Baud rate and symbol rate often refer to the same thing, especially in the context of digital communications. However, they don't necessarily equate to the bit rate. In the digital realm, we're familiar with the concept of 1's and 0's, which represent binary states. When we transmit a single bit, it can be visualized as a digital line being high (for 1) or low (for 0). The rate at which this line transitions from one state to another is called the baud rate or symbol rate.
To understand this further, let's consider a more advanced modulation scheme. Instead of just having two states (high and low) to represent binary bits, imagine we have four distinct states: high, medium-high, medium-low, and low. These states can represent combinations of bits as follows: high = 11, medium-high = 10, medium-low = 01, and low = 00.
In this scenario, each state transition represents a symbol, and since each symbol can represent two bits, the symbol rate (or baud rate) is half of the bit rate. If you know the symbol rate and want to determine the bit rate, you'd multiply the symbol rate by the number of bits per symbol. In this example, you'd multiply the baud rate by two.
Most signals rely on techniques beyond simple voltage differences though to transfer information, and that's when you delve into the world of RF theory. Instead of a discrete voltage, a sine wave is used at a particular frequency. The amplitude of the sine wave can be adjusted just like we adjusted the voltage on that line. If we want even more symbols, maybe 0000 to 1111 or bigger, we can introduce another variation to the sine wave called phase. Phase of a sine wave is just shifting it left or right, but could be visualized as two people on a race track. If they start a race from the same line and run at the same speed in the same direction, they're in phase. If one of them starts a quarter of the way ahead from the other and they both run at the same speed in the same direction, then he's a quarter phase shifted from the other.
That adjustment of phase and amplitude falls into a broad category of RF modulation called QAM, and it's used in more than RF between two radios. It can also be used over Ethernet or PCIe busses.
I could go on rambling for a long time on all this, but hopefully this helps answer your question.
Oops, yeah and it's not quite my domain of expertise. In fact, that's the big draw for me: Amateur radio has been amazing for filling in knowledge gaps of low level electrical engineering details. it takes things way past the simple CPU/system models from university CS class and the Arduino DC logic hobby projects. The educational potential is really top notch.
if there are two possible symbols in your communication medium that you switch between, bit rate is baud rate (with the two symbols being 0 and 1). If you have more symbols, then baud/symbol rate increases will correspond to greater bitrates increases by a factor.
