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Encyclopedia > Digital Subscriber Line
A DSL Modem
A DSL Modem
Comparing DSL & Dial-Up

DSL or xDSL, is a family of technologies that provide digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop, although in recent years, many[attribution needed] have adopted digital subscriber line as a more marketing-friendly term for the most popular version of consumer-ready DSL, ADSL. Look up DSL in Wiktionary, the free dictionary. ... Download high resolution version (2816x2112, 518 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (2816x2112, 518 KB) Wikipedia does not have an article with this exact name. ... Image File history File links Size of this preview: 800 × 534 pixelsFull resolution (858 × 573 pixel, file size: 36 KB, MIME type: image/jpeg) I created this diagram to help display how a DSL connection me too I, the creator of this work, hereby release it into the public domain. ... Image File history File links Size of this preview: 800 × 534 pixelsFull resolution (858 × 573 pixel, file size: 36 KB, MIME type: image/jpeg) I created this diagram to help display how a DSL connection me too I, the creator of this work, hereby release it into the public domain. ... For other uses, see Digital (disambiguation). ... For other uses, see Telephone (disambiguation). ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ...


Typically, the download speed of consumer DSL services ranges from 256 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download speed for Asymmetric Digital Subscriber Line (ADSL) and equal to download speed for Symmetric Digital Subscriber Line (SDSL). Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. ... Symmetric Digital Subscriber Line (SDSL) is a Digital Subscriber Line (DSL) variant with E1-like data rates (72 to 2320 kbit/s). ...

Contents

Voice and data

Some variants of DSL connections, like ADSL and very high speed DSL (VDSL), typically work by dividing the frequencies used in a single phone line into two primary 'bands'. The ISP data is carried over the high frequency band (25 kHz and above) whereas the voice is carried over the lower frequency band (4 kHz and below). (See the ADSL article on how the high frequency band is sub-divided). The user typically installs a DSL filter on each phone. This filters out the high frequencies from the phone, so that the phone only sends or receives the lower frequencies (the human voice), creating two independent 'bands'. Thus the DSL modem and the phone can simultaneously use the same phone line without interfering with each other. ISP may mean: Internet service provider, an organization that offers users access to the Internet and related services. ... A frequence range or frequency band is a range of wave frequencies. ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ... A DSL filter is an analog low-pass filter installed on telephones and other analog devices to prevent interference between such devices and Digital Subscriber Line service operating on the same line. ... Westell Model 6100 ADSL modem An asymmetric digital subscriber line transceiver, also known as an ADSL modem or DSL modem, is a device used to connect a single computer to a DSL phone line, in order to use an ADSL service. ...


History and science

Digital subscriber line technology was originally implemented as part of the ISDN specification, which is later reused as IDSL. Higher speed DSL connections like HDSL and SDSL are developed to extend the range of DS1 services on copper lines. Consumer oriented ADSL is designed to operate also on a BRI ISDN line, which itself is a form of DSL, as well as on an analog phone line. ISDN is also short for isosorbide dinitrate Integrated Services Digital Network (ISDN) is a type of circuit switched telephone network system, designed to allow digital (as opposed to analog) transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds, than available with analog... ISDN Digital Subscriber Line (IDSL) transmits data digitally (rather than analog) on a regular twisted pair copper telephone line, across existing ISDN lines, at a rate of 144 kbit/s, slightly higher than a bonded dual channel ISDN connection at 128kbit/s. ... Digital Subscriber Line, or DSL, is a family of technologies that provide a digital connection over the copper wires of the local telephone network. ... Symmetric Digital Subscriber Line (SDSL) is a Digital Subscriber Line (DSL) variant with E1-like data rates (72 to 2320 kbit/s). ... For the guitar distortion pedal, see BOSS DS-1. ...


