# Baud > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Baud > Markdown URL: https://mediated.wiki/source/Baud.md > Source: https://en.wikipedia.org/wiki/Baud > Source revision: 1321119049 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Symbol rate measurement in telecommunications}} {{other uses}} In [telecommunications](/source/telecommunications) and [electronics](/source/electronics), '''baud''' ({{IPAc-en|b|ɔː|d}}; symbol: '''Bd''') is a common [unit of measurement](/source/unit_of_measurement) of [symbol rate](/source/symbol_rate), which is one of the components that determine the [speed of communication](/source/Speed_of_service) over a [data channel](/source/data_channel). It is the unit for symbol rate or [modulation](/source/modulation) rate in '''symbols per second''' or '''pulses per second'''. It is the number of distinct [symbol](/source/symbol_(data)) changes (signalling events) made to the [transmission medium](/source/transmission_medium) per second in a digitally modulated signal or a bd rate [line code](/source/line_code). Baud is related to ''[gross bit rate](/source/gross_bit_rate)'', which can be expressed in [bits per second](/source/bits_per_second) (bit/s).{{Cite news|url=http://www.electronicdesign.com/communications/what-s-difference-between-bit-rate-and-baud-rate|title=What's The Difference Between Bit Rate And Baud Rate?|date=2012-04-27|work=Electronic Design|access-date=2018-01-18}} If there are precisely two symbols in the system (typically 0 and 1), then baud and bits per second are equivalent. == Naming == The baud unit is named after [Émile Baudot](/source/%C3%89mile_Baudot), the inventor of the [Baudot code](/source/Baudot_code) for [telegraphy](/source/telegraphy), and is represented according to the rules for [SI units](/source/SI_units). That is, the first letter of its symbol is uppercase (Bd), but when the unit is spelled out, it should be written in lowercase (baud) except when it begins a sentence or is capitalized for another reason, such as in title case. It was defined by the CCITT (now the [ITU-T](/source/ITU-T)) in November 1926. The earlier standard had been the number of words per minute, which was a less robust measure since word length can vary.{{Cite web|url=http://www.linfo.org/baud.html|title=Baud definition by The Linux Information Project (LINFO)|website=www.linfo.org|access-date=2018-01-18}} ==Definitions== The symbol duration time, also known as the [unit interval](/source/unit_interval_(data_transmission)), can be directly measured as the time between transitions by looking at an [eye diagram](/source/eye_diagram) of the signal on an [oscilloscope](/source/oscilloscope). The symbol duration time ''T''s can be calculated as: : T_\text{s} = {1 \over f_\text{s}}, where ''f''s is the symbol rate. There is also a chance of miscommunication, which leads to ambiguity. :Example: Communication at the baud rate ''1000 Bd'' means communication by means of sending ''1000 symbols per second''. In the case of a [modem](/source/modem), this corresponds to ''1000 tones per second''; similarly, in the case of a line code, this corresponds to ''1000 pulses per second''. The symbol duration time is ''{{sfrac|1|1000}} second'' (that is, ''1 millisecond''). The baud is scaled using standard [metric prefix](/source/metric_prefix)es, so that, for example *1 kBd (kilobaud) = 1000 Bd *1 MBd (megabaud) = 1000 kBd *1 GBd (gigabaud) = 1000 MBd ==Relationship to gross bit rate== The symbol rate is related to [gross bit rate](/source/gross_bit_rate) expressed in {{nowrap|bit/s}}. The term baud has sometimes incorrectly been used to mean [bit rate](/source/bit_rate),{{cite web |url=http://www.textfiles.com/apple/bitsbaud.txt |title=BITS, BAUD RATE, AND BPS Taking the Mystery Out of Modem Speeds |last1=Banks |first1=Michael A. |date=1990 |publisher=Brady Books/Simon & Schuster |access-date=17 September 2014}} since these rates are the same in old [modem](/source/modem)s as well as in the simplest digital communication links using only one bit per symbol, such that binary digit 0 is represented by one symbol, and binary digit 1 by another symbol. In more advanced modems and data transmission techniques, a symbol may have more than two states, so it may represent more than one [bit](/source/bit). A bit (binary digit) always represents one of two states. If {{mvar|N}} bits are conveyed per symbol, and the gross bit rate is {{mvar|R}}, inclusive of channel coding overhead, the symbol rate {{math|''f''s}} can be calculated as : f_\text{s} = {R \over N}. By taking information per pulse ''N'' in bit/pulse to be the base-2-[logarithm](/source/logarithm) of the number of distinct messages ''M'' that could be sent, [Hartley](/source/Ralph_Hartley){{cite book | title = Information Theory and its Engineering Applications | author = D. A. Bell | edition = 3rd | year = 1962 | publisher = Pitman | location = New York |oclc=1626214}} constructed a measure of the [gross bit rate](/source/gross_bit_rate) ''R'' as : R = f_\text{s} N\quad where \quad N = \left \lceil \log_2(M) \right \rceil. Here, the \left \lceil x \right \rceil denotes the ceiling function of x, where x is taken to be any real number greater than zero, then the ceiling function rounds up to the nearest natural number (e.g. \left \lceil 2.11 \right \rceil = 3). In that case, {{math|1=''M'' = 2''N''}} different symbols are used. In a modem, these may be time-limited [sine wave](/source/sine_wave) tones with unique combinations of amplitude, phase or frequency. For example, in a [64QAM](/source/64QAM) modem, {{math|1=''M'' = 64}}, and so the bit rate is {{math|1=''N'' = log2(64) = 6}} times the baud rate. In a line code, these may be ''M'' different voltage levels. The ratio is not necessarily an integer; in [4B3T](/source/4B3T) coding, the bit rate is {{sfrac|4|3}} of the baud rate. (A typical [basic rate interface](/source/basic_rate_interface) with a {{nowrap|160 kbit/s}} raw data rate operates at 120 kBd.) Codes with many symbols, and thus a bit rate higher than the symbol rate, are most useful on channels such as telephone lines with a limited [bandwidth](/source/Bandwidth_(computing)) but a high [signal-to-noise ratio](/source/signal-to-noise_ratio) within that bandwidth. In other applications, the bit rate is less than the symbol rate. [Eight-to-fourteen modulation](/source/Eight-to-fourteen_modulation) as used on audio CDs has bit rate {{sfrac|8|17}}{{efn|EFM requires three merging bits between adjacent fourteen-bit codewords.}} of the baud rate. ==See also== {{columns-list|colwidth=20em| * [Commonly used symbol rates](/source/Serial_port) * [Constellation diagram](/source/Constellation_diagram) * [List of device bandwidths](/source/List_of_device_bandwidths) * [Mark and space](/source/Mark_and_space) * [Nyquist rate](/source/Nyquist_rate) * [Pulse-code modulation](/source/Pulse-code_modulation) }} ==Notes== {{Notelist}} ==References== {{Reflist}} ==External links== * {{cite journal | title=On the origins of serial communications and data encoding | url=http://www.dbase.com/Knowledgebase/dbulletin/bu07sh.htm | first=Nicolas | last=Martin | journal=dBulletin, the dBASE Developers Bulletin |issue=7 |date=January 2000 | access-date=January 4, 2007 }} * {{cite journal |title=What's The Difference Between Bit Rate And baud? | first=Lou | last=Frenzel | journal=Electronic Design Magazine |date=April 27, 2012 | url=http://electronicdesign.com/communications/what-s-difference-between-bit-rate-and-baud-rate }} Category:Data transmission Category:Units of frequency --- Adapted from the Wikipedia article [Baud](https://en.wikipedia.org/wiki/Baud) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Baud?action=history)). 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