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SolarFlare Communications 10GBASE-T IEEE Tutorial, 11/11/2002 1

10GBASE10GBASE--T TutorialT Tutorial

IEEE 802.3IEEE 802.3

Kauai, HawaiiKauai, Hawaii

November 11, 2002November 11, 2002

SolarFlare CommunicationsSolarFlare Communications


AgendaAgenda

• Introduction, Cabling & Challenges -George Zimmerman, Ph.D.

CEO & CTOFounder

• Implementation & Performance -Bill Jones, Ph.D.

Director, Systems Engr.


10G on UTP Possible or Not?10G on UTP Possible or Not?

• The Problem• Characterization vs. Specification• Cabling & Impairments• Limitations• Capacity

– How to pick the right bandwidth?

• Challenges


Applications OverviewApplications Overview

• 10-Gb/s Ethernet connections </= 100m• Utilize installed base of structured Cat 5e UTP• Upgrade from 1000BASE-T

10GBase-TTransceiver

11/4/2002

MAC 10GBase-TTransceiver MAC

Cat5e UTP(4 pairs)

up to 90m

Wallplateor

Patch Panel

Wallplateor

Patch Panel

up to 5m up to 5m


Ethernet EvolutionEthernet EvolutionSp

eed

Time

New Model Shannon

AFE+DSPMIMO/Multiuser

Channel-Optimized

• 10GBASE-T

• 1000BASE-T

>>1 bit/s/Hz“Divide & Conquer”

DSP, Coded

Conventional Wisdom Shannon

1 bit/s/HzAnalogLinear

• 10BASE-T

Perceived Shannon • 100BASE-T

>1 bit/s/HzAnalog & Digital

Non-Linear

Perceived Shannon


What Makes Shannon Limits?What Makes Shannon Limits?

• NOT modulation-specific• Signal Attenuation (assumed usable bandwidth)• Assumed irreducible noise sources

– Background– Crosstalk

• Crosstalk from other pairs in our sheath• Alien crosstalk – coming from other bundled 4-pair

sheaths– Device noise from transceiver

• Change the assumptions & change the limit!– (to a point…)


Channel ImpairmentsChannel Impairments

R

THYBRID

R

T HYBRID

R

THYBRID

R

T HYBRID

R

THYBRID

R

T HYBRID

R

THYBRID

R

T HYBRID

NEXT14

NEXT12

NEXT13

FEXT14

FEXT13

FEXT12

Far Echo

Near Echo

Alien Crosstalk, EMI


Characterization vs. SpecificationCharacterization vs. Specification

• Cat 5/5e cable must be high quality with minor structural variations to meet TIA-568 requirements

• 100 MHz (or 250 MHz) “limit” imposed by TIA qualification requirements– not the physical limitations of the cable

• Cable properties stable beyond 500 MHz– depends mainly on transmission line geometry and

construction materials

• Minor structural variations and connector discontinuities affect channel transmission, but not catastrophically


Cat 5e Channel: Insertion LossCat 5e Channel: Insertion LossMeasured Cat 5e 100 Meter Channel Insertion Gain at 20 C

0 50 100 150 200 250 300 350 400 450 500-60

-50

-40

-30

-20

-10

0

Frequency (MHz)

Inse

rtion

gai

n (d

B)

Manufacturer AManufacturer BManufacturer CCat 5e limitExtended limit


Cat 5e Channel: NEXTCat 5e Channel: NEXT

0 100 200 300 400 500 600-80

-70

-60

-50

-40

-30

-20

-10

0

Measured Pair-to-pair NEXT Coupling into Cat 5e Pair 1

Frequency (MHz)

Inse

rtion

gai

n (d

B)

NEXT12NEXT13NEXT14

Cat 5e limitExtended limit


Cat 5e Channel: FEXTCat 5e Channel: FEXT

0 50 100 150 200 250 300 350 400 450 500-100

-90

-80

-70

-60

-50

-40

Measured Pair-to-pair FEXT Coupling into Cat 5e Pair 1

Frequency (MHz)

Inse

rtion

gai

n (d

B)

FEXT12FEXT13FEXT14


Alien NEXTAlien NEXT

0 50 100 150 200 250 300 350 400 450 500-80

-70

-60

-50

-40

-30

-20

Frequency (MHz)

Inse

rtion

gai

n (d

B)