DSL, like many other forms of communication, stems directly from Claude Shannon's seminal 1948 scientific paper: A Mathematical Theory of Communication. Joe Lechleider at Bellcore (now Telcordia Technologies) developed ADSL in 1988 by placing wideband digital signals above the existing baseband analog voice signal carried between telephone company central offices and customers on conventional twisted pair cabling.[1] Communication is a process that allows organisms to exchange information by several methods. ... Claude Shannon Claude Elwood Shannon (April 30, 1916 – February 24, 2001), an American electrical engineer and mathematician, has been called the father of information theory,[1] and was the founder of practical digital circuit design theory. ... The article entitled A Mathematical Theory of Communication, published in 1948 by mathematician Claude E. Shannon, was one of the founding works of the field of information theory. ... Telcordia Technologies, formerly Bellcore, is an American telecommunications company created in 1984 after the breakup of AT&T. It was split from the original Bell Labs as part of the negotiated consent decree with the US government, and served Research & Development and standards setting functions for the resulting seven Baby... Telcordia Technologies, formerly Bell Communications Research, Inc. ... Baseband is an adjective that describes signals and systems whose range of frequencies is measured from 0 to a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies starting at 0. ... In the field of telecommunications, a central office or telephone exchange houses equipment that is commonly known as simply a switch, which is a piece of equipment that connects phone calls. ... 25 Pair Color Code Chart 10BASE-T UTP Cable Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. ...


U.S. telephone companies promote DSL to compete with cable modems. DSL service was first provided over a dedicated "dry loop", but when the FCC required the incumbent local exchange carriers ILECs to lease their lines to competing providers such as Earthlink, shared-line DSL became common. Also known as DSL over Unbundled Network Element , this allows a single pair to carry data (via a digital subscriber line access multiplexer DSLAM) and analog voice (via a circuit switched telephone switch) at the same time. Inline low-pass filter/splitters keep the high frequency DSL signals out of the user's telephones. Although DSL avoids the voice frequency band, the nonlinear elements in the phone would otherwise generate audible intermodulation products and impair the operation of the data modem. An outdated model of the Motorola Surfboard cable modem A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. ... An alarm circuit (also dry pair or dry loop) is an unconditioned leased pair of telephone wire from a telco. ... The abbreviation FCC can refer to: Face-centered cubic (usually fcc), a crystallographic structure Federal Communications Commission, a US government organization Farm Credit Corporation/Farm Credit Canada, a Canadian government organization Families with Children from China, an adoption support organization Florida Christian College, a college in central Florida Fresno City... ILEC or Incumbent Local Exchange Carrier is a local telephone company that was in existence at the time of the breakup of AT&T, for example, the Baby Bells and GTE. They compete with upstart Competitive Local Exchange Carriers. ... It has been suggested that this article be split into multiple articles accessible from a disambiguation page. ... Unbundled Network Elements (UNE) are a requirement mandated by the United States Telecommunications Act of 1996. ... A digital subscriber line access multiplexer, (DSLAM) is a multiplexer located in the telephone company exchange that provides consumers access to DSL services over twisted pair copper cabling. ... A low-pass filter passes low frequencies fairly well, but attenuates, or blocks, high frequencies. ... A DSL filter is an analog low-pass filter installed on telephones and other analog devices to prevent interference between such devices and Digital Subscriber Line service operating on the same line. ...


Older ADSL standards can deliver 8 Mbit/s to the customer over about 2 km (1.25 miles) of unshielded twisted pair copper wire. The latest standard, ADSL2+, can deliver up to 24 Mbit/s, depending on the distance from the DSLAM. Distances greater than 2 km (1.25 miles) significantly reduce the bandwidth usable on the wires, thus reducing the data rate. By using an ADSL loop extender, these distances can be increased substantially. Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ... A megabit per second (mbps or mbit/s) is a unit of data transmission equal to 1,000 kilobits per second or 1,000,000 bits per second. ... “km” redirects here. ... It has been suggested that this article or section be merged into Twisted pair. ... TU G.992. ... A megabit per second (mbps or mbit/s) is a unit of data transmission equal to 1,000 kilobits per second or 1,000,000 bits per second. ... A digital subscriber line access multiplexer, (DSLAM) is a multiplexer located in the telephone company exchange that provides consumers access to DSL services over twisted pair copper cabling. ... Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz. ... ADSL speeds are limited by the distance from the central office or DSLAM. An ADSL loop extender (also known as an ADSL repeater) is a device that the telephone company can place midway between the subscriber and the central office to extend the distance and increase the channel capacity of...


