ADSL stands for Asymmetric Digital Subscriber Line and is a common type of DSL communication technology designed to offer faster speeds and greater bandwidth over traditional dial-up connections. ADSL allows faster transmission and more data to be sent over existing copper telephone lines that are used for landlines when compared to traditional modem lines. The word Asymmetric in ADSL refers to the fact that it uses most of its capacity to transmit signals downstream towards the customer in order to provide faster download speed.
History
In the 1980s, Bellcore developed a variation of DSL, called the HDSL (High bit-rate DSL), which gave an equal amount of broadband digital transmission in both directions, i.e., same bandwidth for both downloads and uploads. It had a disadvantage because it required multiple phone lines to do this. In the late 1980s, Joseph Lechleide demonstrated how asymmetry in sending broadband signals would help in better download speed and higher bandwidth by suggesting that a higher rate of data could be sent in one direction. This was a move from analog to digital. The deployment costs were high initially when it was developed, and it was not until the late 1990s when it was rolled out for public use. It got popular in the 2000s, and now almost all the technologies have been upgraded to support ADSL
Characteristics of ADSL
- The ADSL provides both data transmission and voice transmission at the same time using a single copper telephone line.
- The ADSL requires a modem to be installed that allows data traffic between the line itself.
- The ADSL connection consists of three independent transmission lines:
- Data transmission channel Used to send the user’s information to the Internet (upload).
- Data reception channel Used to receive information from the Internet (download). It is the widest of the three channels.
- Regular telephone service channel Used to transmit the telephone calls.
- The data transfer speeds vary significantly between one operator and another.
- ADSL is the broadband connection technology and can reach speeds of up to 6Mbps, but only receives 2Mbps download and 512Kbps upload speeds
Advantages
- ADSL provides a greater bandwidth.
- ADSL is always ‘on’ and it doesn’t require dialing-up each time thus saving time.
- ADSL provides thirty to forty times faster speed than a dial-up connection.
- The voice quality and the browsing speeds are not affected by the fact that they use the same telephone line for transmission.
- ADSL uses the existing infrastructure, thus lowering the installation costs and making it easy to install.
Disadvantages
- Speed is dependent on the distance between your home (or office) and the ISP’s office, which sometimes results in receiving a rate considerably lower than offered.
- Slower upload speed.
- ADSL is susceptible to interference.
- ADSL is affected by the number of users using the same line in the certain area simultaneously.