Adjacent connectorNon-adjacent connectorCat 5e NEXT limitExtended limit

Single (4-pair cable) disturber, 40 meter length unbundled

Cat 5e Power Sum Alien NEXT vs. Patch Panel Position


EMI EMI -- EmittedEmitted

• >100 MHz on Cat 5e can meet FCC Class A~12 dBm launch power limitation

0 100 200 300 400 500 600 700 80020

25

30

35

40

45

50

55

60

W orst-C ase R adiated E m issions at 3 M eters - C at 5e U T P

Frequency (M H z)

Elec

tric

field

(dB

uV/m

)

-80 dB m /H z signalFC C C lass A lim itFC C C lass B lim it


Overall EnvironmentOverall Environment

• Sources require significant cancellation– Extensions from 1000BASE-T– Significantly greater NEXT + FEXT + Equalization challenge

-150

-140

-130

-120

-110

-100

-90

-80

-70

0 100 200 300 400 500 600Frequency (MHz)

Pow

er S

pect

ral D

ensi

ty (

dBm

/Hz)

XmtPSD

RcvPSD

SelfNEXT

SelfFEXT

Alien NEXT


Strawman Strawman ImprovementsImprovements

• Baseline Requirements: ~40 dB Echo & NEXT Cancellation, ~20 dB FEXT CancellationAlien NEXT suppression for crowded installations

Received Signal & Residual Noise Terms

-160.00

-150.00

-140.00

-130.00

-120.00

-110.00

-100.00

-90.00

-80.00

0 50 100 150 200 250 300 350 400

Frequency (MHz)

PSD

ref

to

Inpu

t (d

Bm

/Hz)

-20.0

-10.0

0.0

10.0

20.0

30.0

40.0

50.0

60.0

SNR

(dB

)

Rcv Sig

Res Echo

Res NEXT

Res FEXT

Res ANEXT

Bkgnd

SNR


CapacityCapacity

• 100m Cat 5e, with cancellers• 14.4 Gbps on 100m at 10dBm launch, 600 MHz• 10 Gbps @ 8.9 dB Margin, 430 MHz bandwidth

Bit Capacity

0

2

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250 300 350 400

Frequency (MHz)

Bit

s/Se

c/H

z

BitCap (Bkgd)

Bit Cap (allresiduals)


Conclusion: Conclusion: It CAN be done, but HOW?It CAN be done, but HOW?

• Bandwidth required 400-500 MHz• 40+ dB Echo & NEXT reduction• 20+ dB FEXT reduction• 10-12 dBm launch power• > 8 bits (ENOB) signal processing

– A/D performance, or analog noise performance if analog circuits used

• Shannon limits say “Not Impossible”, just hard!– It’s up to us engineers!


Realizing 10GBASERealizing 10GBASE--TT

• Addressing communication system challenges

• Modern signal processing algorithms

• Low power, high speed digital circuit design

• High linearity, wideband analog circuit design


Communication System ChallengesCommunication System Challenges

• High frequency multiple twisted pair media characterization – Line attenuation, NEXT, FEXT, Alien Xtalk & EMI– Cat 5e specification out to 100MHz

• Sufficient for 1000BASE-T– Utilizing frequencies beyond cable’s initial intended

objective is not new– Case in point: xDSL

• Installation designed for 20kHz max

• Measurements converted for use in system evaluation– No assumptions or short cuts taken– Scaled to worse case specifications (when they exist)


Line Code SelectionLine Code Selection

• Pulse Amplitude Modulation (PAM)• Evolution Of 1000BASE-T

– Builds on proven technology

• Lower AFE requirements– De-stressing an already stressed requirement

• Utilizing an optimal DFE achieves capacity


PAMPAM--10 Coding10 Coding

• Given the characteristics of the channel/disturbers, capacity is maximized with an analog bandwidth around 400MHz

• 10Gbps is achieved with a baud rate of 833MHz and 12 bits/baud or 3 bits/pair (4 pairs)– Minimum requirement of PAM8 for uncoded operation

• PAM9 may be sufficient for Ethernet control symbols• PAM10 needed for both control and Trellis coding• Extension of 1000BASE-T

– 4D, 8-state Trellis code (one dimension per pair)– 6 dB coding gain relative to uncoded 10PAM


Comparison With 1000BASEComparison With 1000BASE--TT

High-Performance FEXT cancellation

No specified FEXT cancellation

High-Performance NEXT cancellation

Moderate NEXT cancellation

833 Mbaud, ~400 MHz used bandwidth

125 Mbaud, ~80 MHz used bandwidth

Full duplex echo-cancelled transmission

Full duplex echo-cancelled transmission

10-level with Trellis code across pairs

5-level with Trellis code across pairs

Multilevel coded PAM signaling (3-bits/symbol)

