
• Separation of security.
• Out-of-band communication.
The design of the point-of-deployment module varies from one
implementation to another. Figure 3-2 shows an example of a typical POD
design.
Copy
Protection
MPEG-2 Engine
MPEG-2 Transport
Demultiplexer
Transport
and
Stream Remultiplexer Payload
Decryption
Engine
POD
Interface
Logic Secure
Out-of-Band Out-of-Band Microprocessor
Serial Data CPU
Processing
Command Memory Controller
Interface
Flash RAM
PCMCIA
POD Module
Connector
Source: OpenCable TM Architecture
Figure 3-2 POD Module Block Diagram
• The MPEG-2 multi-program transport stream enters the POD module via
the PCMCIA connector and is de-multiplexed into its component program
elementary streams. The selected PIDs are filtered and sent to the
payload decryption engine. In addition, the entitlement control messages
are sent to the secure microprocessor where they are decrypted and fed
to the payload decryption engine.
• After the payload is decrypted, it is fed into the copy protection engine,
which encrypts protected content.
• The final payload is re-multiplexed into an MPEG-2 multi-program
transport stream and leaves the POD module via the PCMCIA connector.
• The out-of-band data enters the POD module via the PCMCIA connector
and arrives at the out-of-band processing circuit. This blocks contains
Page 19
data link and media access control functions and provides the out-of-
band communications processing for the POD.
• Messages from the out-of-band processing circuit arrive at the CPU. The
CPU controls and coordinates all POD functions by executing
applications stored in FLASH memory.
• The command interface allows messages to be exchanged between the
host and the POD module by reading and writing locations in RAM.
To-date, SCTE has completed the specifications for IB/OOB transport,
Service Information, Transmission and Multiplexing, Video Characteristic.
Host/POD interface specifications are in full preparation for balloting next
year. It has also recently started some work on its middleware software
specification (OCAP). A table of the list of SCTE standards and specifications
can be found in Appendix B.
3.3 Content Acquisition
The head-end provides a central point in a cable system where programming
(information) is received, from satellite or a wide-area network, and is
converted to a standard format for transmission over the network interface
to the customer. The original work of the OpenCable TM forum has defined an
OCI-H1 interface intended to provide a bridge for the transfer of information
from the content provider to the head-end. However, OCI-H1 interface is
currently only at the first draft level and it was understood that no further
work is being carried out to complete this specification.
3.4 Baseband Processing
Open Cable has selected MPEG-2 as the source coding of video and Dolby
AC-3 as the source coding of audio.
DVS 258 [48], Digital Video Systems Characteristics Standards for Cable
Television, covers the extension and user data part of the video syntax.
These data are inserted at the sequence, Group of Pictures (GOP), and
Page 20
picture level, and are used to carry advanced DTV Closed Captions (CC), as
well as analog cable closed captions and other data that might be present in
the Vertical Blanking Interval (VBI) and analog signal. DVS 026 [61] is the
corresponding subtitling standard defined in SCTE. SCTE also supports
teletext via DVS 053 [62], which is used for the North American Teletext
(NABTS).
DVS 311 [64], IP Multicasting, is being submitted for ballot. DVS 311 [64]
presents a simple mechanism for the Digital STB to efficiently locate IP data
being delivered as part of an MPEG Service.
DVS 234 [42] describes an extensive set of Service Information which are
delivered using an Out-of-Band (OOB) channel. Six profiles are described
with required and optional data specified for out-of-band transport via cable.
Adherence to these profile specifications is necessary for compliance with
SCTE standard transport streams.
• Profile 1 – Baseline. This Baseline Profile reflects a practice in cable
where the Short-form Virtual Channel Table (S-VCT), the Modulation
Mode Subtable and the Carrier Definition Subtable are used for channel
navigation.
• Profile 2 – Revision Detection. Profile 2 uses the same channel navigation
mechanism as Profile 1 while adding a detection mechanism that
facilitates revision handling of tables. The revision detection mechanism
is applicable to the Network Information Table (NIT), Network Text Table
(NTT), and S-VCT that are also used in Profile 1.
• Profile 3 – Parental Advisory. Profile 3 uses Profile 2 as the base and adds
support for the Rating Region Table in order to be compliant with the
FCC-mandated V-chip content advisory scheme.
• Profile 4 – Standard Electronic Program Guide Data. Profile 4 uses Profile
3 as the base and further defines a standard format for delivery of
Electronic Program Guide data by using the Aggregate Event Information
Table (AEIT) and the Aggregate Extended Text Table (AETT).
• Profile 5 – Combination. Support for channel navigation based on Long-
form Virtual Channel Table (L-VCT) and Master Guide Table (MGT) is
added. Backward compatibility with systems operating within profiles 1
Page 21
to 4 is maintained. Using profile 5, a cable operator could have a mixture
of devices requiring the S-VCT, NIT and NTT tables as well as ones
requiring L-VCT and MGT.
• Profile 6 – PSIP Only. Profile 6 is based solely on long-form tables and is
an extension of the terrestrial broadcasting mechanism. Channel
navigation is based on the L-VCT. The AEIT and the optional AETT
streams are used to provide EPG data.
Profile 1 is the SI system that was typically used by MSOs in the United
States who have already digitized their cable systems. Profile 2 to 5 would
provide a progressive upgrade with backward compatibility for these
operators. Profile 6, on the other hand, while incompatible with the existing
MSOs, provides compatibility with the terrestrial ATSC Service Information.
