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Nyquist bandwidth criterion

  1. Dec 2, 2011 #1
    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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  3. Dec 2, 2011 #2

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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.
     
  4. Dec 2, 2011 #3
    ISI is INTERSYMBOL INTERFERENCE
     
  5. Dec 2, 2011 #4

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    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?
     
  6. Dec 2, 2011 #5
    ok
    and what can be the bandwidth of the channel in terms of R to support the transmission ?
     
  7. Dec 2, 2011 #6

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    R/2 as Nyquist states.
     
  8. Dec 2, 2011 #7
    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 ?
     
  9. Dec 2, 2011 #8
    Is this statement true ?
    For ideal Nyquist pulses (sinc), the required bandwidth is only Rs/2 to support an Rs symbol rate
     
  10. Dec 2, 2011 #9

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    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.
     
  11. Dec 2, 2011 #10
    okay
     
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