What is Baud Rate?
Baud rate is a measure of the number of signal changes (symbols) that occur per second in a data transmission system. It's often confused with bit rate, but they're not always the same. The baud rate specifically refers to the modulation rate—the number of times the signal changes state per second.
How to Calculate Baud Rate
The relationship between bit rate and baud rate depends on the number of bits encoded in each signal change (symbol):
$$\text{Bit Rate} = \text{Baud Rate} \cdot \text{Bits per Baud}$$
Or, solving for baud rate:
$$\text{Baud Rate} = \frac{\text{Bit Rate}}{\text{Bits per Baud}}$$
Where:
- Bit Rate is measured in bits per second (bps)
- Baud Rate is measured in symbols per second (bauds/s)
- Bits per Baud is the number of bits encoded in each symbol
Baud Rate Calculation Example
Problem: If a communication system has a bit rate of 2,400 bits per second and each baud carries 6 bits, what is the baud rate?
Solution:
Using the formula:
$$\text{Baud Rate} = \frac{2{,}400}{6} = 400 \text{ bauds/s}$$
However, if we start with a baud rate of 2,400 and 6 bits per baud, the bit rate would be:
$$\text{Bit Rate} = 2{,}400 \cdot 6 = 14{,}400 \text{ bps}$$
Understanding Baud Rate vs Bit Rate
- Baud Rate: The number of signal changes per second
- Bit Rate: The number of bits transmitted per second
In simple modulation schemes where each signal change represents one bit, the baud rate equals the bit rate. However, with more sophisticated modulation (like quadrature amplitude modulation), multiple bits can be encoded in each signal change, making the bit rate higher than the baud rate.
Applications
Baud rate is important in:
- Serial communications (RS-232, UART)
- Modem communications
- Network protocols
- Digital signal processing
- Telecommunications systems