Terminology » Data Communication » Bit vs Symbol: Understanding the Key Differences

Bit vs Symbol: Understanding the Key Differences

bit symbol data communication modulation signal

This page compares Bit vs Symbol and mentions the difference between Bit and Symbol used in data communication with examples.

Introduction:

As shown, bits are converted into symbol or signal format in order to make the system bandwidth efficient.

For BPSK, one symbol (carrier phase) represents one bit, and hence the symbol rate equals the bit rate. Similarly, in AM modulation, each signal element carries one binary data, and hence the symbol rate or baud rate is the same as the bit rate.

BPSK vs QPSK constellation BPSK vs QPSK constellation

In QPSK modulation, 2 bits are represented by one symbol or signal waveform. Hence, the Symbol rate is one half of the bit rate. As a result, it occupies half the bandwidth compared to the BPSK waveform.

QAM constellation QAM constellation

In the 16QAM example, 4 bits are represented by one symbol or complex signal waveform. Hence, the Symbol rate is (1/4)th times the bit rate.

Example:

For an input bit string of “1010”, the complex symbol output is (-3-j*3)*KMOD. Where, KMOD is (1/root(10)).

Symbol rate (i.e., baud rate) = bit rate / Number of bits per symbol.

Tabular difference between Bit and Symbol

The following table mentions the difference between Bit and Symbol with respect to various parameters.

ParametersBitSymbol
FormatIt is in digital binary form. It is either zero (‘0’) or one (‘1’).It is in complex form or analog form.
UsageIt is stored in the memory in one and zero format.Symbols are used to map more than one bit and are used to transmit bits over the channel after baseband and carrier modulation.
Measurement unitBit rate referred to as the number of bits transmitted per second.Symbol rate is referred to as the number of symbols transmitted per second. It is also known as “Baud rate”.
ApplicationRaw data which are in various forms such as texts, numbers, images, audio and video files are usually stored in bit formats.As mentioned above, bits are mapped into symbol forms. These modulated data after modulation are measured in symbols per sec.