xDSL or Digital Subscriber Lines

The term DSL is an acronym for Digital Subscriber Lines and this term is the name of the family that provide technology for digital data transmission through the network over the wires of the local telephone network, which are usually made up of copper wires. The best example of this technology is broadband, where the internet ability is provided to the user over these telephone lines.
The two main categories of this xDSL are ADSL or Asymmetric Digital Subscriber Line and SDSL or Symmetric digital subscriber line. Apart from these two major categories, there are two other types of categories present in the market as well, named HDSL or High Data Rate DSL and VDSL or Very High DSL. These two types of the DSL are quite expensive and are installed only in the large sized enterprise, as they installation and the operational costs are both high. The most common type of the DSL that is used by many people throughout the world is ADSL, as it is cheaper and the operational costs are also low.
This DSL technology basically pack the data on to the copper wire by using a sophisticated modulation technique and schemes and this technology is only used for connection from the telephone lines to homes and offices but not for providing connections between the switching stations. This xDSL technology is quite similar to the ISDN technology as they both operate on the copper wires and both require the short run to the telephone office. However, the major difference between these two lies in the matter of speed.
The xDSL technology is capable of giving speed up to 32 Mbps for upstream traffic and max speed of 1 Mbps for the downstream traffic. This technology is currently undergoing revision and it is quite possible that the speed that this technology has to offer to the users might even increase drastically, after all the main thing is loading the cables with the data packets with the help of modulation schemes.

- A xDSL modem is the device found at the customer’s premise which is used to transmit & receive xDSL signals


Benefits

• High-speed data service–DSL typically >10x faster than 56-kbps analog modem
• Always on connection–No need to “dial-up”
• Uses existing copper wires–Co-exists w/ POTS service
• Reasonably priced today and getting cheaper.
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Applications

• High speed Internet access
• SOHO
• Multimedia, Long distance learning, gaming
• Video on Demand
• VPN
• VoDSL 

Asymmetric” => faster downstream rate vs. upstream

• Suitable for applications such as web-browsing, MP3 downloading, Video on demand (VoD)
• Types of asymmetric DSL
• Asymmetric DSL (ADSL)
• The original and most popular
• Other asymmetric DSL technologies derived from ADSL
• Universal ADSL (UDSL), a.k.a. G.Lite or DSL Lite
• Expedites and reduces cost of deployment process by moving the splitting process from the CP to the CO
• Splitter-less nature slows the bit rate considerably