xDSL

xDSL refers to a family of digital subscriber line technologies that provide broadband Internet access over existing copper telephone lines. The term encompasses several variants designed to deliver different balance points of speed, distance, and symmetry, typically used to deliver high-speed data while allowing ordinary telephone service to operate simultaneously on the same copper pair. Common variants include ADSL, ADSL2+, VDSL, VDSL2, SDSL, HDSL, and the newer G.fast. ADSL and ADSL2+ are the most widely deployed for residential service, offering higher download speeds than upload speeds, while SDSL and HDSL provide more symmetric performance for business use.

How xDSL works is based on transmitting digital data over the copper pair using frequencies that are separate from the voice channel. A DSL modem at the customer premises connects to a DSLAM (digital subscriber line access multiplexer) at the service provider’s central office or pedestal. The network uses filters or splitters to separate voice calls from data signals. The achievable data rate depends on several factors, most notably the length of the copper loop and its electrical quality; performance typically degrades with longer distances from the service point and with increased line noise.

deployment and usage: xDSL technologies primarily rely on existing telephone infrastructure, which keeps costs relatively low compared with installing new fiber to every home. They are widely used for residential broadband and small business connectivity, particularly in areas without fiber access. However, as fiber deployment progresses, higher-speed technologies like VDSL2 and G.fast are increasingly used on shorter copper segments or as parts of hybrid fiber-coax networks, while many providers gradually transition customers to fiber-based services.

See also: ADSL, VDSL, G.fast, DSLAM, copper telephone network, POTS.