The modern world is ripe for the use
of technology DSL. Increasing the flow of information transmitted over the
Internet by companies and private users, and the need for remote access to
corporate networks, has created a need to provide low-cost technology of
digital high-speed data transmission to "narrow" the place of the
digital network - subscriber telephone line. DSL technology can significantly
increase the speed of data transmission over copper telephone wires without the
need to modernize subscriber telephone lines. It is an opportunity to convert
existing telephone lines into high-speed data channels is the main advantage of
technologies DSL.
So what is the
technology of DSL?
Reducing DSL stands for Digital
Subscriber Line (DSL). DSL is a relatively new technology that allows to
significantly expand the bandwidth of the old copper telephone lines between
telephone exchanges to individual subscribers. Any subscriber who uses currently
a conventional telephone service has the option of using DSL technology to
significantly increase the speed of your connection, such as the Internet. It
should be remembered that the organization of the DSL line is used existing
telephone lines; This technology is so good, it does not require laying
additional telephone cables. As a result, you get anytime access to the
Internet while maintaining normal operation of a conventional telephone. None
of your friends will no longer complain that the clock can not you ring a
chime. Due to the variety of DSL technologies, the user can choose a suitable
to him the data rate - from 32 kbit / s to more than 50 Mbit / s. These
technologies allow you to use a standard telephone line for the broadband
systems such as video on demand or distance learning. Modern technology brings
the possibility of organizing DSL high-speed Internet access in every house or
every business small and medium businesses, turning ordinary telephone lines
into high-speed digital circuits. Moreover, the data rate depends on the
quality and length of the line connecting the user and the provider. Thus
providers usually allow the user to choose the bit rate that best suits their
individual needs.
How does DSL
The telephone installed at your home
or in the office connected to the telephone exchange equipment using
twisted-pair copper wires. The traditional telephone is designed for normal
telephone calls to other subscribers of the telephone network. In this network
are transmitted analog signals. The telephone set receives acoustic waves
(which are a natural analog signal) and converts them into an electrical signal
whose amplitude and frequency is constantly changing. Since all the telephone
network is built on the transmission of analog signals, the easiest way, of
course, be used for transmitting information between subscribers or subscriber
and the provider just such a method. That's why you had to buy in addition to
your computer and even a modem that allows demodulate analog signal and turn it
into a series of ones and zeroes of digital information, perceived computer.
When transmitting analog signals
used by only a small amount of bandwidth twisted pair copper telephone wires;
The maximum rate that can be achieved via a conventional modem is about 56 Kbit
/ s. DSL is a technology that eliminates the need to convert the signal from
analog to digital form and vice versa. Digital data is transferred to either
the computer is digital data that enables a much wider bandwidth telephone
line. Thus it is possible to use both analog telephony and high-speed digital
data transmission over the same line, dividing the spectra of these signals.
Various types
of DSL and a brief description of their operation
is a set of DSL various
technologies, allowing to organize the digital subscriber line. In order to
understand these technologies, and to identify areas of practical application,
should understand how these technologies are different. First, one should
always keep in mind the relationship between the distance by which the signal
is transmitted, and the data rate, and the difference in transmission rates
"downlink" (from the network to the user) and the
"upstream" (from the user to the network) data stream.
DSL combines under one roof the
following technologies.
ADSL (Asymmetric Digital Subscriber Line - asymmetric digital
subscriber line)
This technology is asymmetric, i.e.
the data rate on the network to the user is significantly higher than the data
rate from the user to the network. This asymmetry, combined with a state of
"permanent connection" (when eliminating the need for each time dial
a phone number and wait for connection setup), makes ADSL ideal technology for
accessing the Internet, access to local area networks (LAN), etc. The
organization of such compounds, users typically receive much more information
than the pass. ADSL technology provides speed "downlink" the data
stream in the range of 1.5 Mbit / s up to 8 Mbit / s and the velocity of the
"upstream" data stream 640 kbit / s to 1.5 Mbit / s. ADSL can
transmit data at a speed of 1.54 Mbit / s at a distance of 5.5 km on a single
twisted pair of wires. Transmission speed of about 6 - 8 Mbit / s can be
achieved for data transmission over a distance of 3.5 km wire diameter of 0.5
mm.
R-ADSL (Rate-Adaptive Digital Subscriber Line - DSL connection speed
adaptation)
R-ADSL technology provides the same
data transfer rate as the technology of ADSL, but it allows to adapt the
transmission rate to the extent and use of twisted pair wires. When using
technology R-ADSL connection at different telephone lines will have different
data rates. The data rate can be selected when the line synchronization during
connection or by signals from the station.
