cable modems & set- top boxes: a market & technology …

© 2001 Dunelm Services Limited

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CABLE MODEMS & SET-TOP BOXES: A MARKET &TECHNOLOGY REVIEW

A course developed by Dunelm Services Ltd.

Course Workbook

2 University of Surrey, UK

19th March, 2001A / Cable Modems & Set-top Boxes: Market & Technology

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PUBLICATIONS HISTORY

The publications history for this course workbook is:

CoursewareVersion

Date Summary of Amendments

A 19th March, 2001 The first release of this courseware.

3University of Surrey, UK

19th March, 2001 Cable Modems & Set-top Boxes: Market & Technology / A

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PREFACE

This is the workbook which accompanies the one day Dunelm Services course entitled CableModems & Set-top Boxes: Market & Technology. It is intended that this course should actas a review of the key markets and technologies for cable networks.

It should always be borne in mind that the field of communications networking is evolving veryrapidly, particularly in the case of broadband digital cable networking, and that some of thematerial covered in this course is accurate only for a short time – particularly that relating to theactual standards and products, etc. This means that when this material is reviewed in future timesthe reader must take into account this progression of technology. Of course, the fundamentalswill never change – or only very rarely !

The main text is split into three sections:

SECTION A. This presents the information about the organisation of the course and its material.It presents the publications history, contents list, syllabus, timetable, symbol set, an extensive listof relevant abbreviations used in cable networks and set-top boxes, and a tutorial paper on cablemodems.

SECTION B. A copy of every overhead slide used in the course is presented. There is also spacefor the delegate to write in their own accompanying comments. The areas covered in the slidesare: THE MARKETPLACE – the market context for the roll-out of cable network technologies;CABLE MODEM TECHNOLOGY – a review of cable modem standards, specifications andtechnology; SET-TOP BOX TECHNOLOGY – a review of the set-top box standards, specifi-cations and technology; ALTERNATIVE TECHNOLOGIES– a review of the alternative accessnetworking technologies; REVIEW– a review of the materials covered in the rest of the course.

APPENDICES. Appendix A contains a bibliography, Appendix B is a glossary of terms,Appendix C contains a white paper on cable modem performance, Appendix D a data-sheet forat simulation software tool that supports accurate prediction of cable network performance andAppendix E which contains the resume of the course presenter.

Dunelm Services Limited can, in no way, be held responsible for the consequences of anymistakes contained in the course given either verbally or in any printed materials handedout to the delegates. The copyright to this workbook is owned by Dunelm Services Limited.Distribution or duplication in any form or processing of the document or any part of it byelectronic systems may be done ONLY with the explicit permission of DUNELM SERVICES

LIMITED.

This course workbook was written and produced by Colin and ChristineSmythe of Dunelm Services Ltd, at 34 Acorn Hill, Stannington, Sheffield,

S6 6AW, Tel/Fax: 0114-2334009, E-mail: [email protected].



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CONTENTS

Publications History 2

Preface 3

Contents 4

Aims & Objectives 6

Syllabus 7

Timetable 8

Abbreviations 9

Symbol Set 15

Tutorial Paper 16Abstract 161. Introduction 162. Cable Modem Architectures 173. Cable Modem Standardisation 214. DOCSIS & EuroDOCSIS Specifications 275. DVB-RCC/DAVIC Specifications 296. DOCSIS/EuroDOCSIS/DVB-RCC Comparisons 307. Conclusion 31References 32

1. The Marketplace 351.1 Overview 361.2 Objectives 361.3 Slides Summary 371.4 Questions 50

2. Cable Modems 512.1 Overview 522.2 Aims & Objectives 522.3 Slides Summary 532.4 Questions 68



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3. Set-top Boxes 693.1 Overview 703.3 Slides Summary 713.2 Aims & Objectives 713.4 Questions 84

4. Alternative Technologies 854.1 Overview 864.2 Aims & Objectives 874.3 Slides Summary 874.4 Questions 98

5. Review 995.1 Overview 1005.2 Aims & Objectives 1005.3 Slides Summary 1015.4 Questions 110

Appendix A – Bibliography 111

Appendix B – Glossary of Terms 112

Appendix C – White Paper 118Summary 118C1. Introduction 118C2. Scenario 120C3. Results 121C4. Recommendations 122Appendix – Configuration Parameters 122

Appendix D – DocSIM Datasheet 124Customised solutions 124Lighting fast simulation execution times 124DOCSIS model features 124Contact Information 125

Appendix E – Dunelm 126E1 Dunelm Services 126E2 Colin Smythe Resume 127



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AIMS & OBJECTIVES

The aim of this course is:

“To provide an appreciation of the services that will be availablethrough cable modems and set-top boxes."

The objectives for the fulfilment of this aim are to:

1. Introduce the different competing technologies and to explain the strengths and weak-nesses of the services supported by each solution;

2. Describe how the different technologies support quality of service and to explain howthis will be perceived by the user;

3. Show how cable modem and set-top box technologies will evolve to provide an exten-sive set of user services.

It is not the intention of this course to provide an in-depth description of cable networkingbut to provide a basic understanding of some of the new specifications.



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SYLLABUS

1. The MarketplaceA. An operator's perspectiveB. A technology supplier's perspectiveC. A user perspectiveD. Cable modem and set-top box manufacturers

II. Cable Modem TechnologyA. Cable modem standardisation (inc. DOCSIS, IEEE 802.14 and DVB)B. J.83 and J.112 with Annex A and BC. DOCSIS specifications (v1.0 and v1.1) – the servicesD. DVB-RCC, ETS200800, EuroModem – the servicesE. EuroDOCSIS and EuroDOCSIS vs. DVB-RCCF. Performance comparisons and expectationsG. End-to-end services and systems

III. Set-top Box TechnologyA. The EuroBOX specifications – relevance, service strengths/weaknessesB. The OpenCable specifications – relevance, service strengths/weaknessesC. The Multimedia Home PlatformD. Cable modem and set-top box mixed network architectures and servicesE. End-to-end services and systems

IV. Alternative TechnologiesA. Satellite access (VSAT, DVB-RCS)B. Fixed broadband wireless accessC. x-DSL access (from POTS to NISDN and ADSL)D. The killer application and its needs, integration not homogenisation



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TIMETABLE

9:30 -10:00 Introductions

10:00 -11:00 The Marketplace

11:00 -11:30 Coffee Break

11:30 -1:00 Cable Modem Technologies

1:00 - 2:00 Lunch Break

2:00 - 3:15 Set-top Box Technologies

3:15 - 3:45 Tea Break

3:45 - 4:30 Alternative Technologies

4:30 - 5:00 Course Review



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TUTORIAL PAPER

Abstract

The development of a standard for interac-tive multimedia services over CommunityAntenna Television (CATV) networks isdrawing interest from the data communica-tions, telecommunications, broadcasting,consumer electronics and the computersupply industries. Until recently, the solu-tions available for data transfer over HybridFibre Coax (HFC) CATV networks werebased on proprietary random accessprotocols and consequently they cannot beused in an open system. Also, they arelimited when delivering digital audio andvideo streams. A unified standard is re-quired, that will allow the development ofinteroperable hardware and drive down thecost of implementation. In Europe theDigital Video Broadcasting (DVB) and theEuroDOCSIS Cable Modem specificationshave been adopted whereas the Data OverCable Service Interface Specification is thechoice in North America.

1. Introduction

The potential of data delivery over Commu-nity Antenna Television (CATV) networkswas realised as early as the 1960s. The firstto benefit were public institutions while thetechnology was tested by utility companiesfor telemetry applications. Since then thedemand for high bandwidth at the home hasrisen sharply and before a unified standardcould be ratified. The majority of CATVnetworks in North America are based on thetree and branch architecture. Alternativetopologies are the tree and bush, foundmainly in Europe, and the rarely usedswitched star architecture which uses off-premises addressable converters. Fibre hasreplaced coaxial feeds from the head-end tothe initial splitter to create the Hybrid FibreCoax (HFC) topology. The HFC topologyprovides immunity from electromagneticnoise and the elements for the transmissionover large distances, and the cost efficiencyof coax cable for the last mile.

