Disadvantages of digital communication

1. Quantization error
Every signal is analog in nature
Since analog to Digital conversion follows the method described below
Analog->sampling->quantisation->encoding->Digital signal
Quantisation error  is introduced while quantisation process and this error cannot be removed anyhow during its transmission,
hence this error poses a problem for Digital signals.
2. High power consumption
Analog signals need to be converted ito analog and vice versa which requires extra circuitry and hence consumes more power.
3. Infinite bandwidth
Bandwidth  is inversely proportional to the time period of the pulses
As pulse width reduces Bandwidth requirement increases.
Therefore, if we want to have fast switching i.e. fast speed of communication  we will have to reduce the time period of pulses or increase the frequency of pulses, this calls for higher and higher Bandwidth,
moreover if we wish to reduce the time period of pulses to almost zero ,we want an infinite Bandwidth to accomplish our task,which is not possible in any practical communication system.
4. Difficult transmission
Owing to the infinite Bandwidth requirement ,transmission of Digital signals becomes very difficult for communication engineers.