8/6/2019 Adsl Basic

1/24

8/6/2019 Adsl Basic

2/24

Introduction

ADSL is a form of DSL, a data communications

technology that enables faster data transmission over

copper telephone lines

ADSL is capable of providing up to 50 Mbps, and

supports voice, video and data.

ADSL is the #1 Broadband Choice in the World with over60% market share

ADSL is now available in every region of the world

8/6/2019 Adsl Basic

3/24

What does ADSL mean

Asymmetric - The data can flow faster in one directionthan the other. Data transmission has faster downstreamto the subscriber than upstream

Digital - No type of communication is transferred in ananalog method. All data is purely digital, and only at theend, modulated to be carried over the line.

SubscriberLine - The data is carried over a single twistedpair copper loop to the subscriber premises

8/6/2019 Adsl Basic

4/24

ADSL standards :ADSL standards :

Standard nameStandard name Common nameCommon name DownstreamDownstream

raterate

UpstreamUpstream

raterate

ITU G.992.1ITU G.992.1 ADSL (G.DMT) ADSL (G.DMT) 8 Mbit/s8 Mbit/s 1.0 Mbit/s1.0 Mbit/s

ITU G.992.2ITU G.992.2 ADSL Lite (G.Lite)ADSL Lite (G.Lite) 1.5 Mbit/s1.5 Mbit/s 0.5 Mbit/s0.5 Mbit/sITU G.992.3/4ITU G.992.3/4 ADSL2 ADSL2 12 Mbit/s12 Mbit/s 1.0 Mbit/s1.0 Mbit/s

ITU G.992.3/4 Annex JITU G.992.3/4 Annex J ADSL2 ADSL2 12 Mbit/s12 Mbit/s 3.5 Mbit/s3.5 Mbit/s

ITU G.992.3/4 Annex LITU G.992.3/4 Annex L RERE--ADSL2 ADSL2 5 Mbit/s5 Mbit/s 0.8 Mbit/s0.8 Mbit/s

ITU G.992.5ITU G.992.5 ADSL2+ ADSL2+ 24 Mbit/s24 Mbit/s 1.0 Mbit/s1.0 Mbit/s

ITU G.992.5 Annex LITU G.992.5 Annex L RERE--ADSL2+ ADSL2+ 24 Mbit/s24 Mbit/s 1.0 Mbit/s1.0 Mbit/s

ITU G.992.5 Annex MITU G.992.5 Annex M ADSL2+ ADSL2+ 28 Mbit/s28 Mbit/s 3.5 Mbit/s3.5 Mbit/s

8/6/2019 Adsl Basic

5/24

ISDN

ADSL

FTTx,

VDSL2,

ADSL2plus

Enhanced

Copper

Hybrid Fibre/Copper

Pure Fibre

ADSLSpeed Comparison

Voice band

Modem

FTTH

8/6/2019 Adsl Basic

6/24

ADSL Range

In general, the maximum range for DSL without a repeateris 5.5 km

As distance decreases toward the telephone companyoffice, the data rate increases

For larger distances, you may be able to have DSL if yourphone company has extended the local loop with optical

fiber cable

Data Rate Wire gauge Wire size Distance

1.5 or 2 Mbps 24 AWG 0.5 mm 5.5 km

1.5 or 2 Mbps 26 AWG 0.4 mm 4.6 km

6.1 Mbps 24 AWG 0.5 mm 3.7 km1.5 or 2 Mbps 26 AWG 0.4 mm 2.7

8/6/2019 Adsl Basic

7/24

ADSLSpeed Factors

The distance from the local exchange

The type and thickness of wires used

The number and type of joins in the wire

The proximity of the wire to other wires carrying ADSL,

ISDN and other non-voice signals

The proximity of the wires to radio transmitters.

8/6/2019 Adsl Basic

8/24

ADSL network components

The ADSL modem at the customer premises(ATU-R)

The modem of the central office (ATU-C)

DSL access multiplexed (DSLAM)

Broadband Access Server (BAS)

Splitter - an electronic low pass filter that separates the

analogue voice orISDN signal from ADSL data

frequencies DSLAM.

8/6/2019 Adsl Basic

9/24

ADSLLoopArchitecture

ISP

Central Office Subscriber premises

Voice Switch

DSL

8/6/2019 Adsl Basic

10/24

ADSL Requirements

Phone-line, activated by your phone company for ADSL

Filter to separate the phone signal from the Internet signal

ADSL modem

Subscription with an ISP supporting ADSL

8/6/2019 Adsl Basic

11/24

How does ADSL work ADSL exploits theADSL exploits the unused analogue bandwidthunused analogue bandwidth

available in the wiresavailable in the wires

ADSL works by using a frequency splitter device to split aADSL works by using a frequency splitter device to split a

traditional voice telephone line into two frequenciestraditional voice telephone line into two frequencies

4 25,875 138 1104 KHz

PSTNPSTN DownstreamDownstreamUpstreamUpstream

8/6/2019 Adsl Basic

12/24

ADSL Modulation

Modulation is the overlaying of information (or the signal)

onto an electronic or optical carrier waveform

There are two competing and incompatible standards formodulating the ADSL signal:

Carrier less Amplitude Phase (CAP)

Discrete Multi-Tone (DMT)

8/6/2019 Adsl Basic

13/24

Carrierless Amplitude Phase

Carrier less Amplitude Phase (CAP) is an encodingCarrier less Amplitude Phase (CAP) is an encoding

method that divides the signals into two distinct bands:method that divides the signals into two distinct bands:

1.1. The upstream data channel (to the service provider), which isThe upstream data channel (to the service provider), which is

carried in the band between 25 and 160kHzcarried in the band between 25 and 160kHz

1.1. The downstream data channel (to the user), which is carried inThe downstream data channel (to the user), which is carried in

the band from 200kHz to 1.1MHz .the band from 200kHz to 1.1MHz .