Cable Companies are now exploring newtechnologies which can be used to supportdigital interactive multimedia applicationsover their CATV infrastructures, [Azzam,97]. Over the last few years much attentionhas been paid to the development of architec-tural options for CATV networks that willallow the immediate support of broadbandservices as the first step toward enhancedcommunication services for residential users.

Choosing the DOCSIS or DVB/DAVIC Return ChannelPath for Interactive Services

C.SmytheDunelm Services Limited

The author would like to thank SymbionicsLtd, Cambridge, UK and Arris InteractiveInc, Andover, USA, who partially fundedthis work.



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specification for acceptance by theITU-T;

• The Digital Video Broadcasting(DVB) project – the DVB cable system(DVB-C) was completed in 1995.DVB has adopted the DAVIC recom-mendations with respect to CATV andhas been responsible for the develop-ment of the European standard ETS300800.

The following sections of this paper de-scribe:

• Cable Modem Architectures – a re-view of pre-standardisation cablemodems;

• CATV Data Standardisation:A sum-mary of cable modem standardisation;

• DOCSIS Specifications – a review ofthe DOCSIS, versions 1.0 and 1.1,cable modem standard;

• DVB/DAVIC Specifications – areview of the DVB/DAVIC cablemodem standard;

• DOCSIS/EuroDOCSIS/DVB-RCCComparison – a review of the capabili-ties of the DVB-RCC/DAVIC,DOCSIS and EuroDOCSIS cablemodems with relevance to the DigitalInteractive Retailing business.

2. Cable ModemArchitectures

HFC networks were originally designed foranalogue audio and video broadcasts. Pro-viding high performance multimedia servicesto the home over HFC networks presentsdifficulties due to the inherent problems ofthese architectures such as long propagationdelays, signal attenuation, the high level of

These technologies range from the introduc-tion of well established Internet devices tonew access mechanisms. The current CATVstandards activities, [Tzerefos, 98], are:

• IEEE 802.14 – the IEEE committeeproducing a broadband MetropolitanArea Network (MAN) Medium AccessControl (MAC) and Physical layerprotocols and the Advanced HighSpeed Physical Layer;

• ATM Forum Residential BroadbandWorking Group (RBWG) – investigat-ing the provision of AsynchronousTransfer Mode (ATM) across differentCATV network topologies and fordistribution within the home itself;

• Internet Engineering Task Force(IETF) – investigating the use of theInternet Protocol (IP) Over Cable DataNetworks (IPCDN). This work isbased upon the use of routers to inter-connect different logical internetstructures;

• Multimedia Cable Networks Systems(MCNS) partners – producing the DataOver Cable Service Interface Specifi-cations (DOCSIS) on behalf of theNorth American Cable industry andusing cable modem technology;

• Digital Audio-Visual Council(DAVIC) – primarily a Europeandriven group, but including manyinternational companies, looking at thestandards for complete end-to-endinteractive multimedia delivery sys-tems;

• SCTE – an accredited Americanstandards organisation working oncompatibility issues for cable telecom-munications systems. The SCTE hassuccessfully submitted the MCNS



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noise on the upstream direction and thesharing of bandwidth by all homes in thesame loop. Another issue is the integrationof the home network, the bearer HFC and theprovider’s network. The network infrastruc-ture consists of the ‘Head-end’, the ‘Residen-tial’ and the ‘Home’ networks. The Head-end network has to interconnect the serversof the content provider, which need notnecessarily be physically located within thesame premises, and can be built on upon anyof the established MAN and Wide AreaNetwork (WAN) architectures. The Resi-dential network has to provide access to thecontent provider’s servers via the HFCcabling infrastructure. The major limitationof HFC networks is they are broadcastnetworks with simple or no switching and sothe bandwidth is shared among a largenumber (thousands) of nodes within thesame segment. The Home network providesthe communications between the cablemodem (the gateway) and the appropriatedomestic appliances such as television,telephone, PC, etc.

In CATV networks, the spectrum is divided

into the forward (also referred to as thedownlink, downstream and head-end to user)and return (also referred to as the uplink,upstream and user to head-end) frequencies.Table 1 shows the basic downstream andupstream spectrum allocations and the slightvariations in the frequency ranges for Eu-rope, North America and Japan are alsoshown. The downstream channels supportthe legacy analogue broadcast television (80-450MHz, the exact value depending on thecountry) and the multiples of 1-6MHz or 1-8MHz channels in the 450-900Mhz region(the exact value depending on the country).The upstream channels are also divided into1-6MHz but the high ingress noise meansthat the data capacity is only 1-10Mbps perchannel as opposed to the 28-40Mbps avail-able in each downstream channel. In terms ofmodulation schemes, most manufacturershave implemented 64 Quadrature AmplitudeModulation (QAM) for the downstream andQuadrature Phase Shift Keying (QPSK) forthe upstream channels, thereby creating thedifference in data rates between the down-stream and upstream.

Table 1 CATV frequency allocations across the world.

Characteristics Europe Japan North America

Upstream (digital)

Standards ITU-T J.112-A ITU-T J.112-C ITU-T J.112-B

Minimum Frequency (MHz) 5 5 5

Maximum Frequency (MHz) 65 55 42

Channel Bandwidth (MHz) 1-6 1-6 1-6

Downstream (analogue)


Maximum Frequency (MHz) OperatorSpecific

OperatorSpecific

OperatorSpecific

Channel Bandwidth (MHz) 8 6 6

Downstream (digital)

Standards ITU-T J.83-A ITU-T J.83-C ITU-T J.83-B


Maximum Frequency (MHz) 862 770 860

Channel Bandwidth (MHz) 8 6 6



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The downstream cable transmission charac-teristics in different parts of the world havebeen defined by the ITU-T as part of the J.83standard [ITU, 97]. This has three annexes:

• Annex A – derived from the DigitalVideo Broadcast (DVB) standardoriginated in Europe. A Motion Pic-ture Encoding Group 2 TransportStream (MPEG2-TS) is used within an8MHz channel. DAVIC has selectedAnnex A;

• Annex B – a transmission formatwidely accepted in North America. AnMPEG2-TS is used within a 6MHzchannel;

• Annex C – defined for Japan. AnMPEG2-TS is used within an 8MHzchannel.

The upstream cable transmission characteris-tics in different parts of the world have beendefined by the ITU as part of the J.122standard [ITU, 99]. This also has threeannexes:

• Annex A – the upstream definition forDVB/DAVIC based architectures;

• Annex B – the upstream definition forthe DOCSIS based architectures;

• Annex C – the upstream definition forusage in Japan.

The J.112 standard permits the differentupstream systems to be marketed in their‘foreign’ environments e.g. J.112 Annex Ain the US and J.112 Annex B in Europe.

The cable modem technology originallydeployed does not comply with a specificstandard. Instead it is based on proprietaryinterfaces for the cable modem to head-endcommunications, and interoperability isimpossible. The most common interface

between the cable modem and the subscriberdevice is a 10BASET Ethernet connection(USB interfaces are becoming more widelyavailable). Most PCs/workstations aresupplied with Ethernet interfaces and so theycan be easily connected to a cable modem.

In Figure 1 the key components in a cablemodem network are:

• The cable modems/Set-Top Boxes(STB) which are used to supply thesubscriber interface capability. In thecase of the STB, the cable modemfunctionality is supplied as part of anintegrated consumer device. A10BASET Ethernet interface is nor-mally used for interconnection to theuser’s PC/workstation;

• The head-end controller which isresponsible for allocating upstream anddownstream bandwidth, and for for-warding the data from the upstreamonto the downstream. The head-end isalso responsible for aggregating multi-ple upstream channels onto a singledownstream channel;

• The CATV data manager which isresponsible for management of thedata infrastructure. This PC/workstation is responsible for distribut-ing all of the appropriate default con-trol parameters and information;

The router/IP switch which is used to inter-connect the head-ends (each head-end willsupport between 500-2000 cable modemsand so most commercial cable plants willrequire many data head-ends). Head-endsare supplied with a LAN interface and therouter/IP switch is used to provide highspeed interconnection plus internetworkingwith other networks e.g. the Internet.

