ADSL

Topic: Computing
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ADSL stands for Asymmetric Digital Subscriber Line, and is really just one of many techniques (other items: HDSL, VDSL, SDSL, IDSL), which usually go under the generic term xDSL.
A common feature of xDSL technologies is that they go out on the transfer of data over ordinary copper wire megabitfart.

ADSL network design

The ordering ADSL, a station linking, an ADSL modem, which usually has both Ethernet and ATM ports. ATM port is mainly meant for example: television.
The ordering may also be a filter (Split) that divides the signal between the phone and computer, and make sure they do not interfere with each other.

The nearest telecommunications exchange is an ADSL concentrator, DSLAMs, which wrap up several ADSL connections to an ATM link. After that the signals over an ATM network to the nearest location to the Internet.

Image: Per Thornéus

The reason why many want DSL because you plug it in an ordinary copper wire, therefore, a standard modem, but ADSL works only if you live up to three kilometers from an access station, as TELIA meet at least 95 percent of Sweden's telephone connected households that requirement.

ADSL is also asymmetrical, which means that you can receive more data ("downstream") than you can send out ("upstream").

Max downstream speed of ADSL is 8Mbit / s, while upstream is only a maximum of approximately 0.8 Mbps, but for most "surfers" are not a problem.

Another advantage of ADSL is that you can talk on the phone, chased together as you surf without any problems, it is because the ADSL modem and the phone transmitting at different frequencies, but sometimes it may be wrong so therefore it has a filter (Split) that look to the modem only transmits at 25 kHz and upwards to över1 MHz, o the phone only uses frequencies up to 4 kHz.

Image: Per Thornéus

At the other end of an ADSL connection, specifically in the local switch, there is a splitter that divides the signal and sends the telephone signal to the exchanges. ADSL signal entering a DSLAM (Digital Subscriber Line Access Multiplexer), which is xDSLs equivalent to a modem pool.
Unlike a conventional modem pool, which really can sit anywhere in the network, DSLAM must sit directly on the other end of copper wire, in the local switch. This means that your local telecommunications exchange must be upgraded with ADSL equipment before you can be offered ADSL services.
DSLAM equipment concentrating more ADSL connections into one connection. To translate this as used in Sweden, ATM technology is the most oxå IP over SDH transmission technology, which Telia has chosen to use ATM technology to their stations.
"The reason we chose ATM as the transfer technology is simple: ATM has superior features for the service classes, which is a must for TV over ADSL"
explains Stefan Moller at Ericsson partner collaboration with Telia.

From telecommunications exchange can therefore ADSL signals over an ATM network to the nearest location to Telia's IP network (internet). Telia's network is distributed, which means that there are many locations scattered across the country, rather than one large connection center that receives traffic from all over the country. There are certainly more expensive and harder to manage, but it also reduces bottlenecks in the network.
Scientists still graduate on xDSL technology o anu not really agree how it should work, so much can happen in the near future ....

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