Vectoring De-mystified

® Adtran, Inc. 2011 All rights reserved

2® Adtran, Inc. 2011 A rights reserved Proprietary and Confidential

Vectoring De-mystified

• Market Drivers

• Understanding Vectoring

• Vectoring Described

• Benefits of System-Level

Implementation


National Goals by 2020:Ubiquitous 100Mbps Broadband

Reaching 2020 Goal is of National and Global Importance

US:100Mbps to 100 Million households

France:100Mbps to 70% of subscribers

Australia:100 Mbps to 90% households

Germany:100Mbps to 50% of subscribers


It impacts a country’s well being

“Savings in the health sector …to fall between 1.4% and 3.7% as a direct result of having the new network in place.”

ITU National Broadband Plan Recommendations

“… 10 percent increase in broadband penetration …1.3 percent additional growth GDP.”

ITU National Broadband Plan Recommendations


And Drives Business Success

Launched in the last 6 years Super connected subscribers will lead to new industries and companies we can’t even imagine yet

Higher bandwidth results in more exciting applications which leads to increased adoption and higher revenue per user


100Mbps+ Downstream: 25x faster than today’s average

4Mbyte photo in

1/3 second

A complete album in

5 sec

An Entire HD movie in less than 10 min

Multi-angle 3D HDTV

Cloud based Multi-screen 3D Gaming.


100Mbps: A Key Service Offering

• 100Mbps services will be mainstream by 2015

Source: Infonetics 2012

By 201539% plan to provide services >100 Mbps

Today52% of services are 1-10 Mbps


• Numerous national and regional broadband plans give 100Mbps as a targeted speed

• Cable operators are able to offer a 100Mbps tier with DOCSIS 3.0

100Mbps: A Key Service Offering


Can Wireline Service Providers Compete?

• FTTH is the ultimate goal but still cost-prohibitive in many deployment scenarios

• Telcos can be competitive with copper – 100Mbps is practical and economical with VDSL2 vectoring and bonding

• Let’s see how…



• Market Drivers

• Understanding

Vectoring



Implementation


VDSL2 Fundamentals - Discrete Multi-Tone

DMT Line Code Is Made Up of Individual Sinusoidal Carriers Whose Amplitude and Phase Change to Signal the Data Bits

The VDSL2 (G.993.2 ) Has Tone Spacing of 4.3125 kHz – 8.625 kHz for Profile 30a.

The Upstream Spectrum is Separated From Downstream. This Type of Segregation is Frequency Division Duplexing (FDD)

Frequency (MHz)

Upstream

Downstream

Upstream

Downstream

Upstream


DMT Tone Modulation

These figures illustrate the real and imaginary QAM amplitudes for 2, 3 & 4 bit tone modulations on each tone.

Each tone carries some number of bits (1≤ bits ≤ 15) based on its signal-to-noise ratio (SNR).

5

0

1 7

24

3

6

-3 -1 +1 +3

+3

+1

-1

-3

2 0

3 1

1 3

0 2

5 7

4 6

10

11

8

9

1513

12 14

-3 -1 +1 +3

+3

+1

-1

-3

+1

+1

-1

-1

Two bits

Three bits

Four bits


What Is Crosstalk?

DSL2

DSL1DSL1

DSL2

FEXT CouplingFEXT Coupling

DSL2

DSL1DSL1

DSL2

NEXT CouplingNEXT Coupling


ANSI Crosstalk Noise Models

LLfHfnXLnfCouplingFEXT F 20.26.0 ),(),,(_


How Many Bits On Each Tone?

The Number of Bits Carried on Each Tone is Determined by The Effective Signal to Noise Ratio (SNR) Around That Tone.

The Greater the SNR, the More Bits Carried on the Tone

2/

2/10

2

10)(

)(1log)(

ff

ff fNoise

fRcvfC

SNR


ADSL2+ 11 Bit Constellation


What is Vectoring?

G.vectorMultiport

xDSL

Vectored Signal Processing Compensates for the Crosstalk

Between the Cable Pairs

+FEXT

+FEXT

+FEXT

-FEXT

-FEXT

-FEXT+FEXT

+FEXT

+FEXT


G.Vector ITU Recommendation G.993.5

NormalMultiport

xDSL

Crosstalk Between Cables ActsAs Noise Sources in the Upstream

and Downsteam

G.vectorMultiport

xDSL

Vectored Signal Processing Compensates for the Crosstalk

Between the Cable Pairs


Why Vector Profile 17 Instead of Using Profile 30?


Why Vector Profile 17 Instead of Profile 30?