In July, 1999, the Broadband Bob newsletter



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announced the following cable modeminstallations market analysis, shown in Table2. The statistics in Table 2 denote the ship-ping of all types of cable modem i.e. theinclusion of proprietary solutions fromorganisation such as Nortel/Arris, Motorola,Com21, etc. CableLabs keep an accuraterecord of vendors who have certified cablemodems and qualified CMTSs.

At present there is very little independentlyverified information on situation regardingthe supply of DVB/DAVIC compliant cablemodems. It is however clear that for the nextfive years the cable modem market will bebased upon:

• The provision of DOCSISv1.1 compli-ant cable modems for usage in NorthAmerica. It is claimed that someNorth American operators are evaluat-ing DVB/DAVIC-based solutionshowever it is clear that DOCSIS will

be the only accepted cable modemtechnology. The success of theCableLabs interoperability testing(resulting in certification and qualifica-tion) also provides operators with aconfidence is not yet available for theEuroModem solution;

• The UK will be dominated by theusage of DOCSIS and theEuroDOCSIS solutions, in part be-cause most of the UK cable operatorsnow have US ownership. The UK hasa long track record of preferring USproduced data communications equip-ment;

• The rest of Europe will be adopt bothDVB/DAVIC and the EuroDOCSISsolutions.

Head-endcontroller Ethernet hub

PC withEthernet card

Cablemodem

AUI/10BASET

CATVNetwork

Server withEthernet card

Cablemodem

bridge/router

Coaxcable

Manager

Set-TopBox

Ethernet hub

TV/PC

Head-endcontroller Ethernet hub

Router/IP switch

Figure 1 A cable modem architecture.



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3. Cable Modem Stand-ardisation

The current CATV standards activities andorganisations, [Tzerefos, 98], are the:

• ATM Forum Residential BroadbandWorking Group (RBWG);

• Internet Engineering Task Force(IETF);

• Multimedia Cable Networks Systems(MCNS) partners;

• IEEE 802.14 subcommittee;

• Digital Audio-Visual Council(DAVIC);

• Society of Cable TelecommunicationsEngineers (SCTE);

• The Digital Video Broadcasting(DVB);

• International TelecommunicationsUnion for Telecommunications (ITU-T);

• CableLabs;

• EuroCableLabs;

• European Cable CommunicationsAssociation (ECCA);

• DVB/DAVIC Interoperability Consor-tium;

• European Cable Modem Consortium.

3.1 ATM Forum ResidentialBroadband Working Group(ATMF-RBWG)

The RBWG was formed by the ATM Forumin order to promote the deployment of ATMover emerging residential network infrastruc-tures. The efforts of the RBWB focus on thedelivery of ATM to the home and ATMwithin the home. The network topologiesconsidered for delivering ATM down to thelast mile are: ATM over HFC, ATM overFibre To The Curb (FTTC), ATM over FibreTo The Home (FTTH) and ATM overADSL. ATM-To-The-Home (ATTH) isproposed for the support of new generationof interactive services over CATV networks.ATM is a broadband network technologywhich features high bandwidth and guaran-teed quality of service and the ATM Forumhas recently established a group that isstandardising the interfaces for the deploy-ment of ATTH over the different networkarchitectures. The major concern when

Vendor Shipment

Share Vendor Shipment

Share

Motorola 760,000 44% Samsung 20,000 1%

Nortel/Arris 490,000 28% Thomson 20,000 1%

Terayon 145,000 9% NetGame 15,000 1%

Com21 140,000 9% Toshiba 15,000 1%Zenith 35,000 2% Hybrid 15,000 1%

GI 30,000 2% Phasecom 10,000 0.75%

3Com 25,000 1.5% Miscellaneous 10,000 0.75%

Table 2 Cable modem shipments as of July, 1999.



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implementing ATM over CATV networks isthe definition of the protocols that wouldallow the deployment of ATM over thedifferent cabling plants (HFC, FTTH, FTTCand ADSL) already in operation i.e. a legacysystems problem. ATM can be implementedover HFC networks by placing an ATMswitch within the head-end to interconnectthe server with the rest of the cable plant. Inturn each port of the ATM switch must belogically connected to each downstreamchannel. At the subscriber’s end the receivermust be tuned to the right frequency beforedecoding ATM cells. The two basic inter-faces under development are the ATMDigital Terminal (ADT) at the head-end andthe ATM Interface Unit (AIU) at the sub-scriber. The ATMF-RBWG specificationwas ratified in 1998 [ATMF, 98].

3.2 Internet Engineering TaskForce (IETF)

The IETF has formed a working group thatwill produce a framework and requirementsdocument for IP over a CATV infrastructure.Issues to be addressed by the IPCDN WGare the service interface between IP andCATV network, multicast, broadcast, ad-dress mapping and resolution (for IPv4),neighbour discovery (for IPv6) and networkmanagement.

The deliverables, originally expected fromthe WG are:

• RFCs covering the framework archi-tecture, requirements and terms ofreference for Cable Data Networks;

• IPv4-over-HFC access network docu-ment covering the mapping of IP overRF channels, encapsulation and fram-ing of IPv4 packets, IP to modem and/or PC address resolution, multicast and

broadcast;

• IPv6-over-HFC access network docu-ment covering the mapping of IP overRF channels, encapsulation and fram-ing of IPV6, IP to modem and/or PCaddress resolution, neighbour discov-ery, multicast and broadcast;

• A media specific Management Infor-mation Base (MIB) for managing theHFC spectrum;

• A MIB for managing the cable datanetwork services including the man-agement of IP over the CATV networkitself.

The IPCDN has already released an InternetDraft document presented for discussionpurposes only and not for setting any stand-ards. Issues covered are IP service features,IP address assignment using the DynamicHost Configuration Protocol (DHCP), Ad-dress Resolution Protocol (ARP) and otherservice specific issues relating to IP overCATV. At present the primary focus of theIETF’s work is on the adoption and exten-sion of the DOCSIS MIB.

3.3 Multimedia Cable NetworkSystems (MCNS)

The MCNS partners consist of Comcast,CableLabs, TCI, Cox Communications,Time Warner, Continental Cablevision,Rogers Cablesystems, CableLabs and ArthurD. Little. The task of the Data Over CableService Interface Specification (DOCSIS)project was to define, on behalf of the NorthAmerican cable industry, the required com-munications and operations support inter-faces for cable modems. OriginallyCableLabs was producing their own standardbut this was superseded by the activities of



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the MCNS. Thus far DOCSISv1.0 andDCSISv1.1 have been produced and there isdebate about whether or not to developDOCSISv1.2. The DOCSIS cable modemsolution is discussed in Section 4.

3.4 IEEE 802.14 Subcommittee

The IEEE 802.14 subcommittee’s workfocused on the definition of a MAC protocoland network access techniques for datacommunications services over CATV net-works. The access techniques originallyunder consideration were the contentionreservation system, polling and a slottedcollision system that can be extended toinclude reserved bandwidth. In the opinionof the IEEE 802.14 subcommittee, the otherIEEE 802 LAN/MAN access protocols thenavailable did not meet the requirements forthe HFC network:

• FDDI and DQDB could, potentially,have supported the required servicesbut they are based on inappropriatetopologies;

• The LAN standards, such as Ethernet,do not support real-time services andare unsuitable for networks coveringtens of kilometres;

• The IEEE 802.4 Token Passing bus isbased on the same branching coax bustopology as the HFC networks but isdesigned with the needs of industrialinstallations in mind and assumes thatall nodes are on line at all times.

Three IEEE 802.14 cable modem standardswere developed for consideration:

• IEEE 8-2.14a – the original IEEE802.14 CATV protocol. This will onlybe ratified if some vendor decides tomanufacture IEEE 802.14 cable mo-

dems;

• IEEE 8-2.14b – the advanced highspeed physical layer specification;

• IEEE 8-2.14c – adoption of theDOCSISv1.0 standard.

The IEEE 802.14 has been made dormant. Itwill not recommence its work unless at leastone major manufacturer decides to adopt theIEEE 802.14a/b specifications.

