Intersymbol Interference

  • Edward A. Lee
  • David G. Messerschmitt


Chapter 6 described pulse amplitude modulation (PAM), in which a sequence of continuous-time pulses are multiplied by a sequence of symbols and combined for transmission. The output of the channel is filtered and sampled by the receiver, and the received samples are applied to a slicer to yield the detected data symbols. Inter-symbol interference results from linear amplitude and phase dispersion in the channel that broadens the pulses and causes them to interfere with one another. The Nyquist criterion specifies a frequency-domain condition on the received pulses under which there is no intersymbol interference. Generally this or a similar condition is not satisfied unless we equalize the channel, meaning roughly that we filter to compensate for the channel dispersion. Unfortunately, any equalization of amplitude distortion also enhances or amplifies any noise introduced by the channel, called noise enhancement. There is therefore a tradeoff between accurately minimizing intersymbol interference and minimizing the noise at the slicer input.


Matched Filter Data Symbol Pulse Amplitude Modulation INTERSYMBOL Interference Linear Equalizer 
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Copyright information

© Kluwer Academic Publishers, Boston 1988

Authors and Affiliations

  • Edward A. Lee
    • 1
  • David G. Messerschmitt
    • 1
  1. 1.University of California at BerkeleyUSA

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