DMT-VDSL Proposal Page 1Ethernet in the First Mile

Ethernet over VDSL

DMT Concepts and Advantages

IEEE 802.3ah Ethernet in the First Mile

Saint Louis, March 11-14 2002

DMT-VDSL Proposal Page 2Ethernet in the First Mile

Supporters

� Michael Beck, Alcatel

� Behrooz Rezvani, Ikanos

� Christophe Del-Toso, ST Microelectronics

� Sedat Oelcer, IBM

� Tariq Haddad, Zarlink

� Massimo Sorbara, GlobespanVirata

� Doug Artman, Texas Instruments

DMT-VDSL Proposal Page 3Ethernet in the First Mile

Overview

� Ethernet over VDSL for EFM over Point-to-Point Copper� DMT Concepts

� Modulation Technique� Windowing, RFI Canceling� Digital Duplexing

� Specification of DMT-VDSL� Advantages of DMT-VDSL

� RFI Robustness� EMC Friendly� Spectral Flexibility� PSD Control

� Availability of DMT-VDSL� Possible Additions to DMT-VDSL� Conclusions

DMT-VDSL Proposal Page 4Ethernet in the First Mile

EFM over Point-to-Point Copper Ethernet over VDSL

� This line code proposal should be seen as a proposal to further narrow down the existing Ethernet over VDSL baseline.

MAC Control (Optional)

MAC – Media Access Control

Reconciliation

Ethernet-over-VDSL AL

PMS-TC

PMD

MII �

PTM-TC

MDI �voice grade Cu

PCS �

PMA �

PMD �From existing DMT-VDSL standards

TO BE DEFINED

From G.993.1/H

DMT-VDSL Proposal Page 5Ethernet in the First Mile

VDSL-DMT ConceptsModulation Technique

IFFT

ADCFFT

Receiver

Transmitter

TXDataRXData

Extract Cyclic Prefix

CopperPair

××××SI

PO

FEQ

+ R

otor

Dem

appe

r

PISO

Hybrid &

splitter

PISO

Map

per

SIPO DAC

Windowing

Folding

RFI

can

celle

r

Driver××××

WindowingR

otor

Cyclic Prefix

LPF

AGC LPF

FDD DMT VDSL

DMT-VDSL Proposal Page 6Ethernet in the First Mile

DAC

S/P

FFT

FEQ

IFFT P/S

0

Tx clock

Discreteequivalent

channel

Rx clock

p(t)

Tx filter Channel Rx filter

ch(t) r(t) ADC

DMT ConceptsModulation Technique

DMT-VDSL Proposal Page 7Ethernet in the First Mile

DMT ConceptsModulation Technique

� DMT is similar to OFDM (as used in 802.11a, DAB, DVB)� ADSL compatible tone spacing (4.3125 kHz)� 12 MHz bandwidth, as specified in ITU-T

POTSfrequency

psdQAM-modulatedsubchannel (tone) individually optimized as a function of impairments

DMT-VDSL Proposal Page 8Ethernet in the First Mile

� constellation size and power of each tone are optimized in function of loop attenuation and noise environment

� optional rate adaptation at startup to provide maximum rate over given loop

� optional dynamic rate adaptation to track variations in loop attenuation or noise environment

� optional power boost on long lines

� power reduction on short lines (politeness)

� optional spectral shaping (including tone masking)

DMT ConceptsBit Loading

DMT-VDSL Proposal Page 9Ethernet in the First Mile

1 0

1 3

1 6

1 9

2 2

2 5

2 8

- 3

- 2

- 1

0

1

2

3

4

SNR

gi

bi=4

bi=3

bi=2

bi=1

bi=5

)arg

.1(log 2 emgainSNRbi γ

+=Target Bit error rate= 10-7

DMT ConceptsBit Loading

DMT-VDSL Proposal Page 10Ethernet in the First Mile

DMT ConceptsWindowing

CP CSFFT window

windowingat receiver

windowingat transmitter

DMT symbol duration

DMT-VDSL Proposal Page 11Ethernet in the First Mile

� Windowing at the transmitter: � Reduces frequency domain sidelobes

�Reduces the out of band power of the NEXT signal

�Allows for digital duplexing

�Guarantees spectral compatibility with other services

DMT ConceptsWindowing (transmitter)

DMT-VDSL Proposal Page 12Ethernet in the First Mile

DMT ConceptsNEXT with/without Windowing

DMT-VDSL Proposal Page 13Ethernet in the First Mile

DMT ConceptsWindowing (receiver)

� Windowing at the receiver :

� Reduces Inter Symbol Interference (ISI)

� Reduces the susceptibility to RFI

DMT-VDSL Proposal Page 14Ethernet in the First Mile

� Interferer: � 4 kHz wide single side-band signal� AM modulated with Gaussian noise

-120

-100

-80

-60

-40

-20

0

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250

tone index

mag

nitu

de in

dB

residual error basic DMT (rectangular window)

windowing

Tone index

Windowing

Mag

nitu

de in

dB

Basic DMT (rectangular window)

Residual error

DMT ConceptsWindowing (receiver) and RFI Canceling

DMT-VDSL Proposal Page 15Ethernet in the First Mile

DMT Concepts Digital Duplexing

prefix (CP)

suffix (CS)

