Presentation on theme: "Asymmetric Digital Subscriber Line"— Presentation transcript:
1 Asymmetric Digital Subscriber Line ADSLAsymmetric Digital Subscriber LineMiturski MichalMirkovski AngelSacevski Igor
2 IntroductionADSL is a form of DSL, a data communications technology that enables faster data transmission over copper telephone linesADSL is capable of providing up to 50 Mbps, and supports voice, video and data.ADSL is the #1 Broadband Choice in the World with over 60% market shareADSL is now available in every region of the world
3 What does ADSL meanAsymmetric - The data can flow faster in one direction than the other. Data transmission has faster downstream to the subscriber than upstreamDigital - No type of communication is transferred in an analog method. All data is purely digital, and only at the end, modulated to be carried over the line.Subscriber Line - The data is carried over a single twisted pair copper loop to the subscriber premises
4 ADSL standards : Standard name Common name Downstream rate Upstream rateITU G.992.1ADSL (G.DMT)8 Mbit/s1.0 Mbit/sITU G.992.2ADSL Lite (G.Lite)1.5 Mbit/s0.5 Mbit/sITU G.992.3/4ADSL212 Mbit/sITU G.992.3/4 Annex J3.5 Mbit/sITU G.992.3/4 Annex LRE-ADSL25 Mbit/s0.8 Mbit/sITU G.992.5ADSL2+24 Mbit/sITU G Annex LRE-ADSL2+ITU G Annex M28 Mbit/s
5 ADSL Speed Comparison Pure Fibre Hybrid Fibre/Copper FTTH Enhanced FTTx, VDSL2,ADSL2plusADSLISDNVoice band Modem
6 ADSL RangeIn general, the maximum range for DSL without a repeater is 5.5 kmAs distance decreases toward the telephone company office, the data rate increasesFor larger distances, you may be able to have DSL if your phone company has extended the local loop with optical fiber cableData RateWire gaugeWire sizeDistance1.5 or 2 Mbps24 AWG0.5 mm5.5 km26 AWG0.4 mm4.6 km6.1 Mbps3.7 km2.7
7 ADSL Speed Factors The distance from the local exchange The type and thickness of wires usedThe number and type of joins in the wireThe proximity of the wire to other wires carrying ADSL, ISDN and other non-voice signalsThe proximity of the wires to radio transmitters.
8 ADSL network components The ADSL modem at the customer premises(ATU-R)The modem of the central office (ATU-C)DSL access multiplexer (DSLAM)Broadband Access Server (BAS)Splitter - an electronic low pass filter that separates the analogue voice or ISDN signal from ADSL data frequencies DSLAM.
10 ADSL Requirements Phone-line, activated by your phone company for ADSL Filter to separate the phone signal from the Internet signalADSL modemSubscription with an ISP supporting ADSL
11 How does ADSL workADSL exploits the unused analogue bandwidth available in the wiresADSL works by using a frequency splitter device to split a traditional voice telephone line into two frequencies425,8751381104KHzPSTNDownstreamUpstream
12 ADSL ModulationModulation is the overlaying of information (or the signal) onto an electronic or optical carrier waveformThere are two competing and incompatible standards for modulating the ADSL signal:Carrierless Amplitude Phase (CAP)Discrete Multi-Tone (DMT)
13 Carrierless Amplitude Phase Carrierless Amplitude Phase (CAP) is an encoding method that divides the signals into two distinct bands:The upstream data channel (to the service provider), which is carried in the band between 25 and 160kHzThe downstream data channel (to the user), which is carried in the band from 200kHz to 1.1MHz .These channels are widely separated in order to minimize the possibility of interference between the channels.
14 Discrete Multi-tone (DMT) Discrete Multi-Tone (DMT) separates the DSL signal so that the usable frequency range is separated into 256 channels of kHz each.DMT has 224 downstream frequency bins (or carriers) and 32 upstream frequency bins.DMT constantly shifts signals between different channels to ensure that the best channels are used for transmission and reception.
15 The DMT frequency bands Frequency Division Multiplexing (FDM)Echo Cancellation
16 Asynchronous Transfer Mode ATM is a connection-orientated techniqueATM provides cell sequence integrityCells are much smaller than standard packet-switched networks (53 bytes)The quality of transmission links has lead to the omission of overheadsThere is no space between cells
17 Types of ATM services Constant Bit Rate (CBR) Variable Bit Rate (VBR) Unspecified Bit Rate (UBR)Available Bit Rate (ABR)
18 ATM Layer The ATM layer transport information across the network ATM uses virtual connections for the information transportThe connections are divided into two levels:The Virtual ChannelsThe Virtual PathThis mechanism is used to provide quality of service (QoS)
19 ATM ConnectionsThe connection between two endpoints is called a Virtual Channel (VC).A Virtual Path (VP) is a term for a bundle of virtual channel links that all have the same endpoints.Each VC and VP has a unique identifierVirtual paths are used to simplify the ATM addressing structure.
20 ATM Adaptation Layer (AAL) The ATM Adaptation Layer (AAL) converts information from the upper layers into ATM cellsThe standard used for ATM over ADSL services is AAL5AAL5 Encapsulation MethodsVirtual Channel Multiplexing (VCMux)LLC/SNAPFor detailed information please refer to the RFC 1483
21 ADSL Protocol stacks Ethernet over ATM (EoA) IP over ATM (IPoA) PPP over ATM (PPPoA)PPP over Ethernet (PPPoE)Native ATM
22 Point-to-Point Protocol over Ethernet over ATM (PPPoEoA)
23 Conclusion: Pros & Cons Why ADSL?Simultaneous Internet and voice/fax capabilities over a single telephone lineUninterrupted, high-speed Internet access that's always on-lineCost-effective solution for societyData Security that exceeds other technologiesFast download speedsADSL disadvantages:Distance-sensitiveSlower upload speedsPhone line required