History of Dsl

History of DSL

The technological race is a fast-paced one indeed. Improvements are constantly being sought. What had at one time seemed to be amazing advances quickly became yesterday's news. But have you ever wondered where it all started? Has DSL (Digital Subscriber Line) always moved at this speed? This history of DSL Internet access will show just how quickly new technology became old. Any history of the transmission of data begins with Alexander Graham Bell and Samuel Morse, two pioneers who developed the idea that data could be transmitted through copper wire. Of course, they had no idea of the scope of their findings, or where they would actually lead. However, the principles had been laid.

The principles demonstrated by these two great pioneers, Bell and Morse, were instrumental in developing a path for the ever-increasing volume of data transmitted over the Internet. In the late 1980s, Joseph Lechleider, of Bellcore, demonstrated the feasibility of sending broadband signals, establishing his place in history as the originator of broadband technologies. He developed the idea of asymmetry (the A in ADSL), which suggested that a higher rate of data could be sent in one direction. Putting it simply, this was the beginning of the move from analog to digital.

The first efforts of this new technology created ISDN. ISDN, which stands for Integrated Services Digital Network, is a system of digital phone connections which allows voice and data to be transmitted simultaneously across the world. The result of this is that more data could be transmitted at the same time, thus creating more speed. And remember, speed was (and still is) the goal. John Cioffi, who eventually became a professor at Standard University's Department of Electrical Engineering, developed DMT (discrete multitone), a method of separating a DSL signal into 256 frequency bands or channels. Cioffi founded a company called Amati, who, in 1993, designed equipment to perform this task. And this equipment was dramatically better than its competitors in Bellcore testing and became the most common standard.

The earliest variation of DSL to be widely used was HDSL (High bit-rate DSL) which gave an equal amount of wideband digital transmission in both directions. HDSL technology was developed in the early 1990s, making it one of the oldest forms of DSL. It was used between the telephone company and a customer, and also within a corporate site. HDSL service provided equal bandwidth for both downloads and uploads, but required multiple phone lines to do this.

So now the technology was available to achieve the dream of delivering video-on-demand, an idea that had high hopes for the future. At the time, cable companies were promising the possibility of 500 channels and video-on-demand (VOD) could compete with this. However, the idea didn't catch on and the industry never really fulfilled its desires. As the idea of VOD phased out, DSL emerged much differently than was originally expected. Personal computer users needed high-speed access to the Internet, especially in the corporate domain. Considering the fast pace of business and the amount of networked computer systems, high-speed DSL became the solution.

DSL now presented an opportunity to telecommunications companies to meet their customer demand for faster data access on the Internet. Everyone wanted to get in on the act. And to keep order, the Telecommunications Reform Act of 1996 was introduced in the United States, allowing local phone companies, long-distance carriers, cable companies, radio-TV broadcasters, Internet service providers and telecommunications equipment manufacturers to compete in each other's markets. The race to provide faster data transfer was on!

DSL Technical Specifications

Digital Subscriber Line (DSL) is a family of technologies that provide a digital connection over the copper wires of the local telephone network. This allows an ordinary phone line to provide digital communication without blocking access to voice services. There are two main types of Digital Subscriber Line (DSL). Symmetric Digital Subscriber Line DSL (SDSL) and Asymmetric Digital Subscriber Line (ADSL). Symmetric Digital Subscriber Line (SDSL) is a Digital Subscriber Line (DSL) variant with E1- like data ranges generally used for wide web and digital transmission within a corporate site and between the telephone company and a customer.

The main characteristics of SDSL are that SDSL has the same upstream data transfer rate as downstream (symmetrical) and it is balanced: an equal amount of bandwidth is available in both directions and the data rate is in the same in both directions. SDSL can carry as much on a single wire of twisted-pair cable as in a T1 line, (up to 10544 Mbps) but over a somewhat longer range.

Symmetric Digital Subscriber Line (SDSL) services provide the same bandwidth upstream (sending) and downstream (receiving). SDSL DSL services provide identical data rates whether you are sending information, like an email, or receiving information, downloading a file or accessing a web site. Asymmetric Digital Subscriber Line (DSL) provides relatively lower rates upstream but higher rates downstream. The top speed you can you can get from ADSL has 7 or 8 megabits (Mbs) max speed and you must have quality phone lines. With standard ADSL, the band from 25.0875 kHz to 138 kHz is used to upstream communication, while 138 kHz-1104 kHz is used for downstream communication.

Asymmetric Digital Subscriber Line (ADSL) is typically what consumers use and has a faster download and upload is slower. The top speed you can get from ADSL has 7 or 8 megabits (Mbs) max speeds; you must have quality phone lines to have this service. ADSL is ideal for most homes and small businesses. Most of its two-way or duplex bandwidth is devoted to the downstream direction, sending data to the user. Only a small portion of bandwidth is available for upstream or user-interaction messages. Most broadband data graphics and multi-media, for example need lots of downstream bandwidth. At the same time, the average homes or small business generally requires little upstream bandwidth. Using Asymmetric Digital Subscriber Line (ADSL), up to 6.1 megabits per second of data can be sent downstream and up to 640 Kbps. upstream.

The downstream bandwidth means that your telephone line will be able to bring motion video, audio, and 3-D images to your computer or hooked-in TV set. In addition, a small portion of the downstream bandwidth can be devoted to voice rather data, and you can hold phone conversations without requiring a separate line. Unlike a similar broadband service over your cable TV line, ADSL will not complete for bandwidth with neighbors. Although existing