Broadband Access ebook

CONTENTS

Cover

Title Page

Copyright

Dedication

About the Authors

Acknowledgments

List of Abbreviations and Acronyms

Chapter 1: Introduction to Broadband Access Networks and Technologies

1.1 Introduction

1.2 A Brief History of the Access Network

1.3 Digital Subscriber Lines (DSL)

1.4 Hybrid Fiber-Coaxial Cable (HFC)

1.5 Power Line Communications (PLC)

1.6 Fiber in the Loop (FITL)

1.7 Wireless Broadband Access

1.8 Direct Point-to-Point Connections

Appendix 1.A: Voiceband Modems

Chapter 2: Introduction to Fiber Optic Broadband Access Networks and Technologies

2.1 Introduction

2.2 A Brief History of Fiber in the Loop (FITL)

2.3 Introduction to PON Systems

2.4 FITL Technology Considerations

2.5 Introduction to PON Network Protection

2.6 Conclusions

Appendix 2.A: Subscriber Power Considerations

References

Further Reading

Chapter 3: IEEE Passive Optical Networks

3.1 Introduction

3.2 IEEE 802.3ah Ethernet-based PON (EPON)

3.3 IEEE 802.3av 10Gbit/s Ethernet-based PON (10G EPON)

3.4 Summary Comparison of EPON and 10G EPON

3.5 Transport of Timing and Synchronization over EPON and 10G EPON

3.6 Overview of the IEEE 1904.1 Service Interoperability in Ethernet Passive Optical Networks (SIEPON)

3.7 ITU-TG.9801 Ethernet Passive Optical Networks using OMCI

3.8 Conclusions

Appendix 3.A: 64B/66B Line Code

References

Further Readings

Chapter 4: ITU-T/FSAN PON Protocols

4.1 Introduction

4.2 ITU-T G.983 Series B-PON (Broadband PON)

4.3 ITU-T G.984 Series G-PON (Gigabit-capable PON)

4.4 Next Generation PON (NG-PON)

Appendix 4.A: Summary Comparison of EPON and G-PON

References

Further Readings

Chapter 5: Optical Domain PON Technologies

5.1 Introduction

5.2 WDMA (Wavelength Division Multiple Access) PON

5.3 CDMA PON

5.4 Point-to-Point Ethernet

5.5 Subcarrier Multiplexing and OFDM

5.6 Conclusions

References

Further Readings

Chapter 6: Hybrid Fiber Access Technologies

6.1 Introduction and Background

6.2 Evolution of DOCSIS (Data-Over-Cable Service Interface Specification) to Passive Optical Networks

6.3 Radio and Radio Frequency Signals over Fiber

6.4 IEEE 802.3bn Ethernet Protocol over Coaxial Cable (EPoC)

6.5 Conclusions

References

Further Readings

Chapter 7: DSL Technology – Broadband via Telephone Lines

7.1 Introduction to DSL

7.2 DSL Compared to Other Access Technologies

7.3 DSL Overview

7.4 Transmission Channel and Impairments

7.5 DSL Transmission Techniques

References

Further Readings

Chapter 8: The Family of DSL Technologies

8.1 ADSL

8.2 VDSL

8.3 Basic Rate Interface ISDN

8.4 HDSL, HDSL2, and HDLS4

8.5 SHDSL

8.6 G.fast (FTTC DSL)

References

Chapter 9: Advanced DSL Techniques and Home Networking

9.1 Repeaters and Bonding

9.2 Dynamic Spectrum Management (DSM)

9.3 Vectored Transmission

9.4 Home Networking

References

Further Readings

Chapter 10: DSL Standards

10.1 Spectrum Management – ANSIT1.417

10.2 G.hs – ITU-T Rec. G.994.1

10.3 PLOAM – ITU-T Rec. G.997.1

10.4 G.bond – ITU-T Recs. G.998.1, G.998.2, and G.998.3

10.5 G.test – ITU-T Rec. G.996.1

10.6 G.lt – ITU-T Rec. G.996.2

10.7 Broadband Forum DSL Testing Specifications

10.8 Broadband Forum TR-069 – Remote Management of CPE

References

Chapter 11: The DOCSIS (Data-Over-Cable Service Interface Specification) Protocol

11.1 General Introduction

11.2 Introduction to MSO Networks

11.3 Background on Hybrid Fiber Coax (HFC) Networks

11.4 Introduction to DOCSIS

11.5 DOCSIS Network Elements

11.6 Brief History of the DOCSIS Protocol Evolution

11.7 DOCSIS Physical Layer

11.8 Synchronization and Ranging

11.9 DOCSIS MAC Sub-Layer

11.10 CM Provisioning

11.11 Security

11.12 Introduction to Companion Protocols

11.13 Conclusions

References

Further Readings

Chapter 12: Broadband in Gas Line (BIG)

