Asymmetric Digital Subscriber Line

ADSL

Student: Milan Milicevic ,478/09Supervisor: Prof. Miloš D. Đurić

June 2010Faculty of Electrical Engineering, University of Belgrade

What is ADSL?ADSL (Asymmetric Digital

Subscriber Line, or DSL for short) is a high-speed Internet access service that utilizes existing copper telephones lines to send and receive data at speeds that far exceed conventional dial-up modems.

Dial-up/ADSLThe fastest dial-up modems are

rated at 57 kilobits per second (Kbps), and usually operate at about 53 Kbps under good conditions. By comparison, ADSL allows data stream speeds from 1.5 to 8 megabits per second (Mbps).

ADSL MODEM

ADSL Modem is a device used to connect a computer or router to a telephone circuit.

Frequency plan for ADSL

Red area is the frequency range used by normal voice telephony, the green (upstream) and blue (downstream) areas are used for ADSL.

ADSLADSL uses standard telephone lines

to transmit upstream and downstream data on a digital frequency, which sets these datastreams apart from the analog signals telephones and fax machines use.

Telephone use Because the ADSL signal is operating

on a different frequency, the telephone can be used normally, even when surfing the Web with ADSL service.

ADSL connectors

ADSL downloadThe "asymmetric" in ADSL refers to

the fact that the downstream data rate, or the data coming to your computer from the Internet, is traveling faster than upstream data, or the data traveling from your computer to the Internet.

ADSL uploadUpstream data rates are slower because

Web page requests are fairly miniscule data strings that do not require much bandwidth to handle efficiently.

SDSL or Symmetric Digital Subscriber LineSome businesses, however, may require

matching upstream rates for uploading large files. SDSL, or Symmetric Digital Subscriber Line is an option. "Symmetric" indicates that both datastreams are operating at the same speed of 1.5 to 7 Mbps.

SDSL service requires a dedicated telephone line because, unlike ADSL, telephone and fax services cannot share a line with SDSL service.

ADSL requires ADSL service requires an Internet service

provider (ISP), and ADSL modem. The modem is often provided free of charge, and most ISPs that offer ADSL service require subscriber contracts of one year. ADSL is also more expensive than economical dial-up service, which can cost less than $10 per month.

ADSL useADSL is especially suited for gamers, CAD

use, streaming multimedia and downloading large files. Family members can share ADSL accounts, with a basic monthly fee covering several mailboxes. Unlike dial-up service, which stipulates only one session be instigated at a time, multiple members can be using ADSL service simultaneously on various computers in the house without violating policy.

ADSL serviceADSL is an "always on" service, meaning

that as long as your computer is powered on, it will automatically stay connected to the Internet unless you manually disconnect via software or hardware.

ADSL filter

ADSL providersADSL is not available to everyone. ADSL

providers, or even your local phone company, can tell you if service is available in your locale. Speeds will vary depending upon your physical distance from local hubs.

ADSL speed

ADSL2 & ADSL2+Some customers with close proximity

may be able to take advantage of newer varieties of ADSL, called ADSL2 and ADSL2+, which have even greater throughput rates, from 12 to 24 Mbps downstream and 1 to 3.5 Mbps upstream.

ADSL MaxADSL Max is a cover term for the UK telco

BT's range of commercial ADSL services that are rate-adaptive and are deployed over BT phone lines. Such rate-adaptive services are intended to offer the best possible speed attainable, which may vary over time. BT's ADSL Max services were launched in March 2006.

The highest speed ADSL Max services enable customers to receive up to 7.15 Mbit/s

Rate-Adaptive Digital Subscriber Line (RADSL)Rate-Adaptive Digital Subscriber Line

(RADSL) is a variation of Asymmetric Digital Subscriber Line (ADSL) technology. In RADSL the DSL modem adjusts the upstream bandwidth to create a wider frequency band for the downstream traffic. Using this technique the line is more tolerant of errors caused by noise and signal loss.

As the frequency is adjusted, the upstream bandwidth may be markedly decreased if there is a large amount of line noise or signal degradation - this may reduce the upstream bit rate to as little as 64 kbit/s - the same speed as a single

Single-Pair High-speed Digital Subscriber Line (SHDSL)Single-Pair High-speed Digital

Subscriber Line (SHDSL) is a form of DSL, a data communications technology that enables faster data transmission over telephone lines than a conventional voiceband modem can provide.

An optional extended SHDSL mode allows symmetric data rates up to 5696 kbit/s on one pair. Higher data rates may be achieved using two or up to four copper pairs.

Digital Subscriber Line Access MultiplexerA Digital Subscriber Line Access Multiplexer

(DSLAM, often pronounced dee-slam) allows telephone lines to make faster connections to the Internet. It is a network device, located in the telephone exchanges of the service providers, that connects multiple customer Digital Subscriber Lines (DSLs) to a high-speed Internet backbone line using multiplexing techniques.By placing remote DSLAMs at locations remote to the telephone exchange, telephone companies provide DSL service to locations previously beyond effective range.

Speed versus distance25 Mbit/s at 1,000 feet (~300 m)24 Mbit/s at 2,000 feet (~600 m)23 Mbit/s at 3,000 feet (~900 m)22 Mbit/s at 4,000 feet (~1.2 km)21 Mbit/s at 5,000 feet (~1.5 km or ~.95

miles)19 Mbit/s at 6,000 feet (~1.8 km or ~1.14

miles)16 Mbit/s at 7,000 feet (~2.1 km or ~1.33

miles)1.5 Mbit/s at 15,000 feet (4.5 km or ~2.8

miles)800 kbit/s at 17,000 feet (~5.2 km or ~3.2

miles)

Advantages and disadvantagesHere are some advantages of DSL: You can leave your Internet connection open and still use

the phone line for voice calls. The speed is much higher than a regular modem DSL doesn't necessarily require new wiring, it can use the

phone line you already have. The company that offers DSL will usually provide the

modem as part of the installation. But there are disadvantages: A DSL connection works better when you are closer to the

provider's central office. The farther away you get from the central office, the weaker the signal becomes.

The connection is faster for receiving data than it is for sending data over the Internet.

The service is not available everywhere.

ADSL schematic

Thanking for attention

Electrical Engineering, University of Belgrade