3.5 Digital Audio-Visual Council(DAVIC)

The Digital Audio-Visual Council (DAVIC),founded in October 1994 and based in Ge-neva, was a non-profit making Associationwhich has charged itself with the task ofpromoting broadband digital services. Thegoals of DAVIC were declared as “... toidentify, select, augment, develop and obtainthe endorsement by formal standards bodiesof specifications of interfaces, protocols andarchitectures of digital audio-visual applica-tions and services”. The applications ofparticular interest were Video-On-Demand(VOD) and Near VOD (NVOD). DAVICproduced a series of specifications andversion 1.5 was made available in June,1999. The earlier DAVIC specificationsdefine different grades of existing tools oradditional tools which provide compatibilitywith the full range of new Internet facilitiese.g. web browsers and Java, [Donnelly, 97].DAVIC specifications contain normative andinformative parts. The normative parts mustbe implemented as in the specifications inorder to claim conformity and the informa-tive parts are included to help clarify thenormative parts and to give assistance tothose attempting to implement the specifica-tions. The specifications define referencepoints, i.e. points of particular interest in the



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system, and these points have a normativevalue if they are accessible.

A DAVIC delivery system is divided into acore network, an access network and an in-house network. The separation between thecore and access network is formed betweenthe Local Exchange (LE) and the AccessNode (AN). The separation between theaccess node and the in-house network isformed by the Network Termination (NT).In the majority of cases the end-serviceconsumer system will contain a STB whichcan be divided into a network dependant partcalled the Network Interface Unit (NIU) andthe network independent part called the SetTop Unit (STU). The in-house network iscontained between the NT and the STB,however, DAVIC 1.0 ignores the in-housenetwork and considers the STB to be con-nected directly to the NT. DAVIC 1.5 Part 8is equivalent to the DVB-RCC/ETS300800specification. DAVIC 1.5 also contains aspecification for the in-house LAN. DAVICwas disband in June 2000 because the com-mittee considered that its goals had beenachieved.

3.6 Society of Cable Telecommu-nications Engineers (SCTE)

The SCTE is a non-profit organisationformed in 1969 in order to promote thesharing of technical and operational knowl-edge for cable TV and broadband communi-cations. As of August 1995 the SCTE be-came an accredited Standard DevelopingOrganisation of NIST. The Data StandardsSubcommittee role is to promote data deliv-ery in the cable industry and define standardsfor hardware interoperability. In it’s charterit is mentioned that the subcommittee willco-ordinate it’s efforts with the IEEE 802.14,DAVIC and CableLabs. On August 131997, the SCTE submitted the MCNS speci-

fication for the transmission of data overcable to the International Telecommunica-tions Union (ITU). DOCSIS, has alwaysbeen a compromise between the best techno-logical solution and the standard that wouldallow modem manufacturers to produceinteroperable hardware to satisfy the increas-ing demand for data over cable.

3.7 Digital Video Broadcasting(DVB)

The DVB Project emerged from a group,called the Launching Group, of Europeanbroadcasters, consumer electronics manufac-turers and radio regulatory bodies in Septem-ber 1993. It expanded to include public andprivate interest groups and currently com-prises more than 220 members from 30countries. The main focus of DVB is thedelivery of digital TV over satellite, terres-trial and cable links. The DVB-S is satellitespecification designed to operate within arange of transponder bandwidths (26MHz to72MHz, -1dB). The cable network, DVB-Csystem has the same core as the satellitesystem, but the modulation system is basedon quadrature amplitude modulation (QAM)rather than QPSK, and no forward error-correction is needed. Initially DVB recom-mendations did not cater for bi-directionalcommunications. However the implementa-tion of interactive TV will require data onthe reverse direction. Therefore the DVBgroup is turning to other standardising bodiesin order to produce a specification with awider range of applications which will spanbeyond digital TV broadcast such as Internetaccess, videoconferencing etc. At the initialstages DVB was evaluating which standardwould be the most suitable for the deliveryof MPEG-2 audio/video streams over CATVnetworks. At its meeting in July 1997 DVBannounced it would adopt the DAVIC 1.2specification. Both the UK and ECCA an-



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nounced that they were going to support theDAVIC/DVB standard and this has becomea European norm. The ETS 300800 standardhas now been produced as the specificationof the interaction channel for CATV distri-bution systems [ETS, 98]. The DVB-RCCsolution is described in Section 5.

3.8 ITU TelecommunicationsStandardisation (ITU-T)

The ITU is one of the United Nations’ stand-ing committees responsible for the develop-ment of world-wide communications recom-mendations from the suppliers’ perspective(ISO is responsible for the user’s perspec-tive). It has three sub-committees: ITU-Telecommunications standards (ITU-T),ITU-Radio standards (ITU-R) and the WorldAdministration Radio Conference (WARC).Originally ITU-T was known as the Interna-tional Consultative Committee on Telegraphand Telephony (CCITT). It is the ITU-T washas been responsible for the production ofthe ‘J’ series recommendations:

• J.83 – downstream CATV-basedinformation transfer [ITU, 97];

• J.112 – upstream CATV-based infor-mation transfer [ITU, 99].

3.9 CableLabs

Founded in 1988, Cable Television Labora-tories, Inc. (CableLabs®) is a membershiporganisation consisting of cable televisionsystem operators serving cable subscribers inthe U.S., Canada, Mexico, and SouthAmerica. It was established with the goal ofensuring that technology is made practicaland accessible to the cable television indus-try in a timely fashion. Its mission is to planand to fund research and developmentprojects; to transfer relevant technologies to

member companies and industry suppliers;and to serve as a clearinghouse in providingtechnological information to its members.Membership in CableLabs is available tocable system operators based in North andSouth America. CableLabs membership iscomposed of cable television system opera-tors serving more than 85% of the cablesubscribers in the U.S.; 80% of the subscrib-ers in Canada; and 12% in Mexico. In No-vember 1997, the Brazil-based cable opera-tor, Globocabo, became the first SouthAmerican member. Responding to currenttrends in the cable industry and to its mem-bers’ interests, CableLabs is focusing oninteroperability as its key guiding concept.Cable systems are changing rapidly fromislands of service into interconnected re-gional and even national networks capable ofdelivering a plethora of services from avariety of sources. Companies must be ableto count on interoperability, not only be-tween interconnected cable systems, but alsobetween cable systems and other types ofnetworks ranging from telephone companiesto the global Internet. As such CableLabs isresponsible for the following projects:

• DOCSIS – the development andcertification of DOCSIS compliantcable modems;

• OpenCable – the development andcertification of DOCSIS based Set TopBoxes;

• PacketCable – the development ofpacket-based multimedia services overCATV using a DOCSIS solution. Thisincludes work on Voice over IP(VoIP);

• CableNet – the co-ordination of con-ference and exhibition activities relatedto DOCSIS-based solutions.



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3.10 EuroCableLabs

The EuroCableLabs was formed by elevenmembers of ECCA in October 1996. Origi-nally named the ECCA Technical Cell(ETC) it was renamed EuroCableLabs inSeptember 1997 and in March 1998 it wasformed as an independent association.EuroCableLabs is responsible for:

• EuroModem – the European cablemodem specification that conforms tothe ITU-T J.83 Annex A, ITU-T J.112Annex A, ETS 300800 and ETS300429 specifications [ECCA, 99];

• EuroBOX – the European STB specifi-cation [EuroBOX, 98];

• EuroLoader – the specification thatdefines the software download func-tionality within a cable modem orSTB;

• EuroPacketCable– the working-grouplooking at the support of VoIP usingEuroModem technology;

• Future STB Applications & Services –this is a working-group looking atfuture STBs services and applications;

• In-Home Networks (IHN) – a work-ing-group looking at domestic-basednetworking.

