Incomputing,bandwidthis the maximum rate of data transfer across a given path. Bandwidth may be characterized asnetwork bandwidth,[1]data bandwidth,[2]ordigital bandwidth.[3][4]
This definition ofbandwidthis in contrast to the field of signal processing, wireless communications, modem data transmission,digital communications,andelectronics,[citation needed]in whichbandwidthis used to refer to analogsignal bandwidthmeasured inhertz,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 thenoiseon the channel.
Network capacity
editThe termbandwidthsometimes defines thenet bit ratepeak bit rate,information rate,or physical layeruseful bit rate,channel capacity,or themaximum throughputof a logical or physical communication path in a digital communication system. For example,bandwidth testsmeasure the maximum throughput of a computer network. The maximum rate that can be sustained on a link is limited by theShannon–Hartleychannel capacity for these communication systems, which is dependent on thebandwidthin hertz and the noise on the channel.
Network consumption
editTheconsumed bandwidthin bit/s, corresponds to achievedthroughputorgoodput,i.e., the average rate of successful data transfer through a communication path. The consumed bandwidth can be affected by technologies such asbandwidth shaping,bandwidth management,bandwidth throttling,bandwidth cap,bandwidth allocation(for examplebandwidth allocation protocolanddynamic bandwidth allocation), 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 bandwidthmay be confused with useful data throughput (or goodput). For example, a channel withxbit/s may not necessarily transmit data atxrate, since protocols, encryption, and other factors can add appreciable overhead. For instance, much internet traffic uses thetransmission control protocol(TCP), which requires athree-way handshakefor 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
editTheasymptotic bandwidth(formallyasymptotic throughput) for a network is the measure of maximum throughput for agreedy source,for example when the message size (the number of packets per second from a source) approaches close to the maximum amount.[5]
Asymptotic bandwidths are usually estimated by sending a number of very large messages through the network, measuring the end-to-end throughput. As with other bandwidths, the asymptotic bandwidth is measured in multiples of bits per seconds. Since bandwidth spikes can skew the measurement, carriers often use the 95thpercentilemethod. This method continuously measures bandwidth usage and then removes the top 5 percent.[6]
Multimedia
editDigital bandwidth may also refer to:multimedia bit rateoraverage bitrateafter multimediadata compression(source coding), defined as the total amount of data divided by the playback time.
Due to the impractically high bandwidth requirements of uncompresseddigital media,the required multimedia bandwidth can be significantly reduced with data compression.[7]The most widely used data compression technique for media bandwidth reduction is thediscrete cosine transform(DCT), which was first proposed byNasir Ahmedin the early 1970s.[8]DCT compression significantly reduces the amount of memory and bandwidth required for digital signals, capable of achieving adata compression ratioof up to 100:1 compared to uncompressed media.[9]
Web hosting
editInWeb hosting service,the termbandwidthis often incorrectly used to describe the amount of data transferred to or from the website or server within a prescribed period of time, for examplebandwidth consumption accumulated over a monthmeasured in gigabytes per month.[citation needed][10]The more accurate phrase used for this meaning of a maximum amount of data transfer each month or given period ismonthly data transfer.
A similar situation can occur for end-userInternet service providersas well, especially where network capacity is limited (for example in areas with underdeveloped internet connectivity and on wireless networks).
