The term
broadband can have different meanings in different contexts. The term's meaning has undergone substantial shifts.
In telecommunication
Broadband in
telecommunications refers to a signaling method that includes or handles a relatively wide range (or band) of
frequencies, which may be divided into channels or
frequency bins.
Broadband is always a
relative term, understood according to its context. The wider the
bandwidth, the greater the information-carrying capacity. In
radio, for example, a very narrow-band signal will carry
Morse code; a broader band will carry speech; a still broader band is required to carry
music without losing the high
audio frequencies required for realistic
sound reproduction. A
television antenna described as "normal" may be capable of receiving a certain range of channels; one described as "broadband" will receive more channels. In data communications an
analog modem will transmit a bandwidth of 56 kilobits per seconds (kbit/s) over a
telephone line; over the same telephone line a bandwidth of several megabits per second can be handled by
ADSL, which is described as
broadband (relative to a modem over a telephone line, although much less than can be achieved over a
fiber optic circuit).
In data communications
Broadband in
data can refer to
broadband networks or
broadband Internet and may have the same meaning as above, so that
data transmission over a
fiber optic cable would be referred to as broadband as compared to a
telephone modem operating at
56,000 bits per second. However, a worldwide standard for what level of bandwidth and network speeds actually constitute
Broadband has not been determined.
However,
broadband in
data communications is frequently used in a more technical sense to refer to data transmission where multiple pieces of data are sent simultaneously to increase the effective rate of transmission, regardless of
data signaling rate. In
network engineering this term is used for methods where two or more signals share a medium.
Broadband Internet access, often shortened to just broadband, is a high data rate Internet access—typically contrasted with dial-up access using a 56k modem.
Dial-up modems are limited to a bitrate of less than 56 kbit/s (kilobits per second) and require the full use of a telephone line—whereas broadband technologies supply more than double this rate and generally without disrupting telephone use.
In DSL
The various forms of
digital subscriber line (DSL) services are
broadband in the sense that digital information is sent over a high-bandwidth channel (located above the
baseband voice channel on a single pair of wires).
In Ethernet
A
baseband transmission sends one type of signal using a medium's full bandwidth, as in
100BASE-T Ethernet. Ethernet, however, is the common interface to broadband modems such as DSL data links, and has a high data rate itself, so is sometimes referred to as broadband. Ethernet provided over
cable modem is a common alternative to DSL.
In power-line communication
Power lines have also been used for various types of data communication. Although some systems for remote control are based on
narrowband signaling, modern high-speed systems use broadband signaling to achieve very high data rates. One example is the
ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 Gigabit/s)
Local area network using existing home wiring (including power lines, but also phone lines and
coaxial cables).
In video
Broadband in
analog video distribution is traditionally used to refer to systems such as
cable television, where the individual channels are
modulated on carriers at fixed frequencies. In this context,
baseband is the term's
antonym, referring to a single channel of analog video, typically in
composite form with an
audio subcarrier. The act of demodulating converts broadband video to baseband video.
However,
broadband video in the context of
streaming Internet video has come to mean video files that have
bitrates high enough to require
broadband Internet access in order to view them.
Broadband video is also sometimes used to describe
IPTV Video on demand.
See also