3.5 Transmission
The Open Cable Interface Network has the following communication
channels as shown in Figure 3-3.
In-band Channel
• NTSC Analog Application
• FAT (MPEG-2) • EPG
RF Signal • DVS-241
Digital • Broadcast
From/to • Premium
Cable Network • IPPV
Out-of-Band Forward Data Channel • Data
• DVS-167 • EAS
• DVS-178 • VOD
• Web
Out-of-Band Reverse Data Channel
• DVS-167
• DVS-178
OCI-N • DVS-313
Interface
Source: Adapted from OpenCable TM Architecture
Figure 3-3 Channel Types of OpenCable
Page 22
1. Forward Application Transport (FAT) channels, which carry digital
information via MPEG-2 Transport Streams.
2. NTSC Analog channels with Vertical Blanking Interval (VBI) signals for
closed captioning, as may be required.
3. Forward Data Channels (FDC).
4. Reverse Data Channels (RDC).
The FDC and RDC are referred to as Out-of-Band (OOB) channels and are
described in more details in section 3.8. The frequency bands for the FAT
channels and NTSC Analog channels are between 54 to 864 MHz, while that
for the OOB FDCs and OOB RDCs are 70 to 130 MHz and 8 to 42 MHz
respectively.
Video Audio Data
Packetised Elementary Streams (PES)
MPEG-2 Systems (DVS 241)
Conditional Access
64/256 QAM Baseband Signal
64/256 OAM IF
6 MHz FIF Signal/EIA 542
Figure 3-4 FAT Digital Protocol Stacks
Source: OpenCable TM Architecture
The FAT channels are 64 or 256 ITU J83.B[71]/SCTE-DVS031r4[47]
Quadrature Amplitude Modulation (QAM) channels that transport 27 or 39
Mbps, respectively. FAT channels may be located anywhere in the 54-864
MHz range. The FAT digital channels provide video, audio, and data services.
Figure 3-4 illustrates the protocol layers for the Forward Application
Transport (FAT) channels. At the base is the frequency-division multiplexing
layer, which is channelized according to the EIA-542 [70] tuning plan into 6
MHz channels. After tuning, the QAM intermediate frequency is recovered
and demodulated to a baseband signal that is an MPEG-2 multi-program
transport stream as defined by DVS-241 [46].
Page 23
Along with 64 or 256 quadrature amplitude modulation (QAM), the standard
calls for the use of concatenated trellis coded modulation, plus
enhancements such as variable interleaving depth for low latency in delay
sensitive applications such as data and voice. Using 64 QAM, a cable
channel that today carries one analog video channel could carry 27 Mbps of
information, or enough for multiple video programs. Using 256 QAM, the
standard 6 MHz cable channel would carry 38.8 Mbps. Conceptual block
diagram of Open Cable transmission system is shown in Figure 3-5.
Reed-
MPEG-2 MPEG
Solomon Inter-leaver Radomizer
Transport framing
encoder
QAM Modulator
Cable IF Physical Trellis encoder
Network
Interface
Figure 3-5 Open Cable Transmission Conceptual Block Diagram
The analog channels, on the other hand, are NTSC RF AM-VSB modulated
signals in accordance with current cable-system’s practice and applicable
FCC rules. NTSC Analog channels may be located anywhere in the 54-864
MHz range. The Vertical Blanking Interval (VBI) may contain data on line 21
of an analog television signal for closed captioning. The OCI-N interface
defines only in-the -clear analog services.
3.6 Conditional Access
The OpenCable TM Forum has attempted to define an OCI-H2 interface at part
of the head-end (HE) system to provide separation of the conditional access
function from the rest of the head-end functions. This means that one or
more independent CAS (conditional access systems) vendors could connect
to the head-end equipment via a standard interface. Therefore multiple
Page 24
vendors could supply the CAS to work with a head-end equipment will no
longer be necessary. However, the effort (DVS 278 [63]) within the SCTE was
recently rejected due to its inability to provide backward compatibility with
fielded digital cable systems. Major problems revealed its long crypto-period,
lack of support of multiple key types, and cost effectiveness. These issues
need to be resolved before defining the separation of conditional access
systems. Most conditional access systems today in the United States are
tightly coupled into other head-end functions. They are inseparable in order
to assure the most robust security and cost effectiveness.
On the consumer premises side however, significant progress has been
achieved through the specification of the POD module. As this module
provides a standard interface to allow a clean separation of the Conditional
Access and Security functions from the rest of the navigation device
functions, it reaps the following benefits:
1. There is a very small cost impact to the Host because only the minimum
components to support the signaling channel must reside in the Host.
2. The contents of the signaling channel to the Conditional Access and
Security functions remain a protected and closely guarded part of an
otherwise open-systems architecture. This enables the cable operator to take
any technical steps necessary to prevent theft of service by upgrading the
POD Module without any impact to the Host device.
3.7 Interfaces
3.7.1 Professional Interfaces
Open Cable does not defined any standard interface for professional
interfaces, but DHEI and ASI interfaces are very commonly used in North
America.
Page 25
3.7.2 Consumer Interfaces
The OCI-C1 interface was meant to connect the OpenCable TM devices to the
consumer devices in the home. OCI-C1 embraces the subset of the interfaces
that are commonly used today. This subset includes the following interfaces:
• NTSC RF channel ¾
• NTSC Composite
• S-video
• Component video
• Home digital network interface (HDNI)
A family of interfaces, DVS 295 [49] and 301 [51], embrace current analog
NTSC interfaces and a proposed digital interface called the host digital
network interface (HDNI). The objectives are to support standard and high
definition services, transfer of the digital signal quality to the consumer
device, and support for improved content protection.
