DIGITAL SUBSCRIBER LINE DSL ADVANCES

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DIGITAL SUBSCRIBER LINE (DSL) ADVANCES

• Prepared by,
• Pow Jun Jiang (EE 071271)

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What is DSL???

• A modem technology that uses existing
  twisted-pair telephone lines to transport
  high-bandwidth data
• Run on regular copper phone wires which is a
  direct dedicated connection between PC and the
  phone company central office
• Make use of previously unused bandwidth on the
  phone line

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Figure 1 General Overview of DSL
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Figure 2 Signals in Copper Phone Line
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Basic Requirements

• Require 10BaseT Ethernet card
• Basic home DSL lines can connect to regular
  analog phones to RJ-11 jacks
• POTS (Plain Old Telephone Service) splitter can
  also be used.

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Advantages

• Fast
• Doesnt tie up to phone line
• Always on
• Reliable
• Use the phone line
• A router, with DSL modem, allows up to eight
  computers to access the Internet over a single
  DSL line.

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• Far cheaper
• Flexible and scalable, ideal for growing business
  computer networks
• Enable users to work from home, listen to
  streaming audio or watch streaming video while
  working on your computer.

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Disadvantages

• DSL connection works better when user is closer
  to the provider's central office
• The connection is faster for receiving data than
  it is for sending data over the Internet
• The service is not available everywhere

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Network Access Provider Benefits

• Do not need to install more copper or lay down
  miles of expensive fiber
• Eliminate providers' need to constantly upgrade
  their pricey Class 5 switch installations
• DSL bypasses the Class 5 switch for data-only
  calls, so access providers can accept more
  traffic without investing in a huge switch
  upgrade
• Voice and data paths are separated

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• By keeping costs low, service providers can make
  money off the traditionally low-margin business
  of providing Internet access.

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DSL User Benefits

• Can experience high-speed Web browsing and can
  send and receive large documents
• Provide a cost-effective way for telecommuters
  and branch offices to access the corporate
  network, provisioned via secure virtual private
  network services
• Improve the quality and reduce the cost of
  communications among employees via
  videoconferencing

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Types of DSL

• Asymmetrical DSL (ADSL)
• offers high-speed digital service and analog
  voice service over a local loop.
• An ADSL line is for the exclusive use of each
  customer so there is no contention for bandwidth
  on that loop.
• ADSL transfers data as far as 18,000 feet over
  copper wire at a rate of 7 Mbps on the downlink
  and 1 Mbps on the uplink.

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• High Bit Rate DSL (HDSL)
• Provide for T1 service on copper wire.
• Deliver T1 service at a DS1 rate over a four-wire
  loop of two twisted pairs.
• Most established DSL technologies
• Offer full duplex speeds at a DS1 (1.544 Mbps)
  rate or 2Mbps over 3 phone lines.
• Transfer data up to 12,000 feet (can be longer if
  repeatered).

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• High Bit-Rate DSL II (HDSL II)
• Offer the same performance as HDSL, but over a
  single phone line.
• ISDN DSL (IDSL)
• Hybrid of DSL and ISDN technologies
• Used for long duration Internet and remote Local
  Area Network (LAN) access.
• Dedicated to data does not support switched
  voice service.
• Same data encoding technique as of ISDN devices

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• Offers full duplex speed of 128 Kbps.
• Transfer data up to 18,000 feet.
• Symmetric DSL (SDSL)
• Non standard version of HDSL with Plain Old
  Telephone Service (POTS).
• Forerunner to HDSL II.
• Can be done using only one phone line
• Full duplex rates are limited to 384 Kbps for an
  18,000-foot loop. DS1 speeds can be reached on a
  shorter (10,000-foot) loop.

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• Very high bit-rate DSL (VDSL)
• Faster cousin of ADSL. VDSL provides for the
  transmission over copper of both digital data and
  analog voice.
• Currently fastest DSL technology
• Currently in its experimental phase.
• VDSL works at speeds as high as 52 Mbps down and
  1.5 to 2.3 Mbps up.
• VDSL operates over much shorter distances,
  achieving top speed over only 1000 feet of copper
  wire.

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• Rate Adaptive Asymmetric Digital Subscriber Line
  (RADSL)
• Operates at the same bandwidths as ADSL.
• Additional capability of adjusting bandwidth to
  the quality of the phone line during the data
  transmission, instead of just once at the start
  of the connection.
• Up to 7Mbps downstream and up to 1.5 Mbps
  upstream.

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Provider Equipment
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Consumer Equipment
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Figure 3 DSL Network Architecture
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Figure 4 Single Computer Connection
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Figure 5 Multi Computer Connection
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Figure 6 Multiple Computers with Software Proxy
Server
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Figure 7 Multiple Computers With Router/
Firewall
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Figure 8 Multiple Computers Using A Routed
Subnet
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Asymmetric DSL (ADSL)

• ADSL is a new broadband communication technology
  that creates high-speed access to the Internet
  and remote networks using the phone lines that
  are already present in your home. ADSL is
  superior to analog modems in many respects.

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DSLs Speed

• Full-rate ADSL has the potential to deliver data
  at speeds up to 8 Megabits per second
• G.Lite ADSL can deliver up to 1.5 Megabits per
  second during downloads. This is 25 times faster
  than a 56K modem, and 50 times faster than a
  28.8K modem!
• Service providers will also offer slower rates
  (from 256 Kbps and up) at lower costs

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Types of ADSL

• Full-rate ADSL
• Universal ADSL (G.lite)

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Full-rate ADSL

• Data rates ranging from 1.5 to 8 Mbps
  downstream from the Internet
• Upstream data rates from PC to the Internet are
  as high as 1 Mbps
• Potential data rates decrease with increased
  distance from the phone companys CO (central
  office)
• Costs for the service are more expensive than
  G.Lite ADSL

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G.Lite ADSL

• G.Lite ADSL is a scaled-down version that
  delivers up to 1.5 Mbps downstream and 384 Kbps
  up
• Service providers will offer slower rates for
  lower prices
• Less expensive than full-rate ADSL
• Easier to install

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Splitter vs. Splitterless

• Full-rate ADSL requires that a device, known as a
  splitter, be installed on the phone line where it
  enters a home in order to separate the voice
  service from the data service
• G.Lite ADSL will not usually require a splitter,
  although some homes with problematic wiring or
  certain types of telephones will require one.

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DSL In Malaysia

• "tmnet streamyx" service is supported by DSL
• Types of DSL technology chosen to support tmnet
  streamyx are ADSL, SDSL and GLite DSL
• An ADSL system basically consists of two parts
  i.e. the Central Office (CO) which is located at
  the exchange building and the other, Remote
  Termination Unit (RTU) at subscriber's premise
  which are connected via an existing pair of
  copper telephone lines.

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Figure 9 TM Net Streamyx Basic Network
Configuration
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• The Central Office (CO) for ADSL consists of two
  types of chassis.
• The first chassis is the ADSL unit for modem
  cards and control card while the second chassis
  is for the POTS (Plain Old Telephone Service)
  splitter.
• The Remote Terminal Unit (RTU) for ADSL also
  consists of POTS splitter and ADSL modem.

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Conclusion

• ADSL provides a new way to use existing phone
  lines.
• Its faster!
• Its always on!
• Voice and data on one line at the same time!
• ADSL is the best way to get online!