EuroCableLabs is now responsible forvalidating the self certified interoperabilityclaims made by manufacturers

3.11 European Cable Communica-tions Association (ECCA)

The European Cable Communications Asso-ciation is the European Association of cableoperators and groups European cable opera-

tors, as well as their national associations.The main goal of ECCA is to foster co-operation between cable operators, to pro-mote and represent their interests at a Euro-pean level. ECCA gathers European cableoperators who have more than 40 millionsubscribers. The first informal co-operationbetween European cable operators started in1949. As these informal meetings becamemore frequent, a formal structure for Euro-pean co-operation was required and onSeptember 2, 1955, AID (AllianceInternationale de la Distribution par câble)was set up by representatives of Switzerland,Belgium and The Netherlands. In 1993, AIDwas renamed the European Cable Communi-cations Association, thus stressing the com-munication role of its members as well as theEuropean goals of the Association. ECCAnow has 29 members in 17 countries. It alsohas 5 associate members in Central andEastern European. ECCA defends the inter-ests of ‘private’ cable operators, of munici-palities and utility companies operating cablenetworks, as well as those of cable operatorsrelated to telecom organisations. Elevenmembers of ECCA were responsible for thecreation of the ECCA Technical Cell thateventually became the EuroCableLabs.

3.12 DVB/DAVIC InteroperabilityConsortium

The DVB/DAVIC Interoperability Consor-tium was created to develop interoperabilityamong vendors building data over technol-ogy based on a DVB-RCCL/DAVIC solu-tion. The participants include Alcatel,COCOM, DiviCom, Hughes Network Sys-tems, Nokia Multimedia Network Terminals,Sagem, Simac Broadband Technologies,Thomson Broadcast Systems (a subsidiary ofThomson Multimedia), and Thomson Multi-media. One of the consortium’s first actionswas the release of a white paper comparing



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DOCSIS and DVB/DAVIC [DIC, 98].

3.13 European Cable Modem Con-sortium

The European Cable Modem Consortium,launched at the European Cable Communica-tions ‘98 show in London, is a group of 11DOCSIS cable modem vendors and technol-ogy suppliers. The consortium consists of3Com, Broadcom, Cisco, Dassault-AT,DeltaKabel, Elsa, FUBA/GI, Pace, Samsung,Teldat, and Tonna. The solution to promotedto cable operators from this groups consist ofa DOCSIS system modified to operate overEurope’s cable television systems (DVB-C).This solution is known as EuroDOCSIS.

4. DOCSIS &EuroDOCSIS Specifi-cations

In the DOCSIS system [DOCSIS, 96a] thetransmission path over the cable network iscontrolled by the Cable Modem TerminationSystem (CMTS) at the HE and the CableModem (CM) at the customer premises. Thereference architecture shown in Figure 2contains three interface categories:

• Data interfaces which include theCMTS Network Side Interface(CMTS-NSI) between the CMTS andthe data network, specified in[DOCSIS, 96b], and the CM to Cus-tomer premises equipment Interface(CMCI) between the customer’s com-puter and the CM, specified in[DOCSIS, 97a] for DOCSISv1.0 and[DOCSIS, 98] for DOCSISv1.1;

• Operations support systems and tel-ephone return path interfaces whichcorrespond respectively to network

element management layer interfacesbetween the network elements and thehigh level Operations Support Systems(OSSs), defined in [DOCSIS, 97b],and the interface between the CM andthe telephone return path for the caseswhere the return path is not availableor provided from the cable network,specified in [DOCSIS, 97b];

• The RF interfaces, defined in[DOCSIS, 96b] and [DOCSIS, 98],describe interactions between the CMand the cable network, the CMTS andthe cable network (in both the up-stream and downstream paths).

The protocol layers for a DOCSIS architec-ture consist of: the network layer (IP), thedata link layer and the physical layer. Spe-cifically, the data link layer is comprised ofthree sublayers: LLC which conforms to theIEEE 802.2 standard; the link-securitysublayer that supports the basic needs ofprivacy, authorisation and authentication andthe MAC which supports variable-lengthPDUs. The physical layer is comprised ofthe upstream/downstream transmissionconvergence (U/D TC) and the physicalmedia dependent (PMD) sublayers. Themain features of the MAC protocol are:CMTS-controlled mix of contention andreservation transmission opportunities; astream of mini-slots (units for upstreamtransmission opportunities and an integermultiple of 6.25ms increments) in the up-stream; bandwidth efficiency through sup-port of variable-length packets; extensionsprovided for the future support of ATM orother PDUs; support for multiple grades ofservice and support for a range of data rates.

The CMTS allocates bandwidth via MACmanagement messages (MAP) which de-scribes the manner in which the upstreammini-slots must be used. Since the upstreamchannel is modelled as a stream of mini-slots



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the CMTS must use a scheduling algorithmto determine the order of user access to thenetwork. The basic elements of the band-width allocation scheme are:

• Each CM has one or more ServiceIDentifications (SIDs), 14 bits, and a48-bit address. The QoS allocated tothe cable modem is directly related toits SID group;

• CMs may issue requests to the CMTSfor upstream bandwidth any time thateither a request or a data PDU isallowed from a particular station;

• The CMTS schedules all of the trans-fer requests according to priority andthe available bandwidth, and thenreleases the MAP to distribute themini-slot allocation. The CMTS willalso schedule the downstream traffic totake into account the aggregation ofmultiple upstreams plus loads fromtraffic sources which are external tothe CATV network.

A CM, which has a packet to transmit, mustwait until the contention slots, as defined inthe last received MAP, arrive. The CM thenattempts to request bandwidth by accessingone of the contention mini-slots. If morethan one CM attempts to claim any oneminislot then the slot information will becorrupted due to the contention. The CMonly becomes aware if it has successfullyrequested bandwidth when the next MAParrives. If the request was successful thenthe CMs SID will be identified along withthe minislot number in which it can starttransmission and the number of minislotsassigned to it, otherwise the CM must repeatits request attempt using the next batch ofcontention minislots. At registration eachCM declares its service priority and so inheavily used networks a low priority CMmay have access to very little bandwidth.

Within the head-end there are two schedul-ing algorithms: the first is responsible forupstream access scheduling within the MAPand the second multiplexes the upstreamchannels onto the downstream. In both cases

Figure 2 The DOCSIS reference model.

Cablemodem

Backbonenetwork

O/Enode

O/Enode

O/Enode

Tx

Rx

Distributionnetwork

Cable ModemTermination

System (Head-end)

Localconfiguration

server

PSTNRemoteaccessserver

CMTS-DRFSI

CMTS-NSI

DOCS-OSSI

CMTS-SMI

Genericbackbone

switch

CMTS-URFSI

IP/LLC/SNAP over IEEE 802.3/Ethernet/TokenRing/ATM (vendor product range)

CMTRI

CMRI(coax)

CMCI

Telcoreturn

Fibre

IP/LLC/SNAPover IEEE 802.3



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the scheduling algorithm attempts to providethe requested service access and when theseexceed capacity to prioritise according toestablished service priority. In DOCSIS 1.0the QoS provision is limited to prioritisationand frame concatenation (optional) but inDOCSIS 1.1 there is an extensive QoSdefinition which is derived from the InternetProtocol QoS [DOCSIS, 98]. Some work onDOCSIS scheduling algorithms has beenpublished recently [Lin, 98], and this hasfocused on comparisons between IEEE802.14 and DOCSIS in terms of upstreamcontention resolution and the interaction withthree upstream scheduling algorithms.

5. DVB-RCC/DAVICSpecifications

Figure 3 shows the DVB/DAVIC systemsreference model for interactive services[ETS, 98]. In the system model there aretwo channels established between the serviceprovider and the user:

• Broadcast Channel (BC) – a unidirec-tional broadband broadcast channelincluding video, audio and data. TheBC is established from the serviceprovider to the users. It may includethe Forward Interaction path;

• Interaction Channel (IC) – a bi-direc-tional interaction channel is establishedbetween the service provider and theuser for interaction purposes. It isformed by:

– Return interaction path – fromthe user to the service provider.It is used to make requests to theservices provider or to answerquestions. It is a narrowbandchannel, also commonly knownas the return channel

– Forward interaction path –fromthe service provider to the user.It is used to provide some sort ofinformation by the serviceprovider to the user and anyother required communicationfor the interaction service provi-sion. It may be embedded intothe broadcast channel. It ispossible that this channel is notrequired in some simple imple-mentations which make use ofthe BC for the transmission ofdata to user.

