This is because in digital modulation there can be several bits per symbol, however the bandwidth of the modulated signal is determined by the rate of change from one state to another, whereas the num...This is because in digital modulation there can be several bits per symbol, however the bandwidth of the modulated signal is determined by the rate of change from one state to another, whereas the number of bits per transition depends on the number of states. The bits here are the gross bits which includes the information bits and bits added for error correction and others added to aid in identifying the signal, and so ηc is a measure of the performance of the modulation method itself.
