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DSL Technologies and Services Workshop Cairo, 4-6 March 2003

DSL Technologies and Services Workshop Cairo, 4-6 March 2003. Introduction to DSL Abdelfattah Abuqayyas Coordinator Arab Centre of Excellence abdelfattah.abuqayyas@ties. itu. i nt ITU BDT. The Issues.

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DSL Technologies and Services Workshop Cairo, 4-6 March 2003

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  1. DSL Technologies and Services WorkshopCairo, 4-6 March 2003 Introduction to DSL Abdelfattah Abuqayyas Coordinator Arab Centre of Excellence abdelfattah.abuqayyas@ties.itu.int ITU BDT

  2. The Issues • The rapid growth of the Internet combined with the increase in computer hardware and software availability to people has placed an increasing demand on the telecommunications providers to supply faster data rates to the home. • ‘Last mile’ connection between exchange buildings and the user of the network services is usually on a pair of copper wires (twisted pair) • DSL technology uses special modulation and encoding methods to achieve broadband speeds over these ordinary telephone copper wires

  3. xDSL Definition • xDSL can be defined as the “… dedicated, point-to-point, public network access technologies that allow multiple forms of data, voice, and video to be carried over twisted-pair copper wire on the local loop (‘last mile’) between a network service provider’s central office and the customer site.” • xDSL because of the many variations, • Most xDSL technologies today can be used in addition to a normal telephone or ISDN service. • The main goal of xDSL was and is to provide affordable broadband services for homes and offices.

  4. xDSL Overview

  5. 1- Asynchronous Digital Subscriber Line ADSL • The most popular variation of DSL is ADSL. • ADSL was developed in 1989 by Bellcore Labs • This technology was intended to permit the local exchange carriers to compete with the cable television companies. • But today the subscriber also wants a broadband Internet access and ADSL meets this requirement, too.

  6. ADSL-Distance and Speed • ADSL requires a maximum cable distance of 5.5 Km and provides different download speeds and upload speeds. • Typical rates are T1 or E1 downstream and 176 Kbit/s upstream. • The range and the bit rate depend on each other. Without repeaters downstream bit rates of 2Mbit/s can be transmitted over 4km, 4Mbit/s over 3km and 6Mbit/s over 2km

  7. Problems • Although ADSL is being rapidly deployed, there are numerous problems. • frequent outages especially at the limits of the distance, and difficulty determining the availability of ADSL • load coils on the telephone line. • multiple splices between the customer and the CO. • To avoid such problems: • many local telephone companies are systematically eliminating the coils and improving the quality of the splices to permit ADSL.

  8. ADSL Principles • ADSL operates by using higher frequencies than those traditionally used in telephone operations (300 Hz to about 4 KHz). • The copper wire is capable of handling higher frequency signals but the signal strength degrades rapidly, hence the distance and splice limitations. • ADSL and ISDN or POTS over the same telephone line

  9. ADSL Principles • Each end of an ADSL circuit has a special ADSL modem connected to it. • At the customer site a special splitter is employed to separate the high frequency ADSL signals from the telephone signals. • The ADSL modem uses frequency division multiplexing to break the bandwidth into multiple channels. • These channels are combined into a small upstream band, usually at the lower frequencies, and a large downstream band, usually at the higher frequencies.

  10. ADSL Connection

  11. Rate Adaptive Digital Subscriber Line (RADSL) • RADSL is very similar to ADSL. The major difference is in its ability to dynamically adjust the transmission speed to compensate for line noise, long distances, and poor splices • This technology allows people just beyond the ADSL distance limitations to get reasonable Internet speeds and reliability. It can provide services at distances up to 7km with speeds of 640 Kbit/s downstream and 128 Kbit/s upstream . • RADSL requires a splitter at the customer site to filter the higher frequency data signals from the voice channel.

  12. ADSL-Lite IDSL • ADSL-Lite • ADSL-Lite, also called DSL-Lite and G-Lite, is often called splitter less DSL, it is designed to work without a customer site splitter. • The ADSL-Lite methodology yields lower download and upload speeds. • Typical speeds are 1.5 Mbs download and 512 Kbit/s upload • ISDN Digital Subscriber Line (IDSL) • (IDSL) is DSL over ISDN lines, it does not permit voice traffic, the entire line is dedicated to data. • In many areas ADSL is not available but ISDN is and sometimes IDSL can be purchased after the ISDN line is installed.

  13. 2- High Bit-Rate Digital Subscriber Line (HDSL) • HDSL is a variation of DSL technology that requires multiple pairs of wires, but provides fast, symmetric data speeds. • The goal: to replace old T1 or E1 repeatered lines by repeater less systems • The average range is 3 km. 2 twisted pairs for 1.544 Mbit/s in both directions (USA). 1 - 3 twisted pairs for 2.048 Mbit/s in both directions (Europe) • Some of the popular uses of HDSL include connecting PBX systems, Internet servers, and campus based networks.

  14. SDSL, HDSL-2 • SDSL - Symmetric single-pair high bit-rate DSLis a form of Digital Subscriber Line similar to HDSL but providing scalable bit rates between 64 kbit/s and 2048 kbit/s over a single twisted-pair copper line. • HDSL-2 is a symmetric technology intended to replace T1 lines and older generation HDSL technology. • HDSL-2 transports data at rates of up to 1.5 Mbit/s over a single pair of copper wires at distances of up to 3650 m. • HDSL-2 supports voice, data, video ATM, private-line T1 service, and frame relay • G.SHDSL, a multiple-rate version promoted by the ITU. It can accommodate line rates from 384 kbit/s to 2.3 Mbit/s off a single line card.

  15. 3- Very High Bit-Rate Digital Subscriber Line(VDSL) • VDSL is designed to deliver very high-speed data over short distances utilizing existing copper technologies for the final cable segment. • The cost and effort is significant when using Fiber To The Home (FTTH). As an interim solution, Fiber To The Neighborhood (FTTN) or Fiber To The Basement (FTTB) is implemented. Then high-speed data is transmitted over copper for the remaining distance, often called the home run. • It is intended to deliver broadband services and can be used as a bridge to transport both ATM and SDH carriers in the access network.

  16. VDSL • The downstream data rates can reach up to 52 Mbit/s and the upstream data rates up to 26 Mbit/s. • Both data channels will be separated in frequency from bands used for POTS and ISDN,

  17. xDSL Comparison

  18. Bitrate and reach of xDSL Systems

  19. Comparison

  20. Comparison

  21. DSL Services and Technologies WorkshopCairo, 4-6 March 2003 Thank You abdelfattah.abuqayyas@ties.itu.int

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