The user terminal is formed by the NIU andthe STU. The NIU consists of the BroadcastInterface Module (BIM) and the InteractiveInterface Module (IIM). The user terminalprovides an interface to both the broadcastand interaction channels. The interfacebetween the user terminal and the interactionnetwork is via the IIM. The key features ofthe DVB system are:

• The interactive system consists of theforward and return interaction paths;

• Upstream transmission is based upon aslotted Time Division Multiple Access(TDMA) mechanism. One down-stream channel is used to synchroniseup to eight upstream channels, all ofwhich are divided into time slots;

• Three major access modes are pro-vided, namely, contention access andtwo contentionless access schemes;

• Out-of-band (OOB) and in-band (IB)signalling is supported. For OOB aforward interaction path is added. ForIB the forward information path isembedded in the MPEG2-TS of a DVBcable channel whereas for OOB a T1-like frame structure is created;



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• The spectrum allocation is based upon70-130MHz and/or 300-862MHz forthe forward interaction path (down-stream OOB), and 5-65MHz for thereturn interaction path (upstream);

• The upstream and OOB downstreamspectra are divided into separate chan-nels of 1 or 2MHz for downstream and1MHz or 2MHz or 200kHz for up-stream;

• For the interactive downstream OOBchannel a rate of 1.544Mbps or3.088Mbps may be used. For down-stream IB channels no constraintsother than those specified by ETS 300429 exist but it is expected that multi-ples of 8kbps will be used;

• For upstream transmission, there arefour data rates namely 6.176kbps,3.088Mbps, 1.544Mbps or 256kbps;

• Upstream frames consist of packets of512 bits (256 symbols) which are sentin a bursty mode. The upstream slotrates are 6000 (3Mbps), 3000

(1.5Mbps) and 500 (256kbps) slots persecond.

6. DOCSIS/EuroDOCSIS/DVB-RCC Comparisons

A comparison of the service provision of thedifferent standardised cable modems isshown in Table 3. From this comparison it isclearly seen that DOCSIS is a classical IPdata communications protocol whereas bothDVB/DAVIC and the IEEE 802.14 solutionssupport extensive ATM features. However,the answer to question:

“Which cable modem return channel pathshould be selected to support residentialbased interactive services ?”

is not determined by the quality of the tech-nology. Instead, it will be based on thepragmatics of which technology can providea working solution today. OnlyDOCSISv1.0, EuroDOCSISv1.0 andEuroModem Class A cable modems areavailable currently.

Figure 3 The DVB/DAVIC reference model.

Set top box (STB)

Set

top

unit

(ST

U)

BroadcastInterfaceModule

InteractiveInterfaceModule

Broadcastingdeliverymedia

InteractionNetwork

BroadcastService

Provider

InteractiveService

Provider

InteractiveNetworkAdapter

BroadcastNetworkAdapter

Broadcastchannel

Interactionchannels

Forwardinteractionpath

Returninteractionpath

Broadcast channel(DVB transmission systems)

Interaction channel Network InterfaceUnit (NIU)



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7. Conclusion

Cable networks are one of the key emergingbroadband access technologies. The defini-tion of a networking standard for the deliveryof broadband interactive services over Hy-brid Fibre Coaxial (HFC) networks is a

challenging task due the high bandwidthdemands anticipated for the new applicationse.g. home-based video-on-demand, and theirphysical idiosyncrasies (noisy upstreamfrequencies, tree-based architectures etc.).The three predominant standards for cablemodems are: the Data Over Cable Service

Table 3 A comparison of cable modem services and features.

Service/Feature DVB-RCC/DAVIC

DOCSISv1.0/EuroDOCSIS

DOCSISv1.1/EuroDOCSIS

IEEE802.14/HI-PHY

Primary Service End to enddelivery of ATMcells.

Voice over IP.

End-to-enddelivery of IPpackets.

End-to-enddelivery of IPpackets withguaranteed QoS.

Voice over IP.

LLC frametransmission.

ATM celltransmission.

Service Modes Contention access,reserved access,fixed rate accessand rangingaccess.

ATMABRCBRrtVBRnrtVBRUBR.

Best Effort. Unsolicited Grant;

Real-time Polling;

Non-real-timePolling;

Best Effort;

CommittedInformation Rate.

Best Effort;

ATMABRCBRrtVBRnrtVBRUBR.

Data Modes Downstream in-band signalling;

Downstream out-of-band signalling.

Prioritisation;

Concatenation.

Prioritisation;

Concatenation;

Fragmentation.

Permanent VirtualCircuit;

Switched VirtualCircuit.

User (CPE) Interface 10BaseT 10BaseT 10BaseT Undefined butassumed to be10BaseT.

Support Services Main, Quick,Explicit KeyExchange

Ethernet MACbridging;

Point-to-pointprotocol;

RADIUSmanagement.

DES encryption;

TFTP, DHCP,ARP andSpanning TreeProtocol.

SNMP MIBmanagement.

DES encryption;

TFTP, DHCP,ARP andSpanning TreeProtocol.

SNMP MIBmanagement.

Main and QuickKey Exchangewith DES andtriple-DESSecurity.

MIB definition.



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Interface Specification (DOCSIS) for NorthAmerica, the DVB/DAVIC ETS200800specification for Europe, and the IEEE802.14 for its Advanced Physical layerspecification. Roll-out of these new tech-nologies is currently under way and there aremany sites across the world which are evalu-ating these new systems. At present there isvery little informed information about theperformance capabilities of these systemsand most of the published literature is basedon computer simulation.

Recently the EuroDOCSIS specification hasbeen introduced which combines the DVBdownstream physical layer protocol withinthe DOCSIS protocols thereby producing aDOCSIS solution suitable for use withinEurope. While there is a significant amountof development and roll-out of the newCATV technologies, the success of thisapproach is seriously threatened by alterna-tives such as the Asymmetrical DigitalSubscriber Line (ADSL) proposals which asbased upon twisted pair cabling. The suc-cess, or otherwise, of CATV will be deter-mined by the degree to which the data com-munications, telecommunications and broad-casting industries and thus far the conver-gence of technologies by these groups isencouraging.

References

[ATMF, 98] ATM Forum, ATM ForumTechnical Committee: ResidentialBroadband Architectural Framework,AF-RBB-0099.000, ATM Forum,July 1998.

[Azzam, 97] Azzam, A., High SpeedCable Modems, McGraw-Hill, 1997,ISBN 0-07-006417-2.

[DIC, 98] Overview of DVB-RCCL/DAVIC vs. MCNS/DOCSIS, DVB/

DAVIC Interoperability ConsortiumWhite Paper, October 1998.

[DOCSIS, 96a] Cable Modem TerminationSystem-Network Side InterfaceSpecification, Data Over CableInterface Specifications MCNSDocument SP-CMTSNSII01-960702,1996.

[DOCSIS, 96b] Cable Modem to CustomerPremise Equipment Interface Specifi-cation, Data Over Cable InterfaceSpecifications MCSN Document, SP-CMCII01-960702, 1996.

[DOCSIS, 97a] Data-Over-Cable InterfaceSpecifications - Radio FrequencyInterface Specification (Version 1.0),1997, MCNS Consortium, SP-RFII01-970326.

[DOCSIS, 97b] Data-Over-Cable ServiceInterface Specifications - OperationsSupport System Interface Specifica-tion, 1997, MCNS Consortium SP-OSSI-I01-970403.

[DOCSIS, 97c] Data-Over-Cable ServiceInterface Specifications - CableModem Telephony Return InterfaceSpecification, 1997, MCNS Consor-tium SP-CMTRI-I01-970804.

[DOCSIS, 98] Data-Over-Cable InterfaceSpecifications - Radio FrequencyInterface Specification (Version 1.1),1998, MCNS Consortium, SP-RFIv1.1-981214.

[Donelly, 97] Donnelly, A. and Smythe,C., 1997, A Tutorial on the DigitalAudio-Visual Council (DAVIC)Standardisation Activity, IEE ECEJ,Vol.9, No.1, pp.46-56.



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[ECCA, 99] Technical Specification ofa European Cable Modem for DigitalBi-directional Communications viaCable Systems (ECCA EuroModemSpecification) in Compliance withETS 300800 and with Special Con-sideration of EN 50083 and DVBSpecifications, ECCA, Version 1.0,May 1999.

