Broadband

Broadband, communications channel that can support a wide range of frequencies or data rates. A broadband connection can transfer information at a rate of at least 2 megabits per second (mbps). This is almost 40 times faster than a standard narrowband 56 kilobits per second (kbps) modem connection. Some broadband services can even offer 10 mbps connection but, in practice, most transfer information at a rate of around 512 kbps when downloading, and 128 kbps when uploading.

There are a number of options for providing broadband. All involve some sort of link between an end user and a switch connected to a wide area network. The simplest option is to install a dedicated link between the two and install suitable transmission equipment at each end. This allows very high-speed operation but is usually expensive.

A more affordable approach is to reuse existing telephone lines by adding technology that enhances the rate at which information can be transferred over them. There are several ways in which this can be achieved:

• Integrated Services Digital Network (ISDN), which is widely available and allows connection speeds of up to 128 kbps.
• Digital Subscriber Line (DSL), which has recently been introduced and is capable of operating at up to 2 mbps. In its most common format, Asymmetrical Digital Subscriber Line (ADSL), it provides up to 512 kbps downstream and 128 kbps upstream.
• Etherloop, which shares many characteristics of DSL but which follows the format of the ubiquitous local area network technology, Ethernet. Etherloop performance is a little better than DSL.
• Cable modems, which are offered by cable providers for Internet access via existing cable television lines. Although capable of connection speed up to 2 mbps, cable modems operate over shared media and are therefore liable to slow down when many users are active.

The real attraction of broadband from a user’s point of view is that it provides true multimedia (for example, voice, data, and video) without the delay that a narrowband connection incurs.