In telecommunications and electronics, baud (/bɔːd/; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel.
[1] If there are precisely two symbols in the system (typically 0 and 1), then baud and bits per second are equivalent.
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.
In more advanced modems and data transmission techniques, a symbol may have more than two states, so it may represent more than one bit.
If N bits are conveyed per symbol, and the gross bit rate is R, inclusive of channel coding overhead, the symbol rate fs can be calculated as By taking information per pulse N in bit/pulse to be the base-2-logarithm of the number of distinct messages M that could be sent, Hartley[4] constructed a measure of the gross bit rate R as Here, the
In a modem, these may be time-limited sinewave tones with unique combinations of amplitude, phase and/or frequency.
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 but a high signal-to-noise ratio within that bandwidth.