• Market Drivers




Implementation


Vectoring Modifications to StartupG.994.1

Handshake phaseDownstream

Direction

O-P-VECTOR 1Estimation of FEXT channels from the initializing line into

vectored lines

G.992.3 Channel Discovery Phase

O-P-VECTOR 1-1Re-estimation of FEXT

channels from the initializing line into vectored lines

G.992.3Training Phase

O-P-VECTOR 2

O-P-VECTOR 2-1Estimation of FEXT channels

from and into the initializing line

G.992.3Channel Analysis and

Exchange phase

G.994.1 Handshake phase

Upstream Direction

R-P-VECTOR 1Estimation of FEXT channels from the initializing line into

vectored lines

G.992.3 Channel Discovery Phase

R-P-VECTOR 1-1Re-estimation of FEXT

channels from the initializing line into vectored lines

G.992.3Training Phase

R-P-VECTOR 1-2

R-P-VECTOR 2Estimation of FEXT channels

from and into the initializing line

O-P-TRAINING V1

R-P-QUIET V1

G.992.3Channel Analysis and

Exchange phase

O-P VECTOR 1 allows existing vectored pairs to learn FEXT couplings from the new line

O-P Vector 1 composed of pilot modulated sync symbols & quiet symbols

Special OperationsChannel (SOC) Active

New Line Error Feedback


Aligned Synch Symbols Enable Training

Down Synch 1 DMT 2 DMT 3 DMT 4

timeDown Synch 1 DMT 2 DMT 3 DMT 4

timeDown Synch 1 DMT 2 DMT 3 DMT 4

time

DMT 1 DMT 2 DMT 3 Up Synch 4

timeDMT 1 DMT 2 DMT 3 Up Synch 4

timeDMT 1 DMT 2 DMT 3 Up Synch 4

time

Down Synch 1

timeUp Synch 4

time


Estimating the Crosstalk.

Y

X

+1

+1

ex

ey

Constellation boundary

Constellation boundary

ConstellationDecision point

Received normalized

sample

In-phase error

Quadrature error

Complex normalized error

sample

C^

Z

E

The CPE reports the slicer error measured on the synch symbols and sends it back to the DSLAM


DSL Transceivers

EncoderFramer

EncoderFramer

EncoderFramer

EncoderFramer

Modulator

Modulator

Modulator

Modulator

DSL Transceiver

DSL Transceiver

DSL Transceiver

DSL Transceiver


G.993.5: G.vector

EncoderFramer Modulator




Vector Control Entity

Precoder

Precoder

Precoder

Precoder


G.993.5: G.vector






Precoder

Precoder

Precoder

Precoder






Precoder

Precoder

Precoder

Precoder

DSL Modem

DSL Modem

DSL Modem

DSL Modem


G.vector: Vector Control Entity (VCE)

Framer Modulator

Framer Modulator

Framer Modulator

Framer Modulator


Precoder

Precoder

Precoder

Precoder

DSL Modem

DSL Modem

DSL Modem

DSL Modem

Vector Control Entity (VCE):•coordinates initialization of DSL links: orderly join/leave process

Encoder

Encoder

Encoder

Encoder


G.Vector Steady State Operation


VCE:•Synchronizes timing and aligns “sync” symbols on DSL links•VCE instructs encoders to transmit probing signal during sync symbols•Modems send error signals to VCE•VCE updates coefficients for precoders

EncoderFramer ModulatorPrecoder



Data Data Data Sync Data Data Data



Encoder

Encoder

Encoder

DSL Modem

DSL Modem

DSL Modem


G.vector: Adding a Line


• VCE instructs encoder for joining modem to be silent during data symbols • Instructs all encoders to transmit probing signals during sync symbols• Modems send error signals to VCE• VCE learns crosstalk couplings from joining modem, updates coefficients for

precoders• Joining modem can now send data









Encoder

Encoder

Encoder

Encoder

DSL Modem

DSL Modem

DSL Modem

JoiningModem

DSL Modem


Board Level FEXT Cancellation (across DSPs and VCE)

DSP 1 DSP 2

DSP 3 DSP 4

Ca

ble

Pla

nt

32ADTRAN 2010 All rights reserved

Background on Binders

Binder 1

Binder 2Binder 3

New line cards or additional systems added

No 1 to 1 correlation between systems and bindersNo 1 to 1 correlation between systems and binders


The Problem with VectoringSome Pairs Cannot be part of the Team

Crosstalk (FEXT)

Pairs in the same binder need to be handled as a single group to effectively implement vectoring


Deployment Strategy – FEXT Cancellation = Binder Management

24 Port FEXT WD-IDFC with 17.5 dBm VDSL2 (ADTRAN 100 Pair Cable; 75 % Take Rate - 48 Alien)

15

20

25

30

35

40

45

50

55

60

65

1000 1500 2000 2500 3000 3500 4000 4500 5000

Loop Length (ft)

Do

wn

stre

am R

ate

(Mb

ps)

0 Pairs Binder Managed



0 Pairs Random Deployment




Measured Results: Downstream

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rate

(Mbp

s)

Port #

Measured Data: 300 m 17A VDSL2 Downstream(26 AWG ~= 0.4 mm 48 links in 50 pair twisted pair cable

FEXT Free

Cable Vectoring

Binder Vectoring

No Vectoring

67 Mbps

81 Mbps (+21%)

99 Mbps (+50%)

Min Data Rate

Binder Vectoring:24 (Left) Vectored + 24 (Right) unvectored

Cable Vectoring:48 lines (24L (rates shown) + 24R)in one vector group


Measured Results: Upstream

Binder Vectoring:24 (Left) Vectored + 24 (Right) unvectored

Cable Vectoring:48 lines (24L (rates shown) + 24R)in one vector group

0

10

20

30

40

50

60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Rate

(Mbp

s)

