Nyquist bandwidth criterion

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Discussion Overview

The discussion revolves around the Nyquist bandwidth criterion, specifically focusing on the minimum channel bandwidth required for transmission without intersymbol interference (ISI). Participants explore the implications of this criterion in relation to transmission rates and bandwidth requirements.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants assert that according to the Nyquist bandwidth constraint, the minimum channel bandwidth should be R/2 symbols/sec, where R is the transmission rate.
  • One participant seeks clarification on the implications of this criterion if the channel cannot support the full transmission rate.
  • Another participant defines ISI as intersymbol interference and relates it to the Nyquist criterion.
  • There is a discussion about the necessity of sampling at a frequency of at least R/2 to avoid loss of information when transmitting a signal with a frequency of R.
  • One participant questions whether the required bandwidth for ideal Nyquist pulses is indeed Rs/2 to support an Rs symbol rate.
  • Another participant describes the process of using a low-pass filter to transmit a signal while filtering out frequencies above R/2 to prevent information loss.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and interpretation of the Nyquist criterion and its implications, indicating that multiple competing views remain and the discussion is not fully resolved.

Contextual Notes

Some assumptions about the definitions of terms like ISI and the conditions under which the Nyquist criterion applies are not fully explored, leaving room for ambiguity in the discussion.

Who May Find This Useful

Individuals interested in telecommunications, signal processing, and information theory may find this discussion relevant.

erece
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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 ??
 
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What is ISI?

Nyquist says that if you have a discrete signal that should transfer all relevant frequencies, you should use a sample frequency that is at least double the max relevant frequency.
 
ISI is INTERSYMBOL INTERFERENCE
 
Ah, okay. I was not aware of that.
My remark remains the same though.
If you have a transfer rate (as a frequency) of R, you can only transfer frequencies up to R/2 without loss of information.
Or am I misunderstanding your question?
 
ok
and what can be the bandwidth of the channel in terms of R to support the transmission ?
 
R/2 as Nyquist states.
 
okay ..
So we are sampling a signal whose frequency is R at a frequency of R/2 and which should be the minimum bandwidth of channel...
AM I RIGHT ?
 
Is this statement true ?
For ideal Nyquist pulses (sinc), the required bandwidth is only Rs/2 to support an Rs symbol rate
 
I'm not sure what you're asking, so I'll just state what I know.

When you want to transmit a signal using a bandwidth signal at some frequency R, what you do is, you put your signal through a low-pass filter, filtering out all frequencies above R/2.
And then you transmit the signal.
Otherwise you lose information.
 
  • #10
okay
 

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