nyquist bandwidth criterion

[erece]

According to Nyquist bandwidth constraint for transmission without ISI , the minimum channel bandwidth should be R/2 symbols /sec, where R symbols /sec is the transmisson rate.
If this is correct then i want to know that if this channel cannot support full transmission rate then do we use this model ??

 

[BradtheRad]

The Nyquist figure is also tossed around in digital sound processing. Your sample rate must be, at minimum, twice the frequency of the highest frequency you intend to process.

As a guideline it's prominent today because it emerged as a usable concept as the technology was in development.

Not that it's a be-all and end-all guideline. Since it's possible for your sampling window to catch a waveform at zero crossings. Then you get nothing.

Or suppose the waveform is slightly different from half the sample rate. Then you get a subsonic rumble, or other such incongruous result.