Digital subscriber line DSL ; originally digital subscriber loop is a family of technologies that are used to transmit digital data over telephone lines. In ADSL, the data throughput in the upstream direction the direction read more the service provider is lower, hence the designation of asymmetric service. In symmetric digital subscriber line SDSL services, the downstream and upstream data rates are equal.
DSL service can be delivered simultaneously with wired telephone service on the same telephone line since DSL uses higher frequency bands for data transmission. On the customer premises, a DSL filter is installed on each dsl to prevent undesirable interaction between DSL and telephone service. The exact performance is depending on technology, line conditions, and service-level implementation.
Initially, it was believed that ordinary phone lines could only be used hookup modest speeds, usually less than bits per second. In the s, ordinary twisted-pair telephone cable often carried 4 MHz television signals between studios, suggesting that such lines would allow transmitting many megabits per second.
Wiring Diagrams
However, these cables had other impairments besides Gaussian noisepreventing such rates from becoming practical in the field. The s saw the development of techniques for broadband communications that allowed the limit to be greatly extended. A patent was filed in for the use of existing telephone hookup for both telephones and data terminals that were diagram to a remote computer via a digital data carrier system.
Employees at Bellcore now Telcordia Technologies developed asymmetric digital subscriber line ADSL by placing wide-band digital signals at frequencies above the existing baseband analog voice signal carried on conventional twisted pair cabling between telephone exchanges and customers.
Joseph W. Lechleider 's contribution to DSL was his insight free online dating chat room an asymmetric arrangement offered more than double the bandwidth capacity of symmetric DSL. ADSL supports two modes of transport: fast channel and interleaved channel. Fast channel is preferred for streaming multimediawhere an occasional dropped bit is acceptable, but lags are less so. Dsl channel works better for file transfers, where the delivered data must be error-free but latency time delay incurred this web page the retransmission of error-containing packets is acceptable.
Newer variants improved these rates. Distances greater than 2 km 1. Until the late s, the cost of digital signal processors for DSL was prohibitive. All types of DSL employ highly complex digital signal processing algorithms to overcome the inherent limitations of the existing twisted pair wires.
Due to the advancements of very-large-scale integration VLSI technology, the cost of the equipment associated with a DSL deployment lowered significantly. It is possible to set up diagram DSL connection over an 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. The commercial success of DSL and similar technologies largely reflects the advances made in electronics over the decades that have increased performance and reduced costs even while digging trenches in the ground for new cables copper or fiber optic remains expensive. These advantages made ADSL a better proposition for customers requiring Internet access than metered dial up, while also allowing voice calls to be received at the same time as a data connection.
Demand for high bandwidth applications, such as video and file sharing, also dsl to the popularity of ADSL technology. Some of the first field trials for DSL were carried out in Early DSL service required a dedicated dry loopbut when the U.
Also known as DSL over unbundled network elementthis unbundling of services allows hookup single subscriber to receive two separate services from two separate providers on one cable pair. The DSL service provider's equipment is co-located in the same telephone exchange as that of the ILEC supplying the customer's pre-existing voice service.
Sincedsl ISPs have been offering microfilters. Telephones are connected to the telephone exchange via a local loopwhich is a physical pair of wires. The local loop was originally intended mostly for the transmission of speech, encompassing an this web page frequency range of to hertz commercial bandwidth.
However, as long-distance trunks were gradually converted from analog to digital operation, the idea of being able to pass data through the local loop by using frequencies above the voiceband took hold, ultimately leading to DSL. The local loop connecting the telephone exchange to most subscribers has the capability of carrying frequencies well beyond the Hz 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 Allocation of channels continues to higher frequencies up to 1.
Install Your Own DSL Internet Connection
Each channel is evaluated for usability in much the same hookup an analog modem would on a Diagram connection. More usable channels equate to more available bandwidth, which is hookup distance and line quality are a factor the higher frequencies used by DSL travel only short distances. The pool of diagram channels is then split into two different frequency bands for upstream and downstream traffic, based on a preconfigured ratio.
This segregation reduces interference. Once dsl 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 diagram on whether they are usable. Once upstream and downstream circuits are established, a subscriber can connect to a service such as hookup Internet service provider or other network services, like a corporate MPLS network.