[ETS, 99] ETS 200 800, Digital VideoBroadcasting: Interaction Channel forCable TV Distribution Systems(CATV), ETSI, November 1999.

[EuroBOX, 98] Technical Specification ofan Integrated Receiver Decoder(IRD) for Digital DVB-Services viaCable Systems (ECCA-EuroBOXSpecification) in Conformance withthe DVB Systems Specifications andISO/IEC 13818 (MPEG-2), Version3.1, ECCA, December 98.

[ITU, 97] ITU-T, Recommendation J.83Series J: Transmission of Television,Sound Programme and Other Multi-media Signals, ITU-T, April 1997.

[ITU, 99] ITU-T, Recommendation J.112Series J: Transmission of Television,Sound Programme and Other Multi-media Signals, ITU-T, May, 1999.

[Lin, 98] Lin Y-D, Huang C-Y and YinW-M, Allocation and SchedulingAlgorithms for IEEE 802.14 andMCNS in Hybrid Fiber CoaxialNetworks, IEEE Transactions onBroadcasting, Vol.44, No.4, 1998,pp.427-435.

[Tzerefos, 98] Tzerefos, P., Smythe, C.,Stergiou, I., and Cvetkovic, S., Stand-ards for High Speed Digital Commu-nications over Cable TV Networks,Proceedings of the 6th IEE Confer-ence on Telecommunications, IEEPublication No.451, 1998, pp.224-229.



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1. THE MARKETPLACE

To set the context for cable (CATV) basedbroadband digital networking before introduc-ing the actual cable modem and set-top boxtechnology.

The Marketplace



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1.1 Overview

During the last five years the Internet and its associated applications, such as Electronic Mail(E-mail) and the World Wide Web (WWW), have become established as an essential busi-ness tool; it is perhaps salutary to realise that research and development on the Internet isabout to enter its fourth decade ! Digital data, and its transfer, now accounts for the singlelargest part of the revenues for the telecommunications industry, recently surpassing thetraditional voice services. At the same time the data communications, broadcasting, telecom-munications and consumer electronics industries have realised that digital data transport to,and from, the home is an important market. Whilst there are many new technologies underdevelopment for home-based data communications, this convergence is most powerfullyrepresented by Cable Modems (CM) and Set-top Boxes (STB) i.e. the devices that enable thedelivery of digital data into the home. The cable modem is the device that sits in the user’spremises (home) and which is connected to the traditional Community Antenna Television(CATV) infrastructure. Whereas the cable modem delivers a raw data stream, the Set-topbox is a more complex and complete device which delivers application services to the usere.g. broadcast television, video-on-demand, radio, audio-on-demand, etc. In most cases theSTB will contain a cable modem as its network interface unit.

The focus of this course is on the new standardised, digital versions of CM and STB technol-ogy. There are many analogue STBs, some proprietary digital STBs and CMs, and increas-ing numbers of standards compliant CMs. The new standards for CMs and STBs reflect thecomplex and functionally rich features that these devices must provide. This in turn is anideal opportunity for the development and marketing of new products that offer to the userunique capabilities through new combinations of the optional and mandatory features of theCM and STB specifications. This course makes a series of recommendations on the types ofnew CMs and STBs, which, while conforming to the corresponding standards, have clearlydifferentiated, necessary and desirable functional capabilities.

1.2 Objectives

The objectives are to:

1. Describe how the current cable modem and set-top box technology has been devel-oped to respond to the needs of the cable market;

2. Introduce the organisations that have been responsible for the development of therelevant cable modem and set-top box standards and specifications;

3. Describe how the bandwidth allocation for cable networks vary in different regions ofthe world and to show how these are supported by the different set-top box and cablemodem technologies.



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Slide Title Page

1 The Marketplace 38

2 Access Networking 39

3 Trends 40

4 Bandwidth Allocations 41

5 Services & Applications 42

6 Digital Convergence 43

7 Legacy Systems 44

8 Key Players 45

9 History - I 46

10 History - II 47

11 Key Issues 48

12 Review of The Marketplace 49

1.3 Slides Summary

A / Cable Modems & Set-top Boxes: Market & Technology

DELEGATE NOTES


19th March, 2001

The Marketplace

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1

THE MARKETPLACE

F Cable network architectures

F Digital convergence

F Historic perspective

F Key issues


DELEGATE NOTES


The Marketplace

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2

ACCESS NETWORKING

Set-TopBox

HomeCoaxial Domain

Fibre

Satellite dish

HEADEND

Fibre Domain

InternetATMswitch

Server

Video Server

Video Server

Router

Coaxial feeds

FibreNode

Home network Head-end network

Residential/access network


DELEGATE NOTES


19th March, 2001

The Marketplace

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3

TRENDS

Wireless

LANs/MANs

98 99 00 01 02 03 04 05

1K

1000M

10K

1M

10M

100M

100K

Year

Av

aila

ble

su

bsc

rib

er d

ata

rate

(b

ps)

64K

Packet

Circuit

PSTN

Modem

FTTH

ISDNCable

BWA

xDSL


DELEGATE NOTES


The Marketplace

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4

BANDWIDTH ALLOCATIONS

IB signalling {

70-130MHz 300-862MHz

Upstream

Downstream ITU-T J.83A (DVB-C 8MHz)ITU-T J.83B (DOCSIS 6MHz)

ITU-T J.112A (DVB-RCC QPSK 1/2MHz or 200kHz)ITU-T J.112B (DOCSIS)

OpenCable IB FAT

OpenCable - OOB FDC (DVS167 - 1/2MHz, DVS-178 1.5MHz)

OpenCableOOB RDC(DVS167 -1/2MHz, DVS-178 192kHz)

Frequency

OOB signalling - ETS 300800 (QPSK 1/2MHz)


DELEGATE NOTES


19th March, 2001

The Marketplace

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5

SERVICES & APPLICATIONS

F Core service needsw Best effort IP

w IP with QoS

w Tiered bandwidthallocation

w Remote management

w Support for multiple CPEs

w Secure/private datatransfer

w Clear and sustained tariffagreements

F Key application needsw Email

w WWW browsing

w Voice over IP

w Streamed audio

w Streamed video

w Networked games

w On-line support

w Home gateway

w Integrated PC/TV features


DELEGATE NOTES


The Marketplace

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6

DIGITAL CONVERGENCE

Characteristic DataComms

Telecoms Broad-casting

ConsumerElecs

ComputerSupplier

User understanding W W S S W

User support W S W S W

To-the-desktop W W W W N/A

Data broadcasting W W S N/A N/A

Data switch/routing S S W N/A N/A

Interactivity S S W S S

Int digital services W W W W W

Regulation W S S S W

Costs S W W S S

Tariffing W S S S N/A

Quality of service W W W W W

Residential access W S S S W

Network managem’t W S S W N/A

Digital infrastructure S S W W S

Notes:

(a) ‘W’ denotes that

the characteristic

is weak within

that industry

sector

(b) ‘S’ denotes that

the characteristic

is strong within

that industry

sector


DELEGATE NOTES


19th March, 2001

The Marketplace

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7

LEGACY SYSTEMS

Vendor Shipment

Share Vendor Shipment

Share

Motorola 760,000 44% Samsung 20,000 1%Nortel/Arris 490,000 28% Thomson 20,000 1%Terayon 145,000 9% NetGame 15,000 1%Com21 140,000 9% Toshiba 15,000 1%Zenith 35,000 2% Hybrid 15,000 1%GI 30,000 2% Phasecom 10,000 0.75%3Com 25,000 1.5% Miscellaneous 10,000 0.75%

The sales figures for proprietary cable modem systems as of July 1999.