The HDNI specification (DVS 194 [65]) is based on the IEEE 1394 standard
and supports compressed digital transfer of the MPEG-2 transport stream
from the digital set-top to a digital television. The digital television performs
MPEG-2 and Dolby AC-3 decoding functions. Graphics overlays for user
interface are sent separately over the IEEE 1394 link, and the digital
television is responsible for compositing the graphics overlay with video.
The HDNI specification includes provision for digital transmission content
protection (DTCP). DTCP uses digital cryptography to prevent unauthorized
copying of the digital video and audio content. DTCP was also referred to by
DVS 301 [51].
Page 26
3.8 Interactive Channel
As shown in Figure 3-3, there are currently two options for the out-of-band
information transport.
• Mode A, DVS-178 [43]: is originated from Motorola. This option uses a
2.048 Mbps forward channel and a 256 Kbps return channel. It uses
Quadrature Phase Shift Keying (QPSK).
• Mode B, DVS-167 [44]: developed and adapted from DAVIC. This option
uses 1.544 or 3.088 Mbps forward data channel and a 256 Kbps, 1.544
Mbps or 3.088 Mbps reverse data channel. Likewise modulation is by
QPSK.
Since DVS-178 [43] and DVS-167 [44] use the same modulation, it is then
possible to build a unified QPSK receiver that supports both standards.
Furthermore, the POD may also use DOCSIS cable modem for the handling
of IP transport. DOCSIS streams do not process Service Information that is
essential to Video transport and distribution. DOCSIS specifies a 27 or 38
Mbps forward data channel, which uses 64 or 256 QAM modulation and a
320 Kbps to 10.024 Mbps reverse data channel which uses QPSK or QAM.
(DVS 216 [52] specifies the number of IP streams between POD and Host.
DVS 321 [60] specifies how to manage DOCSIS resources. These
specifications are considered for inclusion in DVS 295 [50].) Most work
regarding DOCSIS usage for interactive video or webcasting is still in its
infancy.
3.9 Billing and Operational Support
Early work of the original work of the OpenCable TM Forum also attempted to
define an OCI-H3 interface to support all the operational functions for the
cable system. This interface must support the existing billing systems and
the existing operations of deployed digital cable systems. Standardizing the
OCI-H3 interface provides ease of migration from one billing system to
another. It also must be extensible to allow new service definitions to be
Page 27
added over time. At the present moment, the OCI-H3 is undefined as there
is still considerable work to make a standard operations interface a reality.
The present billing models available today only recognizes subscription and
pay-per view events and is not currently flexible enough to support new
types of service that have different billing models.
3.10 Interoperability
In addition to crafting the core functional requirements and interface
specifications, CableLabs has also created a process and the facilities to test
and certify the interoperability of OpenCable TM devices. These test facilities
enable designers and manufacturers to validate the functionality and
performance of their equipment in a real-world cable network environment
that includes various head-end equipment, and interconnected devices from
multiple vendors.
On June 2000, the OpenCable™ Review Board announced the verification of
the interoperability of digital removable security devices from Motorola and
Scientific-Atlanta. POD security modules will be made available immediately
to cable operators as soon as an order is placed. With the completion of this
testing, CableLabs has finished its initial work on digital POD modules,
enabling cable operators to meet the government imposed July 1, 2000
deadline for POD availability. The OpenCable TM certification process is a
continuous process where CableLabs seeks information from manufacturers
of POD modules and Host devices. The next revision is anticipated for
November 13, 2000 as Wave 5 Certification.
3.11 Summary
The intent of Open Cable devices were to support different advanced features
and services. For this reason, the OpenCable TM technical team has
concentrated on specifying the core requirements for an Open Cable Set-Top
Box (STB) that preserves features in the fielded digital STB, as well as
migration to newer features.
Page 28
Although extended functional requirements for the Open Cable device have
been discussed and specified, it is more difficult to fulfill a new consumer
architecture and garner vendor support in the time allocated by the FCC, not
necessarily by the MSO. Vendors can always innovate in terms of new
features for their advanced Open Cable devices. The acceptance of these new
devices is dependent on customers’ willingness to purchase. The
OpenCable TM approach is a model keen to competition at the retail front, but
several potential issues arise:
• There are only two core services provided by the basic Open Cable set-
top, in-the-clear analog NTSC video and one-way digital television. There
is however, no support for analog de-scrambling in the basic set-top and
two-way functionalities are currently not mandatory.
• The POD module is used to separate the security. It also processes OOB
communications. Since two different types of standards are supported in
the out-of-band channel, there is no guarantee that a retail Open Cable
device will be supported in any cable systems, if the cable network
incorporates only one OOB systems at its head-end systems.
However, if the POD module incorporates both OOB protocols, then
compatibility can be achieved with a HE of either OOB. Vendors have
expressed interest in dual mode chip design. However, the availability
schedule is not clear.
• A few Open Cable interfaces are currently at the draft level or undefined.
It is therefore unclear how each of the interfaces will progress in the
future.
CableLabs has remained the primary driving force behind these
specifications.