These channels are widely separated in order toThese channels are widely separated in order tominimize the possibility of interference between theminimize the possibility of interference between the

channels.channels.

8/6/2019 Adsl Basic

14/24

Discrete Multi-tone (DMT)

Discrete Multi-Tone (DMT) separates the DSL signal so

that the usable frequency range is separated into 256

channels of 4.3125kHz each.

DMT has 224 downstream frequency bins (or carriers)

and 32 upstream frequency bins.

DMT constantly shifts signals between different channelsto ensure that the best channels are used for transmission

and reception.

8/6/2019 Adsl Basic

15/24

The DMT frequency bands

Frequency Division Multiplexing (FDM)

Echo Cancellation

8/6/2019 Adsl Basic

16/24

Asynchronous Transfer ModeAsynchronous Transfer Mode

ATM is a connectionATM is a connection--orientated techniqueorientated technique

ATM provides cell sequence integrityATM provides cell sequence integrity

Cells are much smaller than standard packetCells are much smaller than standard packet--switchedswitched

networks (53 bytes)networks (53 bytes)

The quality of transmission links has lead to the omissionThe quality of transmission links has lead to the omission

of overheadsof overheads

There is no space between cellsThere is no space between cells

8/6/2019 Adsl Basic

17/24

Types ofATM services

Constant Bit Rate (CBR)Constant Bit Rate (CBR)

Variable Bit Rate (VBR)Variable Bit Rate (VBR)

Unspecified Bit Rate (UBR)Unspecified Bit Rate (UBR)

Available Bit Rate (ABR)Available Bit Rate (ABR)

8/6/2019 Adsl Basic

18/24

ATM Layer

The ATM layer transport information across the networkThe ATM layer transport information across the network

ATM uses virtual connections for the information transportATM uses virtual connections for the information transport

The connections are divided into two levels:The connections are divided into two levels:

The Virtual ChannelsThe Virtual Channels

The Virtual PathThe Virtual Path

This mechanism is used to provide quality of service (QoS)This mechanism is used to provide quality of service (QoS)

8/6/2019 Adsl Basic

19/24

ATM Connections

The connection between two endpoints is called a VirtualThe connection between two endpoints is called a Virtual

Channel (VC).Channel (VC).

A Virtual Path (VP) is a term for a bundle of virtualA Virtual Path (VP) is a term for a bundle of virtual

channel links that all have the same endpoints.channel links that all have the same endpoints.

Each VC and VP has a unique identifierEach VC and VP has a unique identifier

Virtual paths are used to simplify the ATM addressingVirtual paths are used to simplify the ATM addressing

structure.structure.

8/6/2019 Adsl Basic

20/24

ATM Adaptation Layer (AAL)

The ATM Adaptation Layer (AAL) converts informationThe ATM Adaptation Layer (AAL) converts information

from the upper layers into ATM cellsfrom the upper layers into ATM cells

The standard used for ATM over ADSL services is AAL5The standard used for ATM over ADSL services is AAL5

AAL5 Encapsulation MethodsAAL5 Encapsulation Methods

Virtual Channel Multiplexing (VCMux)Virtual Channel Multiplexing (VCMux)

LLC/SNAPLLC/SNAP

For detailed information please refer to the RFC 1483For detailed information please refer to the RFC 1483

8/6/2019 Adsl Basic

21/24

ADSL Protocol stacks

Ethernet overEthernet over

ATM (EoA)ATM (EoA)

IP over ATMIP over ATM

(IPoA)(IPoA)

PPP over ATMPPP over ATM

(PPPoA)(PPPoA)

PPP overEthernetPPP overEthernet

(PPPoE)(PPPoE)

Native ATMNative ATM

8/6/2019 Adsl Basic

22/24

PointPoint--toto--Point Protocol overPoint Protocol over

Ethernet overATM (PPPoEoA)Ethernet overATM (PPPoEoA)

8/6/2019 Adsl Basic

23/24

Conclusion: Pros & Cons

Why ADSL?Why ADSL? Simultaneous Internet and voice/fax capabilities overSimultaneous Internet and voice/fax capabilities over

a single telephone linea single telephone line

Uninterrupted, highUninterrupted, high--speed Internet access that'sspeed Internet access that's

always onalways on--lineline CostCost--effective solution for societyeffective solution for society

Data Security that exceeds other technologiesData Security that exceeds other technologies

Fast download speedsFast download speeds

ADSL disadvantages:ADSL disadvantages: DistanceDistance--sensitivesensitive

Slower upload speedsSlower upload speeds

Phone line requiredPhone line required

8/6/2019 Adsl Basic

24/24

Thank You For YourAttention