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In computing, bandwidth is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth, data bandwidth, or digital bandwidth. This definition of ''bandwidth'' is in contrast to the field of signal processing, wireless communications, modem data transmission,
digital communications Data transmission and data reception (or, more broadly, data communication or digital communications) is the transfer and reception of data (a Digital data, digital bitstream or a digitized analog signal) over a Point-to-point (telecommunications) ...
, and
electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control electron flow by amplifier, amplification and rectifie ...
, in which ''bandwidth'' is used to refer to analog
signal bandwidth Bandwidth is the difference between the upper and lower frequencies Frequency is the number of occurrences of a repeating event per unit of time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequen ...
measured in
hertz The hertz (symbol: Hz) is the unit Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, a discrete piece of action (or beat) in a theatric ...

hertz
, meaning the frequency range between lowest and highest attainable frequency while meeting a well-defined impairment level in signal power. The actual bit rate that can be achieved depends not only on the signal bandwidth but also on the noise on the channel.


Network capacity

The term ''bandwidth'' sometimes defines the
net bit rate In telecommunications Telecommunication is the transmission of information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines both its essence and the natur ...
'peak bit rate', 'information rate,' or physical layer 'useful bit rate',
channel capacity Channel capacity, in electrical engineering, computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. ...
, or the
maximum throughput In general terms, throughput is the rate of production or the rate at which something is processed. When used in the context of communication networks, such as Ethernet Ethernet () is a family of wired computer network A computer net ...
of a logical or physical communication path in a digital communication system. For example,
bandwidth test Throughput In general terms, throughput is the rate of production or the rate at which something is processed. When used in the context of communication networks, such as Ethernet or packet radio, throughput or network throughput is the rat ...
s measure the maximum throughput of a computer network. The maximum rate that can be sustained on a link is limited by the Shannon–Hartley
channel capacity Channel capacity, in electrical engineering, computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. ...
for these communication systems, which is dependent on the
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thro ...
in hertz and the noise on the channel.


Network consumption

The ''consumed bandwidth'' in bit/s, corresponds to achieved
throughput In general terms, throughput is the rate of production or the rate at which something is processed. When used in the context of communication networks, such as Ethernet or packet radio, throughput or network throughput is the rate of ''successf ...
or
goodput In computer networks, goodput (a portmanteau A portmanteau (, ) or portmanteau word (from "Portmanteau (luggage), portmanteau") is a Blend word, blend of words
, i.e., the average rate of successful data transfer through a communication path. The consumed bandwidth can be affected by technologies such as
bandwidth shaping A network scheduler, also called packet scheduler, queueing discipline, qdisc or queueing algorithm, is an arbiter on a node in packet switching In telecommunications, packet switching is a method of grouping Data (computing), data that is tran ...
,
bandwidth management Bandwidth management is the process of measuring and controlling the communications (traffic, packets) on a network link, to avoid filling the link to capacity or overfilling the link,https://www.internetsociety.org/wp-content/uploads/2017/08/BWrou ...
,
bandwidth throttling Bandwidth throttling is the intentional slowing or speeding of an internet service by an Internet service provider#REDIRECT Internet service provider {{Redirect category shell, 1= {{R from other capitalisation ... (ISP). It is a reactive measur ...
,
bandwidth cap A data cap, often erroneously referred to as a bandwidth cap, is an artificial restriction imposed on the transfer of data over a network. In particular, it refers to policies imposed by an internet service provider in order to limit customers' ...
,
bandwidth allocation Bandwidth allocation is the process of assigning radio frequencies Radio frequency (RF) is the oscillation Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or ...
(for example
bandwidth allocation protocolThe Bandwidth Allocation Protocol, along with its control protocol, the Bandwidth Allocation Control Protocol, is used to add and remove links in a multilink bundle over PPP, and specifying which peer is responsible for making decisions regarding ba ...
and
dynamic bandwidth allocation Dynamic bandwidth allocation is a technique by which traffic bandwidth in a shared telecommunications medium can be allocated on demand and fairly between different users of that bandwidth. This is a form of bandwidth management, and is essentiall ...
), etc. A bit stream's bandwidth is proportional to the average consumed signal bandwidth in hertz (the average spectral bandwidth of the analog signal representing the bit stream) during a studied time interval. ''Channel bandwidth'' may be confused with useful data throughput (or
goodput In computer networks, goodput (a portmanteau A portmanteau (, ) or portmanteau word (from "Portmanteau (luggage), portmanteau") is a Blend word, blend of words
). For example, a channel with ''x'' bps may not necessarily transmit data at ''x'' rate, since protocols, encryption, and other factors can add appreciable overhead. For instance, much internet traffic uses the
transmission control protocol The Transmission Control Protocol (TCP) is one of the main communications protocol, protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the e ...
(TCP), which requires a three-way handshake for each transaction. Although in many modern implementations the protocol is efficient, it does add significant overhead compared to simpler protocols. Also, data packets may be lost, which further reduces the useful data throughput. In general, for any effective digital communication, a framing protocol is needed; overhead and effective throughput depends on implementation. Useful throughput is less than or equal to the actual channel capacity minus implementation overhead.


