Реферат: ADSL Essay Research Paper Overview
vast majority of their network, taking it from the curb to the customer’s
residence or business was the problem. The cost alone would run into the
billions, and nobody could afford to keep laying fiber in hopes that the
home they went to would use all of the capabilities fiber had to offer.
Enter ADSL. ADSL allows a standard copper telephone line to carry a high-speed
digital signal while simultaneously transmitting a voice conversation.
The asymmetrical part of the service refers to the fact that the high-speed
transmission of data is one-way, from the central office to the home or
business. Since most homes or small businesses only need the speed to
receive information, not transmit it, this works very well. And, initially,
ADSL permitted transmission at 1.5 megabits per second (Mbps) over copper
wire for up to 18,000 feet. The vast majority of small businesses and
residences easily fell within 18,000 feet of a telephone switching office.
Because of the poor initial success of the last great plan to use the
telephone companies’ copper wire, Integrated Services Digital Networks
(ISDN), ADSL was met with skepticism. Many telcos, as well as manufacturers,
originally developed a wait-and-see attitude before investing in the new
service. But, in 1993, a tiny California company called Amati
teamed up with Northern Telecom
to prove that ADSL could be used to send 6 Mbps of full-motion video down
a conventional telephone line. Suddenly the telephone companies had a
weapon, albeit an interim one, that could be used against the cable companies.
Big companies, like Bell Atlantic,
realized that ADSL could be used immediately to stay in the game, removing
the pressure to replace the copper wire with fiber. Instead of spending
time and money to bring hybrid fiber/coax (HFC) or fiber-to-the-curb (FTTC)
into a large area for an unknown number of users, the telcos could now
target specific users who were willing to pay for the equipment necessary
to make the service work.