The term broadband refers to the wide bandwidth characteristics of a transmission medium and
its ability to transport multiple signals and traffic types simultaneously. The medium
can be coaxial cable, optical fiber, twisted pair, DSL local telephone networks or wireless.
In contrast, baseband describes a communication system in which information is transported
across a single channel. Different criteria for "broad" have been applied
in different contexts and at different times. Its origin is in physics, acoustics and radio
systems engineering, where it had been used with a meaning similar to wideband. Later,
with the advent of digital telecommunications, the term was mainly used for transmission
over multiple channels. Whereas a passband signal is also modulated so that it occupies
higher frequencies, it is still occupying a single channel. The key difference is that
what is typically considered a broadband signal in this sense is a signal that occupies multiple
passbands thus allowing for much higher throughput over a single medium, but with additional
complexity in the transmitter/receiver circuitry. Finally, the term became popularized through
the 1990s as a marketing term for Internet access that was faster than dialup access,
the original Internet access technology, which was limited to 56 kbit/s. This meaning is
only distantly related to its original technical meaning.
Broadband refers to a communication bandwidth of at least 256 kbit/s. Each channel is 4 MHz
wide and it uses an extensive range of frequencies to effortlessly relay and receive data between
networks. In telecommunications, a broadband signaling method is one that handles a wide
band of frequencies. Broadband is a relative term, understood according to its context.
The wider the bandwidth of a channel, the greater the information-carrying capacity,
given the same channel quality. In radio, for example, a very narrow-band
will carry Morse code; a broader band will carry speech; a still broader band will carry
music without losing the high audio frequencies required for realistic sound reproduction.
This broad band is often divided into channels or frequency bins using passband techniques
to allow frequency-division multiplexing, instead of sending a higher-quality signal.
A television antenna may be described as "broadband" because it is capable of receiving a wide
range of channels; while a single-frequency or Lo-VHF antenna is "narrowband" since it
receives only 1 to 5 channels. The US federal standard FS-1037C defines "broadband" as a
synonym for wideband. In data communications a 56k modem will transmit
a data rate of 56 kilobits per second over a 4 kilohertz wide telephone line. The various
forms of digital subscriber line services are broadband in the sense that digital information
is sent over multiple channels. Each channel is at higher frequency than the baseband voice
channel, so it can support plain old telephone service on a single pair of wires at the same
time. However when that same line is converted to
a non-loaded twisted-pair wire, it becomes hundreds of kilohertz wide and can carry up
to 60 megabits per second using very-high-bitrate digital subscriber line techniques.
In the late 1980s, the Broadband Integrated Services Digital Network used the term to
refer to a broad range of bit rates, independent of physical modulation details.
In computer networks Many computer networks use a simple line code
to transmit one type of signal using a medium's full bandwidth using its baseband. Most versions
of the popular Ethernet family are given names such as the original 1980s 10BASE5 to indicate
this. Networks that use cable modems on standard cable television infrastructure are called
broadband to indicate the wide range of frequencies that can include multiple data users as well
as traditional television channels on the same cable. Broadband systems usually use
a different radio frequency modulated by the data signal for each band. The total bandwidth
of the medium is larger than the bandwidth of any channel.
The 10BROAD36 broadband variant of Ethernet was standardized by 1985, but was not commercially
successful. The DOCSIS standard became available to consumers in the late 1990s, to provide
Internet access to cable television residential customers. Matters were further confused by
the fact that the 10PASS-TS standard for Ethernet ratified in 2008 used DSL technology, and
both cable and DSL modems often have Ethernet connectors on them.
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 local area network up to 1 Gigabit/s using existing home wiring.
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 separate baseband audio. The act of demodulating converts broadband video to
baseband video. Fiber optic allows the signal to be transmitted farther without being repeated.
Cable companies use a hybrid system using fiber to transmit the signal to neighborhoods
and then changes the signal from light to radio frequency to be transmitted to over
coaxial cable to homes. Doing so reduces the use of having multiple head ends. A head end
gathers all the information from the local cable networks and movie channels and then
feeds the information into the system. 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 for viewing. Broadband video is also sometimes used to
describe IPTV Video on demand. Internet access
The standards group CCITT defined "broadband service" in 1988 as requiring transmission
channels capable of supporting bit rates greater than the primary rate which ranged from about
1.5 to 2 Mbit/s. The US National Information Infrastructure project during the 1990s brought
the term into public policy debates. Broadband became a marketing buzzword for
telephone and cable companies to sell their more expensive higher data rate products,
especially for Internet access. In the US National Broadband Plan of 2009 it was defined
as "Internet access that is always on and faster than the traditional dial-up access".
The same agency has defined it differently through the years.
In 2000, 3% of the US adult population had access to a broadband connection at home.
As of August 2013 70% of US adults accessed the Internet at home through a broadband connection,
while 3% used dial-up. Even though information signals generally
travel between 40% and 70% of the speed of light in the medium no matter what the bit
rate, higher rate services are often marketed as "faster" or "higher speeds". Consumers
are also targeted by advertisements for peak transmission rates, while actual end-to-end
rates observed in practice can be lower due to other factors.
See also Broadband universal service
Mobile broadband Ultra-wideband
Wireless broadband Nation specific:
Broadband mapping in the United States National broadband plans from around the world
References