Page 29
MARKET STUDY
4.1 Introduction
The purpose of this chapter is to provide an understanding of the market
positions of the various international markets as well as the commercial
deployment of both Open Cable and DVB based systems. In addition, an
account of proprietary implementations is also listed.
4.2 United States Cable Market Summary
A summary of the United States cable market Nielsen Media Research; Paul
Kagan Associates, Inc., The Cable TV Financial Databook, 1999. With a home
passed of 97 million, the American market represents a substantial
proportion of the world’s cable market. In terms of digital deployments, the
American market reported a total of 4.9 millions digital cable subscribers at
the end of 1999 based on a findings from Paul Kagan Associates (Refer to
Paul Kagan Associates, Inc., Cable TV Financial Databook, 1999 for details.)
Based on Paul Kagan’s findings [Source: Kagan’s Digital Tier Strategies
2000], the outlook for digital set-top boxes is sturdy for 2000 and 2001. The
set-top market supports a trend that continued in 1999 when digital set-top
gains were up a steep 100% from 1998. It will not continue to double, and
set-top shortages could further crimp growth, but it was forecasted that
digital shipments will be 7.8 millions in 2000, and 10.4 millions in 2001,
before leveling off in 2002. As with any rollout, the pace is expected to drop
off in the near future. It was projected that digital set-top shipments will
peak in 2002, slipping to 9.1 million in 2003 and 7.8 million in 2004.
However, all the boxes deployed so far are based on proprietary designs
mainly from Scientific Atlanta and Motorola. Furthermore, we also noted the
deployment of some DVB based set-top boxes by some cable operators such
as MediaOne. As of today, there is no deployment of fully Open Cable
compliant set-top box in the market yet since the standard is still in its
Page 30
infancy. On the other hand, while the boxes deployed today may not be
classified as Open Cable compliant, they are mostly based on moderately
compatible designs since the Open Cable standard originates from both
Scientific Atlanta and Motorola.
In an OpenCable TM FAQ published on 5th April, 1998, it was reported that a
total of 15 million units were ordered from Motorola by a consortium of cable
operators that includes TCI, Time Warner Cable, MediaOne, Cox
Communications and Comcast Corp. Another group of cable operators has
ordered 1.4 million set tops from Scientific-Atlanta. These operators include
Time Warner Cable, Comcast, Adelphia Communications, Cox
Communications, Marcus Cable, MediaOne, Rogers Cablesystems Ltd.,
Videotron Ltee and Cogeco Cable. It is therefore anticipated that the
projections from 2000 onwards are likely to be based on Open Cable designs,
although it is unclear how many of them will remain proprietary.
4.3 European Cable Market Summary
Details of the European cable market can be found in EuroCable Directory,
7t h Edition, April 2000. Accordingly, while the penetration of Cable TV in
Europe is generally lower than that of the United States, the higher
television households has resulted in an almost equivalent market size for
cable in both Europe and United States. The first European commercial
digital television service was launched in France in April 1996. Since then,
the EU digital TV market has, on the whole, enjoyed a relatively high growth
rate both in terms of number of subscribers and in value terms. It was
estimated that the number of digital households, including cable, satellite,
and terrestrial, could reach a figure close on 10 million by the end of 1999.
DVB has been the standard widely used in Europe, with majority of the
countries starting off with DVB-S as early as 1996, followed by DVB-C.
Countries like the UK, Sweden and Spain have also started introducing
DVB-T as early as 1998 (see report from the Institut de l’ Audiovisuel et des
telecommunications and European Commissions).
Page 31
The digitization of cable networks has enjoyed significant progress since the
end of 1997. In June 1999, nearly 50 million cable connections were
upgraded for digital transmission (65% of homes passed). It was estimated
that there are over 2 million digital cable boxes installed at the end of 1999,
from 750,000 in 1998, which is further projected to reach about 26 millions
by the year 2005. Of the 2 million DVB-C boxes deployed today in Europe
today, it is understand that the United Kingdom has deployed about
700,000 set-top boxes, while the Nordics, Belgium, France, Germany,
Switzerland and Italy, has deployed 48,000, 12,000, 500,000, 600,000,
7,000, and 75,000 set-top boxes respectively. Other countries known to be
deploying DVB-C includes The Netherlands, Spain, South America (mainly
Brazil, Australia, China and USA.
4.4 Asia-Pacific Cable Market
In comparison with the European and the American markets, the Asia-
Pacific regions has a much higher number of television households in view of
the larger populations, but a much lower cable penetration of 20%
corresponding to 135 millions homes passed. Detail on the Asia-Pacific cable
market can be found in Kagan’s Asia-Pacific Cable/Pay TV 2000, July 1999.
The Asia Pacific region too has fully embraced the age of convergence with
leading countries launching digital and multimedia services. While there was
no digital TV implementation in 1998, it was noted that countries including
Japan, Hong Kong, Taiwan, Indonesia, and China, had all began trials and
deployments of digital TV systems over cable although no official statistics
are available today. Most of the systems deployed were understood to be
based on the DVB-C standard.
Page 32
4.5 Interactive Channel Market Summary
The Open Cable standard has defined both DVS-167 and DVS-178 as return
channel. The DVB on the other hand, has similarly defined an associated
return channel for cable networks commonly known as the DVB-RCC.
However, both the Open Cable standard and the DVB-RCC are still in the
early stages of commercial acceptance. As a result, there exist a variety of
different return channels adopted by different cable operators today,
including telephone return, DAVIC/DVB-RCC, DOCSIS, DVS-167, DVS-178.
