A Seminar Topic on ADSL Asymmetric digital subscriber line

Contents  Introduction  xDSL and ADSL  Other DSL Technology  What does ADSL mean  ADSL Speed Factors  ADSL Network Components  ADSL Requirements  How does ADSL work?  ADSL Modulation CAP(Carrierless Amplitude Phase) DMT(Discrete Multi Tone)  ADSL vs Cable Modem  Features of ADSL  What can you do with ADSL  Pros & Cons  An Insight  Conclusion

Introduction This era of competition among communication service provider provides all the services their customers needs. They position their networks in such a way that they can provide all the services the customer wants. This paper addresses an important component of the network which is capable of providing both broadband and narrowband services which is ADSL.

xDSL and ADSL  xDSL or Digital Subscriber Line collectively refers to a group of technologies that utilize the unused bandwidth in the existing copper access network to deliver high-speed data services from the distribution center, or central office, to the end user.  Asymmetric Digital Subscriber Line (ADSL) is one such form of the Digital Subscriber Line technology. It is a data communication technology that enables faster data transmission over copper telephone lines than a conventional voice-band modem can provide.

Other DSL Technologies ADSL: Asymmetric DSL SDSL: Single line DSL HDSL: High-bit-rate DSL VDSL: Very High-bit-rate DSL R-ADSL: Rate Adaptive DSL

What does ADSL mean : 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. Subscriber Line - The data is carried over a single twisted pair copper loop to the subscriber premises.

ADSL Speed Factors  The distance from the local exchange  The type and thickness of wires used  The proximity of the wire to other wires carrying ADSL, ISDN and other non-voice signals  The proximity of the wires to radio transmitters.

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.

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

ADSL Loop Architecture ISP Central Office Subscriber premises Voice Switch DSL

ADSL MODEM

How does ADSL work ADSL exploits the unused analogue bandwidth available in the wires 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 ADSL works by using a frequency splitter device to split a traditional voice telephone line into two frequencies 425, KHz PSTNDownstreamUpstream

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 for modulating the ADSL signal:  Carrierless Amplitude Phase (CAP)  Discrete Multi-Tone (DMT)

Carrierless Amplitude Phase  Carrierless Amplitude Phase (CAP) is an encoding method that divides the signals into two distinct bands: 1. The upstream data channel (to the service provider), which is carried in the band between 25 and 160kHz. 2. The 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.

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.

ADSL Standards : Standard name Common name Downstream rate Downstream rate Upstream rate ITU G ADSL (G.DMT) 8 Mbit/s 1.0 Mbit/s ITU G ADSL Lite (G.Lite) 1.5 Mbit/s 0.5 Mbit/s ITU G.992.3/4 ADSL2 12 Mbit/s 1.0 Mbit/s ITU G.992.3/4 Annex J ADSL2 12 Mbit/s 3.5 Mbit/s ITU G.992.3/4 Annex L RE-ADSL2 5 Mbit/s 0.8 Mbit/s ITU G ADSL2+ 24 Mbit/s 1.0 Mbit/s ITU G Annex L RE-ADSL2+ 24 Mbit/s 1.0 Mbit/s ITU G Annex M ADSL2+ 28 Mbit/s 3.5 Mbit/s

ADSL Range  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

ADSL vs Cable Modem  Pro:  Secure. “Point to point connectivity” of ADSL ensures the security of the service. Cable, by contrast, is shared media and is not secure at all.  Bigger coverage area.  Cheap. ADSL uses existing twisted pair, hence is cheap in installation and also cheap in monthly payment.  Cons:  Bandwidth. ADSL has about 1.1MHz BW due to loop limitations, while cable modem has about 745MHz BW.  Bridge taps, DLCs, load coils can lead to problems.  Mutual noise among different DSL lines.

Features of ADSL :

What can you do with ADSL? Conventional uses:  Surf or browse the web  Send or receive electronic messages or s Business uses:  Promote a company, product or service (advertising online)  Retrieve information using search engines  Download files (software; media; etc.)  Buy and sell (online shopping/comparing offers and prices)  Financial transactions (banking operations, stock exchange, etc.)  E-services (e-learning, telemedicine, etc.) Other uses:  ADSL access to TV programmes  Telephony(VoIP)

Pros & Cons  Why ADSL?  Simultaneous Internet and voice/fax capabilities over a single telephone line  Uninterrupted, high-speed Internet access that's always on-line  Cost-effective solution for society  Better Data Security  Fast download speeds  ADSL Limitations:  Distance-sensitive  Slower upload speeds  Phone line required

An Insight Into the Improved ADSL ADSL2 Approved by ITU-T as G July 2002 Features Improved rate –up to 12Mbps by 1Mbps Improved reach –around 600ft / 180m Better modulation efficiency Bonding of lines ADSL2+ Approved by ITU-T as G January 2003 Features Much increased rates –up to 28Mbps by 1Mbps Doubled downstream frequency band to 2.2Mhz Reduced cross talk Builds on all ADSL2 features

Conclusion Future is bright for the improvements in this technology. Users mainly everybody has a craze or need for internet which has made ADSL a part of human life to certain extent and it is trying to succeed.If it does the human life will change for ever.

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