Q. Sampling of digital communication systems?

Sampling of an analog signal makes it discrete in time. A bandlimited signal can be recovered exactly from its samples, taken periodically in time at a rate at least equal to twice the signal's bandwidth. If a message f (t) has a spectral extent of Wf rad/s, the sampling rate fs (samples per second) must satisfy

from the sampling theorem. The minimum rate Wf /π (samples per second) is known as the Nyquist rate. If the exact message samples could be transmitted through the digital system, the original f (t) could be exactly reconstructed at all times, with no error by the receiver. However, since the exact samples cannot be conveyed, they must be converted to discrete samples in a process known as quantization.