In radio, for example, a very narrow band will carry Morse code, a broader
band will carry speech, and 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 U.S. federal standard FS-1037C defines "broadband" as a synonym
for wideband.[3]
In data communications a 56k modem will transmit a data rate of 56 kilobits
per second (kbit/s) over a 4-kilohertz-wide telephone line (narrowband or
voiceband). The various forms of digital subscriber line (DSL) 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.[4]
However, when that same line is converted to a non-loaded twisted-pair wire
(no telephone filters), it becomes hundreds of kilohertz wide (broadband) and
can carry up to 60 megabits per second using very-high-bitrate digital
subscriber line (VDSL or VHDSL) techniques.
In the late 1980s, the Broadband Integrated Services Digital Network
(B-ISDN) used the term to refer to a broad range of bit rates, independent of
physical modulation details.[5]
In computer networks[edit]
Many computer networks use a simple line code to transmit one type of
signal using a medium's full bandwidth using its baseband (from zero through
the highest frequency needed). 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.[6] The total bandwidth of the medium is larger than the
bandwidth of any channel.[7]
The 10BROAD36 broadband variant of Ethernet was standardized by 1985, but
was not commercially successful.[8][9] 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 (which is considered high-speed as of
2014) using existing home wiring (including power lines, but also phone lines
and coaxial cables).
In video[edit]
"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.[10] 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.[11] 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.[12]
Internet access[edit]
Main article: Internet access § Hardwired broadband access
In the context of Internet access, the term "broadband" is used
loosely to mean "access that is always on and faster than the traditional
dial-up access".[13][14]
A range of more precise definitions of speed have been prescribed at times,
including:
"Greater than the primary rate" (which ranged from about 1.5 to 2
Mbit/s) - CCITT in "broadband service" in 1988.[15]
"Internet access that is always on and faster than the traditional
dial-up access",[13] - US National Broadband Plan of 2009[16]
4 Mb/s down, 1 Mbit/s up - FCC, 2010[17]
25 Mb/s down, 3 Mb/s up - FCC, 2015[17]
Broadband Internet service is now effectively treated or managed as a
public utility by net neutrality rules.[18][19][20][21][22]
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