Operation

The local loop of the Public Switched Telephone Network was initially designed to carry POTS voice communication and signaling, since the concept of data communications as we know it today did not exist. For reasons of economy, the phone system nominally passes audio between 300 and 3,400 Hz, which is regarded as the range required for human speech to be clearly intelligible. This is known as voiceband or commercial bandwidth. In telecommunications, the local loop is the wiring between the central office (telephone exchange in British English) and the customers premises demarcation point. ... The public switched telephone network (PSTN) is the network of the worlds public circuit-switched telephone networks, in much the same way that the Internet is the network of the worlds public IP-based packet-switched networks. ... Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ... This article is about the SI unit of frequency. ... In electronics, voiceband means the typical human hearing frequency range that is from 20Hz to 20KHz. ... Commercial bandwidth is a term for the regular capacity of the phone network required for intelligible speech. ...


At the local telephone exchange (UK terminology) or central office (US terminology) the speech is generally digitized into a 64 kbit/s data stream in the form of an 8 bit signal using a sampling rate of 8,000 Hz, therefore – according to the Nyquist theorem – any signal above 4,000 Hz is not passed by the phone network (and has to be blocked by a filter to prevent aliasing effects). In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... This article is about the unit of information. ... Hz or hz may mean: Herero language (ISO 639 alpha-2, hz) Hertz, unit of frequency This is a disambiguation page — a list of articles associated with the same title. ... The Nyquist-Shannon sampling theorem is the fundamental theorem in the field of information theory, in particular telecommunications. ... Hz or hz may mean: Herero language (ISO 639 alpha-2, hz) Hertz, unit of frequency This is a disambiguation page — a list of articles associated with the same title. ... Properly sampled image of brick wall. ...


The laws of physics – specifically, the Shannon limit – cap the speed of data transmission. For a long time, it was believed that a conventional phone line couldn't be pushed beyond the low speed limits (typically under 9600 bit/s). In the 1950s, 4 MHz television signals were often carried between studios on ordinary twisted pair telephone cable, suggesting that the Shannon Limit would allow transmitting many Megabits per second. However, these cables had other impairments besides Gaussian noise, preventing such rates from becoming practical in the field. In the 1980s techniques were developed for broadband communications that allowed the limit to be greatly extended. A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... In information theory, the Shannon–Hartley theorem is an application of the noisy channel coding theorem to the archetypal case of a continuous-time analog communications channel subject to Gaussian noise. ... Data transmission is the conveyance of any kind of information from one space to another. ... Broadband in telecommunications is a term that refers to a signaling method that includes or handles a relatively wide range of frequencies, which may be divided into channels or frequency bins. ...


The local loop connecting the telephone exchange to most subscribers is capable of carrying frequencies well beyond the 3.4 kHz upper limit of POTS. Depending on the length and quality of the loop, the upper limit can be tens of megahertz. DSL takes advantage of this unused bandwidth of the local loop by creating 4312.5 Hz wide channels starting between 10 and 100 kHz, depending on how the system is configured. Allocation of channels continues at higher and higher frequencies (up to 1.1 MHz for ADSL) until new channels are deemed unusable. Each channel is evaluated for usability in much the same way an analog modem would on a POTS connection. More usable channels equates to more available bandwidth, which is why distance and line quality are a factor (the higher frequencies used by DSL travel only short distances). The pool of usable channels is then split into two different frequency bands for upstream and downstream traffic, based on a preconfigured ratio. This segregation reduces interference. Once the channel groups have been established, the individual channels are bonded into a pair of virtual circuits, one in each direction. Like analog modems, DSL transceivers constantly monitor the quality of each channel and will add or remove them from service depending on whether they are usable. A telephone operator manually connecting calls with patch cables at a telephone switchboard. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz. ... Hz or hz may mean: Herero language (ISO 639 alpha-2, hz) Hertz, unit of frequency This is a disambiguation page — a list of articles associated with the same title. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... A megahertz (MHz) is one million (106) hertz, a measure of frequency. ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ... An analog or analogue signal is any time continuous signal where some time varying feature of the signal is a representation of some other time varying quantity. ... Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ... For other uses, see Frequency (disambiguation). ... The term upstream has several possible meanings: In geography, upstream means literally towards the source of a stream or river, against the normal direction of water flow. ... The term downstream has several possible meanings: In geography, downstream means literally away from the source of a stream or river, along the normal direction of water flow. ... Channel, in communications (sometimes called communications channel), refers to the medium used to convey information from a sender (or transmitter) to a receiver. ... Channel bonding in computer networking is an arrangement in which two or more network interfaces on a host computer are combined for redundancy or increased throughput. ... An analog or analogue signal is any time continuous signal where some time varying feature of the signal is a representation of some other time varying quantity. ... A modem (a portmanteau word constructed from modulator and demodulator) is a device that modulates an analog carrier signal (sound), to encode digital information, and that also demodulates such a carrier signal to decode the transmitted information. ... A transceiver is a device that has both a transmitter and a receiver which are combined in to one. ...


