ADSL stands for Asymmetric Digital Subscriber Line. In ADSL, Bandwidth and bit rate are asymmetric, meaning greater toward the customer premises (max of 20 Mbps downstream) than the reverse (max of 1 Mbps upstream).
While the standard speed specs for ADSL are 20/1 most users will not achieve these speeds. The main factors affecting speed at a particular location are distance from the exchange and quality of the copper line to the premises.
Most Australian users that are within 2 kilometres from the exchange can expect 7 to 14 Mbps download speed, once you pass 2 kilometres in distance the speed can drop down to around 2 to 4 Mbps, most connections can expect 0.5 to 0.8 Mbps upload speed.
The reasons for an asymmetric connection are that, firstly, most users of internet traffic will require less data to be uploaded than downloaded. For example, in normal web browsing, a user will visit a number of web sites and will need to download the data that comprises the web pages from the site, images, text, sound files etc. but they will only upload a small amount of data.
ADSL works by using the frequency spectrum above the band used by voice telephone calls. With a DSL filter, often called splitter, the frequency bands are isolated, permitting a single telephone line to be used for both ADSL service and telephone calls at the same time. ADSL is generally only installed for short distances from the telephone exchange typically less than 4 kilometres.
At the telephone exchange, the line generally terminates at a digital subscriber line access multiplexer (DSLAM) where another frequency splitter separates the voice band signal for the conventional phone network.
Logistics
Comments