What is the difference between bit rate and baud rate?

What is the difference between bit rate and baud rate, and when is bit rate equal to baud rate?

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Bit rate is a measure of the number of data bits (that's 0's and 1's) transmitted in one second. A figure of 2400 bits per second means 2400 zeros or ones can be transmitted in one second, hence the abbreviation 'bps'.

Baud rate by definition means the number of times a signal in a communications channel changes state. For example, a 2400 baud rate means that the channel can change states up to 2400 times per second. When I say 'change state' I mean that it can change from 0 to 1 up to 2400 times per second. If you think about this, it's pretty much similar to the bit rate, which in the above example was 2400 bps.

Whether you can transmit 2400 zeros or ones in one second (bit rate), or change the state of a digital signal up to 2400 times per second (baud rate), it the same thing.

So we can conclude that in the above example, the bit rate is the same as the baud rate. Hence, 1 bit rate = 1 baud rate for this example.

There are cases though where a channel can send 4 bits per baud, meaning that for every 4 bits, we have one change, and in this case, the baud rate is 1/4th of the bit rate.

This was first published in July 2003

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