One of Lechlider's greatest contributions to DSL was his insight that an asymmetric arrangement offered more than double the bandwidth capacity of synchronous DSL. This allowed Internet Service Providers to offer efficient service to consumers, who benefitted greatly from the ability to download large amounts of data but rarely needed to upload comparable amounts. ADSL supports two modes of transport: fast channel and interleaved channel. Fast channel is preferred for streaming multimedia, where an occasional dropped bit is acceptable, but lags are less so. Interleaved channel works better for file transfers, where transmission errors are impermissible, even though resending packets may increase latency. “Interleaver” redirects here. ... This article is about the unit of information. ...


Because DSL operates at above the 3.4 kHz voice limit, it cannot be passed through a load coil. Load coils are, in essence, filters that block out any non-voice frequency. They are commonly set at regular intervals in lines placed only for POTS service. A DSL signal cannot pass through a properly installed and working load coil, nor can voice service be maintained past a certain distance without such coils. Some areas that are within range for DSL service are disqualified from eligibility because of load coil placement. Because of this phone companies are endeavoring to remove load coils on copper loops that can operate without them, and conditioning lines to not need them through the use of fiber to the neighborhood or node FTTN. In electronics, a loading coil is a coil (inductor) that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. ... Fiber To The Node is a broadband architecture that provides high speed Internet and other services to the home by running fiber to the node and VDSL over the existing telephone copper plant to the home. ...


The commercial success of DSL and similar technologies largely reflects the advances made in electronics, that, over the past few decades, have been getting faster and cheaper even while digging trenches in the ground for new cables (copper or fiber optic) remains expensive. Several factors contributed to the popularization of DSL technology: This article is about the engineering discipline. ...

  • Until the late 1990s, the cost of digital signal processors for DSL was prohibitive. Due to the advancements of VLSI technology, the cost of the equipment associated with a DSL deployment (a DSLAM at one end and a DSL "modem" at the other end) lowered significantly.
  • A DSL line can be deployed over existing cable. Such deployment, even including equipment, is much cheaper than installing a new, high-bandwidth fiber-optic cable over the same route and distance. This is true both for ADSL and SDSL variations.
  • In the case of ADSL, competition in Internet access caused subscription fees to drop significantly over the years, thus making ADSL more economical when compared to dial up access. Telephone companies were pressured into moving to ADSL largely due to competition from cable companies, which use DOCSIS cable modem technology to achieve similar speeds. Demand for high bandwidth applications, such as video and file sharing, also contributed to popularize ADSL technology.