It is important to note that the choice of the interactive return channel can
be made independent of the DTV downstream.
DOCSIS in particular, with a significantly larger market in the standalone
cable modems market, has recently emerged as the choice of several cable
operators, such as NTL, UPC and Telewest, for its interactive channel.
DOCSIS silicon manufacturers are very much further down the integration
path with production-ready silicon - placing DVB-RCC in a difficult 'catch-
up' game. With a first mover advantage and a large customer base, DOCSIS-
based silicon is already developing a significant cost advantage. Against this,
the DVB-RCC standard may now find it difficult to achieve sufficient
economies of scale to compete - suffering as operators increasingly opt for
the cheaper, leading standard.
For an objective understanding of the return channel from the market
perspective, it is therefore useful to provide a segregation of the different
implementations.
Page 33
3,000,000
1. DOCSIS Standalone Cable Modems
2,500,000 2. DVB-RC Standalone Cable Modems
3. DVB-C with DOCSIS Set-top Boxes
2,000,000 4. DVB-C with DAVIC/DVB-RC STBs
5. Open Cable with DVS 167/178 STBs
1,500,000
6. Proprietary with DAVIC/DVB-RC STBs
1,000,000
500,000
-
1 2 3 4 5 6
Source: Nokia
Figure 4-1 Breakdown of Cable Modems and STB return Channels
Figure 4-1 provides a breakdown of the deployment status of the various
interactive channels both as standalone cable modems and integrated set-
top boxes. The number of standard based standalone DOCSIS modems
deployed is significantly larger than the rest. DVB/DAVIC based standalone
cable modems stands at 10,000 today with projection to reach about
200,000 before June 2001 (Source: Nokia). DVB-C set-top boxes with
integrated DOCSIS modem, as noted, are widely used in Europe with
estimated deployment of around 280,000 today.
On the other hand, while there may be no Open Cable compliant set-top
boxes deployments today, the proprietary set-top boxes by Scientific Atlanta
which uses a DAVIC based DVS-167 return channel has achieved a
immense amount of close to 1.5 millions in United States. Open Cable based
STB from Motorola using DVS-178 return channel protocol has achieved a
even greater development status of over 15 millions in the United States.
Page 34
DISCUSSION AND RECOMMENDATIONS
5.1 Limitations of the Study
This study and recommendation of the digital cable standard was carried out
based on both academic and commercial inputs from all members of the
committee in absence of a site visit lab evaluation, or public trial. The
committee has deemed that it is unnecessary to carry out any form of trial
as there is no diverging views among the TWC members in the selection of
DVB-C as the standard. Moreover, this study is reinforced through the
rigorous comments and inputs provided by the TWC members, from various
companies, organizations and academia. Outstanding issues such as
conversion between the various formats are implementation-specific and
these should be dealt with separately from the study.
5.2 Discussion and Recommendations
5.2.1 Standard Maturity and Comprehensiveness
The Digital Video Broadcasting Project (DVB) includes over 300 well known
organisations in more than 30 countries worldwide. Members include
broadcasters, manufacturers, network operators and regulatory bodies,
committed to designing a global family of standards for the delivery of digital
television. DVB-compliant digital broadcasting and reception equipment for
professional, commercial and consumer applications is widely available on
the market. Numerous broadcast services using DVB standards are now
operational, in Europe, North and South America, Africa, Asia, and
Australasia. The DVB Project has generated a comprehensive set of
international standards covering all programme delivery media: satellite,
cable, terrestrial, microwave, MMDS, CATV, SMATV.
The key driving industry effort behind Open Cable – the OpenCable TM Forum,
on the other hand, is an initiative led by Cable Television Laboratories
Page 35
(CableLabs) on behalf of the cable operators. Its membership initially
consists of primarily cable television Multiple Systems Operators (MSO)
located in North, Central, or South America or the Caribbean; and interested
manufacturers. Its current member list currently comprises of some 55
major cable operators, signifying substantial support from the cable
operators. The process of OpenCable™ entails a team of CableLabs technical
staff working with technical representatives from member companies.
Request for Information (RFI) is used as a means to solicit for technical
inputs from leading manufacturers in the consumer electronics and
computer industries. The major contributors of the specification work
include companies like Motorola, Scientific Atlanta, SONY, Philips,
Panasonic, Nokia, Harmonic, etc. Future development on OCAP will involve
Liberate, Microsoft, Network Computers Inc., Oracle, Sun Microsystems and
others.
To-date, SCTE has completed the specifications for IB/OOB transport,
Service Information, Transmission and Multiplexing, Video Characteristic.
Host/POD interface specifications are in full preparation for balloting next
year. It has also recently started some work on its middleware software
specification (OCAP). However, many of the Open Cable interfaces are new. It
is therefore unclear how each of the interfaces will be modified to satisfy the
certification process. The DVB specifications are apparently more complete
at this present stage although we can also expect substantial regulatory
forces for Open Cable to speed up its specification work.
