Broadband Myth

Broadband Communications:Myth and Reality

Professor Stephen McLaughlin

School of Engineering & Electronics

University of Edinburgh

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Royal Society of Edinburgh, Broadband Communications

10th May, 2004

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10th May, 2004

Contents of PresentationContents of Presentation

- What do we mean by Broadband?- Some Broadband Myths- Flavours of Broadband Communication

- Fibre to the Home- DSL- Wireless LAN

- Future Technologies- Conclusions

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What will What will II mean by mean by BroadbandBroadband??

A transmission facility having a bandwidth sufficient to carry multiple voice, video or data channels simultaneously. Each channel occupies (is modulated to) a different frequency bandwidth on the transmission medium and is demodulated to its original frequency at the receiving end; NB used originally to describe a channel with more bandwidth than a standard 48 KHz voice grade channel.

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What is commonly meant by What is commonly meant by BroadbandBroadband??

At present, there is no internationally agreed definition of broadband. In general, broadband often refers to internet access service with transmission speed from hundreds of kbps (kilobits per second) to several Mbps (Megabits per second)

Note that 'dedicated bandwidth' or 'shared bandwidth' services advertised by ISPs normally refers to the transmission speed of the customer access circuit between the customer's premise and the nearest exchange. The active users still have to share the public network resources outside the exchange, including local and external transmission circuit.

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Some Broadband MythsSome Broadband Myths

• You can never have too much bandwidth.– i.e. If you build it, they will come

• Internet traffic is doubling every three months.• Everyone needs more bandwidth because of the

new killer applications!

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You can never have too much bandwidthYou can never have too much bandwidth

• If you build it, they will come.– Q: How quickly will they come?– A: Not as quickly as many had hoped.

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Internet Traffic doubles every 3 monthsInternet Traffic doubles every 3 months

• The reality….?– Backbone traffic growth:

• about 100% per year in 1990 through 1994• about 1,000% per year in 1995 and 1996• about 100% per year in 1997 through 2000

– Overall data traffic growth:• around 20 to 30% per year in the 1980s • 30 to 40% per year in 1990 through 1998• accelerating towards 100% per year

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SWITCH traffic and capacity across the AtlanticSWITCH traffic and capacity across the Atlantic

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We need more bandwidthWe need more bandwidthTraffic is not the same as bandwidth!

– Factors decreasing bandwidth demand:• Elimination of SONET rings, ATM “cell tax,” etc.• VPNs over public network replacing private lines

– Factors increasing bandwidth demand:• Optical switching• Demand for low transaction latency

• DWDM is doubling transmission capacity each year!– However, magnetic storage is also doubling each year!

• So location matters…………………………

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Some reasonable conclusionsSome reasonable conclusions

• Transmission capacity is growing at about the same rate as traffic

• Magnetic storage is doubling each year• Streaming media traffic is unlikely to be a dominant

factor– local store and replay will have a strong role

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Flavours of Broadband CommunicationsFlavours of Broadband Communications

• Fibre optics– Fibre to the home?

• DSL/Cable Modems– Data rates cost etc

• Wireless– IEEE802.11

• Mobile– 3G and beyond

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What about Fibre to the Home?What about Fibre to the Home?

• For 25 years researchers and telcos have been talking about delivering fibre to the home…– Currently connection costs to premises are $1500 for fibre

and $200 for copper DSL (assuming large scale deployments)!

– Fibre to the home is a long term goal but in the near and medium term DSL and developments thereof will be the main delivery mechanism for broadband services to the home.

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What is Digital Subscriber Line?What is Digital Subscriber Line?

• DSL is a generic name for a group of technologies which transport data at high rates over the access part of the network.

• DSLs are distinct from conventional modems in that the data is only transmitted as far as the local exchange.

• The signal bandwidth greatly exceeds 4kHz• Based on secondary use of existing cables

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DSL:The Access NetworkDSL:The Access Network

• Construction and Topology• Signal Degradation• Noise and Interference

NTE

Street

Cabinet or

PCP

Switch

Overhead DP

NTE

Underground DP

Exchange to flexibility point 1-3kmFlexibility point to DP 0.5 to 1kmDP to customers premises 50m

Fibre optics is onlyIn the core

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Flavours of DSLFlavours of DSL

• ADSL operates in 300kHz to 1.1MHz band– 1.5Mbits/s to 6Mbits/s downstream, 640kbits/s downstream– Always on (operates above baseband)

• G-HDSL (SHDSL)– Single line 1Mb/s symmetric service

• VDSL potentially operates up to 30MHz– 52Mbits/s@ 300m, 26Mbits/s@ 900m, 13Mbits/s@ 1.5km

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• Both ADSL and VDSL use DMT modulation (Discrete Multi-Tone)

unused tonesdue to line conditions

tone spacing(4.3 kHz)

frequency

=QAM-modulatedsubchannel (tone)individually optimizedas a function of impairments

20 kHz4 kHz 1.1 MHz

powerspectrum

spectrum usedfor downstream data

spectrum usedfor upstream data

POTS

unused tonesdue to line conditions

tone spacing(4.3 kHz)

frequency

=QAM-modulatedsubchannel (tone)individually optimizedas a function of impairments

20 kHz4 kHz 1.1 MHz

powerspectrum

spectrum usedfor downstream data

spectrum usedfor upstream data

POTS

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DSL Bit rates vs ReachDSL Bit rates vs Reach

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Global Ranking

CountryDSL Subscribers31 December 2003

DSL per100 phone lines

31 December 2003

1 China 10,950,000 5.1

2 Japan 10,272,052 14.4

3 USA 9,119,000 4.8

4South Korea 6,435,955 27.7

5 Germany 4,500,000 8.4

6 France 3,262,700 9.6

7 Taiwan 2,800,000 21.4

8 Italy 2,280,000 8.3

9 Canada 2,170,243 10.9

10 UK 1,820,230 5.2

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Q4 2002 and Q4 2003 Regional Growth

