End to End xDSL Technology

Doğan ÖZMENOct, 2009

ISTANBUL

Introduction

ISTANBUL

3

POTS vs non-POTS modem communication

DSL technologies use other frequencies outside the voice band tomodulate information on your local telephone line.ADSL provides you a high speed connection on your local line.

Frequency (fHz)300Hz 3400Hz

Other frequencies used by DSL technologies:

ADSL > up to 1,1MHz

ADSL2+> up to 2.2 Mhz

Voice band

used by

POTS modems

(V.32, V.90, …)

Spectrum of local telephone line

4

Solutions offered by ADSL

PROBLEM

Bitrate of analogue modem limited to 64 kb/s

PSTN not suited for high speed data traffic

ADSL - modem

Redirection of data traffic to specific

network

SOLUTION

5

ADSL

Local exchange

Unshielded Twisted Pair (UTP)

up to 8,1 Mb/sDownstream

ADSL : Digital Subscriber Line

up to 800 kb/sUpstream

Asymmetric

0 - 5,4 km

Customer Premises

6

ADSL spectrum

Upstream DownstreamPOTS

300Hz

3400Hz

1,1 MHz30kHz 125 kHz 164 kHz

ADSL uses frequencies on the local line up to 1,1MHz.These frequencies do NOT overlap with the POTS band and is so allowing simultaneous voice communication.

ADSL

POTS

Copperwire

±8Mbps

±800kbps

138 kHz

7

POTS splitter (PS)

The lower frequencies used by ADSL can disturb the audible spectrum and need to be filtered out towards the telephone set.With on-hook and off-hook situations of your telephone the line impedance changes which will have an impact on the ADSL modem communication.

FILTER

SPLITTER

& UTP to LEX

8

Voice / Data over DSL ?

DataStandard ADSL

POTSTelephone Line

ADSLADSL CPE

PS

xDSL suitable for all types of communication (voice&data&video)

9

E2E xDSL Technology

PSTN

BASMPLS

ISP/Internet

IPPOTS,ISDN

ANT

Residential

VOICE

ADSL modem to modem

PVC Connection

E2E data connection

DATA

LTNT

7302ISAM

10

E2E DSL

Internet Access Provider

PSTN

BASMPLS

ISP/Internet

POTS,ISDN

ANT

Residential

ADSL

TELECOM OPERATOR

Internet Service Provider

Mevcut a-b hattı

IP

7302ISAM

ATM

ADSL modem to modem

ATM connection

E2E data connection

MPLS connection

11

xDSL

� ADSL

� first approach to deliver high bandwidth over existing UTP

� killer technology for residential internet access

� SHDSL

� symmetrical high bandwidth service mostly for business users

� VDSL

� very high speed bandwidth for BB entertainment (video)

� can work both in symmetrical & asymmetrical mode

� FTTU

� fiber to the user = optical fiber all the way to the customer.

12

SHDSL

� Single-pair High speed DSL

� 192 kbps … 2.312 Mbps bidirectional (Single pair UTP)

� 384 kbps … 4.624 Mbps bidirectional (Double pair UTP)

� IMA support via SMLT board : combine 8 SHDSL lines links into one virtual link (8 x 2,312 Mbps)

� Limited in distance

� max 2,5 km loops

� No POTS/ISDN service

� SHDSL uses the entire frequency range

� no splitters required

Standards

14

ANSI standards

ANSI T1.413 Issue 1 1995First ADSL specification out in 1995 was STM based and not clearly build

ANSI T1.413 Issue 2 1998Second ADSL specification which was mostly driven by Alcatel and ATM based as is used today.

15

ITU-T standards

ITU-T G.dmt or G992.1Specification by ITU-T which is based on the ANSI T1.413 issue2 standard plus an extra handshaking protocol.Annex A: specifies operation above the POTS bandAnnex B: specifies operation above the ISDN band

16

Spectrum

UP DOWN

PO

TS

UP DOWNISDN

1,1MHz

1,1MHz30kHz

138kHz

G.dmt Annex A

G.dmt Annex B

138kHz

17

Shannon-Hartley : Capacity vs. Distance

km

1 2 3 4 5 6UTP Cable length

CapacityMb/s

25

20

15

10

5

Shannon Hartley capacityADSL

8,1 Mb/s

2 Mb/s

6 Mb/s

Modulation

19

Quadrature Amplitude Modulation (QAM)

Transmitted data = Constellation

2

3

1

0

-1

-2

-3

0,5 1 1,5 2 2,5 3

1111 1001

0000

00110111 0101 0001

0110

1110

1101 1011

1100 1000 1010

0100 0010

1001 0000 1111

Symbol length (Ts)