12.1 Introduction to BIG

12.2 Proposed Technology

12.3 Potential Drawbacks for BIG

12.4 Broadband Sewage Line

Reference

Chapter 13: Power Line Communications

13.1 Introduction

13.2 The Early Years

13.3 Narrowband PLC*

13.4 Broadband PLC*

13.5 Power Grid Topologies*

13.6 Outdoor and In-Home Channel Characterization

13.7 Power Line Channel Modeling*

13.8 The IEEE 1901 Broadband over Power Line Standard

13.9 PLC and the Smart Grid*

13.10 Conclusions

References

Further Reading

Chapter 14: Wireless Broadband Access: Air Interface Fundamentals

14.1 Introduction

14.2 Duplexing Techniques

14.3 Physical Layer Concepts

14.4 Access Technology Concepts

14.5 Cross-Layer Algorithms

14.6 Example Application: Satellite Broadband Access

14.7 Summary

Further Reading

Chapter 15: WiFi: IEEE 802.11 Wireless LAN

15.1 Introduction

15.2 Technology Basics

15.3 Technology Evolution

15.4 WLAN Network Architecture

15.5 TV White Space and 802.11 af

15.6 Summary

Further Readings

Chapter 16: UMTS: W-CDMA and HSPA

16.1 Introduction

16.2 Technology Basics

16.3 UMTS Technology Evolution

16.4 CDMA2000

16.5 Summary

Further Readings

Chapter 17: Fourth Generation Systems: LTE and LTE-Advanced

17.1 Introduction

17.2 Release 8: The Basics of LTE

17.3 Release 9: eMBMS and SON

17.4 Release 10: LTE-Advanced

17.5 Future of LTE-Advanced: Release 11 and Beyond

17.6 IEEE 802.16 and WiMAX Systems

17.7 Summary

Further Readings

Chapter 18: Conclusions Regarding Broadband Access Networks and Technologies

Index

End User License Agreement

List of Tables

Table 2.1

Table 2.2

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 3.5

Table 3.6

Table 4.1

Table 4.2

Table 4.3

Table 4.4

Table 4.5

Table 4.6

Table 4.7

Table 4.8

Table 4.9

Table 4.10

Table 6.1

Table 8.1

Table 8.2

Table 11.1

Table 11.2

Table 11.3

Table 11.4

Table 11.5

Table 13.1

Table 13.2

Table 13.3

Table 15.1

Table 15.2

Table 15.3

Table 17.1

Table 17.2

Table 17.3

Table 17.4

Table 17.5

List of Illustrations

Figure 1.1

Figure 1.2

Figure 1.3

Figure 1.4

Figure 2.1

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

Figure 2.6

Figure 2.7

Figure 2.8

Figure 2.9

Figure 2.10

Figure 2.11

Figure 2.12

Figure 2.13

Figure 2.14

Figure 2.15

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

Figure 3.5

Figure 3.6

Figure 3.7

Figure 3.8

Figure 3.9

Figure 3.10

Figure 3.11

Figure 3.12

Figure 3.13

Figure 3.14

Figure 4.1

Figure 4.2

Figure 4.3

Figure 4.4

Figure 4.5

Figure 4.6

Figure 4.7

Figure 4.8

Figure 4.9

Figure 4.10

Figure 4.11

Figure 4.12

Figure 4.13

Figure 4.14

Figure 4.15

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Figure 5.5

Figure 5.6

Figure 5.7

Figure 5.8

Figure 5.9

Figure 6.1

Figure 6.2

Figure 6.3

Figure 6.4

Figure 6.5

Figure 7.1

Figure 7.2

Figure 7.3

Figure 7.4

Figure 7.5

Figure 7.6

Figure 7.7

Figure 7.8

Figure 7.9

Figure 7.10

Figure 7.11

Figure 7.12

Figure 7.13

Figure 7.14

Figure 7.15

Figure 7.16

Figure 7.17

Figure 7.18

Figure 7.19

Figure 7.20

Figure 7.21

Figure 7.22

Figure 7.23

Figure 7.24

Figure 8.1

Figure 8.2

Figure 8.3

Figure 8.4

Figure 8.5

Figure 8.6

Figure 8.7

Figure 8.8

Figure 9.1

Figure 9.2

Figure 11.1

Figure 11.2

Figure 11.3

Figure 11.4

Figure 11.5

Figure 11.6

Figure 11.7

Figure 11.8

Figure 11.9

Figure 11.10

Figure 11.11

Figure 11.12

Figure 11.13

Figure 11.14

Figure 11.15

Figure 11.16

Figure 11.17

Figure 11.18

Figure 11.19

Figure 12.1

Figure 13.1

Figure 13.2

Figure 13.3

Figure 13.4

Figure 13.5

Figure 13.6

Figure 13.7

Figure 13.8

Figure 13.9

Figure 13.10

Figure 13.11

Figure 13.12

Figure 14.1

Figure 14.2

Figure 14.3

Figure 14.4

Figure 14.5

Figure 14.6

Figure 14.7

Figure 14.8

Figure 14.9

Figure 14.10

Figure 15.1

Figure 15.2

Figure 15.3

Figure 15.4

Figure 15.5

Figure 15.6

Figure 15.7

Figure 15.8

Figure 15.9

Figure 15.10

Figure 15.11

Figure 16.1

Figure 16.2

Figure 16.3

Figure 16.4

Figure 16.5

Figure 16.6

Figure 16.7

Figure 16.8

Figure 16.9

Figure 16.10

Figure 16.11

Figure 16.12

Figure 16.13

Figure 16.14

Figure 16.15

Figure 16.16

Figure 16.17

Figure 17.1

Figure 17.2

Figure 17.3

Figure 17.4

Figure 17.5

Figure 17.6

Figure 17.7

Figure 17.8

Figure 17.9

Figure 17.10

Figure 17.11

Figure 17.12

Figure 17.13

Figure 17.14

Figure 17.15

Figure 17.16

Figure 17.17

Figure 17.18

Figure 17.19

Figure 17.20

Figure 17.21

Figure 17.22

Figure 17.23

Figure 17.24

Figure 17.25

Figure 17.26

Figure 17.27

Figure 17.28

Figure 17.29

Figure 17.30

Figure 17.31

Guide

Cover

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Broadband Access

Wireline and Wireless – Alternatives for Internet Services

This edition first published 2014

© 2014 John Wiley & Sons, Ltd

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John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom

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Library of Congress Cataloging-in-Publication Data applied for

ISBN: 9780470741801

Dedication

To my wife Bonnie Gorshe, and sons Alex and Ian Gorshe; S.D.G.

To the Lord, in the spirit of Karma Yoga.

To my wife, Marilynn Starr.

To Tobey and Hannah.

About the Authors

Steve Gorshe

Steve Gorshe is a Distinguished Engineer in the CTO organization of PMC-Sierra, Inc., where his work since 2000 has included technology development and telecommunications standards. He received his BSEE from the University of Idaho (1980) and both his MSEE (1982) and PhD (2002) degrees from Oregon State University. Since 1983, he has worked in product development, applied research, and systems architecture of telecommunications access and transport systems. His standards activity includes over 300 contributions across six standards bodies, serving as technical editor for nine North American and international standards, and currently serving as Associate Rapporteur for the Q11 group of ITU-T Study Group 15.

Steve is a Fellow of the IEEE. His IEEE activities include Communications Magazine Editor-in-Chief (2010–2012), Associate Editor-in-Chief (2006–2009), and Broadband Access Series co-editor (1999–2006). He has also served as the IEEE Communications Society Director of Magazines and Chair of the Transmission, Access and Optical Systems Technical Committee.

Steve has 37 patents issued or pending, over 24 published papers, and is co-author of two textbooks and co-author of chapters in three other textbooks.

Arvind R. Raghavan

Arvind R. Raghavan heads research and development at Blue Clover Devices, where he is involved with the design and implementation of innovative products for the Internet of Things, with current emphasis on Bluetooth Low Energy technology. Before joining Blue Clover Devices, he was part of the Radio Technology and Strategy group at AT&T Labs, where his work focused on the impact of QoS on LTE, design and analysis of heterogeneous networks, and advanced MIMO techniques for standardization in 3GPP. Prior to joining AT&T Labs, he played a lead role in the Systems Engineering group at ArrayComm, LLC, where they developed specifications for their multi-antenna signal processing products, conducted performance analyses, and made contributions to the standardization of WiMAX systems. Arvind holds MS and PhD degrees in Electrical Engineering from Clemson University.

Thomas Starr

Thomas Starr is a Lead Member of Technical Staff at AT&T Laboratories in Hoffman Estates, Illinois. Thomas is responsible for the development and standardization of local access and home networking technologies for AT&T's network. These technologies include ADSL, HDSL, SHDSL, VDSL and G.hn. In 2009, Thomas received the prestigious AT&T Science and Technology Medal. He serves as Chairman of the Broadband Forum and has also served as a member of the Board of Directors since its inception as the ADSL Forum in 1994. Thomas has been a distinguished fellow of the Broadband Forum From 1988 to 2000, has served as Chairperson of ANSI accredited standards working group T1E1.4, which develops xDSL standards for the United States, received the Committee T1 Outstanding Leadership Award in 2001, and now serves at ATIS COAST-NAI Chairman. In the ITU-T SG15, Thomas serves as Chairman of Working Party 1, addressing fiber, DSL, and home networking standards, and participates in the ITU SG15 Q4 group on xDSL international standards.