FFT-size

NT Tx

LT Rxuseful

LT Tx

time

CS > propagation delay

LT Rx FFT-window

1 symbolpropagation delay

LT Rxecho

echo

DMT-VDSL Proposal Page 16Ethernet in the First Mile

Digital DuplexingSingle Solution Supporting Multiple Frequency Plans

down up updown

� plan 997 (ETSI + ITU-T) - optimized for symmetry

0.138 3.0 5.1 7.05 12.0 MHz

down up updown

� plan 998 (ETSI + T1E1 + ITU-T) - optimized for asymmetry

0.138 3.75 5.2 8.5 12.0 MHz

ADSL

0.138 1.1 MHz

down up updown

� flexible plan Fx (ITU-T)

0.138 3.752.5 Fx 12.0 MHz

DMT-VDSL Proposal Page 17Ethernet in the First Mile

Specification of DMT-VDSL

� DMT-VDSL standards are available:

� Very-High-Speed Digital Subscriber Lines (VDSL) Metallic Interface, Part 3: Technical specification of Multi-Carrier Modulation (MCM) Transceiver, ANSI, T1E1.4/01-013R2,Draft Specification.

� Transmission and Multiplexing (TM); Access transmission systems on metallic access cables; Very High speed Digital Subscriber Line (VDSL); Part 2: Transceiver specification, ref :ETSI, TS 101 270-2.

� DMT is also the line code of ADSL (standardized in ETSI, T1E1 and ITU-T) and G.Lite (ITU-T).

DMT-VDSL Proposal Page 18Ethernet in the First Mile

Advantages of DMT-VDSL

POTSfrequency

psd

DMT-VDSL Proposal Page 19Ethernet in the First Mile

unused tones

flexible carrier allocation to up- or downstream

POTSfrequency

psd

psd optimizedon tone per tone basis

� digital duplexing – different spectral plans with same hardware� easy spectral shaping

� ADSL/VDSL co-existence/co-location

� upstream power back-off� prevent radio ingress/egress (HAM radio)

Advantages of DMT-VDSLSpectral Flexibility

DMT-VDSL Proposal Page 20Ethernet in the First Mile

Advantages of DMT-VDSLSpectral Flexibility

� Three existing bandplans for public networks can be supported by the same hardware (the IFFT/FFT performs the filtering).

� New bandplans may be defined to suit specific requirements:

� Improved symmetry in private networks

� Improved spectral compatibility with legacy in-building networks (HPNA, 10/100BASE-T, …).

DMT-VDSL Proposal Page 21Ethernet in the First Mile

Advantages of DMTPSD Flexibility

� Upstream Power Back-Off:

� Standard UPBO requires shaped PSDs

� Improved Spectral Compatibility (fine granularity)

� w.r.t. other DSLs

� w.r.t. legacy in-building services

DMT-VDSL Proposal Page 22Ethernet in the First Mile

The flexibility of DMT modems is impressive. We can even draw pictures on the spectrum analyzer !

Confidential

Advantages of DMTPSD Flexibility

DMT-VDSL Proposal Page 23Ethernet in the First Mile

Advantages of DMTProven Technology

� DMT adapts itself to all line and noise conditions.

� DMT is the dominant line code in deployed DSL systems. ADSL has millions of lines active in the field.

� DMT-VDSL is available today.

DMT-VDSL Proposal Page 24Ethernet in the First Mile

Advantages of DMT-VDSLSimilarity between ADSL and VDSL

� DMT is the line code used by ADSL.

� DMT-VDSL hardware can be designed to be backward compatible with ADSL.

� DMT-VDSL can be used to create a scalable multi-mode system as described in nov01/del-toso_1_1101.pdf .

DMT-VDSL Proposal Page 25Ethernet in the First Mile

Advantages of DMTRFI Overview

E-field Types of interferers :a AM broadcast

(MW and SW)a Amateurs radio bands

(HAM radio)a Public safety & distress

bands

Common mode to differential mode conversion

Ingress Egress

Vcm

Vd

E-field

Vcm

Vd

E’-field

DMT-VDSL Proposal Page 26Ethernet in the First Mile

Advantages of DMTRFI Robustness

Effect of RFI on 1 km 24AWG loop

0

20

40

60

0 10Frequency in MHz

SNR

in d

B

No RFI1 RFI -20dBm @ 1.96 MHz1 RFI -20dBm @ 3.51 MHz2 RFIs -25dBm2 RFIs without cancellation

DMT-VDSL Proposal Page 27Ethernet in the First Mile

Possible Additions to DMT-VDSL

� New band plans (e.g. use of extended optional upstream band to provide more symmetry)

� Alternative Power Back-Off

� Advanced Coding Schemes

DMT-VDSL Proposal Page 28Ethernet in the First Mile

Availability of DMT-VDSL

� Multiple vendors have DMT-VDSL silicon on the market today.

� Several other vendors will have DMT-VDSL silicon on the market by end of 2002.

� Five of these have declared their intention to provide interoperable systems by end of 2002.

DMT-VDSL Proposal Page 29Ethernet in the First Mile

Conclusions

� DMT-VDSL is well suited for use in EFM/Copper:

� Frequency plan flexibility thanks to digital duplexing.

� Flexible PSDs thanks to IFFT based modulation.

� Similar architecture as ADSL allows for backward compatibility with this very successful technology.

� DMT-VDSL is fully standardized in ETSI and T1E1.4.

� Standard compliant transceiver chipsets are available from multiple vendors.