Internet connections
edit| Bit rate | Connection type |
|---|---|
| 56 kbit/s | Dialup |
| 1.5 Mbit/s | ADSL Lite |
| 1.544 Mbit/s | T1/DS1 |
| 2.048 Mbit/s | E1 /E-carrier |
| 4 Mbit/s | ADSL1 |
| 10 Mbit/s | Ethernet |
| 11 Mbit/s | Wireless802.11b |
| 24 Mbit/s | ADSL2+ |
| 44.736 Mbit/s | T3/DS3 |
| 54 Mbit/s | Wireless802.11g |
| 100 Mbit/s | Fast Ethernet |
| 155 Mbit/s | OC3 |
| 600 Mbit/s | Wireless802.11n |
| 622 Mbit/s | OC12 |
| 1 Gbit/s | Gigabit Ethernet |
| 1.3 Gbit/s | Wireless802.11ac |
| 2.5 Gbit/s | OC48 |
| 5 Gbit/s | SuperSpeed USB |
| 7 Gbit/s | Wireless802.11ad |
| 9.6 Gbit/s | OC192 |
| 10 Gbit/s | 10 Gigabit Ethernet,SuperSpeed USB 10 Gbit/s |
| 20 Gbit/s | SuperSpeed USB 20 Gbit/s |
| 40 Gbit/s | Thunderbolt 3 |
| 100 Gbit/s | 100 Gigabit Ethernet |
Edholm's law
editEdholm's law,proposed by and named after Phil Edholm in 2004,[11]holds that the bandwidth oftelecommunication networksdouble every 18 months, which has proven to be true since the 1970s.[11][12]The trend is evident in the cases ofInternet,[11]cellular(mobile),wireless LANandwireless personal area networks.[12]
TheMOSFET(metal–oxide–semiconductor field-effect transistor) is the most important factor enabling the rapid increase in bandwidth.[13]The MOSFET (MOS transistor) was invented byMohamed M. AtallaandDawon KahngatBell Labsin 1959,[14][15][16]and went on to become the basic building block of moderntelecommunicationstechnology.[17][18]ContinuousMOSFET scaling,along with various advances in MOS technology, has enabled bothMoore's law(transistor countsinintegrated circuitchips doubling every two years) and Edholm's law (communication bandwidth doubling every 18 months).[13]
References
edit- ^Douglas Comer,Computer Networks and Internets,page 99 ff, Prentice Hall 2008.
- ^Fred Halsall,to data+communications and computer networks,page 108, Addison-Wesley, 1985.
- ^Cisco Networking Academy Program: CCNA 1 and 2 companion guide, Volym 1–2,Cisco Academy 2003
- ^Behrouz A. Forouzan,Data communications and networking,McGraw-Hill, 2007
- ^Chou, C. Y.; et al. (2006). "Modeling Message Passing Overhead". In Chung, Yeh-Ching; Moreira, José E. (eds.).Advances in Grid and Pervasive Computing: First International Conference, GPC 2006.Springer. pp. 299–307.ISBN3540338098.
- ^"What is Bandwidth? - Definition and Details".www.paessler.com.Retrieved2019-04-18.
- ^Lee, Jack (2005).Scalable Continuous Media Streaming Systems: Architecture, Design, Analysis and Implementation.John Wiley & Sons.p. 25.ISBN9780470857649.
- ^Stanković, Radomir S.; Astola, Jaakko T. (2012)."Reminiscences of the Early Work in DCT: Interview with K.R. Rao"(PDF).Reprints from the Early Days of Information Sciences.60.Retrieved13 October2019.
- ^Lea, William (1994).Video on demand: Research Paper 94/68.House of Commons Library.Archived fromthe originalon 20 September 2019.Retrieved20 September2019.
- ^Low, Jerry (27 March 2022)."How Much Hosting Bandwidth Do I Need For My Website?".WHSR.
- ^abcCherry, Steven (2004). "Edholm's law of bandwidth".IEEE Spectrum.41(7): 58–60.doi:10.1109/MSPEC.2004.1309810.S2CID27580722.
- ^abDeng, Wei; Mahmoudi, Reza; van Roermund, Arthur (2012).Time Multiplexed Beam-Forming with Space-Frequency Transformation.New York: Springer. p. 1.ISBN9781461450450.
- ^abJindal, Renuka P. (2009)."From millibits to terabits per second and beyond - over 60 years of innovation".2009 2nd International Workshop on Electron Devices and Semiconductor Technology.pp. 1–6.doi:10.1109/EDST.2009.5166093.ISBN978-1-4244-3831-0.S2CID25112828.
- ^"1960 - Metal Oxide Semiconductor (MOS) Transistor Demonstrated".The Silicon Engine.Computer History Museum.
- ^Lojek, Bo (2007).History of Semiconductor Engineering.Springer Science & Business Media.pp. 321–3.ISBN9783540342588.
- ^"Who Invented the Transistor?".Computer History Museum.4 December 2013.Retrieved20 July2019.
- ^"Triumph of the MOS Transistor".YouTube.Computer History Museum.6 August 2010.Archivedfrom the original on 2021-11-07.Retrieved21 July2019.
- ^Raymer, Michael G. (2009).The Silicon Web: Physics for the Internet Age.CRC Press.p. 365.ISBN9781439803127.