Multilevel coded PAM signaling (2-bits/symbol)

Straw Man 10GBASE-T1000BASE-T


PCS SER & BER Straw Man GoalPCS SER & BER Straw Man Goal

Slicer Input SNR (dB)

1000BASE-TReqm’t

19 20 21 22 23 24 25 26 2710

-14

10-12

10-10

10-8

10-6

10-4

10-2

100

Coded PAM10 simulation SERCoded PAM10 Theory SERCoded PAM10 Theory BER

25.3 dB


PMD Performance Straw Man GoalPMD Performance Straw Man Goal

• TSB 67 Channel

10GBASE-TTransceiver

11/7/2002

MAC 10GBASE-TTransceiver MAC

Cat 5e UTP(4 pairs)

up to 90m

Wallplateor

Patch Panel

Wallplateor

Patch Panel

up to 5m up to 5m

• Consider an aggregate slicer SNR of 25.3 dB with five dominating noise terms requires individually around 32 dB SNR


Channel ImpairmentsChannel Impairments-- ISIISI• Pre- & Post-Cursor Interference from limited

Bandwidth• Post-Cursor Dominates (>100 terms)• Feedforward & Decision

Feedback EqualizationSolution

FeedForwardEqualizer

DecisionFeedbackEqualizer

Slicer

_+


EchoEcho

• Full duplex needed for limited BW• Compromise hybrid for Tx/Rx isolation• Impedance mismatches

require residual echocancellation

• > 40 dB rejection


NEXTNEXT

• High-level interference from transmitters• Very long response time• > 40dB NEXT cancellation

wireline

Tx Channel 0

Rx Channel 1(target rcvr)

NextCoupling

wireline

Rx Channel 0(victim rcvr)

Tx Channel 1(interfering xmtr)


FEXT ImpairmentFEXT Impairment

• Pre- and post-cursor elements of interference• Based on an equal-level FEXT (ELFEXT) model• Uncompensated in 1000BASE-T• Must be cancelled in 10GBASE-T• > 20 dB cancellation

wireline

Tx Channel 0

Tx Channel 1(interfering xmtr)

FextCoupling

wireline

Rx Channel 0(victim rcvr)

Rx Channel 1(target rcvr)

chanelffext HHH ⋅=


Challenging ImplementationChallenging Implementation

• A new approach to problem solving needed to meet SNR requirement (>25.3 dB)

• Efficient reuse of resources in MIMO modeling

• Utilization of parallel structures


Traditional Signal ProcessingTraditional Signal Processing

SISOSISOSISOSISO

SISOSISOSISOSISOSISOSISOSISOSISO

SISOSISOSISOSISO

T4T3T2T1

++++ ++++ ++++ ++++ R4

• Echo & NEXT cancellation

• 16 Single Input Single Output (SISO) processing elements(scalar filters)

• With canceller taps on the order of several hundred10 Tera Operations (TOps)!


Modern Signal ProcessingModern Signal Processing• Echo & NEXT Cancellation

R4

T4T3T2

MIMO

T1

• One Multiple Input Multiple Output (MIMO) processingelement (matrix filter)

• Exploits correlation to reduce interference common to all received channels

• Enables massive reuse of computing resources


Modern Signal ProcessingModern Signal Processing• Data recovery & Fext cancellation

d1

d2

d3

d4

T1

T2

T3

T4

R1

R2

R3

R4

H1

F21

F31

F41

MIMOCHANNEL

MUD

d1

d2

d3

d4

• Multiuser Detector (MUD) of MIMO channel providessimultaneous data decisions & interference removal


Parallelizing FIRsParallelizing FIRs• One high rate N tap filter

( ) )()( 21

120 zHzzHzH −+=

x(n)H(z)

y(n)

H0(z)

H1(z)

H1(z)

H0(z)

Z-1

x(n)

Z-1

+

+ +

Z-1

y(n)

2

2

2

2

• Good for clock limited or high speed applications• Four half rate N/2 tap filters• Equivalent number of operations per unit time


Efficient Parallelization Efficient Parallelization

H0(z)

H0(z)+H1(z)

H0(z)

Z-1

x(n)

Z-1

+

+ +

Z-1

y(n)

2

2

2

2+ +_

_

• Four filters reduced to three

• 25% improvement in efficiency

•Greater efficiency with greater parallelism


Digital Circuit Straw Man GoalsDigital Circuit Straw Man Goals

• Puts total DSP requirements at 1.5 Tera Operations (TOps)

• Quad 1000BASE-T requires 1.0 TOps 150% increase in possible aggregation with 50%

increase in complexity today!