Port #

Measured Data: 300 m 17A VDSL2 Upstream(26 AWG ~= 0.4 mm 48 links in 50 pair twisted pair cable

FEXT Free

Cable Vectoring

Binder Vectoring

No Vectoring

17 Mbps

27 Mbps (+56%)

36 Mbps (+111%)

Min Data Rate



• Market Drivers


• Crosstalk, Bonding and

Binder Management


• Benefits of System-

Level Implementation


System Level FEXT Cancellation

DSP 1 DSP 2

DSP 3 DSP 4 Ca

ble

Pla

nt

DSP 1 DSP 2

DSP 3 DSP 4 Ca

ble

Pla

nt

DSP 1 DSP 2

DSP 3 DSP 4 Ca

ble

Pla

nt


The Solution is a System ApproachLetting Everyone Join the Team

Crosstalk (FEXT)

Multiple OSP DSLAMs or Chassis Cards need to work together as a “system” so that vectoring can be performed across line cards or other OSP DSLAMs


Board Level to System Level Upgradeability

DSL Modem

Binder

Card 1

DSL Modem

DSL Modem

Card 2

Resource

Card 3

Card 44 Cards = 192 Ports

3 Cards = 144 Ports

2 Cards = 96 Ports

1 Cards = 48 Ports


OSP Board Level to System Level Upgradeability

DSL Modem

Binder

DSL Modem

DSL Modem

System level vectoring OSPs

DSL Modem

Initially Single OSP has internal BLV


FEXT Cancelled Group 96 Pairs No Alien Disturbers

96 Port FEXT WD-IDFC with 17.5 dBm VDSL2 (100 Pair Cable; ~100% Take Rate - No Alien)

46.0

975

42.3

628

39.3

223

35.4

266

28.7

862

23.9

531

22.6

768

19.9

8

17.0

189

52.2

771

48.6

027

45.4

476

40.7

892

33.0

877

27.4

467

24.5

257

21.5

953

18.2

989

54.1

611

50.4

584

47.1

874

42.2

592

34.2

689

28.5

832

25.2

749

22.2

604

18.9

67

55.7

737

52.1

054

48.7

38

43.4

046

35.1

866

29.3

747

25.9

316

22.7

762

19.3

414

59.8

433

56.2

349

52.7

167

46.4

136

37.4

983

31.2

089

27.4

054

23.9

024

20.2

696

67.0

601

63.3

984

59.0

322

51.0

869

40.8

826

33.7

211

29.2

111

25.3

735

21.4

84

82.3

435

70.5

867

57.3

389

44.4

597

35.9

737

31.3

308

26.8

474

22.5

406

91.7

855

0

10

20

30

40

50

60

70

80

90

100

1000 1500 2000 2500 3000 3500 4000 4500 5000

Loop Length (ft)

Do

wn

stre

am R

ate

(Mb

ps)

No Pairs Removed 1%

4 Pairs Removed 1%

8 Pairs Removed 1%

12 Pairs Removed 1%

24 Pairs Removed 1%

48 Pairs Removed 1%

96 Pairs Removed 1%


Vectoring Benefits and Considerations

• Vectoring has the potential to cancel crosstalk in a binder:• All users see rates as if

they were the onlyuser in the cable

Benefits– 30-50% improvement in

speed– Reach 100Mpbs with 2

pair bonding

Considerations– Limited to short loops

(less than 3,000ft)– Need system level

approach

0

20

40

60

80

100

120

140

500 1000 1500 2000 2500 3000

Rate

(Mbp

s)

Reach (feet)

Upstream, 12-self crosstalk

26 AWG equivalent: Multiply vectored reach by 1.3 for 24 AWG

100

Mbp

s to

> 2

500

ft,

Usi

ng 2

pai

rs


Downstream Performance Full Cancellation


Upstream Performance Full Cancellation


Conclusions

• Complexity of FEXT cancellation will result in longer port training times.

• FEXT cancellation for VDSL2 shows great promise for applications in which:–cable size matches the in-domain group size–system level deployment is implemented and group size matches

or exceeds the binder size– loops are short–alien crosstalk is minimal.

• After FEXT is removed, the resulting low noise floor will likely increase performance sensitivity to impulse noise and component non-linearity


Key Takeaways

• System-level approach is best

• Best gains (30-50%) with short loops. (<1000ft)

• Vectoring is a short loop technology not suitable for CO deployments

• ADTRAN knows vectoring.

In 2008, ADTRAN received the “Award for Outstanding Contributions to an ATIS Forum or Committee”. This achievement was in recognition for our initiative to provide the industry with a FEXT Channel Model needed for the analysis of FEXT cancellation techniques used in vectoring.

® Adtran, Inc. 2011 All rights reserved

Thank YouPlease visit: http://adtran.com to learn more.Email [email protected] or call 800-9ADTRAN

Documents

Vectoring De-mystified