All types of DSL employ highly complex digital signal processing algorithms to overcome the inherent limitations of the existing twisted pair wires. Not long ago, the cost of such signal processing would have been prohibitive but because of VLSI technology, the cost of installing DSL on an existing local loop, with a DSLAM at one end and a DSL "modem" at the other end is orders of magnitude less than would be the cost of installing a new, high-bandwidth fiber-optic cable over the same route and distance. A digital signal processor (DSP) is a specialized microprocessor designed specifically for digital signal processing, generally in real-time. ... It has been suggested that VHSIC be merged into this article or section. ... Siemens DSLAM SURPASS hiX 5625 A Digital Subscriber Line Access Multiplexer (DSLAM) allows telephone lines to make faster connections to the Internet. ... For other uses, see Modem (disambiguation). ... Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ... Data Over Cable Service Interface Specification (DOCSIS) is an international standard developed by CableLabs and contributing companies that include: ARRIS, BigBand Networks, Broadcom, Cisco, Conexant, Correlant, Intel, Motorola, Netgear, Terayon, and Texas Instruments. ... Digital signal processing (DSP) is the study of signals in a digital representation and the processing methods of these signals. ... 25 Pair Color Code Chart 10BASE-T UTP Cable Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. ... VLSI may refer to: Very-large-scale integration, a process for the creation of electronic integrated circuits VLSI Technology (1979–1999), a former American integrated circuit manufacturer, now a part of Philips Electronics VLSI Solution, a Finnish integrated circuit manufacturer Category: ... Siemens DSLAM SURPASS hiX 5625 A Digital Subscriber Line Access Multiplexer (DSLAM) allows telephone lines to make faster connections to the Internet. ... For other uses, see Modem (disambiguation). ... An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. ... Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ...


Most residential and small-office DSL implementations reserve low frequencies for POTS service, so that with suitable filters and/or splitters the existing voice service continues to operate independent of the DSL service. Thus POTS-based communications, including fax machines and analog modems, can share the wires with DSL. Only one DSL "modem" can use the subscriber line at a time. The standard way to let multiple computers share a DSL connection is to use a router that establishes a connection between the DSL modem and a local Ethernet, Powerline, or Wi-Fi network on the customer's premises. Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ... A modem (a portmanteau word constructed from modulator and demodulator) is a device that modulates an analog carrier signal (sound), to encode digital information, and that also demodulates such a carrier signal to decode the transmitted information. ... For other uses, see Modem (disambiguation). ... In telecommunications, the local loop (also referred to as a subscriber line) is the physical link or circuit, that connects from the demarcation point of the customer premises to the edge of the carrier, or telecommunications service provider, network. ... This article is about a computer networking device. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... For other uses, see Power band. ... Official Wi-Fi logo Wi-Fi (pronounced wye-fye, IPA: ), also unofficially known as Wireless Fidelity, is a wireless technology brand owned by the Wi-Fi Alliance intended to improve the interoperability of wireless local area network products based on the IEEE 802. ...


Once upstream and downstream channels are established, they are used to connect the subscriber to a service such as an Internet service provider. Subscriber: In a public switched telecommunications network such as the common telephone system, the ultimate user, customer, of a communications service. ... “ISP” redirects here. ...


Dry-loop DSL or "naked DSL," which does not require the subscriber to have traditional land-line telephone service, started making a comeback in the US in 2004 when Qwest started offering it, closely followed by Speakeasy. As a result of AT&T's merger with SBC,[1] and Verizon's merger with MCI,[2] those telephone companies are required to offer naked DSL to consumers. A naked DSL (a. ... For other uses, see Telephone (disambiguation). ... This article does not cite any references or sources. ... Speakeasy, Inc. ... This article is about the current AT&T. For the 1885-2005 company, see American Telephone & Telegraph. ... SBC may refer to: Session Border Controller (VoIP, NGN term) // South Birmingham College, a college of Further Education in Birmingham, England St. ... This article or section should include material from Bell Atlantic This article or section should include material from GTE Verizon Communications (NYSE: VZ) is a local exchange telephone company formed by the merger of Bell Atlantic, a former Bell Operating Company, and GTE, which was the largest independant local exchange... MCI logo MCI, Inc. ...


Even without the regulatory mandate, however, many ILECs offer naked DSL to consumers. The number of telephone landlines in the US has dropped from 188 million in 2000 to 172 million in 2005, while the number of cellular subscribers has grown to 195 million. [2]. This lack of demand for landline service has resulted in the expansion of naked DSL availability. ILEC, short for incumbent local exchange carrier, is a local telephone company in the United States that was in existence at the time of the break up of AT&T into the Regional Bell Operating Companies (RBOCs) also known as the Baby Bells. GTE was the second largest ILEC after... A landline or main line is a telephone line which travels through a solid medium, either metal wire or optical fibre. ...