• CMOS technology


Analog Circuit Straw Man GoalsAnalog Circuit Straw Man Goals

• Transmitter: DAC & Line driver– >40 dB Linearity– 450 MHz Bandwidth

• Receiver: Hybrid, LNA & ADC– >8 bits ENOB– 833 MSPS

• PLL & Clock recovery– 833 MHz

• CMOS technology


ISI ImpairmentISI Impairment-- After EqualizationAfter Equalization

0 0.5 1 1.5 2 2.5 3 3.5 4x 108

-70

-60

-50

-40

-30

-20

-10

0

10

Frequency

Spec

trum

(dB)

Equalized Signal

Residual ISI

• FFE scales to produce unit variance hard decisions

Tx MAG MAG Rx ENFX EQCat 5e cable


ISI ImpairmentISI Impairment-- Symbol StreamSymbol Stream

a)

b)

0 1 2 3 4 5 6 7 8 9 10

x 104

-2

-1

0

1

2a) Rx Far End Signal b) Slicer Input Vs. time

0 1 2 3 4 5 6 7 8 9 10

x 104

-2

-1

0

1

2

MAG MAG Rx ENFX EQCat 5e cable

a b

Tx


Echo ImpairmentEcho Impairment-- After CancellationAfter Cancellation

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5x 108

-100

-80

-60

-40

-20

0

20

Frequency

Spec

trum

(dB)

Rx Echo

Cancelled Echo

Cat 5e cable

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5x 108

-100

-80

-60

-40

-20

0

20

Frequency

Spec

trum

(dB)

Rx far end signal

Rx echo

(a) (b)

a b

Tx MAG MAG Rx ENFX EQ


Echo ImpairmentEcho Impairment-- SNR @ DetectorSNR @ Detector

0 0.5 1 1.5 2 2.5 3 3.5 4x 108

-70

-60

-50

-40

-30

-20

-10

0

10

Frequency

Spec

trum

(dB)

Equalized Signal

Residual Echo




NEXT ImpairmentNEXT Impairment-- After CancellationAfter Cancellation

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

x 108

-140

-120

-100

-80

-60

-40

-20

0

20

Frequency

Spe

ctru

m (d

B)

Rx Next(3)

Cancelled Next(3)

4.58

(b)


a b

0 0.5 1 1.5 2 2.5 3 3.5 4x 10

-140

-120

-100

-80

-60

-40

-20

0

20

Frequency

Spec

trum

(dB)

Rx far end signal

Rx Next(3)

(a)


NEXT ImpairmentNEXT Impairment-- SNR @ DetectorSNR @ Detector


0 0.5 1 1.5 2 2.5 3 3.5 4x 10

8

-70

-60

-50

-40

-30

-20

-10

0

10

Frequency

Spec

trum

(dB)

Equalized Signal

Residual Next(3)

Cat 5e cable



FEXT ImpairmentFEXT Impairment-- After CancellationAfter CancellationCat 5e cable

(a) (b)

a b



FEXT ImpairmentFEXT Impairment-- SNR @ DetectorSNR @ Detector




Total Total Slicer Slicer SNRSNR

Tx MAG MAG Rx ENX EQCat 5e cable

0 0.5 1 1.5 2 2.5 3 3.5 4x 10

8

-60

-50

-40

-30

-20

-10

0

10

Frequency

Spec

trum

(dB)

Equalized Signal

Total Noise

Total Noise Power Goal (-25.3) • FFE scales to produce unit variance hard decisions


Eye DiagramEye Diagram

Slicer input, including all noise sources vs. time

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000-2

-1.5

-1

-0.5

0

0.5

1

1.5

2


Sequenced StartupSequenced StartupN E, P F DONE

DONEFE, TNSLAVE

MASTER

N = ECHO/NEXT Canceller Convergence T = Tim ing AcquisitionP = Phase Adjustment

F = FEXT Canceller ConvergenceE = Equalizer Convergence


Summary: Realizing 10GBASESummary: Realizing 10GBASE--TT

• Careful attention to media characterization beyond 100MHz

• Evolution of 1000BASE-T

• Modern signal processing methods

• Feasible CMOS realizations of digital & analog circuits

• Q&A

SolarFlare 10GBASE-T Tutorial Nov 02€¦ · SolarFlare Communications 10GBASE-T IEEE Tutorial,...

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