5.2.2 Key strengths and weaknesses
The key strengths of both DVB and Open Cable in each of the categories can
be summarized as follows:
Key DVB strengths over Open Cable:
• Comprehensive and complete set of International standards covering all
programme delivery media
• Support of 6, 7 and 8 MHz channelisation
• Support of in-band signaling
Page 36
• Support for Simulcrypt with standardized common scrambling algorithm
• Relative compatibility with satellite and terrestrial transmissions for ease
of content acquisition and distributions
Key Open Cable strengths over DVB:
• With Trellis coding improved noise immunity
• Provides support of emergency alert system
• With POD module improve the secrecy of the encryption
• More efficient and effective for navigation and channel mapping
In essence, as it is today, DVB has a clear edge over Open Cable on the DTV
cable front in most aspects. Amongst all, the interoperability of equipment,
compatibility of DVB with different transmission media, and worldwide
implementation of DVB standards helps to ensure economies of scale and
scalability.
5.2.3 Recommendation One
"that Singapore adopt DVB-C as the Digital Television Standard of
transmission over Cable."
The NCSC Technical Working Committee recommended DVB-C as the digital
television standard of broadcast transmission over cable in Singapore. The
various strengths and weaknesses of OpenCable TM and DVB, such as
technology maturity, interoperability and availability of equipment,
scalability, current and future market deployments, are carefully compared
and analyzed.
This recommendation also includes the following five broadcasting areas,
which use the standards and specifications defined under DVB.
• MPEG (DVB-MPEG)
• Multiplexing (DVB-SI, DVB-TXT, DVB-VBI, DVB-DATA)
• Subtitling (DVB-SUB)
Page 37
• Conditional Access (DVB-CSA, DVB-SIM)
• Interfacing (DVB-CI, DVB-PI, DVB-IRDI, DVB-PDH, DVB-SDH, DVB-
ATM)
5.2.4 Recommendation Two
"that the option of the return channel be left open for commercial
considerations."
For support of interactive applications, the NCSC Technical Working
Committee recommends leaving the option of the return channel open for
commercial considerations, acknowledging that interactivity on television is
still in the evolutionary stage today.
Page 38
REFERENCES
CENELEC documents:
[1] CENELEC prEN 50083-9 (March 1996): "Cabled Distribution Systems
for Television, Sound and Interactive Multimedia Signals; Part 9:
Interfaces for CATV/SMATV Headends and similar Professional
Equipment".
[2] CENELEC prEN 50201 (June 1996): "Interfaces for DVB-IRDs".
[3] CENELEC prEN 50221 (June 1996): "Common Interface Specification
for Conditional Access and other Digital Video Broadcasting Decoder
Applications".
[4] ETR 154: "Digital Video Broadcasting (DVB); Implementation
guidelines for the use of MPEG-2 Systems, Video and Audio in
satellite, cable and terrestrial broadcasting applications".
[5] ETR 162: "Digital Video Broadcasting (DVB); Allocation of Service
Information (SI) codes for DVB systems".
[6] ETR 211: "Digital Video Broadcasting (DVB); Guidelines on
implementation and usage of Service Information (SI)".
[7] ETR 289: "Digital Video Broadcasting (DVB); Support for use of
scrambling and Conditional Access (CA) within digital broadcasting
systems".
[8] ETR 290: "Digital Video Broadcasting (DVB); Measurement guidelines
for DVB systems".
[9] EN 300 421: "Digital Video Broadcasting (DVB); DVB framing
structure, channel coding and modulation for 11/12 GHz satellite
services". Known as (DVB-S).
[10] EN 300 429: "Digital Video Broadcasting (DVB); DVB framing
structure, channel coding and modulation for cable systems". Known
as (DVB-C).
[11] prEN 300 468: "Digital Video Broadcasting (DVB); Specification for
Service Information (SI) in DVB systems". Known as (DVB-SI).
Page 39
[12] EN 300 472: "Digital Video Broadcasting (DVB); Specification for
conveying ITU-R System B Teletext in DVB bitstreams". Known as
(DVB-TXT).
[13] EN 300 473: "Digital Video Broadcasting (DVB); Satellite Master
Antenna Television (SMATV) distribution systems". Known as (DVB-
CS).
[14] prETS 300 743: "Digital Video Broadcasting (DVB); DVB subtitling
system".
[15] EN 300 744: "Digital Video Broadcasting (DVB); Framing structure,
channel coding and modulation for digital terrestrial television".
Known as (DVB-T).
[16] EN 300 748: "Digital Video Broadcasting (DVB); Multipoint Video
Distribution Systems (MVDS) at 10 GHz and above". Known as (DVB-
MS).
[17] EN 300 749: "Digital Video Broadcasting (DVB); Microwave Multipoint
Distribution Systems (MMDS) below 10 GHz". Known as (DVB-MC).
[18] prETS 300 800: "Digital Video Broadcasting (DVB); Interaction
channel for Cable TV distribution systems (CATV)".
[19] ETS 300 801: "Digital Video Broadcasting (DVB); Interaction channel
through Public Switched Telecommunications Network (PSTN) /
Integrated Services Digital Network (ISDN)".
[20] prETS 300 802: "Digital Video Broadcasting (DVB); Network-
independent protocols for DVB interactive services".
[21] prEN 300 803: "Digital Video Broadcasting (DVB); Interaction channel
for Cable TV distribution systems (CATV)".
[22] prETS 300 813: "Digital Video Broadcasting (DVB); Interfaces to
Plesiochronous Digital Hierarchy (PDH) networks".
[23] prETS 300 814: "Digital Video Broadcasting (DVB); Interfaces to
Synchronous Digital Hierarchy (SDH) networks".
[24] prEN 300 815: "Digital Video Broadcasting (DVB); Interfaces to
Asynchronous Transfer Mode (ATM) networks".