Typical setup and connection procedures

The first step is the physical connection. On the customer side, the DSL modem is hooked up to a phone line. The telephone company(telco) connects the other end of the line to a DSLAM, which concentrates a large number of individual DSL connections into a single box. The location of the DSLAM depends on the telco, but it cannot be located too far from the user because of 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. It is common for a few residential blocks to be connected to one DSLAM. When the DSL modem is powered up, it goes through a sync procedure. The actual process varies from modem to modem but can be generally described as: A digital subscriber line access multiplexer, (DSLAM) is a multiplexer located in the telephone company exchange that provides consumers access to DSL services over twisted pair copper cabling. ... This article is about Physics. ...

  1. The modem does a self-test.
  2. The modem checks the connection between the modem and the computer. For residential variations of DSL, this is usually the Ethernet port or a USB port; in rare models, a FireWire port is used. Older DSL modems sported a native ATM interface (usually, a 25 MBit serial interface). Also, some variations of DSL (such as SDSL) use synchronous serial connections.
  3. The modem then attempts to synchronize with the DSLAM. Data can only come into the computer when the DSLAM and the modem are synchronized. The synchronization process is relatively quick (in the range of seconds) but is very complex, involving extensive tests that allow both sides of the connection to optimize the performance according to the characteristics of the line in use. External, or stand-alone modem units have an indicator labeled "CD", "DSL", or "LINK", which can be used to tell if the modem is synchronized. During synchronization the light flashes; when synchronized, the light stays lit, usually with a green color.

Modern DSL gateways have more functionality and usually go through an initialization procedure that is very similar to a PC starting up. The system image is loaded from the flash memory; the system boots, synchronizes the DSL connection and establishes the IP connection between the local network and the service provider, using protocols such as DHCP or PPPoE. The system image can usually be updated to correct bugs, or to add new functionality. Look up connection, connected, connectivity in Wiktionary, the free dictionary. ... This article is about the machine. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... Note: USB may also mean upper sideband in radio. ... The 6-pin and 4-pin FireWire Connectors The alternative ethernet-style cabling used by 1394c FireWire is Apple Inc. ... Synchronization is coordination with respect to time. ... A digital subscriber line access multiplexer, (DSLAM) is a multiplexer located in the telephone company exchange that provides consumers access to DSL services over twisted pair copper cabling. ... A digital subscriber line access multiplexer, (DSLAM) is a multiplexer located in the telephone company exchange that provides consumers access to DSL services over twisted pair copper cabling. ... In telecommunications, the term gateway has the following meanings: In a communications network, a network node equipped for interfacing with another network that uses different protocols. ... A USB flash drive. ... DHCP in the context of computing can stand for: Dynamic Host Configuration Protocol - one of the protocols in the TCP/IP networking suite Decentralized Hospital Computer Program of the United States Department of Veterans Affairs This article consisting of a 4-letter acronym or initialism is a disambiguation page — a... PPPoE, point-to-point protocol over Ethernet, is a network protocol for encapsulating PPP frames in Ethernet frames. ...


Equipment

The customer end of the connection consists of a DSL modem. This converts data from the digital signals used by computers into a voltage signal of a suitable frequency range which is then applied to the phone line. Westell Model 6100 ADSL modem An asymmetric digital subscriber line transceiver, also known as an ADSL modem or DSL modem, is a device used to connect a single computer to a DSL phone line, in order to use an ADSL service. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ...


In some DSL variations (for example, HDSL), the modem is directly connected to the computer via a serial interface, using protocols such as RS-232 or V.35. In other cases (particularly ADSL), it's common for the customer equipment to be integrated with higher level functionality, such as routing, firewalling, or other application-specific hardware and software. In this case, the entire equipment is usually referred to as a DSL router or DSL gateway. Digital Subscriber Line, or DSL, is a family of technologies that provide a digital connection over the copper wires of the local telephone network. ... RS-232 (also referred to as EIA RS-232C or V.24) is a standard for serial binary data interchange between a DTE (Data terminal equipment) and a DCE (Data communication equipment). ... It is an ITU-T standard (International Telecommunication Union Telecommunication Standardization Sector) Located on layer 1 on the OSI model Max speed of 2 Mbit/s See also V.24 ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ...


