[1] In telecommunications and electronics, baud (Bd) is a measurement unit of symbol rate, a components determining communication speed over a data channel.
Note: Do not confuse baud rate with bits per second, which often have the same values at times.
It's the unit for the symbol rate or modulation rate in symbols or (signal state change) per second or pulses per second in a communication channel and the number of distinct symbol changes (signalling events) made to the transmission medium per second in a digitally modulated signal or a bd rate line code.
symbol: single distinct state/change in physical signal
The baud rate formula is:
baud = # bits/seconds
baud = BPS/bps
bps or b/s (bits/symbol) = how many bits are represented per symbol
[2] Baud rate vs Bit Rate The baud rate measures the number of state changes occuring or symbol per second.
Bit rate measures the actual number of binary bits transmitted per second, establishing a linear relationship via the number of bits encoded per symbol logs(M) through modulation techniques like QAM or BPSK.
E.g., suppose a RS-232 connection uses:
Baud rate: 9,600 baud
Data bits: 8
Parity: None
Stop bits: 1
The number of bits per character is: 1 start bit + 1 stop bit + 0 parity parity bit + 8 data bits = 10 bits/character, meaning that each character typed, the receiver gets 10 transmitted bits.
The effective character rate or the character per seconds is: 9600/10 = 960 symbol/s.
Then to transmit HELLO (5 characters) via text, it'll take: 5x10 = bits for a transmission time of 50/9600 = 5.21 ms.