Thomas is a co-author of the books DSL Advances, published by Prentice Hall in 2003, and Understanding Digital Subscriber Line Technology, published by Prentice Hall in 1999. Thomas is also the author of the Science Fiction novel Virtual Vengeance. Thomas previously worked for 12 years at AT&T Bell Laboratories on ISDN and local telephone switching systems, and twenty US patents in the field to telecommunications have been issued to him. Thomas holds a MS degree in Computer Science and a BS degree in Computer Engineering from the University of Illinois in Urbana, Illinois.

Stefano Galli

Stefano Galli received his MS and PhD degrees in Electrical Engineering from the University of Rome “La Sapienza” (Italy) in 1994 and 1998, respectively. He is currently the Director of Technology Strategy of ASSIA – the leading developer of automated management and diagnostics tools for broadband networks. Prior to this position, he held the role of Director of Energy Solutions R&D for Panasonic Corporation and Senior Scientist at Bellcore.

Dr. Galli is serving as Chief Information Officer of the IEEE Communications Society (ComSoc), director of Smart Grid activities for the IEEE ComSoc Technical Committee on Power Line Communications, member of the Energy and Policy Committee of IEEE-USA, and as Editor for the IEEE Transactions on Communications and the IEEE Communications Magazine. Dr. Galli is also serving as Rapporteur for the ITU-T Q15/15 “Communications for Smart Grid” standardization group. Past positions include serving as Co-Chair of the “Communications Technology” Task Force of IEEE 2030 (Smart Grid), Leader of the “Theoretical and Mathematical Models” Group of IEEE 1901 (Broadband over Power Lines standard), Coexistence sub-group Chair of the SGIP/NIST PAP 15, elected Member-at-Large of the IEEE Communications Society (ComSoc) Board of Governors, and a variety of other leadership positions in the IEEE. He has also served as Founder and first Chair of the IEEE ComSoc Technical Committee on Power Line Communications.

Dr. Galli is a Fellow of the IEEE, has received the 2013 IEEE Donald G. Fink Best Paper Award for his paper on Smart Grid and Power Line Communications, the 2011 IEEE ComSoc Donald W. McLellan Meritorious Service Award, the 2011 Outstanding Service Award from the IEEE ComSoc Technical Committee on Power Line Communications, and the 2010 IEEE ISPLC Best Paper Award. He holds several issued and pending patents, has published over 90 peer-reviewed papers, has co-authored three book chapters on power line communications, and has made numerous standards contributions to the IEEE, the ITU-T, the Broadband Forum, and the UK NICC.

Acknowledgments

Thanks are given to the experts who provided assistance for the chapters on DSL technology: George Ginis, Ken Kerpez, Vladimir Oksman, Craig Schelp, Massimo Sorbara, and Arlynn Wilson. Thanks also are given to Marilynn Starr for her support and assistance.

Steve would like to thank the following people for their generous help, excellent comments and reviews for portions of his chapters: Frank Effenberger, Alon Bernstein, Chris Look, Onn Haran, Jeff Mandin, Lior Khermosh, Bob Murray, Valy Ossman, and Jim Dahl. Steve also wants to thank PMC-Sierra for allowing some of his white paper material to be adapted for this book.

Arvind would like to acknowledge the significant contributions of his wife, Sanchita Shetty, for painstakingly generating all the figures in the wireless chapters, and her unwavering support throughout the writing of this book. He would also like to express his heartfelt gratitude to Paul Chiuchiolo, Rich Kobylinski, Milap Majmundar, and Tom Novlan, for reviewing the wireless section of the book and providing excellent feedback for improving the quality and accuracy of the manuscript. Finally, he would like to thank his family and all his wonderful friends in Austin for their love and encouragement.

List of Abbreviations and Acronyms

2G

Second Generation

3G

Third Generation

3GPP

Third Generation Partnership Project

10GE

10 Gigabit/s Ethernet specified in IEEE 802.3

10G EPON

10 Gbit/s Ethernet Passive Optical Network specified in IEEE 802.3

ABS

Almost Blank Subframes

AC

Alternating Current

AC

Access Category

ACK

Acknowledgement

ACM

Adaptive Coding and Modulation

ADC

Analog-to-Digital Converter

ADSL

Asymmetric Digital Subscriber Line specified in ITU-T G.992.1

ADSL2

Asymmetric Digital Subscriber Line 2 specified in ITU-T G.992.3

ADSL2plus

Asymmetric Digital Subscriber Line 2plus specified in ITU-T G.992.5

AES

Advanced Encryption Standard

AFE

Analog Front End

AICH

Acquisition Indicator Channel

AM

Acknowledged Mode

AMI

Advanced Metering Infrastructure

A-MPDU

Aggregate MAC Protocol Data Unit

AMPS

Advanced Mobile Phone System

AMR

Automatic Meter Reading

A-MSDU

Aggregate MAC Service Data Unit

ANSI

American National Standards Institute

AP

Access Point

APD

Avalanche Photo Diode

APS

Automatic Protection Switching

ARIB

Association of Radio Industries and Businesses

ARP

Allocation and Retention Priority

ARQ

Automatic Repeat Request, Retransmission

AS

Access Stratum

ASE

Amplified Spontaneous Emission

ASF

DOCSIS Aggregated Service Flow

A-TDMA

Advanced TDMA (used with DOCSIS)

ATIS

Alliance for Telecommunications Industry Solutions

ATM

Asynchronous Transfer Mode protocol

AWG

American Wire Gauge

AWG

Arrayed Waveguide Grating WDM filter/multiplexer

BB

Broad Band

BCCH

Broadcast Control Channel

BCH

Broadcast Channel

BE

Best Effort service

BEMS

Building Energy Management System

BER

Bit Error Rate (or Ratio)

BIP

Bit Interleaved Parity

BMC

Broadcast Multicast Control

BMSC

Broadcast Multicast Service Center

B-ONU

DPoE Bridge ONU

BPL

Broadband over Power Lines

B-PON

FSAN/ITU-T Broadband PON protocol specified in the ITU-T G.983 series

BRI-ISDN

Basic Rate Integrated Services Digital network

BSS

Basic Service Set

BTS

Base Transceiver Station (for a wireless network)