[25] TR 101 190: "Digital Video Broadcasting (DVB); Implementation
guidelines for DVB terrestrial services; Transmission aspects".
[26] TS 101 191: "Digital Video Broadcasting (DVB); Mega-frame for Single
Frequency Network (SFN) synchronization".
Page 40
[27] prEN 301 192: "Digital Video Broadcasting (DVB); Specification for
data broadcasting".
[28] prEN 301 193: "Digital Video Broadcasting (DVB); Interaction channel
through the Digital Enhanced Cordless Telecommunications (DECT)".
[29] TR 101 194: "Digital Video Broadcasting (DVB); Guidelines for
implementation and usage of the specification of network independent
protocols for DVB interactive services".
[30] prEN 301 195: "Digital Video Broadcasting (DVB); Interaction channel
for terrestrial systems based on Synchronous Frequency Division
Multiple Access (SFDMA)".
[31] prTR 101 196: "Digital Video Broadcasting (DVB); Guidelines for use
of DVB return channel on Hybrid Fiber Coaxial (HFC) networks;
Netrwork-dependent layers for interactive services".
[32] TS 101 197-1: "Digital Video Broadcasting (DVB); DVB SimulCrypt;
Part 1: Head-end architecture and synchronization".
[33] prTS 101 197-2: "Digital Video Broadcasting (DVB); DVB SimulCrypt;
Part 2: Extended interoperability and control".
[34] TR 101 198: "Digital Video Broadcasting (DVB); Implementation of
Binary Phase Shift Keying (BPSK) in DVB satellite transmission
systems".
[35] prEN 301 199: "Digital Video Broadcasting (DVB); DVB interaction
channel for Local Multipoint Distribution System (LMDS) distribution
systems".
[36] TR 101 200: "Digital Video Broadcasting (DVB); A guideline for the
use of DVB specifications and standards".
[37] TR 101 201: "Digital Video Broadcasting (DVB); Interaction channel
for Satellite Master Antenna TV (SMATV) distribution systems;
Guidelines for versions based on satellite and coaxial sections".
[38] prTR 101 202: "Digital Video Broadcasting (DVB); Guidelines for the
implementation and usage of the DVB data broadcasting
specification".
[39] dEN 301 790: "Interaction channel for Satellite Distribution Systems".
[40] TR 101 812: "Multimedia Home Platform".
Page 41
SCTE documents:
[41] DVS-313: "Digital Cable Network Interface Standard".
[42] DVS-234: "Service Information Delivered Out-of-Band for Digital
Cable Television".
[43] DVS-178: "Digital Broadband Delivery System: Out Of Band
Transport - Mode A".
[44] DVS-167: "Digital Broadband Delivery System: Out Of Band
Transport - Mode B".
[45] DVS-208: "Emergency Alert Message for Cable".
[46] DVS-241: "Digital Video Service Multiplex and Transport System
Standard for Cable Television".
[47] DVS-031: "Digital Video Transmission Standard for Cable Television".
[48] DVS-258: "Digital Video Systems Characteristics Standard for Cable
Television".
[49] DVS-259: "Corrigendum 1 to DVS-053 Rev. 6".
[50] DVS-295: "Host-POD Interface Specification".
[51] DVS-301: "POD Copy Protection System".
[52] DVS-216: "POD Extended Channel Specification".
[53] DVS-217: "Point of Deployment (POD) Power Requirement".
[54] DVS-221: "Point of Deployment (POD) Module Initialization".
[55] DVS-223: "Standby Power Management Control for the Point of
Deployment (POD) Module".
[56] DVS-266: "Point-of-Deployment (POD) Module Generic Feature
Control".
[57] DVS-267: "Point-of-Deployment (POD) Module Firmware Upgrade
Host Interface".
[58] DVS-303: "Multi-stream POD Interface".
[59] DVS-304: "Host Firmware Download Interface".
[60] DVS-321: "POD/Host IP Flow Initialization and Management".
[61] DVS-026: "Subtitling Methods for Broadcast Cable".
[62] DVS-053: "Standard for Carriage of NTSC VBI Data in Cable Digital
Transport Streams".
[63] DVS-278: "Head-end Implementation of OpenCAS™".
[64] DVS-311: "IP Multicast for Digital MPEG Networks".
[65] DVS-194: "Home Digital Network Interface Specification".
Page 42
Other documents:
[66] ISO/IEC 13818-1: "Information Technology - Generic Coding of
Moving Pictures and Associated Audio Information. Part 1: Systems".
[67] ISO/IEC 13818-2: "Information Technology - Generic Coding of
Moving Pictures and Associated Audio Information. Part 2: Video".
[68] ISO/IEC 13818-3: "Information Technology - Generic Coding of
Moving Pictures and Associated Audio Information. Part 3: Audio".
[69] ISO/IEC 13818-6: "Information Technology - Generic Coding of
Moving Pictures and Associated Audio Information. Part 6: Extension
for Digital Storage Media Command and Control(DSM-CC)".
[70] EIA 542: "Cable Television Channel Identification Plan".
[71] ITU-T J.83: "Digital multi-programme systems for television, sound
and data services for cable distribution".
[72] ITU-T J.112: "Transmission systems for interactive cable television
services".
[73] OCI-N: "OpenCable Network Interface Specification".
Reference Books and Papers
[74] "OpenCable ™ Architecture ", Michael Adams, Cisco press, 2000.
[75] "DTV Survival Guide", Jim Boston, McGraw-Hill, 1999.
