future challenges for dsl systems · xdsl deployment scenarios central office f/o feed dslam...

Future Challenges for DSL Systems

Dr. Axel Clausen

Copyright © Infineon Technologies 2008. All rights reserved. 2009/09/29

Infineon Wireline Communication

! ADSL/VDSL! Network

Processor! VoIP! Ethernet! WLAN! DECT modems

Carrier Access(CA)

Voice Infrastructure

(VI)Customer Premises

Equipment(CPE)

! ADSL/SHDSL/VDSL! Access Network Processors! Voice/VoIP

! T/E Carrier! HDLC! ATM/IP! ISDN! DECT

DSL CPEHome Network

IP-DSLAM/ MSAN

Cellular Backhaul

2009/09/29 Copyright © Infineon Technologies 2008. All rights reserved.

Broadband Infrastructure Drivers for 2009/10

IPTV/Video enters growth stage1

NGN deployments starting2

3 Mobile broadband drives investment in backhaul network

Broadband white spots drive investment for rural areas

4


Next Generation Network (NGN)

DSLAM

INTERNET

Customer Premises

Splitter

CPE

Copper Line

VOICE

TV

Next Generation Network (NGN)

All-IP

" Drivers for Telecom Operators:

# Reduction of network elements

# Real estate and OPEX

# Flexible service bundling

" Deployment Concepts:

# All-Digital DSL + multiservice CPE

# FTTx + multiservice MDU/ONT

" Operator Requirements:

# Maintain Quality-of-Service level

# Reuse of network test and customer support infrastructure

" Technology Requirements:

# Transition to VDSL2 / GPON

# Integrated MELT + DSL

# Decentralized Voice aggregation

Key Elements of NGN

DSLAM

INTERNET

Customer Premises

Splitter

CPE

Copper Line

Splitter

VOICE

TVCable/Satellite/DVB-T

POTS

Traditional Network Architecture

ATM


Future Challenges for DSL Systems …

Line Management /

Testing

reduced

Power Consumption

increased

Stability

increased

Datarate


Agenda

" Introduction xDSL

" Datarate Increase – Vectoring

" Stability Improvement – Retransmission / Virtual Noise

" Line Testing – Metallic Access Line Testing (MELT)

" Power Consumption


Introduction


xDSL Technology Overview

" DS data rate

" US data rate

" Typ. loop length

" Layer 2 Transp.

" Typ. Deployment

" Max. Signal BW

" Modulation DS

" Modulation US

" Transmit Power

" Coding

" POTS / ISDN

ADSL /ADSL2

16 Mbps

1~3 Mbps

12…20 kFt

ATM(Eth)

Ex, Cab

1.1 MHz

DMT 256

DMT 32/64

20.5 dBm

RS/Trellis

Overlayed/Splitter

100 Mbps

100 Mbps

3...12 kFt

Eth, (ATM)

Ex, Cab, Bl.

30 MHz

DMT 4096

DMT 4096

20.5 dBm

RS/Trellis

Overlayed/ Splitter

VDSL2

5.7 Mbps

5.7 Mbps

24 kFt

Eth,ATM,TDM

Ex

1.4 MHz

PAM 16/32

PAM 16/32

14.5 dBm

Trellis

Inband

SHDSL ADSL2+

28 Mbps

1~3 Mbps

12…20 kFt

ATM(Eth)

Ex, Cab

2.2 MHz

DMT 512

DMT 32/64

20.5 dBm

RS/Trellis

Overlayed/Splitter


Insertion loss of Twisted-Pair Cable

0 1 2-60

-50

-40

-30

-20

-10

0

f / MHz

dB

0 5 10 15 20 25 30-120

-100

-80

-60

-40

-20

0TP100 (-) TP1 (- -)

f / MHz

dB

0.2 km0.5 km1.0 km1.5 km2.0 km

kmMHzdB 18),(aTP100

lflf ⋅⋅≈

Cable: AWG-26 (0.4 mm)


