Broadband and Cable Modem Technology

Broadband refers to internet access that is always on and that carries much more data per second than the dial-up modems it replaced. Instead of tying up a telephone line for a single call, broadband connections transmit data continuously over a wide range of frequencies. Two of the most common delivery methods for homes have been cable, which uses the coaxial network built for cable television, and the various forms of digital subscriber line that run over telephone wiring.

A cable modem connects a computer or router to a cable television network. The same coaxial cable that carries television channels also carries internet data on separate frequency channels. Because the cable in a neighbourhood is often shared among many subscribers, the capacity is divided among active users, so speeds can vary with local demand. The standards governing cable internet have evolved over time to support progressively higher speeds.

The xDSL family covers several related technologies that run over copper telephone lines. ADSL is asymmetric, giving faster download than upload, while SDSL is symmetric, offering equal speeds in both directions, which suits users who upload a lot. Later versions such as ADSL2+ and VDSL widen the frequency range used on the line to deliver higher bandwidth, though performance still depends on the distance between the subscriber and the network equipment. In all cases the effective speed available to a user depends on the technology, line quality and distance involved.

Frequently asked questions

What is broadband?

Broadband is always-on internet access that carries far more data per second than dial-up, delivered over cable, DSL, fibre or other high-capacity media.

How does a cable modem work?

It sends and receives internet data over dedicated frequency channels on the same coaxial network used for cable television, sharing capacity among local users.

What is the difference between ADSL and SDSL?

ADSL gives faster download than upload speeds, while SDSL provides equal speeds in both directions, which is useful for sending large amounts of data.