The underlying technology of transport across DSL facilities uses modulation of high-frequency carrier wavesan analog signal transmission. A DSL circuit terminates at each end in a modem which modulates patterns of bits into certain high-frequency impulses for transmission to diagram opposing modem. Signals received from the far-end modem are demodulated to yield a corresponding bit pattern just click for source the modem passes on, in digital form, to its interfaced equipment, such as a computer, router, switch, etc.
Unlike traditional dial-up modems, which modulate bits into signals in the — Hz audio baseband, DSL modems modulate frequencies from Hz to as high as 4 MHz. This frequency band separation enables DSL service and plain old telephone service POTS to coexist on the same cables, known as voice-grade cables. Also, nonlinear elements in the phone hookup otherwise generate audible intermodulation and may impair the operation of the data modem in the absence of these low-pass filters.
Because DSL operates above the 3. Loading coils are commonly set at regular intervals in POTS lines. Voice service cannot be maintained past a certain distance without such coils. Therefore, some areas that are within range for DSL service are disqualified from eligibility because of loading coil placement.
Because of this, phone companies endeavor to remove loading coils on copper loops that can operate without them. Longer lines that require them can be replaced with fiber to the neighborhood or node FTTN. Only one DSL modem can use the subscriber line at a time. The standard way to let multiple computers share a DSL connection uses a router that establishes a connection between the DSL modem and a local Ethernetpowerlineor Wi-Fi network on the customer's premises.
The theoretical foundations of DSL, like much of communication technology, can be traced back to Claude Shannon 's seminal paper, " A Mathematical Theory of Communication ". Generally, higher bit diagram transmissions require a wider frequency band, though the ratio of bit rate to symbol rate and thus to bandwidth are not linear due to significant innovations in digital signal processing and digital modulation methods. It is useful when the customer does not need the traditional telephony voice service because voice service is received either on top of the DSL services usually VoIP or through another network E.
It started making a comeback in the United States in when Qwest started offering it, closely followed by Speakeasy. On the customer side, a DSL modem is hooked up to a phone line. The telephone company connects the dsl end of the line to a DSLAM diagram, which concentrates hookup large number of individual DSL connections into a single box.
The above figure is a schematic of a simple DSL connection in blue. The left side shows the customer premises equipment with an optional router. The router manages a local area network which connects PCs and other local devices. The customer may opt for a modem that contains dsl a router and wireless access.
This option within the dashed bubble often simplifies the connection. At the exchange, a digital subscriber line access multiplexer DSLAM terminates the DSL circuits and aggregates them, where they learn more here handed off to other networking transports. In the case of ADSL, the voice component is also separated at this step, either by a filter or splitter integrated in the DSLAM or by specialized filtering equipment installed before it.
The customer end of the connection consists of a DSL modem. This converts data between the digital signals used by computers and the analog voltage signal of a suitable dsl range which is then applied to the phone line. In other cases particularly ADSLit is 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 dsl is referred to as a gateway. The separation can take place either at the demarcation pointor with filters installed at the telephone outlets inside the customer premises. It is possible for a DSL gateway to integrate the filter, and allow telephones to connect through the gateway. Modern DSL gateways often integrate routing and other functionality. 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.
DSL implementations may create bridged or routed networks. Diagram a bridged configuration, the group of subscriber computers effectively connect into a single subnetwork. The line-length limitations check this out telephone exchange to subscriber impose severe limits on data transmission rates. Technologies such as VDSL provide very high-speed but short-range links. VDSL is used as a method of delivering hookup play services typically implemented in fiber to the curb network architectures.
Terabit DSL, is a technology that proposes the use of the space between the dielectrics insulators on copper twisted pair lines in telephone cables, as waveguides for GHz signals that can offer speeds of up to 1 terabit per second at distances of up to meters, gigabits per second for meters, and 10 gigabits per second for meters.
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From the Pole to the House
Tools Tools. Download as PDF Printable version. In other projects. Wikimedia Commons Wikidata item. Family of technologies that are used to transmit digital data over telephone lines. For other uses, see DSL disambiguation. History [ edit ]. Operation [ edit ]. This section does not cite any sources.