VDSL2 Downstream PerformanceMbps 8b=998-M2xB, 17a=998-M2xB+DS 12…17MHz

8b DS WN17a DS WN8b DS 12 Self17a DS 12 Self

500m 1000m

2000m

8,4Mbps

160,00

140,00

120,00

100,00

80,00

60,0050MBit/s

40,00

24MBit/s20,00

0,002743 m305 610 914 1219 1524 1829 2133 24380

AWGN @ -140 dBm/Hz


VDSL2 Upstream PerformanceMbps 8b=998-M2xB, 17a=998-M2xB+DS 12…17MHz

305 610 914 1219 1524 1829 2133 2438 2743 m

20,00

40,00

8b US WN17a US WN8b US 12 Self17a US 12 Self

500m

20MBit/s

1000m

2000m

0,75Mbps

70,00

60,00

50,00

30,00

6MBit/s 10,00

0,000

AWGN @ -140 dBm/Hz


xDSL Deployment Scenarios

CentralOffice

F/O FeedDSLAM

Residential

Business

Residential

ONTF/O

FTTC

F/O

Business / Residential /

MxU

Cabinet Residential

ONU

F/O

ONT

F/O

NT

NT

MxU

FTTB

FTTCab

FTTEx

VDSL2

xDSL

xDSL

VDSL2


Down 1 Up 1 Down 2 Up 2Up

0ADSL

ADSL2+

Down / UpDown 2

25 138 3000 5100 12000

f (kHz)

30000

-60

-50

-40

Deployment from Cabinet / MDU

Deployment from Exchange/ Cabinet/ FTTN

7050 880

PS

D (d

Bm

/Hz)

ADSL / VDSL2 Transmit PSD VDSL2

Profile 12 ProfilVDSL2

e 17VDSL2

Profile 30VDSL2 � Profile 8

176000

" All DMT based xDSL flavours use Frequency Division Duplexing

" VDSL2 uses several profiles depending on deployment scenario


Mixed Deployment Central Office / Cabinet

For the ADSL service, VDSL2 looks like „just another ADSL“► powerful PSD Shaping in 138kHz...2.2MHz range► crosstalk of VDSL2 = crosstalk of ADSL

+⋅+−≤

)()(

1log10)()()( 10refdist

refmainmainADSLDPBO fa

fafafPSDfPSD

�boost mode�

ADSL Data Rates not affected by VDSL2 deployment

VDSLCabinet

VDSLCPE

ADSLCPE

ADSLCO

USDS

2.2MHz 2.2MHz

DSUS

2.2MHz

DSUS

FEXT

2.2MHz

US DS

2.2MHz

US


Reference System: 72 Channel ADSL2+ IP-DSLAM

Digital Frontend

PCB layers: 8No. of components: 4470 No. of pins: 24176No. of nets: 4237No. of through holes: 5734Min. trace width: 120 umTotal trace length: 192.6 m

Network Processor

Analog Frontend


Datarate Increase: Vectoring


Scenario

" Telephone lines are deployed in large cable bundles

" Crosstalk is the dominant noise source in most deployment scenarios

" Crosstalk can be distinguished:

# NEXT – Near End Crosstalk

# FEXT – Far End Crosstalk

# Self and Alien Crosstalk


Measured Crosstalk Channel

104

105

106

107

-160

-140

-120

-100

-80

-60

-40

-20

0Measured single channel and crosstalk channel transfer functions

f [Hz]

|Hij|2 [d

B]

Direct channel |Hii|2

104

105

106

107

-160

-140

-120

-100

-80

-60

-40

-20

0Measured single channel and crosstalk channel transfer functions

f [Hz]

|Hij|2 [d

B]

Direct channel |Hii|2

17.6 MHz

Crosstalk channels |Hij|2, ≠i j

Parameter:

Number of cables: 20Cable length: 1 kmDiameter: 0.4 mm

FEXT is the dominant crosstalk for ADSL and VDSL2 systems


common processing of several lines with the purpose of cancelling self-crosstalk

Definition:

1. NEXT Avoidance

# VDSL2 uses Frequency Division Duplexing

# Synchronized Digital Duplexing (same Cyclic Extension, Clock, Timing Advance and DMT symbolstart for all lines in a loop)

2. FEXT Cancellation:

# estimation of FEXT channels; single pointof processing for all channels required

# upstream: CO-only realization; cancellation

# downstream: communication of error information from CPE to CO; pre-distortion

Two-step Approach:

