I am confused with regard to how bandwidth increases with increase in number of bits transmitted for given duration.
1) Usually say in PCM system, when we increase the number of bits (n) for a given sampling frequency (fs), the bitrate increases and minimum transmission bandwidth thus increases.
Rb = nFs and Bandwidth = Rb/2.
2)While in M-ary schemes,when the number of bits is increased the bandwidth decreases because in time domain the signal is expanding,so obviously in frequency domain the overall width should reduce.
I am not able to understand the context in which either is true!