CA

Carrier Aggregation

CAPEX

Capital Expense

CAPWAP

Control and Provisioning of Wireless Access Points

CATV

Community Access Television

CBR

Constant Bit Rate

CBS

Committed Burst Size

CC

Component Carrier

CCA

Clear Channel Assessment

CCCH

Common Control Channel

CCK

Complementary Code Keying

CCO

Capacity and Coverage Optimization

CDD

Cyclic-Delay Diversity

CDMA

Code Division Multiple Access

CENELEC

European Committee for Electotechnical Standardization

CEPCA

Consumer Electronics Powerline Alliance

CES

Circuit Emulation Service

CFP

Contention Free Period

CIF

Carrier Indicator Field

CIR

Committed Information Rate

CM

Cable Modem

CMCI

DOCSIS Cable Modem CPE Interface

CMTS

DOCSIS Cable Modem Terminating System

CN

Core Network

CO

Telephone company Central Office

CoMP

Cooperative Multi-Point

CP

Contention Period

CP

Cyclic Prefix

CPC

Continuous Packet Connectivity

CPE

Customer Premises Equipment

CPICH

Common Pilot Channel

CPRI

Common Public Radio Interface

CQI

Channel Quality Information

CRC

Cyclic Redundancy Check

CRE

Cell Range Expansion

CRS

Cell-specific Reference Signal

CS

Circuit Switched

CS

Channel Sensing

CSA

Carrier Serving Area

CS/CB

Coordinated Scheduling/Coordinated Beamforming

CSG

Closed Subscriber Group

CSI-RS

Channel State Information Reference Signal

CSM

Collaborative Spatial Multiplexing

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance

CSO

Cell Selection Offset

CTCH

Common Traffic Channel

CTS

Clear-to-send

CTS

Common Technical Specification for G-PON

CV

Code Violation

C-VID

Customer VLAN Identifier (Ethernet)

CWDM

Coarse Wavelength Division Multiplexing

DAC

Digital-to-Analog Converter

DAS

Distributed Antenna System

dB

Decibel, ten times the common logarithm of the ration of two powers

DBA

Dynamic Bandwidth Assignment

DBC

Dynamic Bonding Change (in DOCSIS 3.0)

DBG

Downstream Bonding Group (in DOCSIS 3.0)

DBR

Dynamic Bandwidth Report

DC

Direct Current

DCCH

Dedicated Control Channel

DCF

Distributed Coordination Function

DCH

Dedicated Channel

DCS

Downstream Channel Set (in DOCSIS 3.0)

DELT

Dual Ended Line Test

DEMARC

Carrier owned Demarcation device between the carrier and the CPE

DER

Distributed Energy Resources

DFE

Decision Feedback Equalizer

DFT

Discrete-time Fourier Transform

DHCP

Dynamic Host Configuration Protocol

DIFS

Distributed Interframe Spacing

DL

Downlink

DLC

Digital Loop Carrier

DLL

Data Link Layer

DL-SCH

Downlink Shared Channel

DM-RS

Demodulation Reference Signal

DMT

Discrete Multi Tone modulation

DOCSIS

Data Over Cable Service Interface Specification

D-ONU

DPoE ONU

Downstream

Data flowing towards the customer

DPB

Dynamic Point Blanking

DPCCH

Dedicated Physical Control Channel

DPDCH

Dedicated Physical Data Channel

DPoE

DOCSIS Protocol over Ethernet protocol

DPS

Dynamic Point Selection

DPSK

Differential Phase Shift Keying

DQPSK

Differential Quadrature Phase Shift Keying

DR

Demand Response

DRX

Discontinuous Reception

DS

Direct Sequence

DS1

Digital Signal level 1 in the North American asynchronous telephone network hierarchy

DS-CDMA

Direct Sequence Code Division Multiple Access

DSCP

DiffServ Code Point

DSID

Downstream Service ID (in DOCSIS 3.0)

DSL

Digital Subscriber Line

DSLAM

DSL Access Multiplexer

DSM

Dynamic Spectrum Management (in DSL)

DSM

Demand Side Management (in Smart Grid)

DSP

Digital Signal Processing

DSSS

Direct Sequence Spread Spectrum

DTX

Discontinuous Transmission

DVB

Digital Video Broadcast

DVB-RCS

Digital Video Broadcast Return Channel via Satellite

DVB-S2

Digital Video Broadcasting - Satellite - Second generation

DWDM

Dense Wavelength Division Multiplexing

E-AGCH

Enhanced Absolute Grant Channel

EBS

Excess Burst Size

ECH

Echo Cancelled Hybrid

eCM

embedded Cable Modem

EDCA

Enhanced Distributed Channel Access

E-DCH

Enhanced Dedicated Channel

EDFA

Erbium Doped Fiber Amplifier

EDGE

Enhanced Data-rates for GSM Evolution

E-DPCCH

Enhanced Dedicated Physical Control Channel

E-DPDCH

Enhanced Dedicated Physical Data Channel

E-HICH

Enhanced HARQ Indicator Channel

eICIC

Enhanced Inter-Cell Interference Coordination

EIR

Excess Information Rate

eMBMS

Enhanced Multimedia Broadcast and Multicast Service

EMC

Electro-Magnetic Compatibility

EMS

Element Management System

EO

Electrical to Optical signal conversion

eOAM

Extended OAM messages used in DPoE

EOC

Embedded Operations Channel

EONT

Embedded ONT

eNodeB

Evolved Node-B

EPC

Evolved Packet Core

EPON

Ethernet Passive Optical Network (1 Gbit/s rate)

EPS

Evolved Packet System

E-RGCH

Enhanced Relative Grant Channel

eSAFE

embedded Service/Application Functional Entity

ESP

Ethernet Service Path

ESS

Extended Service Set

ETSI

European Telecommunications Standards Institute

E-UTRAN

Evolved UMTS Terrestrial Radio Access Network

EVC

Ethernet Virtual Circuit

EVSE

Electric Vehicle Supply Equipment

FACH

Forward Access Channel

FBI

Feedback Information

FCC

Federal Communications Commission

FCS

Frame Check Sequence

FDD

Frequency Division Duplexing

FDM

Frequency Division Multiplexing

FDMA

Frequency Division Multiple Access

F-DPCH

Fractional Dedicated Physical Channel

FEC

Forward Error Correction

FeICIC

Further Enhanced Inter-Cell Interference Coordination

FEXT

Far End crosstalk

FFT

Fast Fourier Transform

FH

Frequency Hopping

FH-CDMA

Frequency Hopping Code Division Multiple Access

FHSS

Frequency Hopping Spread Spectrum

FITL

Fiber in the Loop

FN

Fiber Node (in a HFC network)

