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9 - Intersymbol interference and equalization

Published online by Cambridge University Press:  05 June 2012

Tri T. Ha
Tri T. Ha
Affiliation:
Naval Postgraduate School, Monterey, California
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Summary

Introduction

Intersymbol interference (ISI) is a phenomenon in which the energy of a symbol spills over into succeeding symbols causing interference. Tight filtering at the transmitter and receiver and/or channel distortion can cause the waveform that represents a symbol to spread out into succeeding symbol periods. In a terrestrial wireless channel, a signal can travel from the transmitter to the receiver via multiple delayed paths (echoes). If the delays between paths are large compared to a symbol period, the energy carried by these echoes can cause significant ISI to the succeeding symbols. In this chapter, we study the Nyquist criterion for zero ISI and provide the design of an optimum demodulator that can achieve both maximum output signal-to-noise ratio and zero ISI. We then study linear equalizers, such as the zero-forcing linear equalizer (ZF-LE), and the mean-square error linear equalizer (MSE-LE), and nonlinear equalizers, such as the zero-forcing decision-feedback equalizer (ZF-DFE) and the mean-square error decision-feedback equalizer (MSE-DFE). Both nonlinear equalizers perform better than their linear counterparts. We then study the maximum likelihood sequence detection (MLSD), which is the optimum nonlinear equalization technique. Finally, the fractionally spaced equalizer is introduced to solve the timing error problem in the previous equalizers.

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Theory and Design of Digital Communication Systems , pp. 473 - 521
Publisher: Cambridge University Press
Print publication year: 2010

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  • Intersymbol interference and equalization
  • Tri T. Ha, Naval Postgraduate School, Monterey, California
  • Book: Theory and Design of Digital Communication Systems
  • Online publication: 05 June 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9780511778681.010
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  • Intersymbol interference and equalization
  • Tri T. Ha, Naval Postgraduate School, Monterey, California
  • Book: Theory and Design of Digital Communication Systems
  • Online publication: 05 June 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9780511778681.010
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Intersymbol interference and equalization
  • Tri T. Ha, Naval Postgraduate School, Monterey, California
  • Book: Theory and Design of Digital Communication Systems
  • Online publication: 05 June 2012
  • Chapter DOI: https://doi.org/10.1017/CBO9780511778681.010
Available formats
×