1. Asymmetric Digital Subscriber Line ADSL H.KEERTHI08B21A0415

2. Asymmetric Digital Subscriber Lines (ADSL) demonstrates the deliver high-rate digital data over existing ordinary phone-lines. A new modulation technology called Discrete Multitone (DMT) allows the transmission of high speed data. DSL facilitates the simultaneous use of normal telephone services, ISDN, and high speed data transmission, e.g., video. DMT-based DSL can be seen as the transition from existing copper-lines to the future fiber-cables They can offer customers high speed data services even before switching to fiber-optics. ADSL found many applications in different fields like voice over DSL etc., Copper based High speed network access technology Supports voice, video and data without affecting one another. Rapidly growing broadband access solution for home networking and small business systems. Supports data rates up to 6144 Kbps downstream and 640 Kbps upstream.

3. BSNL is the largest telecom service provider in India.. Broadband refers to telecommunication that provides multiple channels of data over a single communications medium, using some form of frequency or wave division multiplexing. It is a telecommunications signal of greater bandwidth. Wired line Wireless DSL (Digital Sub’s Line) 3G Mobile Cable Modem WI-Fi (Wireless Fidelity) PLC (Power Line Communication) Wi-Max (World Wide Interoperability for Microwave Access) Optical Fiber Technologies LMDS & MMDS FSO (Free Space Optics) SATELLITE

4.  DSL is a technology for bringing high-speed and high-bandwidth, which is directly proportional to the amount of data transmitted or received per unit time, information to homes and small businesses. ADSL is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines.  There are currently six different types of DSL. They are Asymmetric Digital Subscriber Line (ADSL), Symmetric Digital Subscriber Line (SDSL), ISDN Digital Subscriber Line (IDSL), High-bit-rate Digital Subscriber Line (HDSL), Very high-bit-rate Digital Subscriber Line (VDSL), and Rate-Adaptive Digital Subscriber Line (RADSL).  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 over 60% market share  ADSL is now available in every region of the world

5.  Asymmetric - The data can flow faster in one direction than the other. Data transmission has faster downstream to the subscriber than upstream  Digital - 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

6. ISDN ADSL VDSL2, ADSL2plus Enhanced Copper Hybrid Fibre/Copper Pure Fibre Voice band Modem FTTH

7.  In general, the maximum range for DSL without a repeater is 5.5 km  As distance decreases toward the telephone company office, the data rate increases  For larger distances, you may be able to have DSL if your phone company has extended the local loop with optical fiber cable Data RateWire gaugeWire sizeDistance 1.5 or 2 Mbps24 AWG0.5 mm5.5 km 1.5 or 2 Mbps26 AWG0.4 mm4.6 km 6.1 Mbps24 AWG0.5 mm3.7 km 1.5 or 2 Mbps26 AWG0.4 mm2.7 km

8.  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.

9. ISP Central Office Subscriber Premises Voice Switch DSL

10.  ADSL Filter/Splitter Separates the analogue voice (phone) traffic from data (ADSL) traffic.  The ADSL modem uses a combination of several advanced signal processing techniques to achieve the required throughput speeds  The Public Switched Telephone Network (PSTN) is the network of the world's public circuit-switched telephone networks.  ATM provides data link layer services that run over OSI Layer 1 physical links.ATM is a connection-orientated technique  The ISP usually provides other services like mail and news servers, and may cache frequently-used pages from the Internet so that you can access them more quickly.  The DSLAM is the piece of equipment at your local exchange that is at the other end of your ADSL connection. It houses a bank of ADSL modems on one side and has a single fiber-optic data connection on the other.

11. ADSL exploits the unused analogue bandwidth available in the wires ADSL works by using a frequency splitter device to split a traditional voice telephone line into two frequencies 425.8751381104KHz PSTNDownstreamUpstream

12.  Modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted.  There are two competing and incompatible standards for modulating the ADSL signal: Carrier less Amplitude Phase (CAP) Discrete Multi-Tone (DMT)

13. Carrier less Amplitude Phase (CAP) is an encoding method that divides the signals on the telephone line into three distinct bands into two distinct bands:  The upstream data channel (to the service provider), which is carried in the band between 25 and 160kHz.  The downstream data channel (to the user), which is carried in the band from 240kHz to 1.5MHz.