[76] "DTV, the Revolution in Digital Video, Second Edition", Jerry
Whitaker, McGraw-Hill, 1999.
[77] "Broadband Return Systems for Hybid Fibre/Coax Cable TV
Networks", Donald Raskin & Dean Stoneback, Prentice Hall PTR,
1998.
[78] "Digital Television MPEG-1, MPEG-2 and principles of the DVB
system", Herve Benoit, Arnold, 1997.
[79] "Considerations on the Choice of DAVIC or DOCSIS Protocol in a
settop Box Environment", Bill Wall, Technical Director, Scientific
Atlanta.
Page 43
GLOSSARY OF ABBREVIATION
AEIT Aggregate Event Information Table
AETT Aggregate Extended Text Table
ANSI American National Standards Institute
API Application Programming Interface
ASI Asynchronous Serial Interface
ATM Asynchronous Transfer Mode
ATSC Advanced Television Systems Committee
BAT Bouquet Association Table
BC Broadcast Channel
CA Conditional Access
CAS Conditional Access System
CAT Conditional Access Table
CBR Constant Bit Rate
CC Closed Captions
CEA Consumer Electronics Association
CENELEC European Committee for Electrotechnical Standardization
CMTS Cable Modem Termination System
CPE Customer Premises Equipment
CSA Common Scrambling Algorithm
DAVIC Digital Audio Video Council
DAVIC PAS DAVIC Publicly Available Specification
DECT Digital Enhanced Cordless Telecommunications
DHCP Dynamic Host Configuration Protocol
DHEI Digital Head-end Extension Interface
DOCSIS Data-over-Cable Service Interface Specifications
DSM-CC Digital Storage Media Command and Control protocol
DTCP Digital Transmission Content Protection
DVB Digital Video Broadcasting
DVB-C DVB baseline system for digital cable television
DVB-S DVB baseline system for digital satellite television
DVB-T DVB baseline system for digital terrestrial television
DVS Digital Video Subcommittee
EBU European Broadcasting Union
Page 44
ECCA European Cable Communications Association
ECM Entitlement Control Message
EE Execution Engine
EIA Electronic Industries Association
EIT Event Information Table
EMM Entitlement Management Messages
EPG Electronic Programme Guide
ETSI European Telecommunications Standards Institute
FAT Forward Application Transport
FCC Federal Communications Commission
FDC Forward Data Channels
FEC Forward Error Correction
GOP Group of Pictures
GSM Global System for Mobile communication
HDNI Home Digital Network Interface
HDTV High-Definition Television
HE Head-end
HFC Hybrid Fiber Coaxial
HTML Hypertext Markup Language
IB In-Band
IBC International Broadband Convention
IC Interaction Channe l
IDATE Institut de l' Audiovisuel et des telecommunications
IEC International Engineering Consortium
IEEE Institute of Electrical and Electronics Engineers
IF Intermediate Frequency
INA Independent Network Adapter
IP Internet Protocol
IRD Integrated Receiver Decoder
ISDN Integrated Services Digital Network
ISO International Organization for Standardization
ITU International Telecommunications Union
ITU-R ITU - Radiocommunication Sector
ITU-T ITU - Telecommunication Sector
LMDS Local Multipoint Distribution Services
L-VCT Long-form Virtual Channel Table
Page 45
MAC Media Access Control
MGT Master Guide Table
MHP Multimedia Home Platform
MMDS Multi-point Microwave Distribution System
MPEG Motion Picture Experts Group
MSO Multiple System Operators
MVP Modulating Video Processor
NABTS North American Teletext
NIT Network Information Table
NIU Network Interface Unit
NTSC National Television Systems Committee
NTT Network Text Table
OCAP OpenCable™ Application Platform
OCI-N OpenCable Interface-Network
OOB Out-of-Band
OSI Open Systems Interconnection
PAL Phase Alternating Line
PAT Program Association Table
PCM Pulse Code Modulation
PCMCIA Personal Computer Memory Card International Association
PCR Program Clock Reference
PDH Plesiochronous Digital Hierarchy
PE Presentation Engine
PES Packetized Elementary Stream
PHY Physical Layer
PID Program Identifier
PMT Program Map Table
POD Point-of-Deployment
PRBS Pseudo Random Binary Sequence
PSI Program Specific Information
PSIP Program and System Information Protocol
PSTN Public Switched Telephone Network
QAM Quadrature Amplitude Modulation
QoS Quality of Service
QPSK Quaternary Phase Shift Keying
RDC Reverse Data Channels
Page 46
RF Radio Frequency
RFI Request for Information
RS Reed-Solomon
RST Running Status Table
S-VCT Short-form Virtual Channel Table
SCTE Society of Cable Communications Engineers
SDH Synchronous Digital Hierarchy
SDT Service Description Table
SDTV Standard Definition Television
SI Service Information
SMATV Satellite Master Antenna Television System
SNMP Simple Network Management Protocol
SPI Synchronous Parallel Interface
SSI Synchronous Serial Interface
STB Set-Top Box
TC Transmission Convergence
TCP Transmission Control Protocol
TCS Television Corporation of Singapore
TDMA Time Division Multiple Access
TDT Time and Date Table
TOT Time Offset Table
TS Transport Stream
UDP User Datagram Protocol
USB Universal Serial Bus
VBI Vertical Blanking Interval
VM Virtual Machine
VSB Vestigial Side-Band
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