FSAN

Full Service Access Network industry consortium

FSK

Frequency Shift Keying

FTTC

Fiber to the Curb

FTTCab

Fiber to the Cabinet

FTTCell

Fiber to the Cell site

FTTH

Fiber to the Home

FTTN

Fiber to the Node

FTTO

Fiber to the Office

FTTP

Fiber to the Premises

G.hn

ITU-T G.9960/9961 home networking standard

G.hs

ITU-T G.994.1 DSL handshake protocol

G.lite

ITU-T G.992.2 reduced complexity ADSL

G.lt

ITU-T G.996.2 standard for DSL line test functions

G.test

ITU-T G.996.1 standard for testing of DSL modems

GBR

Guaranteed Bit Rate

GE

Gigabit/s Ethernet

GEM

G-PON Encapsulation Method

GERAN

GSM Edge Radio Access Network

GFP

Generic Framing Procedure specified in ITU-T G.7041

GGSN

Gateway GPRS Support Node

GMSC

Gateway Mobile Switching Center

GP

Guard Period

G-PON

FSAN/ITU-T Gigabit-capable PON protocol specified in the ITU-T G.984 series

GPRS

GSM Packet Radio System

gPTP

generalized Precision Timing Protocol

GSM

Global System for Mobile communications

GTC

G-PON Transmission Convergence

HAN

Home Area Network

HARQ

Hybrid Automatic Repeat Request

HCF

Hybrid Coordination Function

HD-PLC

High Definition Power Line Communication

HDR

High Data Rate

HDSL

High bit rate Digital Subscriber Line

HDSL2

High bit rate Digital Subscriber Line, 2 wire version

HDSL4

High bit rate Digital Subscriber Line, 4 wire version

HE

Head End

HEC

Header Error Check

HEMS

Home Energy Management System

HetNet

Heterogeneous Network

HF

High Frequency

HFC

Hybrid Fiber-Coaxial cable network

HLR

Home Location Register

HSDPA

High Speed Downlink Packet Access

HS-DPCCH

High Speed Dedicated Physical Control Channel

HS-DSCH

High Speed Downlink Shared Channel

HSPA

High Speed Packet Access

HS-PDSCH

High Speed Physical Downlink Shared Channel

HS-SCCH

High Speed Shared Control Channel

HSS

Home Subscriber Server

HSUPA

High Speed Uplink Packet Access

HV

High Voltage

IAD

Integrated Access Device

ICIC

Inter-cell Interference Coordination

IEC

International Electrotechnical Commission

IED

Intelligent Electronic Devices

IEEE

Institute of Electrical and Electronic Engineers

IETF

Internet Engineering Task Force

IFS

Inter-Frame Spacing

IGMP

Internet Group Management Protocol

IMT

International Mobile Telecommunications

IP

Internet Protocol

IP-HSD

DOCSIS IP High-Speed Data service

IPP

Inter-PHY Protocol

IPTV

Television delivered over Internet Protocol

IPv6

Internet Protocol version 6

IR

Infra-Red

IR

Incremental Redundancy

IRC

Interference Rejection Combining

IS-54

A second generation cellular standard

IS-136

A second generation cellular standard, an improvement on IS-54ISI Intersymbol interference

ISI

Inter-symbol Interference

ISM

Industrial, Scientific, and Medical

ISO

International Organization for Standardization

ISP

Internet Service Provider

ISP

IEEE 1901 Inter System Protocol

ITU-T

International Telecommunication Union – Telecommunication Standardization Sector

JP

Joint Processing

JT

Joint Transmission

kft

kilofeet (length of wire)

L1

Layer-1

L2

Layer-2

L3

Layer-3

LAN

Local Area Network

LDPC

Low Density Parity Check

LDR

Low Data Rate

LED

Light Emitting Diode

LF

Low Frequency

LLID

Ethernet Logical Link Identifier

LOF

Loss Of Frame

LoS

Line of Sight

LOS

Loss Of Signal

LSB

Least Significant Bit

LTE

Long Term Evolution (mobile telephone standard)

LV

Low Voltage

MAC

Medium Access Control

MAN

Metro Area Network

MBMS-GW

Multimedia Broadcast Multicast Service Gateway

MBR

Maximum Bit Rate

MBSFN

Multicast Broadcast Single Frequency Network

MCCA

MCF Controlled Channel Access

MCE

Multicell/Multicast Coordination Entity

MCF

Mesh Coordination Function

M-CMTS

Modular CMTS

MCS

Modulation and Coding Scheme

MEF

Metro Ethernet Forum

MELT

Metallic line test

MF

Medium Frequency

MF-TDMA

Multi-Frequency Time Division Multiple Access

MIB

Management Information Base

MIMO

Multiple Input Multiple Out

MLB

Mobility Load Balancing

MLME

MAC Layer Management Entity

MME

Mobility Management Entity

MMSE

Minimum Mean Squared Error

MoCA

Multimedia over Coax Alliance

Modem

Modulator/Demodulator, a transceiver

MPCPDU

Multi-Point Control Protocol PDU

MPDU

MAC Protocol Data Unit

MPEG

Motion Picture Experts Group video compression standards

MRC

Maximal Ratio Combining

MRO

Mobility Robustness Optimization

MSB

Most Significant Bit

MSC

Mobile Switching Center

MSDU

MAC Service Data Unit

MSO

Multiple System Operator (cable network operator)

MTA

Multimedia Terminal Adapter

MTL

Multi-Conductor Transmission Line

MU-MIMO

Multi-user Multiple Input Multiple Output

MV

Medium Voltage

NACK

Negative Acknowledgement

NAS

Non-Access Stratum

NAV

Network Allocation Vector

NB

Narrow Band

NE

Network Element

NEXT

near end crosstalk

NG-PON

FSAN/ITU-T Next Generation PON protocol

NI

Network Interface

NID

Network Interface Device

NMS

Network Management System

Node-B

Base Station in a third generation cellular system

nrt-PS

Non-real-time Poling Service (DOCSIS)

NRZ

Non-Return to Zero line code

NSR

Non-Status Reporting

NTU

Network Termination Units

OAM

Operations, Administration and Maintenance

OAM&P

Operations, Administration, Maintenance and Provisioning

OBSAI

Open Base Station Architecture Initiative

ODN

Optical Distribution Network

OE

Optical to Electrical signal conversion

OEO

Optical to Electrical to Optical signal conversion (repeater)

OFDM

Orthogonal Frequency Division Multiplexing

OFDMA

Orthogonal Frequency Division Multiple Access

OLT

Optical Line Terminal

OLU

Optical Line Unit

OMCC

ONU Management and Control Channel

OMCI

ONU Management and Control Interface

ONT

Optical Network Terminal

ONU

Optical Network Unit

OTN

Optical Transport Network (ITU-T G.709)