DELEGATE NOTES


The Marketplace

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8

KEY PLAYERS

OpenCable

PacketCable

EuroModem EuroBOX

CableLabs

EuroCableLabs

ITU

IEEE 802.14

IETF

ATSC

Cable Modem

StandardisationSet-top Box

Standardisation

DVB

ATM-F

DAVIC

SCTE

DOCSIS

ITU-T J.83

ITU-T J.112


DELEGATE NOTES


19th March, 2001

The Marketplace

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9

HISTORY - I

F Sept, 93 DVB established

F July, 94 IEEE 802.14 established

F Aug, 94 DAVIC established

F Jan, 96 MCNS DOCSIS started

F Mar, 97 DOCSISv1.0 released

F Sept, 97 OpenCable startedEuroCableLabs established

F Nov, 97 IEEE 802.14 Hi-PhyIETF take over DOCSIS MIB

F Mar, 98 ETS300800 approved asJ.112ADOCSISv1.0 approved as J.112BDOCSISv1.1 started

F Jul, 98 ATM-Forum RBB specification

F Oct, 98 DDIC createdECMC created


DELEGATE NOTES


The Marketplace

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10

HISTORY - II

F Jun, 99 DAVIC 1.5 releasedPacketCable interop

F Jul, 99 OpenCable planningfor interop testing

F Aug, 99 OpenCable specs release for comment

F Sep, 99 DAVIC disbanded

F Oct, 99 EuroDOCSIS certification launched

F Jul, 00 First EuroModem interop approved

F Nov, 98 EuroDOCSISDOCSISv1.2 started!!

F Dec, 98 PacketCable startsEuroBOXv3.1 releasedEuroModem WG established

F Mar, 99 First DOCSIS head-endqualifiedDOCSISv1.1 releasedIEEE 802.14b released(Hi-Phy)

F May, 99 EuroModem released


DELEGATE NOTES


19th March, 2001

The Marketplace

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11

KEY ISSUES

F Manufacturer/venderw Cost of manufacture

w Regional bandwidthallocation differences

w Achieving interoperability

w The ‘Killer App’

w Scheduling algorithmfeatures

w Alternative technologycompetition

F Operator/userw Multiplicity of standards

w Interoperability andtechnology interworking

w Bandwidth managementand tariffing

w Ease of installation

w Services supported

w Home gateway suitability

w Which access technology

w Home integration


DELEGATE NOTES


The Marketplace

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12

REVIEW

F Services and application - SOHO needs

F Range of choicew Standards & specifications

w Alternative technologies & range of vendors

F Classical competitionw Telecomms vs. data comms

w Broadcast vs. circuit-based

w North America vs. Europe

DELEGATE NOTES



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1.4 Questions

1. What roles would the Internet Engineering Task Force (IETF) and the ATM Forum(ATM-F) be expected to undertake with respect to the development of standards forcable modems and set-top boxes ?

2. When was version 1.0 of the Data Over Cable Service Interface Specification(DOCSIS) released as a completed specification and when was it formally adopted bythe International Telecommunications Union (ITU).



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5. Review

A review of the all the materials presentedthus far on cable modems and set-top boxes.

Review



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5.1 Overview

Cable networks are one of the key emerging broadband access technologies. The definition ofa networking standard for the delivery of broadband interactive services over Hybrid FibreCoaxial (HFC) networks is a challenging task due the high bandwidth demands anticipatedfor the new applications e.g. home-based video-on-demand, and their physical idiosyncrasies(noisy upstream frequencies, tree-based architectures etc.). The two predominant standardsfor cable modems are: the Data Over Cable Service Interface Specification (DOCSIS) forNorth America and the DVB/DAVIC ETS200800 specification for Europe; the IEEE 802.14Advanced Physical layer specification is interesting but development seems to have stopped.Roll-out of these new technologies is currently under way and there are many sites across theworld which are evaluating these new systems. At present there is very little informed infor-mation about the performance capabilities of these systems and most of the published litera-ture is based on computer simulation. The EuroDOCSIS specification has been introducedwhich combines the DVB downstream physical layer protocol within the DOCSIS protocolsthereby producing a DOCSIS solution suitable for use within Europe.

For set-top boxes there are also two competing specifications: the OpenCable for NorthAmerica and the EuroBOX for Europe. In both cases there are no commercial productsavailable that comply with these specifications. The OpenCable specification is very featurerich in comparison to the EuroBOX.

While there is a significant amount of development and roll-out of the new CATV technolo-gies, the success of this approach is seriously threatened by alternatives such as the Asym-metrical Digital Subscriber Line (ADSL) proposals which as based upon twisted pair cabling.The success, or otherwise, of CATV will be determined by the degree to which the datacommunications, telecommunications and broadcasting industries and thus far the conver-gence of technologies by these groups is encouraging.

5.2 Aims & Objectives

The objectives are to:

1. Review the information on cable modems;

2. Review the information on set-top boxes;

3. Summarise the key manufacturers of set-top box and cable modem devices.



Dunelm

5.3 Slides Summary

Slide Title Page

49 Review 102

50 Competition & Collaboration 103

51 End-to-End Systems 104

52 Manufacturers (CMs) 105

53 Manufacturer (Head-ends) 106

54 Manufacturer (STBs) 107

55 Cable Network Future Prospects 108

56 Conclusion 109


DELEGATE NOTES


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49

REVIEW

F Competition & collaboration

F Device manufacturers

F Future prospects


DELEGATE NOTES


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50

COMPETITION & COLLABORATION

F Competitionw Device scheduling

algorithm capabilities

w North American vs.European technology

w Cheap consumer devicesbut expensive operatordevices

w Manufacturers backing alltechnologies

F Collaborationw Specification development

w Interoperability testing

w Creating the marketplace

w Commitment to IP-basedservices

w Making Quality of servicework


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51

END-TO-END SYSTEMS

Homenetwork

Household

HomeGateway

AccessNetwork

Operator

CoreNetwork

Localservers

Head-end/CMTS

Router

PSTN

PSTNInterface


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MANUFACTURERS (CMS)

F EuroModem (Class A)w Cisco (DVB CAR100)*

w COM21*

w Hughes Network Systems(CS2510/CS2520)

w Terayon (UCM-220)*

w The industree (CableJet900/910)*

w Thomson/Alcatel*

F DOCSISv1.0 (Certified)w 41 separate manufacturers

w Thomson (first)

w Toshiba (best of breed)

F EuroDOCSIS v1.0 (Certified)w Askey

w Dassault

w Ericsson

w Motorola

w TechnoTrend

w Thomson Multimedia* = Interoperability certified


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MANUFACTURERS (HEAD-ENDS)

F DVB INA (Class A)w Cisco (CoCom)

w Hughes

w Terayon (DiviCom)

w Barco (The industree)

w Alcatel/Thomson

w COM21

w Philips Research

F DOCSISv1.0 Qualified CMTSw Arris (ex Nortel/LANCity)

w Motorola, 3COM, Cisco

w ADC (Broadband Access Systems)

w RiverDelta, Riverstone, Terayon

F EuroDOCSISv1.0 QualifiedCMTSw 3COM

w ADC, Arris

w Motorola, Terayon


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MANUFACTURERS (STBS)

F EuroBOXw No compliant STBs yet

available

w Nokia Mediamaster DVB9730

w Pace NTL Di4001 DigitalCable Box (recognisedmarket leader)

w Philips Digital Networks

w Sagem

F OpenCablew No compliant STB yet

available

w Potential manufacturers• Scientific Atlanta

• PACE

• Philips Digital Networks


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CABLE NETWORK FUTURE PROSPECTS

F Strengthsw IP and IP QoS capable

w High speed services

w STB integration

w Integrated to telecoms/datacomms infrastructure

F Weaknessesw Two key standards

w Unclear service tariffs

w Slow roll-out

F Opportunitiesw Slow ADSL roll-out

w Depth of penetration of thephysical infrastructure

F Threatsw Alternative access

technologies

w Cable company survival

w Streamed-service overload


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CONCLUSION

F North Americaw DOCSIS and OpenCable

F Europew EuroModem and EuroDOCSIS

w EuroBOX and EuroLoader

F Wide range of devices now available but a lot ofdevelopment still to be completed

F Cable network solution not guaranteed to be the preferredSOHO data services supplier

DELEGATE NOTES



Dunelm

5.4 Questions

1. Given the nature of their respective approaches, what problems in interoperabilitycould arise for each of the four specifications ?

2. In what way could the work of the IEEE 802.14 Advanced Physical layer be adoptedby the established cable modem specifications ?

cable modems & set- top boxes: a market & technology …

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