Vectoring – Basic Principles


Infineon Vectoring Solution

" Data is passed in the frequency domain (before IFFT) to the Vector Engine

" FEXT Precoder performs linear precoding

" In upstream, data is passed after the FFT to the Vector Engine

" Vinax Data Frontend (DFE) performs VDSL2 Processing

" Vectoring Engine performs Crosstalk-Cancellation

" Control- / Synchronization split between Vectoring Engine / Vinax

" Maximum Number of Lines only limited by Vectoring Engine

Vectoring Engine

Highspeed IF

Highspeed IF

VINAX Rev. 2/3

Highspeed IF

VINAX DFE

Analog Frontend / LineSystem

Interface(Backplane)

Mapper #0

FEXTPrecoder

IFFT #0

IFFT #1

IFFT #N

Mapper #1

Mapper #N

Vector Engine

VINAXDatapump

VINAXDatapump

Vectoring Solution: System Partioning:


Infineon Vectoring Solution (Demonstrator)

DSP Module

Vectoring EvaluationBoard

Vectoring Adapter Board Rev1.3

Vectoring Controller Board with FPGA

Demonstration System based on actual IFX VDSL2 Chipset available


Performance – Downstream Measurement

" 16 Channel Vector System @ 300m

" Datarates:

# single line: 103.9 Mbit/s

# Vectoring: 100.8 Mbit/s

# w/o Vectoring: 47.9 Mbit/s

0 500 1000 1500 2000 2500 3000 3500 4000 45000

10

20

30

40

50

60

70SNR Plot - Line # 5

SN

R [d

B]

Toneindex

single linewith Vectoringw/o Vectoring

Datarate improvement of more than 100% achievable


Performance – Upstream Measurements Average SNR improvement over all used carriers

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12Channel

dB

Test Conditions:

" 12 VDSL2 channels in Showtime

" VDSL2, Profile 17a + US0

" 150m PE0.35 cable @ DTAG Labs

Datarate improvement over all used carriers

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12Channel

data

rate

[Mbp

s]

with DSMw/o DSM

US SNR measurements, 150m, 0.35mm

0

10

20

30

40

50

60

0 5 000 10 000Carrier [kHz]

SNR

[dB

]

Ch1 of 12 Ch with DSMCh1 of 12 Ch w/o DSMCh1 only


Standardization

" Consent for ITU Standard g.vector is planned for next week

" Comment resolution of standard will require some more month –expected publication: Spring / Summer 2010

Status:

" Crosstalk estimation based on pilot symbol sequences

" Joining Procedure:

# Allows seamless joining of new line to an active vectoring group

" Backchannel Definition:

# Quantized slicer errors of pilot symbols are reported from CPE to CO

Major Agreements:


Challenges for commercial deployments …

" Cable bundles consists of 100 to 500 lines – depending on operator / deployment scenario

" Operator are not able to sort lines according to crosstalk

" Lines are connected to several linecards – data needs to be exchanged between linecards

" Alien crosstalk or non-vectored systems will reduce performance increase

Network Topology:Coefficient Memory Size (Profile 17)

0,00

100,00

200,00

300,00

400,00

500,00

600,00

16 32 48 64 80 96 192

Number of Lines

Coef

ficie

nt M

emor

y [M

Byt

es]

MAC Operations

0

100

200

300

400

500

600

700

16 32 48 64 80 96 192

Number of Lines

GM

ACs " Required computational and memory

resources increase quadratic with the number of supported lines

" Coefficient memory size and memory access becomes the main bottleneck of an architecture

Complexity:


Smoothness of Crosstalk Coefficients

" Crosstalk Coefficients are slowly changing (“smooth”) over frequency

" Smoothness will be utilized for large vectored systems:

# Coefficient Memory:

Storing coefficient matrices for every nth carrier - other coefficient matrices will be interpolated

# Backchannel:

Slicer error values are only reported for every nth carrier

" Utilizing smoothness makes systems for more than 100 lines realistic

0 2 4 6 8 10 12 14 16-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1Crosstalk Coefficients (Victim #0, Disturber #1)

Frequency [MHz]