OVSF

Orthogonal Variable Spreading Factor

PAM

Pulse Amplitude Modulation

PAP

Priority Action Plan

PBCH

Physical Broadcast Channel

PBR

Prioritized Bit Rate

PCB

Physical layer Control Block

PCC

Primary Component Carrier

PCCH

Paging Control Channel

PCCPCH

Primary Common Control Physical Channel

PCF

Point Coordination Function

PCFICH

Physical Control Format Indicator Channel

PCH

Paging Channel

PCI

Pre-coder Indicator

PCMM

Packet Cable Multi-Media protocol

PCRF

Policy and Charging Rules Function

PDCCH

Physical Downlink Control Channel

PDCP

Packet Data Convergence Protocol

PDFA

Praseodymium Doped Fiber Amplifier

PDN

Packet Data Network

PDN

Premises Distribution Network

PDSCH

Physical Downlink Shared Channel

PDU

Protocol Data Unit

PEIN

Prolonged Electrical Impulse Noise

PF

Proportionally Fair

P-GW

PDN Gateway

PHEV

Plug-in (Hybrid) Electric Vehicles

PHICH

Physical HARQ Indicator Channel

PHS

Payload Header Suppression

PHY

Physical Layer

PIFS

PCF Inter-Frame Spacing

PIN

Photo diode constructed with P-type, Intrinsic, and N-type semiconductor regions

PL

Power Line

PLC

Power Line Communications

PLCP

Physical Layer Convergence Procedure

PLI

Payload Length Indicator

PLO

Physical Layer Overhead

PLOAM

Physical Layer OAM

PMCH

Physical Multicast Channel

PMD

Physical Medium Dependent sublayer

PMI

Precoding Matrix Indicator

PMS-TC

Physical media specific transmission convergence sublayer

PON

Passive Optical Network

POTS

Plain Old Telephone Service

PRACH

Physical Random Access Channel

PRB

Physical Resource Block

PRIME

Powerline Related Intelligent Metering

PS

Packet Switched

PSB

Physical Layer Synchronization Block

PSD

Power Spectral Density

PSS

Primary Synchronization Signal

PSTN

Public Switched Telephone Network

PTI

Payload Type Indicator

PTP

Precision Timing Protocol

PUCCH

Physical Uplink Control Channel

PUSCH

Physical Uplink Shared Channel

QAM

Quadrature Amplitude Modulation

QCI

QoS Class Identifier

QoS

Quality of Service

RACH

Random Access Channel

RAN

Radio Access Network

RAT

Radio Access Technology

RB

Resource Block

RCS

Ripple Carrier Signaling

RDI

Remote Defect Indication

RE

Resource Element

REIN

Repetitive Electrical Impulse Noise

RF

Radio Frequency

RFI

Radio Frequency Interference

RFoG

Radio Frequency over Glass

RI

Rank Indicator

RIT

Radio Interface Technology

RLC

Radio Link Control

RMS-DB

Root Mean Square - Delay Spread

RNC

Radio Network Controller

RoF

Radio over Fiber

RoHC

Robust Header Compression

R-ONU

RFoG Optical Network Unit

RP

Repeater

RP

Reception Point

RRC

Radio Resource Control

RRH

Remote Radio Head

RS

Reed Solomon

RSOA

Reflective Semiconductor Optical Amplifier

RT

Remote Terminal

RTD

Round Trip Delay

rt-PS

Real-time Poling Service (DOCSIS)

RTS

Request-to-send

RTT

Round Trip Time

SA

System Architecture

SAE

Society of Automotive Engineers

SAI

Serving Area Interface

SCADA

Supervisory Control and Data Acquisition

SCB

Single Copy Broadcast Ethernet frame

SCC

Secondary Component Carrier

SCCPCH

Secondary Common Control Physical Channel

SC-FDMA

Single-Carrier Frequency Division Multiple Access

SCH

Synchronization Channel

SCTE

Society of Cable Telecommunications Engineers

SDF

Service Data Flow

SDO

Standard Development Organization

SDU

Service Data Unit

SELT

Single Ended Line Test

SES

Severely Error Seconds

SF

DOCSIS Service Flow

SFBC

Space Frequency Block Coding

SFD

Ethernet Start of Frame Delimiter

SGSN

Serving GPRS Support Node

S-GW

Serving Gateway

SHDSL

Symmetric High bit rate Digital Subscriber Line, ITU-T G.991.2

SHINE

Short High amplitude Impulse Noise Event

SID

Service Identifier

SIEPON

Standard for Service Interoperability in Ethernet Passive Optical Networks

SIFS

Short Inter-Frame Spacing

SIM

Subscriber Identity Module

SINR

Signal-to-Interference-and-Noise Ratio

SIR

Signal-to-Interference Ratio

SLA

Service Level Agreement

SLF

Super Low Frequency

SMB

Small or Medium sized Business

SNMP

Simple Network Management Protocol

SNR

Signal to Noise Ratio

SOA

Semiconductor Optical Amplifier

SON

Self-Optimizing Network

S-ONU

DPoE Standalone ONU

SPS

Semi-Persistent Scheduling

SR

Status Reporting

SR

Scheduling Request

SRS

Sounding Reference Signal

S-SCMA

Synchronous CDMA (used with DOCSIS)

SSID

Service Set Identifier

SSS

Secondary Synchronization Signal

STA

Station

STB

Set-Top Box

STBC

Space Time Block Coding

STM

Synchronous Transfer Mode

SU-MIMO

Single-user Multiple Input Multiple Output

S-VID

Service VLAN Identifier (Ethernet)

T1

Repeatered 1.544 Mbit/s transmission line using Alternate Mark Inversion coding

T1E1.4

United States DSL standards committee now called COAST-NAI

TC

Transmission Convergence

TCM

Time Compression Multiplexing

TCM

Trellis Code Modulation

T-CONT

G-PON Transmission Container

TCP

Transmission Control Protocol

TC-PAM

Trellis Coded Pulse Amplitude Modulation

TDD

Time Division Duplexing

TDFA

Thulium Doped Fiber Amplifier

TDM

Time Division Multiplexing

TDMA

Time Division Multiple Access

TD-SCDMA

Time Division Synchronous Code Division Multiple Access

TFCI

Transport Format Combination Indicator

TFT

Traffic Flow Template

TFTP

Trivial File Transfer Protocol

TG

Task Group

TIA

Transimpedance Amplifier

TL

Transmission Line

TLV

Type-Length-Value field

TM

Transparent Mode

TM

Transmission Mode

ToD

Time of Day

TOS

Type of Service

TP

Transmission Point

TPC

Transmit Power Control

TR-069

Broadband Forum standard for remote management of CPE

TPS-TC

Transport protocol specific transmission convergence sublayer

TTI

Transmission Time Interval

TWACS

Two-Way Automatic Communications System

TWDM

Concurrent time and wavelength division multiplexing

UCD

DOCSIS Upstream Channel Descriptor

UE

User Equipment

UGS

Unsolicited Grant Service (DOCSIS)

UGS-AD

Unsolicited Grant Service with Activity Detection (DOCSIS)

UL

Uplink

ULF

Ultra Low Frequency

UL-SCH

Uplink Shared Channel

UM

Unacknowledged Mode

UMTS

Universal Mobile Telecommunication System

UNB

Ultra Narrowband

UNI

User-Network Interface

U-NII

Unlicensed National Information Infrastructure

UPBO

Upstream Power Back Off

Upstream

Data flowing from the customer

UTRAN

UMTS Terrestrial Radio Access Network

VBR

Variable Bit Rate

vCM

virtual Cable Modem

VCSEL

Vertical-Cavity Surface-Emitting Laser

VDSL1

Very high bit rate Digital Subscriber Line 1, ITU-T G.993.1

VDSL2

Very high bit rate Digital Subscriber Line 2, ITU-T G.993.2

VID

VLAN Identifier

VLAN

Ethernet Virtual LAN

VLF

Very Low Frequency

VoIP

Voice over Internet Protocol

VoLTE

Voice over Long Term Evolution

VSAT

Very Small Aperture Terminal

WAN

Wide Area Network

WARC

World Administrative Radio Conference

WBF

Wavelength Blocking Filter

W-CDMA

Wideband Code Division Multiple Access

WDM

Wavelength Division Multiplexing

WDMA

Wavelength Division Multiple Access

WG

Working Group

WiMAX

A fourth generation cellular standard based on OFDM/OFDMA

WLAN

Wireless Local Area Network

WSD

White-Space Device

XGEM

XG-PON Encapsulation Method

XG-PON

FSAN/ITU-T 10 Gbit/s PON protocol specified in the ITU-T G.987 series

XGTC

XG-PON Transmission Convergence

1Introduction to Broadband Access Networks and Technologies

1.1 Introduction

In the mid-1990s, there were many doubts about the future of broadband access. No one was sure if the mass market needed or wanted more than 100 kbit/s; what applications would drive that need; what broadband access would cost to deploy and operate; what customers were willing to pay; whether the technology could provide reliable service in the real world; or which access technology would “win.” Government regulation in many countries made it unclear if investment in broadband would yield profits. It seemed that broadband access would be available only to wealthy businesses. Fortunately, there were some people who had a vision of a broadband world and who also had the faith to carry on despite the doubts.

