1. Digital Subscriber Line
Oral presentation by Momchil Ivanov

2. What does DSL do and how useful is it?
It provides digital data transmission over the wire of a telephone network.
the download speed of consumer DSL services ranges from 256kbit/s to 24,000kbit/s, depending on DSL technology, line conditions and service level implemented.

3. History
Digital Subscriber Line technology was originally implemented as part of the Integrated Services Digital Network (ISDN) specification, thus can operate on a BRI ISDN line as well as an analog phone line.
DSL stem directly from Claude Shannon’s seminal 1948 scientific paper describing a theory of digital communication.

4. basic elements of DSL and any digital communication:
An information source which produces a message
A transmitter which operates on the message to create a signal which can be sent through a channel
A channel, which is the medium over which the signal, carrying the information that comprises the message, is sent

5. A receiver, which transforms the signal back into the message intended for delivery
A destination, which can be a person or a machine, for whom or which the message is intended

6. Setup and Connection Procedures
Physical connection - on the customer side, the DSL modem is hooked up to a phone line. The telco connects the other end of the line to a Digital Subscriber Line Access Multiplexer (DSLAM) , which concentrates a large number of individual DSL connections into a single box and allows telephone lines to make faster connection to the internet.

7. The DSLAM location should be within a couple of miles from the user to prevent attenuation, the loss of data due to the large amount of electrical resistance encountered as the data moves between the DSLAM and the user's DSL modem.
Generally, when the DSL modem is powered up, it goes through a sync procedure. First the modem does a self-check, then checks for connection to the computer, and finally attempts to synchronize with the DSLAM.

8. Types of DSL
Asymmetric Digital Subscriber Line (ADSL) – download speed is faster than upload speed
Symmetric Digital Subscriber Line – download speed is as fast as the upload speed
ISDN Digital Subscriber Line (IDSL) - transmits data digitally (rather than analog) on a regular twisted pair copper telephone line
VDSL or VHDSL (Very High Speed DSL) is an xDSL technology providing faster data transmission over a single twisted pair of wires. The maximum available bit rates are achieved at a range of about 300 meters (1000 ft), which allows for 26 Mbit/s symmetric access or up to 52Mbit/s down – 12Mbit/s up asymmetric access.

9. source WIKIPEDIA, THE FREE ENCYCLOPEDIA
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