Some kinds of DSL technology require installation of appropriate filters to separate, or "split", the DSL signal from the low frequency voice signal. The separation can be done either at the demarcation point, or can be done with filters installed at the telephone outlets inside the customer premises. Either way has its practical and economical limitations. See ADSL for more information about this. In telephone networks, the demarcation point is the point at which the telephone companys local loop network ends and connects with the telephone system or wiring at the customers premises. ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ...


At the exchange, a digital subscriber line access multiplexer (DSLAM) terminates the DSL circuits and aggregates them, where they are handed off onto other networking transports. In the case of ADSL, the voice component is also separated at this step, either by a filter integrated in the DSLAM or by a specialized filtering equipment installed before it. The DSLAM terminates all connections and recovers the original digital information. Siemens DSLAM SURPASS hiX 5625 A Digital Subscriber Line Access Multiplexer (DSLAM) allows telephone lines to make faster connections to the Internet. ...


Protocols and configurations

Many DSL technologies implement an asynchronous transfer mode ATM layer over the low-level bitstream layer to enable the adaptation of a number of different technologies over the same link. Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ...


DSL implementations may create bridged or routed networks. In a bridged configuration, the group of subscriber computers effectively connect into a single subnet. The earliest implementations used DHCP to provide network details such as the IP address to the subscriber equipment, with authentication via MAC address or an assigned host name. Later implementations often use PPP over Ethernet or ATM (PPPoE or PPPoA), while authenticating with a userid and password and using PPP mechanisms to provide network details. Bridging is a forwarding technique used in packet-switched computer networks. ... This article is about routing (or routeing) in computer networks. ... DHCP redirects here. ... An IP address (Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address. ... For other uses of the terms authentication, authentic and authenticity, see authenticity. ... In computer networking a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA) or hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NICs). ... In computing, the Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between two nodes. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operate at many speeds for local area networks (LANs). ... Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ... PPPoE, Point-to-Point Protocol over Ethernet, is a network protocol for encapsulating PPP frames in Ethernet frames. ... PPPOA or PPPoA, Point-to-Point Protocol (PPP) over ATM, is a network protocol for encapsulating PPP frames in ATM AAL5. ... In computing, the Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between two nodes. ...


DSL also has contention ratios which need to be taken into consideration when deciding between broadband technologies. In telecommunication, the term contention has the following meanings: A condition that arises when two or more data stations attempt to transmit at the same time over a shared channel, or when two data stations attempt to transmit at the same time in two-way alternate communication. ...


DSL technologies

The line length limitations from telephone exchange to subscriber are more restrictive for higher data transmission rates. Technologies such as VDSL provide very high speed, short-range links as a method of delivering "triple play" services (typically implemented in fiber to the curb network architectures). Technologies likes GDSL can further increase the data rate of DSL. It has been suggested that VDSL2 be merged into this article or section. ... In telecommunications, the Triple Play service is a marketing term for the provisioning of the three services: high-speed Internet, television (Video on Demand or regular broadcasts) and telephone service over a single broadband connection. ... Fiber To The Curb (FTTC) refers to a telecomunications system based on fiber-optic cables run to a platform that serves several customers. ...


Example DSL technologies (sometimes called xDSL) include:

High Data Rate Digital Subscriber Line (HDSL) was the first DSL technology that uses a higher frequency spectrum of copper, twisted pair cables. ... Symmetric Digital Subscriber Line (SDSL) is a Digital Subscriber Line (DSL) variant with E1-like data rates (72 to 2320 kbit/s). ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. ... ISDN Digital Subscriber Line (IDSL) transmits data digitally (rather than analog) on a regular twisted pair copper telephone line, across existing ISDN lines, at a rate of 144 kbit/s, slightly higher than a bonded dual channel ISDN connection at 128kbit/s. ... Rate-adaptive DSL (RADSL) is a variation of ADSL technology. ... VDSL or VHDSL (Very High Speed DSL) is an xDSL technology providing faster data transmission over a single twisted pair of wires. ... VDSL2 (Very High Speed Digital Subscriber Line 2) is an access technology that exploits the existing infrastructure of copper wires that were originally deployed for POTS services. ... Symmetric high-speed digital subscriber line (SHDSL) is a telecommunications technology for Digital Subscriber Line (DSL) subscriber lines. ... Power line communication (PLC), also called Mains Communication or Power Line Telecoms (PLT) or Powerband, is a term describing several different systems for using power distribution wires for simultaneous distribution of data. ... Uni-DSL (UDSL) is a DSL-technology developed by Texas Instruments which would provide at least 200 Mbit/s[1] in aggregate on the downstream and upstream paths. ... Etherloop is a kind of next generation DSL technology that combines the features of Ethernet and DSL. It allows the combination of voice and data transmission on standard phone lines. ...