We now live in a world where broadband access is the norm and households without it are the exception. No one asks today why the average household would need broadband access. The answer is obvious: we need internet access, with its ever-growing number of applications, and VOD (video on demand). With more than 600 million customers connected to broadband networks, no one asks if the technology works or whether it can meet the customer's willingness to pay.

Furthermore, a growing application of broadband access is the support of femtocells, and small cells in general. Resorting to small cells has today become the most promising trend pursued for increasing wireless spectral efficiency, and the key to its success is the availability of a high capacity wired line to the home. Also, a growing fraction of cellular data is today generated indoors. In addition, it has become clear that no single broadband access technology will win the entire market, and that the market shares of the different technologies will change over time.

Each access technology has its strengths and weaknesses. A common constraint is that we can have it fast, low cost, and everywhere – but not all at the same time. In many cases, the choice of broadband access technology is driven by the legacy network infrastructure of the network provider. In other cases, national regulatory considerations are a significant factor. As a result, each access technology has its areas of dominance in terms of geography, applications, and political domains.

The book is divided into three sections:

The chapters in the first section of the book cover technologies and standard protocols for broadband access over fiber-based access networks.

The chapters in the second section cover technologies and standards associated with non-fiber, non-wireless broadband access.

The chapters in the final section of the book address wireless broadband access technology and standards. Some of these technologies have been widely deployed, while others are anticipated to see deployment soon.

1.2 A Brief History of the Access Network

The traditional access network consisted of point-to-point wireline connections between telephone subscribers and an electronic multiplexing or switching system. The early access network used a dedicated pair of wires (referred to as a copper line or “loop”) between the subscriber and the central office (CO) switch.1 As the cost of multiplexing technology decreased, it became more economical in many cases to connect subscribers to a remotely located terminal. This remote terminal (RT) would multiplex calls from multiple subscribers onto a smaller number of wires for the connection to the CO. Network cost was reduced by having far fewer pairs of wires from the CO to the remote areas. As the technology evolved from analog frequency domain multiplexing (FDM) to digital time domain multiplexing (TDM), the RT systems became known as digital loop carrier (DLC) systems.

Data access to the telephone network began with the introduction of voiceband modems that could transmit the data as a modulated signal within the nominally 4 kHz voiceband pass-band frequency. The shorter lines (loops) allowed by DLCs made increasingly efficient modulation technologies practical. However, as explained in Appendix 1.A, the maximum data capacity of voiceband modems was limited to 33.6 kbit/s, or 56 kbit/s under special circumstances. Modems and their evolution are also discussed briefly in Appendix 1.A.

As a result, out-of-band technologies were introduced that transmitted signals over the copper line at frequencies outside the voiceband. Since these technologies sent digital information in the out-of-band signals, they became known collectively as digital subscriber line (DSL) technology. DSL is discussed further in Section 1.3 and Chapter 7–10.

Since the subscriber lines are implemented with twisted wire pairs, with multiple lines sharing the same cable without being shielded from each other, there are limits on the bandwidth that is achievable with DSL. For this reason, network providers became interested in alternatives to the subscriber line for providing broadband access. The three main contending technologies are coaxial cable, fiber optic cable, and wireless radio frequency connections. Each of these technologies is reviewed in later chapters of this book.

Coaxial cable networks were deployed by community access cable television (CATV) companies to provide broadcast video distribution. Due to the high bandwidth capabilities of coaxial cables, they had the potential for offering broadband services to their subscribers. In order to offer broadband data services, CATV companies evolved their networks to support upstream data transmission, and introduced fiber optic cables for higher performance in the feeder portion of their networks. As discussed below and in Chapter 11, coaxial networks have their own challenges as well as advantages.

Telephone network providers responded to the potential broadband advantages of the CATV companies by deploying additional fiber in their access networks. Telephone companies have deployed fiber directly to each subscriber's premises in some areas. Others are deploying fiber to terminals near enough to the subscribers' premises that broadband services can be provided by the latest very high-speed DSL technologies. The most attractive aspect to fiber is its virtually unlimited bandwidth capability. The primary drawback has been the relatively high cost of the network and its associated optical components.

Wireless access had not originally been a significant contending technology for residential broadband access. However, as wireless mobile networks have become widely deployed, and new technologies and protocols have been developed, wireless broadband access has become increasingly important. It is especially attractive in regions that lacked a legacy wireline infrastructure capable of evolution to broadband services. Examples of such regions include developing nations and rural areas. It also offers the very significant advantage of allowing mobile, ubiquitous service rather than being restricted to service at the subscriber's premises.

Since a limited amount of spectrum is available for use in broadband services, the networks to support it have become increasingly complex. For spectrum efficiency, wireless networks use grids of antenna, where each subscriber only needs enough signal power to reach the nearest antenna. The region covered by each antenna is referred to as a cell. The result is that the same frequencies can be used by subscribers in non-adjacent cells, since their signals should not propagate far enough to interfere with each other. The signal formats have been optimized in the latest protocols to approach the Shannon limit for data bits transmitted per Hertz of transmission channel bandwidth. Capacity is further increased by re-use of the spectrum through smaller cells and smart antenna technologies. Both add cost, and radio signals are always more vulnerable to various types of interference than wireline technologies. Wireless technologies are discussed further in Section 1.6 below, and in detail in Chapter 14–17.

1.3 Digital Subscriber Lines (DSL)

1.3.1 DSL Technologies and Their Evolution

DSL operates over a copper line at frequencies outside the voiceband, sending digital data directly from the subscriber, and thus avoiding the need for an analog to digital conversion. Since the telephone lines were designed to provide good quality for voiceband signals, they are often not particularly well suited for higher rate data signals. Reflections become a significant problem in the electrical domain at rates beyond the voiceband. One of the worst sources of reflections in North American networks is bridge taps. When the feeder cables are installed from the CO into the loop area, they go to splice boxes where the wires going to the subscribers are connected. When service is disconnected to a subscriber (e.g., due to the homeowner moving), a second pair of wires may be connected to the feeder cable to serve a different subscriber without removing the other line. The result is a bridge tap, and it is possible to have bridge taps at more than one location along the connection to a subscriber. The unterminated end of the unused line(s) causes electrical reflections of the DSL signals, and these reflections can cause destructive interference for certain frequencies (any impedance mismatch along the copper connection to the CO to the subscriber can cause harmful reflections, but the bridge taps are especially bad).