Nor

mal

ized

Am

plitu

de

real partimaginary part


Robustness Increase: Virtual Noise / Retransmission


Triple-Play Requirements for DSL

" Video / IPTV

# High Data Rate (e.g. HDTV); always guaranteed

# Low Packet-Loss, < 1 / hour

# Small Error Rate

# No retrains

" VoIP

# Low Rate; always guaranteed

# Low Jitter, Low Delay

# No retrains

" Internet Access

# High Data Rate (variable rate acceptable)

# Low to medium delay (gaming)

Video and VoIP applications require higher robustness of the DSL link


Noise Sources" Stationary Noise

# Background Noise

# Crosstalk

" Radio Frequency

Ingress

# AM / Ham Radio ingress

" Impulse Noise

# SHINE – Single High Impulse Noise Event (up to 10 ms):

# REIN – Repetitive Impulse Noise:Impulse Length Inter Arrival Time

protection by „Virtual Noise“

protection by „Retransmission“


Virtual Noise – Basic Idea …

SNR for Bitloading

Noise margin

Background Noise

Tx

Rx

Loop Attenuation

Frequency

Pow

er S

pect

ral D

ensi

ty

Starting Point:Static Noise

SNR for Bitloading

Noise margin

Tx

Rx

Loop Attenuation

Frequency

Pow

er S

pect

ral D

ensi

ty

Background Noise

Dynamic Noiseleading to Retrain

Dynamic Noise (RFI, �)

Frequency

SNR for Bitloading

Noise margin

Tx

Rx

Loop Attenuation

Pow

er S

pect

ral D

ensi

ty

VirtualNoise

Virtual Noise

Background Noise

Dynamic Noise (RFI, �)

Virtual Noise corresponds to frequency specific SNR Margin


Retransmission – basic idea …

¬ Retransmission: another tool for combating infrequent and long impulse noise (SHINE and PEIN)

CO Modem CPE Modem

Buffer-Size determined by► Data-Rate► Round-Trip Delay► Desired Level of Protection


Robustness Features of DSL Systems

11

10

9

8

7

6

5

4

3

2

1

#

complements interleaving/FEC for (REIN), SHINE, PEINRetransmission

Coexistance of VDSL2 and ADSL in same bundle; mixed CO-Cabinet deployments

Downstream PowerBack-Off (DPBO)

Similar Upstream-Rate for all CPEs regardless of loop length

Upstream PowerBack-Off (UPBO)

Mitigate RFI ingress and avoid egressRFI Notching and Mitigation

Change of Data-Rate and Framing / ILV parameters on-the fly as response to changing loop conditions

Online Reconfiguration (SRA...)

Survival of sudden noise without retrainSOS

Conservative bit-loading in expectation of future (virtual) noise sources

Virtual Noise

Doubles INP (alternatively: improves rate for same INP)Erasure Decoding

Better INP for higher Data-Rates/Delays, i.e.ADSL2+ 8ms, INP=16, 16 MBit/s

Extended Interleaving

Better INP for higher Data-Rates, i.e.ADSL2+ 8ms, INP=16, 11 MBit/s

Extended Framing

Forward Error Correction provides baseline INP, i.e. ADSL2+ 8ms, INP=16, 1.5 MBit/s

General Convolutional Interleaving + Reed Solomon Coding

BenefitMeasure


Line Testing


Line Testing Overview

" Possible Tests:

# Detection and Measurement of Foreign Voltages

# Detection of Unbalance about Earth (Resistive Fault to Ground/Battery, Bad isolation Resistance, Capacitive Unbalance)

# Detection of Nonlinear Elements (PPA, Receiver Offhook, xDSL Signature)

# Measurement behind a Splitter (e.g. Ringer Load)

" Applications:

# Test electrical characteristics of line

SELT (Single Ended Line Test) MELT (Metallic Line Test)

" Possible Tests:

# Loop length

# Attenuation

# Achievable Bitrate

# Bridge tap presence and localization

# Quiet Line Noise

# Crosstalk estimation

# RFI Analysis

" Applications:

# Loop pre-qualification (no CPE required)


Evolution towards Next Generations Networks

IntegratedMELT

" On-chip line testing is going to replace MELT test heads

" With the transition towards a single NGN network (PSTN substitution) MELT needs to test, diagnose and locate line impairments on pure DSL lines

" SELT in combination with MELT could complete the line testing & monitoring function

New Test Methodology

DSLAM

AggregationNetwork

Customer Premises

Splitter

CPE

Customer ServiceTest Server, Database and Expert System

TODAYTOMORROW

Local Loop

MDF

…MELT Test

Heads

Splitter

PSTN (Voice)

DIV #

CPE

+ SELT


Efficiency Improvements with New Line Testing

DSLAM

AggregationNetwork

Customer Premises

Customer ServiceTest Server, Database and Expert System

Local Loop

MELT

MDF CPE

TOMORROW

+ SELT

" Same procedure and accuracy in NGN to test, diagnose and locate line impairments

