History of DSL

Digital subscriber line technology was developed by Joe Lechleider at Bellcore (later renamed Telcordia Technologies). The first type of DSL, ADSL (Asymmetric Digital Subscriber Line) was created in 1988, through placing digital signals above the baseband analog voice signal used to carry out phone conversations.

US phone companies will promote DSL to compete with cable internet service. The first DSL services were provided through a dry loop, but once the Federal Communications Commission (FCC) made it mandatory for incumbent local exchange carriers share their lines with competing providers such as Verizon, the shared line became very common. This system allows for a single pair to transmit information with a DSLAM, and analog voice (phone conversion), at the same time.

Earlier ADSL standards were able to deliver 8 Mbit/s to the user over roughly 2km of ethernet cables (unshielded twisted pair copper wire). With the newest ADSL standard (ADSL2+), it is possible to deliver up to 24 Mbit/s, based on the distance from the DSLAM (usually located at the providers offices). Many customers are unfortunate, and further away from the provider than 2KM, which will result in reduced data transfer rates.

Edited by Administrator - 05 Apr 2007 at 6:31pm

In the 1980s Joseph Lechleider came up with the solution for this very problem. He figured out how to transmit data over broadband signals. For this, he is credited as being the father of broadband technologies. Along with the idea of broadband, he came up with the idea of ADSL (Asymmetrical DSL). This was significant because it allowed users to download data at a faster rate than they uploaded it. This system mirrored the way most users used the Internet- downloading many more items than the ever uploaded, making the need for a faster download speed than upload speed.

ADSL started the move from analog connections to digital connections.

Next came DMT (Discrete multitone) which was developed by John Cioffi. DMT separated a DSL signal into 256 frequency channels.

HDSL (high bit-rate DSL) was the version of DSL which was the most widely used. It was developed in the early 1990s and gave an equal amount bandwidth in both directions. This was primarily used for data transfers between the telephone company and the consumer and also within a corporation.