T 1 E 1 O Hdsl Technology example essay topic

HDSL What does HDSL stand for? High-bit-rate Digital Subscriber Line. When I first took on this topic I really was not sure what HDSL stood for. I knew about DSL but there were so many forms of DSL I really did not know one from the other. So I started at the basics.

What is DSL? A digital subscriber link, a way to digitally connect residences and businesses to the Internet or remotely to a LAN. DSL offers high-speed transmission over already existing twisted-pair copper wire. The twisted-pair copper cables into homes or offices can usually carry more than 64 kb /'s but the telephone company needs to handle the signal as digital rather than analog. DSL is an alternative to ISDN, it is offered in many variations such as ADSL, SDSL, HDSL, and VDSL. So the term xDSL was formed, implying the "x" could be any one of the variation variables.

This has been in use for some years in some countries to provide broad band facilities to business premises (leased line), providing 2 Mbps across up to three miles of wire. DSL stands for Digital Subscriber Line: o Digital - means a line able to carry data traffic in its original form, as opposed to analogue (see below) o Subscriber Line - the line connecting the individual subscriber (e.g. a household) to the local exchange o Analogue - the phone lines we have used for voice phone calls until today have been analogue lines and we have used Modems (Modulator-Demodulator) to convert the digital output of the computer to analogue form for transmission and back into digital form at the other end for use by the computer. The performance of conventional modems and analogue lines has restricted bandwidth - the speeds at which computers can be connected across the phone network and the capacity of the networks to handle traffic. The use of digital lines makes transmission of computer information faster and more reliable. It also allows much faster connect and disconnect, eliminating the slow process required for modems to establish a connection and start handling traffic. Over time its expected that all future telephony will be digital.

In order to achieve data transmission rates of up to 300 times faster than analog modems, DSL technologies use a wider band of frequencies. Also, because DSL uses a digital signal, DSL transmissions do not pass through the regular analog voice telephone network, but instead are routed on a parallel data network. This element of DSL can clear up the "congestion" that a lot of dial-up Internet traffic causes, routing allows multiple persons to simultaneously use one DSL line. For example, a husband could be surfing the web while his wife is on another computer checking e-mail with the same DSL connection. xDSL variations require different customer interface equipment and operate at varying speeds. Copper networking covers almost every mile of the country and is currently the most cost-effective way for carriers to deploy services. As long as copper telephone wires are used for transporting data and voice, DSL will be a viable technology.

HDSL, is one form of Digital Subscriber Line (DSL), providing 1.544 Mbps T 1 or 2.048 Mbps E 1 (Europe) connections over two or three twisted-pair copper lines, respectively. HDSL technology links a user to a central office over two twisted-pairs that have the same speed in both directions (symmetric). The data stream, which can transmit for distances up to about 6 km, is divided into two streams each at half rate (i.e. 784 kbps). These are independently transmitted over the cables and the data is then recombined at the receiving end.

HDSL is an alternative to traditional T 1/E 1 connections, such as connecting P BXs to telco offices, and is usually cheaper. HDSL uses less bandwidth (than T 1 line) and does not require repeaters. Eliminating repeaters allows for minimal administration and maintenance. Installation, which is quick and easy, is only necessary at the central office and the demarcation point of the customer premises. HDSL technology uses 2 B 1 Q line coding developed for ISDN. Since HDSL can live in the same cable binders as other lines, it has been designed to eliminate crosstalk from other DSL interference, as well as reduce electromagnetic coupling.

HDSL and HDSL 2 were designed to be compatible with other services such as ADSL or T 1, which reduces engineering time and costs. Still, HDSL is lacking equipment interoperability which is an inconvenience for carriers. HDSL has developed as an industry standard, as defined by Bellcore TA-210 modulation scheme. The high-capacity services offered by HDSL meet customer serving area (CSA) guidelines since it is offered over already existing copper lines. High Bit Rate DSL is a symmetric technology, which provides the same transmission rate in both directions.

HDSL is the most mature DSL, because it has been used to provide T 1 transmission over existing twisted pair without the additional provisioning typically required for setting up T 1 circuits such as the removal of bridged taps and the installation of repeaters. HDSL requires two cable pairs and goes up to 12,000 feet, while HDSL-2 requires only one cable pair and supports distances up to 18,000 feet. HDSL does not allow line sharing with analog phones. HDSL-based hardware can be installed in central office units as a stare alone transport system located near a DS-1 cross-connect frame, in the outside plant or at the customer premises.

It also is being integrated into multimedia access / transport platforms based on the synchronous optical network. There are several issues driving the development of HDSL technology for high-capacity, T-1 service over copper: o There is fierce competition among service providers in metropolitan areas. o Most customers are impatient about the long provisioning intervals for services that typically can be provided over conditioned copper T-I lines. o The majority of these customers need only access and transport because the high-capacity services come to them from an inter-exchange carrier through the LEC. o The major service providers have tight budgets and shrinking human resources to manage and deliver service. o The current medium in the local loop is copper, and it is likely to remain that way for some time. o Neither customers nor regulators will allow carriers to pass on, with any significance, the additional expense of duplicating an already existing copper network with fiber. Because HDSL is an electronic technology that eliminates the need for conditioned lines, it is an excellent solution to these problems. Using existing technologies, lines have to be conditioned by the separation of transmit and receive pairs, removal of bridge taps and addition of line repeaters. Benefits of HDSL o Fiber optic-like quality of transmission over already existing copper wire. o High-speed communications without having to invest in new infrastructure. o Simpler installation and cheaper than T 1/E 1. o HDSL technology does not require repeaters to enhance signal strength and distance (T 1/E 1 technology does). Distances extend from four to six kilometers.

Applications o Campus Applications: LAN-to-LAN connectivity, LAN / WAN interconnection, PBX network to distribute voice traffic, remote data center access, video-teleconferencing, traditional copper circuits connect with high-speed fiber optic backbones. o Fiber Access Applications: HDSL can provide digital link access to SDH and SONET fiber backbone networks. o Cellular Applications: HDSL can provide link between remote cell locations and central sites. Satellite locations can be inter-linked. HDSL By Debbie Chalmers 3 Questions 1. What does HDSL stand for? High-bit-rate Digital Subscriber line 2. What is one Advantage of HSD L?

Choice of 4 Fiber optic-like quality of transmission over already existing copper wire. High-speed communications without having to invest in new infrastructure. Simpler installation and cheaper than T 1/E 1. HDSL technology does not require repeaters to enhance signal strength and distance (T 1/E 1 technology does). 3. Is HDSL symmetric or asymmetric?

Symmetric.