0

5000

10000

15000

20000

25000

NorthAmerica

LatinAmerica& Carib

WesternEurope

EasternEurope

Southand East

Asia

Asia-Pacific

MiddleEast and

Africa

Q4 2002

Q4 2003

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• Problem of crosstalk in the network

• DSM = Dynamic Spectrum Management– Adapt transmit spectrum dynamically – Reduce crosstalk (=noise) for other users in the network.– DMT is very suited to apply DSM (flexible spectrum allocation)

CentralOffice

UserModem

UserModem

CentralOffice

Future enhancements to DSLFuture enhancements to DSL

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DSM principlesDSM principles

Rate-Adaptive (RA)use all available power (fixed)

to maximize bit rate while maintaining fixed margin

bit rate

noisemargin

tran

smit

PS

D

Margin-Adaptive (RA)use all available power (fixed)

to maximize margin while maintaining fixed bit rate

bit rate

noisemargin

tran

smit

PS

D

current deployment

practice

Margin-Adaptive (RA)use all available power (fixed)

to maximize margin while maintaining fixed bit rate

bit rate

noisemargin

tran

smit

PS

D

current deployment

practice

Power-Adaptive (PA)= Fixed-Margin (FM)

minimize power while maintaining fixed bit rate

and fixed noise margin

bit rate

noisemargin

tran

smit

PS

D

DSMDSM

Power-Adaptive (PA)= Fixed-Margin (FM)

minimize power while maintaining fixed bit rate

and fixed noise margin

bit rate

noisemargin

tran

smit

PS

D

DSMDSM

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Wireless TechnologiesWireless Technologies• WLAN

– IEEE 802.11b and 802.11g standards transmit at 2.4 GHz, while those that comply with the 802.11a standard transmit at 5 GHz offering data rates of 11-54Mbits/s.

– Limited range of around 30m with discontinuous coverage.– Frequency bands are unlicensed Interference!

• Mobile– Operates between 1-2GHz in licensed bands– Moderate data rates around 64kbits/s– Extensive coverage and range

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Wireless LAN and DSLWireless LAN and DSL

• Wireless routers with an inbuilt ADSL modem are available for around £70

• So wireless LAN avoids having to wire your house with CAT5 cable!

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Wireless LAN:What is the underlying technology?Wireless LAN:What is the underlying technology?• Orthogonal frequency division multiplexing (OFDM) is a communications technique

that divides a communications channel into a number of equally spaced frequency bands. A subcarrier carrying a portion of the user information is transmitted in each band. Each subcarrier is independent of each other.

• OFDM is the modulation technique for DSL, wireless LANs, Digital Audio Broadcast and Digital Video Broadcast systems and a candidate for future mobile systems.

Use

r i

Use

r j

Use

r k

Use

r l

Use

r m

Subcarriers

1 2 3 4 5 N

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The Future………..The Future………..

• So what does the future hold…..?

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The DriversThe Drivers

VOICE (A) VOICE (D) MULTIMEDIA WIRELESSWORLD (WW)

Digital- Quality- Security- Reliability- Capacity- Roaming

Services- Mixed services- Capacity- Flexible billing- Personalisation

Integrated WW- Mixed networks(WAN,WLAN,DVB,etc.)- IP based/connected- Ambient awareness- Ubiquity/flexibility- ‘Always connected’

1G 2G 3G B3G

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““B3G” Design ChallengesB3G” Design Challenges

Although 3G is an important first step, several basic issues still need to be addressed for next generation wireless systems:

Fast/reliable broadband radios (PHY/MAC) with QoS~100 Kbps 1-10 Mbps with adaptivity, link reliability & QoS

– Scalable system capacity for mass-market services • high service penetration implies ~Gbps/Sq-Km

– Integration of multiple radios into single IP network• unified mobility architecture, “open” networks with modular services

– New networking modes, e.g. multicast, multihop & peer-to-peer• ...lower-cost infrastructure, networks that grow organically

– Truly “useful” mobile information services• ...beyond web browsing on phones/PDA’s, new portable devices

scaling capacity& lower costper bit

more flexiblenetworks

adaptive services

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B3G systems can exploit Moore’s law advances in radio speed, but need to work with shorter range...

1990 1995 2000Year

1

10

100

1000

Mhz

1

10

100

1000

Kbps

1

10

100

1000

Mbps

1

10

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AN

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itch

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Loc

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Wireless

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3G Mobile

802.11bWLAN,

CableModem

DSL

GbpsRouter

ATM

56K modem

Sw Ethernet

802.11a, UWB,..,

short-rangeradio speedsoutpacing Moore’slaw over last~5 yrs!

Implications: (1) 4G must support short-range radios(2) System should accept new radios as they emerge

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• Hierarchical, self-organizing network concept currently under consideration, based on: 3 service tiers (cellular, WLAN, personal area) BS’s, AP’s, FN’s (forwarding radio nodes), user devices automatic discovery and power mgmt protocols hierarchical, ad-hoc multihop routing

InternetInternet

Forwarding node

low-tier(e.g. sensor)user nodes

Access Point

FN

APBTS

3G cell

personal-areapico-cell

WLANmicro-cell

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ConclusionsConclusions

• Present– Moderate data rates across multiple non-interacting

systems• Near to medium term

– Increase in data rates• Long term

– Truly broadband services with networks interworking

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10th May, 2004

Thank You

Any Questions?

Technology

Broadband Myth