Symbol is represented by a variation of amplitude & phase for a particular frequencyy = A . sin (2ππππ f.t + ϕϕϕϕ)

4 bits/symbol

>> QAM-16

t

A

ϕϕϕϕA

20

QAM vs. SNR

Bits/symbolQAM Signal/Noise ratio (dB) for

BER<10-7

4 QAM-16 21,8

6 QAM-64 27,8

8 QAM-256 33,8

9 QAM-512 36,8

10 QAM-1.024 39,9

12 QAM-4.096 45,9

14 QAM-16.384 51,9

table can be used in 2 ways : (a) what is minimum required SNR to modulate N bits on a carrier(b) how many bits can be modulated given a SNR of Y dB

21

Discrete Multi Tone (DMT)

� For ADSL, multiple carrier frequencies are modulated on the 1 ADSL line using QAM.

� These frequencies are equally spaced and for each carrier the SNR is measured to determine the maximum achievable QAM.

� The sum of all frequencies is put on the line

� This concept is called Discrete Multi Tone (DMT)

22

Discrete Multi Tone example

Ts (Symbol Time)

QAM-4 1

QAM-16 2

QAM-4 3

ΣΣΣΣ = DMT

1 DMT Symbol

23

ƒƒƒƒ1

ƒƒƒƒ2

ƒƒƒƒi

ƒƒƒƒ255

ƒƒƒƒj

10101100101111101010110010111110

1010001010110010100010101100

11111111

1010

010010

1011010110

1010

ΣΣΣΣ

Modem ADSLModem ADSL

ƒƒƒƒk

ƒƒƒƒm

ƒƒƒƒ...

ƒƒƒƒ...

QAM-4

QAM-16

QAM-8

QAM-4

QAM-32

RRÉÉCCCCEEPPTTIIOONN

EEMMIISSSSIIOONN

Symbol

(Discrete Multi Tone)

24

DMT and ADSL

� The spectrum used for ADSL is divided into 255 carriers.

� each carrier is situated at n x 4,3125 kHz

� For the upstream direction, carriers 7 to 29 are used

� For the downstream direction, carriers 38 to 255 are used

� On each carrier the SNR is measured and the QAM determined.

� minimum : QAM-4 2 bits/symbol

� maximum : QAM-16384 14 bits/symbol

� Symbol period for each carrier : 250 µs

25

Overview of the new standards

G.dmt = G.992.1 = current ADSL

G.dmt.bis = G.992.3 = second generation ADSL2

G.adslplus = ∆∆∆∆ on G.992.3 = ADSL2+

ITU-T

READSL= ∆∆∆∆ on G.992.3 = Reach Extended DSL

� G.dmt.bis = G992.3 = ADSL2

� performance : raising the bar

� loop diagnostics tools

� improved initialization & fast start-up

� power management improvements

� agreed Jan 2003

� G.adslplus = G992.5 = ADSL2+

� delta to ADSL2

� consent reached Jan 2003

� downstream bandwidth increase by doubling the frequency spectrum range up to 2,2 MHz

� at least 16Mbps should be supported

� READSL

� Reach Extended ADSL2

� target : 192 kbps DS - 96 kbps US on 6km 0,4mm loops

� consent targetted Sept 2003.

26

ANTCPE

Central OfficePSTN

WWW Datanetwork

LEX

7300/7301/7302

MDF

3400Hz 1,1 MHz30kHz

Up Down

138 kHz

POTS

300Hz

Customer Premises

voicedata/voice

BB Access Server

Asymmetric Digital Subscriber Line (ADSL) access

data

data

voice “splitter”

“splitter”

27

MDF cabling UD - upstream traffic

PSTNPSTNPSTNPSTN

MDF

data

voice

Customer PremisesEquipment

Central Office

data +

voice

voice

data

data

www

28

www

PSTNPSTNPSTNPSTN

MDF

voice

voice

data

data

data +

voice

Customer PremisesEquipment

Central Office

data

MDF cabling UD - downstream traffic

29

ASAM Equipment practice evolution

Standard Density

High Density

Ultra Density

Extreme Density

4 lines/board144 lines/rack

12 lines/board384 lines/rack

24 lines/board768 lines/rack

48 lines/board2,304 lines/rack

Flexible Density

48 lines/board864 lines/rack

30

ATM

WWW

IP/Eth

BTV

VoD

GigE

4 * E1E3

STM-1

STM-1STM-4

4 * E1E3

STM-1STM-4

ATM/SDH

7300 ASAM (R4)

7301 ASAM (R5)

BAS

ADSLSHDSLVDSL

ADSL2(+) …

7302 ISAM

7300/7301 ASAM

The 730x ASAM in the access network…

GigE