" One line testing for ADSL, VDSL, SHDSL & Voice

" Frequent and parallel testing possible

" Saves splitters, MELT test heads, CO/RT space

" Line testing & wetting with no DSL disturbance

" Reuse of expert system without changes to customer service operations

Benefit


IFX Integrated Line Testing for All Digital Loop

InfineonxDSLAFE Infineon

LD

LD

InfineonLD

LD

MELT

SELT&DELT

InfineonVINETICTM-LTCSmart SLIC®-T

Infineon

MU

X

xDSLAFE

xDSLDFE

Perfect solution in terms of cost, density and reliability

" MELT function will be performed by a chipset solution of a Smart SLIC with inbuilt multiplexer and a Line Test Controller (VINETIC-LTC)

" VINETIC-LTC is able to control up to 128 xDSL ports

" Full MELT capabilities, integrated with DSL on one card at low cost

" Depending on configuration several ports can be tested simultaneously

" One line testing API for ADSL, VDSL, SHDSL

" Wetting current parallel to DSL

" Line testing & wetting with no DSL disturbance

" No mechanical components (relays, switching matrix etc.)

" Minor density impact

Benefit


Power Reduction


Motivation

" Increasing number of customers use DSL for “triple play”

" Consequences:

# Higher bandwidth needed to support new services

# “always-on” of equipment is required for some services

Customer:

" Telecom Italia:

# requires more than 2 TWh per year

# roughly 1% of Italia's energy demand

# 2nd largest energy consumer (next to Italian railway)

" European Union:

# expects consumption of 50 TWh in 2015 for Broadband Equipment (corresponds to four modern nuclear power plants)

Operator:

Reduction of power consumption has high priority for operator, system vendor, and chip industry


European Union – Code of Conduct

CoC Version from July 2007" Updated version of CoC

# Technical lead: Swisscom & TI

# Infineon actively involved and contributing

" Status

# in force (1.1.2009)

" References ETSI TS 102 533 for measurement conditions

V3 from

Nov 18th 2008

CoC V3 from 11/08, DSL-CO


Power Consumption

" Linedriver:

# Proper choic of amplifier class can reduce power consumption significantly

# ADSL (Source: Scott Wurcer, ADI):

¬ Class A/B: 710 mW

¬ Class G: 485 mW

¬ Class H: 410 mW

" Semiconductor Technology:

Producing chips in most advanced technology (45nm, 65nm instead of 90nm, 130nm)

" Other topics:

# A/D and D/A Converter

# Digital Filter (Highpass / Interpolation / Decimation) Concepts

Source: Huawei, ITU Contribution C832, Jan. 08

0

500

1000

1500

2000

2500

ADSL VDSL2, Profile 17 VDSL2, Profile 8

Pow

er C

onsu

mpt

ion

[mW

]

Datapump + AFE [mW]

Line Driver[mW]

Options for Power ReductionCoC V3

Limit 2011


Low Power Mode

" VDSL2 has no standardized low power mode

" ADSL low power mode is not widely used because of fluctuating crosstalk

Current Status:

" Several operator and chip manufacturer push for an efficient low power mode

" Debate ongoing about required standard changes and power saving potential of different options

Current Activities:


DSL System – today …

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

IP-TVFile Download Internet

0.6 W

0.8 W

1.0 W

1.2 W

1.4 W

0 W

Constant Power-

Consumption regardless of

Traffic!

DATADATA DATADATA DATADATAIDLEIDLEIDLEIDLE

Signal:


Vision …

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

IP-TV

DATADATA DATADATA DATADATAIDLEIDLEIDLEIDLEDATADATA DATADATA DATADATAIDLEIDLEIDLEIDLE

Signal:

File Download

Internet

0.6 W

0.8 W

1.0 W

1.2 W

1.4 W

0 W

Low Power Mode

Low PowerMode

Power-Consumption should adapt to Data Traffic!


Conclusions


Future Challenges for DSL Systems …

Line Management /

Testing

- MELT / SELT

Power Reduction Increased Stability

- Virtual Noise

- Retransmission

Increased Datarate

- Vectoring

… several challenges are addressed more innovations needed to fulfill all customer needs /

requirements

future challenges for dsl systems · xdsl deployment scenarios central office f/o feed dslam...

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