14.  DMT scores over CAP in terms of the speed of data transfer, efficiency of bandwidth allocation, and power consumption, and these have been key considerations in its widespread adoption.  Discrete Multi-Tone (DMT) separates the DSL signal so that the usable frequency range is separated into 247 frequency bands or channels of 4.3125kHz each through a process called frequency- division multiplexing)  DMT has 256 downstream frequency bins (or carriers) and 20 upstream frequency bins.  DMT constantly shifts signals between different channels to ensure that the best channels are used for transmission and reception.

15.  For transmitting data across each sub channel, the technique of Quadrature Amplitude Modulation (QAM) is used. Two sinusoidal carriers of the same frequency that differ in phase by 90 degrees constitute the QAM signal. Upstream access: 20 carriers x 8 bits x 4 KHz = 640 Kbps Downstream access: 256 carriers x 8 bits x 4 KHz = 8.1 Mbps  Two of the channels (16 and 64) can be used for transmitting pilot signals for specific applications or tests.  When the modem is activated during network access, the signal-to-noise ratio in the channel is automatically measured.  Sub channels that experience unacceptable throughput of the signal owing to interference are turned off, and their traffic is redirected to other suitable sub channels, thus optimizing the overall transmission throughput.

16. SERIAL TO PARAL LEL CONVE RTER DMT Symbol Encod er IFFTIFFT D/A Line Filter DMT Symbols Transmitted Serially N (Complex Sub Channels Symbols) Data Input Data Output 1 2 N IMPLEMENTATION ADSL TRANSMITTER PARA LLEL TO SERI AL CONV ERTE R The reverse operation is ADSL receiver.

17.  Frequency Division Multiplexing (FDM)  Echo Cancellation

19.  DSL is Always On, 24 hrs A Day.  Data security  Cost Effective  It does not require the use of a second phone line.  Fast download speeds  It can be installed on demand, unlike fiber cabling, which requires substantial underground work.  No dial up is needed as the connection is always on. There are some disadvantages with ADSL: Distance- sensitive, Slower upload speeds, Phone line required

20. Standard nameCommon nameDownstream rate Upstream rate ITU G.992.1ADSL (G.DMT)8 Mbit/s1.0 Mbit/s ITU G.992.2ADSL Lite (G.Lite)1.5 Mbit/s0.5 Mbit/s ITU G.992.3/4ADSL212 Mbit/s1.0 Mbit/s ITU G.992.3/4 Annex JADSL212 Mbit/s3.5 Mbit/s ITU G.992.3/4 Annex LRE-ADSL25 Mbit/s0.8 Mbit/s ITU G.992.5ADSL2+24 Mbit/s1.0 Mbit/s ITU G.992.5 Annex LRE-ADSL2+24 Mbit/s1.0 Mbit/s ITU G.992.5 Annex MADSL2+28 Mbit/s3.5 Mbit/s

21.  Telemedicine  E-Government  Agriculture  Distance learning  Public safety  National safety  Small business assistance  Information gathering  Tourism  E-commerce  Entertainment

22. ADSL promises to be the technology for the new millennium, enjoying enormous popularity from both service providers and their customers. The future looks bright for ADSL. While yesterday's obstacles and negative predictions fade away, many are watching ADSL with renewed interest. The "need for speed" is increasing, and the ADSL industry is working hard to make sure that broadband ADSL continues to be the global choice.

23.  Implementation and Applications of DSL Technology Philip Golden  Fundamentals of DSL Technology Philip Golden  ADSL, VDSL, and Multicarrier Modulation John A. C. Bingham  ADSL & DSL Technologies Walter J. Goral ski  Understanding Digital Subscriber Line Technology & DSL Advances Thomas Starr REFERENCE ON WEB : REFERENCE ON WEB :  www.howstuff.com  www.dsl.net  www.athenet.net  www.adsl.com  Magazine referred: Electronics for You