Maximum throughput

The
asymptotic bandwidth In general terms, throughput is the rate of production or the rate at which something is processed. When used in the context of communication networks, such as Ethernet or packet radio, throughput or network throughput is the rate of ''successfu ...
(formally ''asymptotic throughput'') for a network is the measure of maximum
throughput In general terms, throughput is the rate of production or the rate at which something is processed. When used in the context of communication networks, such as Ethernet or packet radio, throughput or network throughput is the rate of ''successf ...
for a
greedy sourceA greedy source is a traffic generator that generates data at the maximum rate possible and at the earliest opportunity possible. Each source always has data to transmit, and is never in idle state due to congestion avoidance or other local host tr ...
, for example when the message size (the number of packets per second from a source) approaches close to the maximum amount. Asymptotic bandwidths are usually estimated by sending a number of very large messages through the network, measuring the end-to-end throughput. As other bandwidths, the asymptotic bandwidth is measured in multiples of bits per seconds. Since bandwidth spikes can skew the measurement, carriers often use the 95th
percentile In statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industrial, or social problem, it is conventional to begin wit ...

percentile
method. This method continuously measures bandwidth usage and then removes the top 5 percent.


Multimedia

Digital bandwidth may also refer to:
multimedia bit rate
multimedia bit rate
or
average bitrateAverage bitrate (ABR) refers to the average amount of data transferred per unit of time, usually measured per second, commonly for digital music or video. An MP3 file, for example, that has an average bit rate of 128 kbit/s transfers, on average, 12 ...
after multimedia
data compression In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Signal ...
(
source coding In signal processing Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as audio signal processing, sound, image processing, images, and scientific measurements. Signal ...
), defined as the total amount of data divided by the playback time. Due to the impractically high bandwidth requirements of uncompressed
digital media Digital media means any communication media that operate with the use of any of various encoded machine-readable data Machine-readable data, or computer-readable data, is data Data are units of information Information can be thought ...
, the required multimedia bandwidth can be significantly reduced with data compression. The most widely used data compression technique for media bandwidth reduction is the
discrete cosine transform A discrete cosine transform (DCT) expresses a finite sequence of data points In statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to ...
(DCT), which was first proposed by Nasir Ahmed in the early 1970s. DCT compression significantly reduces the amount of memory and bandwidth required for digital signals, capable of achieving a
data compression ratio Data compression ratio, also known as compression power, is a measurement of the relative reduction in size of data representation produced by a data compression algorithm. It is typically expressed as the division of uncompressed size by compressed ...
of up to 100:1 compared to uncompressed media.


Web hosting

In
Web hosting service A web hosting service is a type of Internet hosting service The Internet ( or internet) is the global system of interconnected computer network A computer network is a group of computers that use a set of common communication ...
, the term ''bandwidth'' is often incorrectly used to describe the amount of data transferred to or from the website or server within a prescribed period of time, for example ''bandwidth consumption accumulated over a month'' measured in gigabytes per month. The more accurate phrase used for this meaning of a maximum amount of data transfer each month or given period is ''monthly data transfer''. A similar situation can occur for end user ISPs as well, especially where network capacity is limited (for example in areas with underdeveloped internet connectivity and on wireless networks).


Internet connections

This table shows the maximum bandwidth (the physical layer
net bit rate In telecommunications Telecommunication is the transmission of information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines both its essence and the natur ...
) of common Internet access technologies. For more detailed lists see *
List of device bandwidths This is a list of interface bit rates, is a measure of information rate, information transfer rates, or bandwidth (computing), digital bandwidth capacity, at which digital interfaces in a computer or networking hardware, network can communicate ove ...
* *


Edholm's law

Edholm's law Edholm's law, proposed by and named after Phil Edholm, refers to the observation that the three categories of telecommunication Telecommunication is the transmission of information Information can be thought of as the resolution of uncert ...
, proposed by and named after Phil Edholm in 2004, holds that the bandwidth of
telecommunication network A telecommunications network is a group of nodes In general, a node is a localized swelling (a "knot") or a point of intersection (a Vertex (graph theory), vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathema ...
s double every 18 months, which has proven to be true since the 1970s. The trend is evident in the cases of
Internet The Internet (Capitalization of Internet, or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a ''network of networks'' t ...

Internet
, cellular (mobile),
wireless Wireless communication (or just wireless, when the context allows) is the telecommunication, transfer of information between two or more points that do not use an electrical conductor as a medium by which to perform the transfer. The most common ...
LAN A local area network (LAN) is a computer network A computer network is a group of computers that use a set of common communication protocols over digital signal, digital interconnections for the purpose of sharing resources located on or ...
and wireless personal area networks. The
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate field-effect transistor The field-effect trans ...

MOSFET
(metal-oxide-semiconductor field-effect transistor) is the most important factor enabling the rapid increase in bandwidth. The MOSFET (MOS transistor) was invented by and
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics. He is best known for inventing the MOSFET (metal–oxide–semiconductor field-effect ...

Dawon Kahng
at
Bell Labs Nokia Bell Labs (formerly named Bell Labs Innovations (1996–2007), AT&T Bell Laboratories (1984–1996) and Bell Telephone Laboratories (1925–1984)) is an American industrial Research and development, research and scientific development S.A. ...
in 1959, and went on to become the basic building block of modern
telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, Optical system, optical, or other Electromagnetism, electromagnetic systems. It has its origin in the desire of humans for communication ove ...
technology. Continuous
MOSFET scaling The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate field-effect transistor that is fabricated by th ...
, along with various advances in MOS technology, has enabled both
Moore's law Moore's law is the observation that Transistor count, the number of transistors in a dense integrated circuit (IC) doubles about every two years. Moore's law is an observation and Forecasting, projection of a historical trend. Rather than a phy ...
(
transistor count The transistor count is the number of transistors in an electronic device. It typically refers to the number of MOSFETs (metal-oxide-semiconductor field-effect transistors, or MOS transistors) on an integrated circuit (IC) chip, as all modern IC ...
s in
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Transistor count, Larg ...

integrated circuit
chips doubling every two years) and Edholm's law (communication bandwidth doubling every 18 months).


References

{{Telecommunications Network performance Information theory Temporal rates