Transmission methods

Transmission methods vary by market, region, carrier, and equipment.

Carrierless Amplitude Phase Modulation is a non-standard variation of quadrature amplitude modulation (QAM). ... Orthogonal frequency division modulation (OFDM, also called orthogonal frequency division multiplexing) is a technique for the modulation of digital information onto an analog carrier electromagnetic (e. ... Orthogonal Frequency-Division Multiplexing (OFDM) — essentially identical to Coded OFDM (COFDM) — is a digital multi-carrier modulation scheme, which uses a large number of closely-spaced orthogonal sub-carriers. ...

See also

A WildBlue Satellite Internet dish. ... This article is becoming very long. ... Siemens DSLAM SURPASS hiX 5625 A Digital Subscriber Line Access Multiplexer (DSLAM) allows telephone lines to make faster connections to the Internet. ... Dynamic Spectrum Management (DSM) is a technique being researched to improve Digital Subscriber Line (DSL) performance over ordinary copper phone lines by reducing or eliminating crosstalk between DSL phone lines that are close together. ... Television signal splitter consisting of a hi-pass filter (left) and a low-pass filter (right). ... ISDN redirects here. ... For other uses, see Modem (disambiguation). ... Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ... This article is about a computer networking device. ... In telecommunications, the Triple Play service is a marketing term for the provisioning of the three services: high-speed Internet, television (Video on Demand or regular broadcasts) and telephone service over a single broadband connection. ... Official Wi-Fi logo Wi-Fi (pronounced wye-fye, IPA: ), also unofficially known as Wireless Fidelity, is a wireless technology brand owned by the Wi-Fi Alliance intended to improve the interoperability of wireless local area network products based on the IEEE 802. ...

References

  1. ^ SBC ATT Merger
  2. ^ Verizon MCI merger
  3. ^ B. Lee, J. Cioffi, et al. (September, 2007). "Gigabit DSL". IEEE Transactions on Communication. 55 (9): 1689-1692. 
  • Burstein, Dave (2002). DSL. John Wiley and Sons, New York. ISBN 0-471-08390-9.  pp 53-86
  • Lechleider, Joseph, High Bit Rate Digital Subscriber Lines: A Review of HDSL Progress, IEEE Journal 9:6 (August 1991) pp 769-84
  • B. Lee, J.Cioffi, et al, Gigabit DSL, IEEE Transaction on Communication, Sep, 2007, pp 1689-1692

External links


  Results from FactBites:
 
Digital Subscriber Line (DSL) (1978 words)
DSL (Digital Subscriber Line) is a relatively new method of achieving high speed internet access using the existing twisted copper pair telephone lines which currently provide conventional POTS (Plain Old Telephone Service) from the subscribers premises to the central office.
High-speed data service over existing lines is possible because of the electrical characteristics of the copper line, which, if the line is not too long, permit useful signals to be transmitted over a band of frequencies as high as one megahertz.
When a new line is required in any one building at a future date the subscriber is simply connected to the "bridged tap" which was fortuitously installed when line installation crews were available in the past.
Digital subscriber line - Wikipedia, the free encyclopedia (1749 words)
DSL or xDSL, is a family of technologies that provide digital data transmission over the wires of a local telephone network.
Digital Subscriber Line technology was originally implemented as part of the ISDN specification.
DSL is the principal competition of cable modems for providing high speed Internet access to home consumers in Europe and North America.
  More results at FactBites »

 
 

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