The first widely deployed services using a digital subscriber line were the Digital Data Service (DDS) from AT&T. DDS used baseband signals over the line and offered data rates including 2400, 4800 and 9600 bits/s, and 56 kbit/s. The lower rate signals were sometimes converted to analog signals at the CO and then mapped into a voiceband channel, thus avoiding any noise or distortion from the subscriber line. DDS required the end-to-end service be synchronized to a common atomic clock. DDS circuits also usually required that the line be groomed to remove impairments such as bridge taps. While DDS circuits were very valuable for some customers (e.g., banks using them for connections to ATM machines), they were too expensive to deploy to residential subscribers or even to many business subscribers.

The first serious attempt to provide higher data rates to subscribers was the basic rate interface of the Integrated Services Digital Network (ISDN-BRI). ISDN-BRI used baseband signals2 over the subscriber line to offer bidirectional data rates of 144 kbit/s. ISDN-BRI was designed to operate over most subscriber lines of up to 18 000 feet without having to remove impairments such as bridge taps from the lines. The 144 kbit/s signal was typically divided into two 64 kbit/s bearer (B) channels and a 16 kbit/s data (D) channel. The B channels could be used for voice or data, while the D channel carried the connection signaling information, with its leftover bandwidth available to carry subscriber data packets. It was also possible to merge the two B channels or merge the Bs and D channel into a single 144 kbit/s channel. The cost of ISDN-BRI was relatively expensive, however, and there were no driving subscriber applications to generate high demand. ISDN also required that the connection signaling protocol be processed by the CO switch, which meant a major upgrade to the switches. By the time that Internet connectivity became a driving application, much higher rates were practical for DSL.3 In effect, ISDN BRI provided too little bandwidth, too late, with too much network complexity.4

DSL modems that were dedicated to data services began to be widely deployed instead of ISDN-BRI. Initially, there were two broad categories of DSL. The first was a high speed DSL (HDSL) that provided bidirectional symmetric service at half the DS1 rate over a single pair,5 or symmetric full DS1 rate over two pairs (half on each pair). Although it would seem that HDSL had no advantage over T16 service, which also uses two pairs, HDSL was capable of operating over much longer line lengths than T1, and it could do so without requiring repeaters. The total cost of HDSL was less than half of T1 lines, mainly due to eliminating most of the labor needed to install repeaters and remove bridged taps. It became common for carriers to use HDSL as the primary technology for providing DS1 connections to business customers. The current generation of HDSL is HDSL2, which allows bidirectional symmetric transmission of up to 2.048 Mbit/s payloads over a single wire pair.

The second category is the DSL lines optimized for residential subscriber access. The first generation was called ADSL (asymmetric DSL) due to its use of asymmetric data rates in the upstream and downstream directions. Since residential subscriber are typically downloading more information than they are providing to the network, they typically require much higher data rates from the network (downstream) than they do for upstream. This asymmetry in the desired data rates per direction was exploited to achieve the higher downstream rates. The service rate for ADSL is affected by several factors, but line length is the primary one. Over the past 25 years, telephone companies have tried to limit the line lengths to 12 000 feet.7 Rates of 768 kbit/s downstream with 384 kbit/s upstream are possible over most of these lines. The actual rate is often determined adaptively as the system uses feedback to determine the frequency response of the line. In addition to higher data rates, another advantage of these DSL systems over ISDN-BRI was that they left the voiceband frequencies available for voice signals. This allowed analog POTS (Plain Old Telephone Service) signals to “ride underneath” the DSL data in its native format, which kept the voice and data signals separate within the network and allowed subscribers to use their existing telephone sets without conversion to digital signals at the subscriber premises.

ADSL rates and signal formats have been standardized by the ADSL Forum (now the Broadband Forum), by T1E1 (now ATIS COAST-NAI) and by the ITU-T SG15. SG15 is the primary body developing the current generation of DSL standards. The latest generation of ADSL is specified in the ITU-T G.992.5 standard for ADSL2plus which enables up to 20 Mb/s, with 12 Mb/s possible at 3000 feet.

Video delivery will require rates of 10–50 Mbit/s, depending on the service. For these rates, very high-speed DSL (VDSL) is required. VDSL requires lines lengths limited to 5000 feet. ITU-T SG15 has developed the VDSL2 standard, whose specifications are provided in ITU-T G.993.2 which enables rates up to 100 Mb/s upstream and downstream with 25 Mb/s downstream possible at 3000 feet. The ITU-T is developing the G.fast standard which promises to achieve bit rates up to 1 Gb/s over short copper lines.

Both ADSL2plus and VDSL2 support transmission of packet transport mode (PTM), asynchronous transport mode, and synchronous transport mode (STM). ITU-T G.997.1 specifies management parameters for ADSL2plus and VDSL2.

1.3.2 DSL System Technologies

The first generation of DSL equipment connected DSL modems at the subscriber premises to DSL access multiplexers (DSLAMs) located in the central office. DSLAMs were next deployed in remote locations that were often co-located with DLC RTs. If the DLC RT was served by a SONET fiber connection, the DSLAM traffic would be multiplexed onto the same SONET signal as the DLC voice traffic. One of the challenges of co-locating the DSLAM and RT is that the DSLAMs require much more power per line than DLC equipment. This leads to heat dissipation issues when they shared the same cabinet, which can restrict the number of DSL lines that can be served. The DSLAM is not connected to the RTs backup batteries, however, since there is no requirement to maintain DSL service during a power outage.8

DSL was developed at a time when Asynchronous Transfer Mode (ATM) appeared to the preferred multiplexing technology for next generation networks. ATM provided adaptation techniques to carry a wide variety of packet-oriented data and constant bit rate (CBR) traffic such as voice signals. Hence, ATM was a natural choice for the encapsulation technology over the DSL line and for the multiplexing technology within the DSLAM. ATM allowed some statistical multiplexing for more efficient bandwidth utilization on the trunk from the remote DSLAM to the CO, or within the network.

There are two drawbacks to ATM, however. The first is that it adds at least five bytes of overhead to each 53-byte cell, causing a roughly 10% bandwidth overhead penalty. The bandwidth penalty is sometimes referred to as the ATM “cell tax.” The other drawback to ATM is that it typically uses a rather complex signaling protocol that is overkill for purposes such as carrying connections to the Internet. Since most of the data going over DSL systems uses the Internet Protocol (IP) for Layer 3, it makes sense to use lower layer protocols that are more efficient with IP packets. Consequently, the emerging generation of DSLAMs is IP-based and uses Ethernet for the Layer 2 protocol instead ATM. These are commonly referred to as IP-DSLAMs.

1.4 Hybrid Fiber-Coaxial Cable (HFC)