2006 Telecoms Infrastructure Technology - Volume 1 - Last Mile

SUMMARY

This report has been written to serve the needs of managers, investors and technical people who require a solid, independent introduction to Last Mile broadband technologies. Last Mile access networks - the millions of separate connections between the carrier's core network and the homes, factories, farms and offices of its customers - are arguably the greatest challenge in telecommunications today.

They require huge investments and must last for decades with minimal maintenance, while at the same time providing an increasing range of voice, video, Internet and private networking services.

Executive Summary

Firstly we discuss the traditional (POTS - Plain Old Telephone Service) and ISDN (Integrated Digital Services Network) uses of twisted pair copper telephone lines. We then discuss the highest performing technology, Fibre to the Premises, including elegant Passive Optical Networks (PONs) - where a single fibre is split to provide >100MB/s services to dozens of homes.

Despite the superiority of pure fibre networks, the majority of broadband services in the foreseeable future are likely to be provided with ADSL or VDSL (Asymmetrical and Very High Rate Digital Subscriber Line). We explore the history of these technologies, the characteristics of their latest versions (ADSL2+ and VDSL2) and the practical problems of implementing VDSL2 Fibre to the Curb (FttC, also known as Fibre to the Node) with its complex switching, modulation and power requirements in thousands of widely distributed cabinets.

Hybrid Fibre Coax Cable (HFC) networks are the other main broadband last mile technology. We discuss the history of HFC, its forthcoming DOCSIS 3.0 standard and HFC's emerging Switched Digital Video architecture. Finally, we discuss Free Space Optical technologies, which have unique advantages for links within urban areas with direct line-of-sight paths.

Carriers, service providers and regulators face many challenges understanding the various last mile technologies, in terms of their principles, applicability to particular urban and rural areas and their capacity to provide a variety of services. Since the technical characteristics of all last mile technologies favour a single network with a single owner, regulators need a great deal of technical insight to craft arrangements which favour competitive access whilst encouraging the large investments necessary to build these networks.

The report provides vital information to enable readers to answer many important questions, such as:

• The cost and performance differences between an ADSL2 network based on existing exchange buildings and a VDSL2/FTTC network with new fibre and nodes located within 200 metres of customers' premises.
• The impact on exchange and core network architectures of converting the existing twisted pair copper infrastructure to VDSL2.
• The capacity of ADSL2, VDSL2, HFC and FTTP to support fully digital video delivery, for multiple streams of standard and high definition television.
• The ability of both HFC and Passive Optical Networks to carry a hundred or so RF channels of analogue and digitally modulated video.
• The benefits and challenges of replacing HFC's analogue and distributive digital video channels with Switched Digital Video.

TABLE OF CONTENTS

1. INFRASTRUCTURE - KEY CONCEPTS

• 1.1 Communication, signals and data
  • 1.1.1 Light and sound
  • 1.1.2 Analogue electronics
  • 1.1.3 Digital conversion
  • 1.1.4 Binary numbers
  • 1.1.5 ASCII text
  • 1.1.6 Data storage and compression
• 1.2 The pace of electronic technology development
• 1.3 Types of communication system
  • 1.3.1 Basic communication principles
  • 1.3.2 Basic characteristics of communication technologies
  • 1.3.3 Analogue and digital
  • 1.3.4 Analogue vs digital
• 1.4 The OSI layered model of networks and applications
  • 1.4.1 Distributed information system
  • 1.4.2 Purpose of OSI
  • 1.4.3 Functions and examples
  • 1.4.4 How the model works
• 1.5 The increasing importance of the Internet
  • 1.5.1 From smoke signals to Internet
  • 1.5.2 New foundation for future systems
  • 1.5.3 The importance of the Internet

2. LAST MILE TELECOMMUNICATIONS TECHNOLOGIES

• 2.1 Twisted Pair, POTS, ISDN
  • 2.1.1 Introduction and historical perspective
  • 2.1.2 Twisted pair copper for analogue telephony
  • 2.1.3 Twisted pair copper for ISDN
• 2.2 Fibre - FTTP, Passive Optical Networks
  • 2.2.1 Introduction
  • 2.2.2 Customer needs
  • 2.2.3 Needs of telecommunications carriers
  • 2.2.4 Standards organisations and industry bodies
  • 2.2.5 Architectural considerations
• 2.3 Fibre - Metro Ethernet, GPON
  • 2.3.1 'Carrier grade' reliability and management
  • 2.3.2 Alternative fibre strategies
  • 2.3.3 Metro Ethernet services
  • 2.3.4 ITU G.983 APON/BPON
  • 2.3.5 ITU G.984 GPON
  • 2.3.6 ITU G.985 Point-to-point
  • 2.3.7 802.3ah Point-to-Point
  • 2.3.8 802.3ah EPON
• 2.4 ADSL principles
  • 2.4.1 Common characteristics of XDSL
  • 2.4.2 Frequency allocations
  • 2.4.3 ADSL modems and DSLAMs
  • 2.4.4 Obstacles to deployment
  • 2.4.5 Modulation schemes
• 2.5 ADSL & ADSL2 technical standards
  • 2.5.1 ADSL technical standards
  • 2.5.2 Data rates and distances
  • 2.5.3 Comparing ADSL and HFC
• 2.6 Symmetrical SHDSL, VoDSL
  • 2.6.1 Symmetrical DSL
  • 2.6.2 T1 and E1
  • 2.6.3 BR-ISDN and IDSL
  • 2.6.4 HDSL
  • 2.6.5 SDSL
  • 2.6.6 SHDSL G.991.2
  • 2.6.7 Voice over broadband (VoBB)
  • 2.6.8 Latency and delay
  • 2.6.9 VODSL - Voice over DSL
  • 2.6.10 CVODSL - Channelised Voice over DSL
• 2.7 FTTC, VDSL Principles
  • 2.7.1 Introduction
  • 2.7.2 Single and multi-carrier modulation techniques
  • 2.7.3 DMT - OFDM
  • 2.7.4 Early, non-ITU, standards
• 2.8 FTTC, VDSL2 technical standards
  • 2.8.1 Frequency plans
  • 2.8.2 ITU G.993.2 VDSL2
  • 2.8.3 Ethernet rather than ATM for DSL
  • 2.8.4 Competition implications
  • 2.8.5 ADSL2+ / VDSL Futures
• 2.9 HFC - principles, DOCSIS 1.x & 2.0
  • 2.9.1 Introduction
  • 2.9.2 HFC's stringent design and maintenance requirements
  • 2.9.3 DOCSIS 1.x and 2.0
• 2.10 HFC - DOCSIS 3.0, Switched Digital Video
  • 2.10.1 DOCSIS-related standards
  • 2.10.2 Node splitting and frequency re-alignment
  • 2.10.3 High frequency expansion
  • 2.10.4 DOCSIS 3.0
  • 2.10.5 Switched Digital Video
  • 2.10.6 HFC future prospects
• 2.11 Free Space Optical
  • 2.11.1 Free Space Optical communications

3. GLOSSARY OF ABBREVIATIONS

• Exhibit 1 - OSI layered model: a web-browsing example
• Exhibit 2 - Comparison of ADSL/VDSL and HFC systems
• Exhibit 3 - Access node deployment scenarios
  • Table 1 - Properties of major DSL versions - 2006
  • Table 2 - HDSL reach (km) versus wire gauge
  • Table 3 - ITU VDSL band-plans
  • Table 4 - G.993.2 VDSL2 profiles