1. Broadband on Fixed Services, ADSL
Presentation by
Dale N. Hatfield
Adjunct Professor, University of Colorado at Boulder
At the
Access to Broadband
“Universal Service Opportunities and Challenges”
An ARNET Professional Development Workshop
In collaboration with the
International Telecommunications Union
Sharm El Sheikh, Egypt
5 March 2005

2. Outline Background and Introduction
Digital Subscriber Line (DSL) Technology
DSL Position in the Broadband Market
Opportunities and Challenges for DSL Technology in Achieving Universal Service
Selected Policy Issues Relating to DSL
Summary and Conclusions

3. Background and Introduction
Notion of Bandwidth (Review)
In simple terms, bandwidth is an analog concept which refers to the range of signal frequencies that a circuit (channel) will pass
The larger the bandwidth, the more information that can be transmitted in a given amount of time
In the digital world, bandwidth is measured in bits per second
Analogous measures: vehicles per hour or liters per minute

4. Background and Introduction
Notion of Bandwidth (Review)
Computer Monitor
Illustration of the Importance of Bandwidth

5. Background and Introduction
Bandwidth of Different Transmission Media
Twisted-pair copper cable
Coaxial cable
Fiber optic cable
Radio

6. Background and Introduction
Applications and Required Bit-rates
Application
Bit-rate Required
VoIP
16 kbps
Full screen video conferencing (H.263)
384 kbps
Basic web browsing
1 Mbps
5 Mpixel JPEG photo in 10 seconds
1.5 Mbps
SDTV (MPEG2)
4 Mbps
SDTV (MPEG4)
HDTV (MPEG2)
15 Mbps
HDTV (MPEG4)
7 to 9 Mbps
Uncompressed medical X-ray in 2.5 seconds
25 Mbps
Source: Adopted from DSL Forum; rates include overhead

7. Background and Introduction
The Traditional Local Telephone Network
Trunks
PBX
Exchange
Switch
Feeder
Distribution
Inside
Wiring
Lines or
Local Loops
Drop/Service
Wire
Feeder-Distribution
Interface

8. DSL Technology Asymmetrical DSL (ADSL) Systems (Notional)
Frequency Response or “Bandwidth”
Of the Local Loop
Existing Telephone
Service
Amplitude
Downstream Channel
To Residence/Business
Upstream Channel
To Network
4 30
Frequency (kHz)

9. DSL Technology Varieties of DSL
Asymmetrical Digital Subscriber Line - ADSL
High bit-rate Digital Subscriber Line - HDSL
Single-pair HDSL – SHDSL
Very high bit-rate DSL - VDSL
Others

10. DSL Technology ADSL Circuit Switch DSLAM Voice & Voice Band Data
Analog Voice
Analog Voice
Circuit Switch
Splitter
DSLAM
Data
Splitter
Data
Residence
Data to ISP or Corporate Network*
Central Office
DSLAM=Digital Subscriber Line Access Multiplexer

11. DSL Technology Unbundled Loop with ADSL ILEC Central Office Loop PSTN
Splitter
Splitter
ISP/Internet
DSLAM
Line sharing
Unbundled
Loop with ADSL MX
CLEC
Network
Unbundled
Loop

12. DSL Technology ADSL bit-rates: ADLS2+ bit-rates up to 20 Mbps
Up to 8 Mbps downstream over 2 km of copper wires; longer lengths less (e.g., 384 kbps downstream at 5.5 km)
Typical offerings 1.5 Mbps down and 384 kbps up or 3.0 Mbps down and 768 kbps up
ADLS2+ bit-rates up to 20 Mbps
VDSL2 bit-rates up to 50 Mbps

13. DSL Position in the Worldwide Market
Notes:
Number of DSL lines worldwide on the order of 100 million at EOY 2004; growing rapidly
In the US, DSL to cable modem service is about 1:2 but recently, in terms of new lines, competition is about even
Even better success in many other markets; technological characteristics of existing network have an important influence on the speed of rollout

14. DSL Position in the Worldwide Market
No. of Lines in 1,000s
(3rdQtr)
Source: DSL Forum and Point Topic

15. ADSL Position in the Broadband Market
Percentage DSL Subscribers by Region
Source: DSL Forum and Point Topic

16. ADSL Position in the Broadband Market

17. Opportunities and Challenges for DSL Technology in Achieving Universal Service
Advantages
Comparative low incremental cost over an existing copper based telephone infrastructure
Standardization and large volumes in developed countries drive down costs
Competition with cable company provided cable modem service and licensed and unlicensed wireless service drives technological advances

18. Opportunities and Challenges
Advantages (Continued)
Can provide convenient backhaul for WLANs and Wireless ISPs (WISPs) in low density environments
Challenges
May not be the technology of choice where telephone infrastructure does not already exist
Despite rapid development, loop distance limitations still a factor in low density environments

19. Opportunities and Challenges
Challenges (Continued)
In addition to the loop length constraint, problems may still arise depending upon loop quality (e.g., faults) and architecture (e.g., presence of loading coils or Digital Loop Carrier systems)
Very high data-rate versions (e.g., VDSL) may require a change in architecture (e.g., FTTx) and, hence, additional investment

20. Selected Policy Issues
Loop Unbundling
Price of Unbundled Loop
Collocation and Collocation Pricing
Loop Sharing (Different Providers for Voice and Data on Common Loop)
DSL Service Without Voice Service on Loop

21. Summary and Conclusions

22. Contact Information
Dale N. Hatfield
Adjunct Professor
Interdisciplinary Telecommunications Program
University of Colorado at Boulder
Engineering Center - ECOT-317
Campus Box 530
Boulder, CO
Main Tel:
Direct Dial:
Fax:
Cell Phone: or