Baud rate

If you have arrived on this article, it's because you either do know what Baud rate is and want to make sure the article has explained it correctly, or you do not know what Baud rate is and want to know what it is. In either case, bless your heart.

Simple Definition

Baud rate (or just Baud, if you prefer) is the number of times per second a signal can change state when transmitting data. It's named after Émile Baudot, a 19th-century French telegraph operator.

A Simple Example: 2-FSK

In its most intuitive form, consider 2-FSK, used in systems like RTTY. The transmitter switches between two frequencies where one frequency, referred to as the space, is treated as "0", and another frequency, referred to as the mark, is treated as "1". Anyways, the Baud rate is defined as how often the transmitter is able to switch from 0 to 1 or vice versa within a single second.

Complication

Unfortunately, Baud rate is also discussed in the context of multi-level modulation schemes like QPSK, 8-PSK, 16-QAM, and other acronyms used by people who were extremely popular in high school.

In these schemes:

• Each "symbol" (signal state change) can represent multiple bits
• The Baud rate measures symbol rate, not bit rate
• A single phase shift might encode 2, 3, 4, or more bits simultaneously
• The relationship becomes: Bit rate = Baud rate × bits per symbol

So that when someone documents something like 2400 baud 8-PSK, they're technically talking about 2400 symbol changes per second, where each symbol carries 3 bits, yielding 7200 bits per second. Does anyone intuitively understand what "2400 Baud" means in an example such as this? No. Does anyone understand, in any way whatsoever, what "2400 Baud" means in an example such as this? (Also no.)