G. Lite
(ADSL.Lite) is a cheap and
easy-to-install version of the technology ADSL, providing speed of
"top-down" data flow of up to 1.5 Mbit / s and the rate of
"bottom-up" data stream up to 512 kbit / s or 256 kbit / s in both
directions.
IDSL (ISDN Digital Subscriber Line - digital subscriber line IDSN)
IDSL technology provides full duplex
data transmission at speeds up to 144 kbit / s. Unlike ADSL capabilities IDSL
limited data transmission. Despite the fact that IDSL, as well as ISDN,
modulation uses 2B1Q, between them there are some differences. Unlike ISDN line
IDSL is nonswitched line does not lead to an increase in the load on the
switching equipment provider. Also IDSL line is "permanently enabled"
(as well as any line organized using technology DSL), whereas ISDN
connectionless.
HDSL (High Bit-Rate Digital Subscriber Line - High Speed Digital
Subscriber Line)
HDSL technology provides
organization symmetrical data transmission lines, that is, the data rate from
the user to the network and from the network to the user are equal. Thanks to
the transmission rate (1.544 Mbit / s over two pairs of wires, and 2.048 Mbit /
s over three pairs of wires) telecommunication companies use technology HDSL
alternatively lines T1 / E1. (T1 lines used in North America and provide a data
rate of 1.544 Mbit / s and E1 lines are used in Europe, and provide a data rate
of 2.048 Mbits / sec.) Although the distance that the HDSL system transmits
data (which is about 3.5 - 4.5 km), is less than when using technology ADSL,
for an inexpensive, yet effective, increasing the length of the HDSL line
telephone company may install special repeaters. Using HDSL line for the
organization of two or three twisted pairs of telephone wires makes this system
an ideal solution for connecting PBX, servers, Internet, local area networks,
etc. HDSL2 technology is a logical result of the development of technology
HDSL. This technique provides the same characteristics as the technology HDSL,
but uses only a single pair of wires.
SDSL (Single Line Digital Subscriber Line - Single Line Digital
Subscriber Line)
As well as the technology HDSL, SDSL
technology provides symmetric data transfer speed as T1 / E1, but SDSL
technology has two important differences. Firstly, it uses only one twisted
pair of wires, and secondly, the maximum transmission distance is limited 3km.
Within this distance SDSL technology provides, for example, the system video
conferencing when required to maintain the same data flows in both directions.
In a sense, technology is a precursor of SDSL technology HDSL2.
VDSL (Very High Bit-Rate Digital Subscriber Line - very high speed
digital subscriber line)
VDSL technology is the most
"fast" technology xDSL. It provides a data transfer rate
"downward" flux ranging from 13 to 52 Mbit / s and the data rate
"uplink" in the flow range of 1.5 to 2.3 Mbit / s, over a single
twisted pair telephone wires. In the symmetric mode, the speed up to 26 Mbit /
s. VDSL technology may be regarded as a cost-effective alternative to pave the
fiber optic cable to the end user. However, the maximum transmission distance
for this technique is from 300 meters to 1300 meters. That is, a length of the
subscriber line should not exceed this value, or fiber-optic cable should be
positioned closer to the user (for example, the head of the building, which is
a lot of potential users). VDSL technology can be used for the same purposes as
the ADSL; moreover, it can be used for signal transmission of high definition
television (HDTV), video on demand, etc.
Technology DSL, allowing to send
voice, data and video on the existing cable network consisting of twisted-pair
telephone wire, best reflects the needs of users in high-speed transmission
systems.
First, the DSL technology provides
high data rate. Different variants of DSL provide different data transfer
speed, but in any case, this rate is much higher than the speed of the fastest
analog modem.
Secondly, DSL technology is left to
you to enjoy a normal telephone line, despite the fact that they use for their
work subscriber telephone line . Using DSL technology, you no longer have to
worry about what you do not get time to important news, or that for an ordinary
phone call you first need to exit the Internet.
And finally, a DSL line always
works. The connection is always set, and you do not have to dial a phone number
and wait for the connection every time you want to connect. Do not have to
worry about what will happen in the network accidental disconnection, and you
lose the connection at precisely the moment when the load from the network data
that you just vital. E-mail you will receive at the time of receipt, but not
when it decide to check. In general, the line will always work, but you will
always be on the line.
Posted By: Wasim Javed
